Most likely stick, I dont have a spare stick and have plenty of autos but I like to shift
Ill have to find a stick, got the pedals and bellhousing and most other things.
340 build
- Thread starter 1930
- Start date
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Ill have to find a stick, got the pedals and bellhousing and most other things.
1930 wrote
I wonder if all the goop ( there was a ton of it on the intake manifold ) was because the head gasket was too tall ( just throwin it out there )
Mr Gasket make a intake gasket that's fairly thick and come with 2 stainless steel shims, used to block off the heat crossover.
Us them gaskets without the SS block offs
I wonder if all the goop ( there was a ton of it on the intake manifold ) was because the head gasket was too tall ( just throwin it out there )
Mr Gasket make a intake gasket that's fairly thick and come with 2 stainless steel shims, used to block off the heat crossover.
Us them gaskets without the SS block offs
No the truck as it is setup for auto. ( assuming I put it in the truck I was thinking of putting it in.....Im undecided ) I have all the manual stuff and hate to not use it, plus I prefer the manuals
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nm9stheham
Well-Known Member
Lightweight checking springs can be any light spring from the hardware store that fits close to the regular valve spring.
Hope I dont ruffle any feathers here, coudnt have gotten this far with everyones help so far and last thing I want to do is seem as if Im questioning buuuuut.
I cant stop thinking about a few things, mainly post # 61. Too me I cant understand why this would not makes the most sense, Ive got a couple of issues still with this engine.
1- I have the wrong heads, I dont want to sell these, Id be lucky to get 500 bucks for them here locally and Im NOT doing that. I dont have alot of money, never have never will and aluminum heads are a big bragging right I dont want to give up.
2- technically I have a deck surface that isnt flat ( boy thats buggin me, I know that its pretty standard on these older cast iron blocks but too know its there and not do anything about just seems like Im ignoring something ) ( dont ask dont tell crap )
3- When I took the engine apart the intake manifold was LITERALLY glued to the block thick and I MEAN THICK. I pryed and tapped and pryed and tapped and pryed and BEAT on that manifold till I ws blue in the face to remove it.
In the end I ended up cutting it off.
I am thinking that there is an alignment issue, I am thinking that the goop was put there to seal things up AKA a band aid, I dont like band aid.
Im also thinking that the head gasket I pulled out of there was not standard but instead an already extra thick head gasket to try and fix a problem.
Id like to know when I put this thing back together that I am doing the best that I can ( within reason )
Id like some feedback on how I can tell just how much I can cut off the top of these pistons without causing an issue there such as blow thru cause they became too thin.
If I cut the piston down than I could have
A- a flat deck ( let them take the high end down so all the pistons are within reason sticking out the same height
B- I could use a reasonable head gasket ( without getting too crazy )
C- I could use my heads without worry about valves hitting
D- I wouldnt have to goop the heck out of my manifold just to get it too seal.
Can someone tell my where Im wrong ?
I cant stop thinking about a few things, mainly post # 61. Too me I cant understand why this would not makes the most sense, Ive got a couple of issues still with this engine.
1- I have the wrong heads, I dont want to sell these, Id be lucky to get 500 bucks for them here locally and Im NOT doing that. I dont have alot of money, never have never will and aluminum heads are a big bragging right I dont want to give up.
2- technically I have a deck surface that isnt flat ( boy thats buggin me, I know that its pretty standard on these older cast iron blocks but too know its there and not do anything about just seems like Im ignoring something ) ( dont ask dont tell crap )
3- When I took the engine apart the intake manifold was LITERALLY glued to the block thick and I MEAN THICK. I pryed and tapped and pryed and tapped and pryed and BEAT on that manifold till I ws blue in the face to remove it.
In the end I ended up cutting it off.
I am thinking that there is an alignment issue, I am thinking that the goop was put there to seal things up AKA a band aid, I dont like band aid.
Im also thinking that the head gasket I pulled out of there was not standard but instead an already extra thick head gasket to try and fix a problem.
Id like to know when I put this thing back together that I am doing the best that I can ( within reason )
Id like some feedback on how I can tell just how much I can cut off the top of these pistons without causing an issue there such as blow thru cause they became too thin.
If I cut the piston down than I could have
A- a flat deck ( let them take the high end down so all the pistons are within reason sticking out the same height
B- I could use a reasonable head gasket ( without getting too crazy )
C- I could use my heads without worry about valves hitting
D- I wouldnt have to goop the heck out of my manifold just to get it too seal.
Can someone tell my where Im wrong ?
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This post was made from internet searches discussing the matter of removing material from Piston top nothing more.
If you mean grind/cut the tops, of course you can. Depending on the piston, it'll determine how much you can cut. This is normally done on a lathe from what the machine shop told me. I had to do this on an engine and based on Wiseco's recommendation, we were able to cut down .030" off the top without sacrificing the strength. Well, I guess that might be debatable but they said that builders have done this many times before and we wouldn't be the last.
Turning down the top off pistons is part of blue printing. You should check deck height on all pistons, sometimes you’d have to move rods and pistons around to get the perfect deck height, and then the last resort would be turning down the top of the piston. This can be done in a conventional lathe. You’d need to balance the pistons after your done. There are other things you can do, but not going to get into it.
It is fairly common in the performance community to spot face pistons for increased valve/piston clearence.
As posted above it should be done on a milling machine not by hand with a grinder. You also need to consider the thickness of the piston crown. If you mill off too much you will break the piston due to the weak spot you created.
You need to do some homework to figure out some things before you decide what you need to do.
You need to measure the piston crown thickness where the valve pocket would need to be machined.
You would need to determine how much interference you currently have plus additional clearence you need to prevent valve/piston contact during over-rev or high engine rpm due to valve float.
Then you need to determine if there is enough "meat" on the piston to allow you to correct the problem. The proper way to do it is probably to order special pistons to your specs for this build and sell your current pistons.
You really need to get on the phone with the major engine builders like Axis Power, and Cobb they both have probably already determined what the likely clearences are and how successfull the "corrective machining" would be.
Custom machining the pistons after the fact is probably not cost effective. It is much cheaper to do this sort of work when the pistons are ordered unless the engine build shop routinly does this sort of work and already has fixtures set up that are suitable for these pistons.
If you mean grind/cut the tops, of course you can. Depending on the piston, it'll determine how much you can cut. This is normally done on a lathe from what the machine shop told me. I had to do this on an engine and based on Wiseco's recommendation, we were able to cut down .030" off the top without sacrificing the strength. Well, I guess that might be debatable but they said that builders have done this many times before and we wouldn't be the last.
Turning down the top off pistons is part of blue printing. You should check deck height on all pistons, sometimes you’d have to move rods and pistons around to get the perfect deck height, and then the last resort would be turning down the top of the piston. This can be done in a conventional lathe. You’d need to balance the pistons after your done. There are other things you can do, but not going to get into it.
It is fairly common in the performance community to spot face pistons for increased valve/piston clearence.
As posted above it should be done on a milling machine not by hand with a grinder. You also need to consider the thickness of the piston crown. If you mill off too much you will break the piston due to the weak spot you created.
You need to do some homework to figure out some things before you decide what you need to do.
You need to measure the piston crown thickness where the valve pocket would need to be machined.
You would need to determine how much interference you currently have plus additional clearence you need to prevent valve/piston contact during over-rev or high engine rpm due to valve float.
Then you need to determine if there is enough "meat" on the piston to allow you to correct the problem. The proper way to do it is probably to order special pistons to your specs for this build and sell your current pistons.
You really need to get on the phone with the major engine builders like Axis Power, and Cobb they both have probably already determined what the likely clearences are and how successfull the "corrective machining" would be.
Custom machining the pistons after the fact is probably not cost effective. It is much cheaper to do this sort of work when the pistons are ordered unless the engine build shop routinly does this sort of work and already has fixtures set up that are suitable for these pistons.
Not to oversimplify things but if the highest piston is .020 above the deck and the lowest is .011 above the deck would it be safe to say that if I were able to remove .020 from the piston top that would put me at approx zero deck.
I could then get the deck square and true
Maybe I still need to address how that is gonna affect the valve reliefs and combustion but off the top of my head I can imagine how .020 is gonna make much of a difference there.
Here at the shop now I can see that the ledge itself is thicker than .030 thou. Why not take the pistons ( assuming its cost affective ) to my buddy with the lathe and have him remove .030 though from the face, that will put me approx .010 in the hole, I can get away with the standard head gasket ( If I remember right crushed thickness of .030-.040 thou ) and all is good?
If I did .030 thou and the engine got revved to 6 or 65 than Id still prob. be golden?
I cant get too technical cause I have a hard time comprehending what comes easy for some of you guys.
I could then get the deck square and true
Maybe I still need to address how that is gonna affect the valve reliefs and combustion but off the top of my head I can imagine how .020 is gonna make much of a difference there.
Here at the shop now I can see that the ledge itself is thicker than .030 thou. Why not take the pistons ( assuming its cost affective ) to my buddy with the lathe and have him remove .030 though from the face, that will put me approx .010 in the hole, I can get away with the standard head gasket ( If I remember right crushed thickness of .030-.040 thou ) and all is good?
If I did .030 thou and the engine got revved to 6 or 65 than Id still prob. be golden?
I cant get too technical cause I have a hard time comprehending what comes easy for some of you guys.
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You need to look at the bottom of the piston, there may be some variations in thickness to be aware of.
The first step is to call the manufacturer and see how much is safe to be removed.
I like you plan but if you remove two much, and you loose a tight quench........well you have shot yourself in the foot, so to speak.
a .040 head gasket is common and inexpensive.
shave .010 to .015 of the piston and now you're .020" piston goes down to .005 -.010 above deck. have the block decked. you low deck hole(.020) will lose deck height by at the most,.002"(ask you machinist i'm only guessing)
#1 call manufacture of piston and ask how much can be removed safely
#2 Verify that the tallest piston is .020 out of the hole(Remember, .002" makes a hug different in you planning)
#3 find out from machinist how much will have to be removed from the lowest spot on the deck (it my only be a half of a thousand aka .0005"
Note: AJ/Forms said that he had run as tight of a piston to head clearance a .023" without any head to piston kissing!!! Keep that in mind as you figure this all out.
The first step is to call the manufacturer and see how much is safe to be removed.
I like you plan but if you remove two much, and you loose a tight quench........well you have shot yourself in the foot, so to speak.
a .040 head gasket is common and inexpensive.
shave .010 to .015 of the piston and now you're .020" piston goes down to .005 -.010 above deck. have the block decked. you low deck hole(.020) will lose deck height by at the most,.002"(ask you machinist i'm only guessing)
#1 call manufacture of piston and ask how much can be removed safely
#2 Verify that the tallest piston is .020 out of the hole(Remember, .002" makes a hug different in you planning)
#3 find out from machinist how much will have to be removed from the lowest spot on the deck (it my only be a half of a thousand aka .0005"
Note: AJ/Forms said that he had run as tight of a piston to head clearance a .023" without any head to piston kissing!!! Keep that in mind as you figure this all out.
nm9stheham
Well-Known Member
Waste of time to work over the pistons for piston to head clearance. My son's 340 has the pistons above the deck with the same heads, and we just adjusted the gasket thickness like you have been encouraged to do.
You DON'T have the wrong heads at all. (In some ways, what you have is a better chamber. ) You just adjust the head gaskets to work with what you have. The heads with the recesses machined on the underside of the heads just come that way so you don't have to work over the piston with standard head gaskets. Both head flow and work the same.
A local machinist who does tones of 4 banger races engine uses .025" as a minimum; he has seen the the pistons kiss the heads with that clearance. That is for racing. AJ may have run .023" but that is VERY marginal. The general rule of thumb for .035" clearance allows for a lot of variations. It also allows for more bore wear over the long term; as the bores wear, the pistons will rock more and more and the high point of the piston gets closer to the heads. If AJ was using hypereutectic pitons the are a lot tighter in the bores and don't rock nearly as much as the forged pistons that you have; so those pistons can be run at a tighter head to piston clearance. Your pistons are going to be on loose side with more rocking so beware. Long term for TROUBLE-FREE operation, work with the .035" piston to head minimum clearance.
Now if you really want to spend the $$ on the piston machining to use lower cost head gaskets, and it costs you nothing, then go for it. But I would not go .010" below deck. I would stay .005" above deck with the tallest piston and use a .039 thick Felpro 1008 head gasket. You then have .035" head clearance to the tallest piston, and .044" to the shortest. (And you may be able swap rods around to get less height variation.)
The reason to keep the gap in the .040" range +/- is for something called quench; read up on that term. It helps reduce any tendency for the combustion process to detonate, which can be a piston destroyer. With the AL heads, small combustion chamber and the tight quench gap, you are as good as you can get in that regard. It will be good to do all you can in this area of eliminating detonation for running this engine in a heavy truck.
Valve to piston clearance is another matter entirely.
You DON'T have the wrong heads at all. (In some ways, what you have is a better chamber. ) You just adjust the head gaskets to work with what you have. The heads with the recesses machined on the underside of the heads just come that way so you don't have to work over the piston with standard head gaskets. Both head flow and work the same.
A local machinist who does tones of 4 banger races engine uses .025" as a minimum; he has seen the the pistons kiss the heads with that clearance. That is for racing. AJ may have run .023" but that is VERY marginal. The general rule of thumb for .035" clearance allows for a lot of variations. It also allows for more bore wear over the long term; as the bores wear, the pistons will rock more and more and the high point of the piston gets closer to the heads. If AJ was using hypereutectic pitons the are a lot tighter in the bores and don't rock nearly as much as the forged pistons that you have; so those pistons can be run at a tighter head to piston clearance. Your pistons are going to be on loose side with more rocking so beware. Long term for TROUBLE-FREE operation, work with the .035" piston to head minimum clearance.
Now if you really want to spend the $$ on the piston machining to use lower cost head gaskets, and it costs you nothing, then go for it. But I would not go .010" below deck. I would stay .005" above deck with the tallest piston and use a .039 thick Felpro 1008 head gasket. You then have .035" head clearance to the tallest piston, and .044" to the shortest. (And you may be able swap rods around to get less height variation.)
The reason to keep the gap in the .040" range +/- is for something called quench; read up on that term. It helps reduce any tendency for the combustion process to detonate, which can be a piston destroyer. With the AL heads, small combustion chamber and the tight quench gap, you are as good as you can get in that regard. It will be good to do all you can in this area of eliminating detonation for running this engine in a heavy truck.
Valve to piston clearance is another matter entirely.
Sorry for the confusion and the way Im approaching this.... anyway my buddy cant turn the pistons in his lathe accurately bu someone else I know has a special fixture ( havent seen it yet ) that he loaned to a buddy of his that Ive contacted and am on my way out there now.
He will do all 8 for 50 bucks, he evidently owes the guy that has lent him his tool.
I know there prob isnt time to get an answer right now so Im gonna drop them off and then tell him Ill get back with him to tell him how much to remove.
I want to get the block squared that means taking off .020 thou, the highest one is sticking out the hole .020 ( approx ) so that means according to whats been given above that I should have no more than .015 taken off the piston unless Im mistaken.
That will let me run a standard head gasket and I wont have to be worried about intake/head sealing issues.
I look forward to response
He will do all 8 for 50 bucks, he evidently owes the guy that has lent him his tool.
I know there prob isnt time to get an answer right now so Im gonna drop them off and then tell him Ill get back with him to tell him how much to remove.
I want to get the block squared that means taking off .020 thou, the highest one is sticking out the hole .020 ( approx ) so that means according to whats been given above that I should have no more than .015 taken off the piston unless Im mistaken.
That will let me run a standard head gasket and I wont have to be worried about intake/head sealing issues.
I look forward to response
nm9stheham
Well-Known Member
Well you won't have intake/head sealing issues with a .055" or .060" Cometic head gasket. And the Cometics are re-usable unlike standard head gaskets.
A few more parameters before you act; what do you mean bay 'standard head gasket'? The standard ones out of the Felpro gakset sets are NOMINALLY .051" thick. I don't think their thickness is all that well controlled so for tight clearance use, I would not use them personally. (Someone has reported the 8553PT's as thin as .046" thick compressed.) The Felpro 1008 gaskets are .039" thick and I think that thickness is better controlled. You have to buy them in addition to the standard gasket set.
(BTW, you can but a lower end gasket set and an intake set and save a few $$ to put towards the Cometics or Felpro 1008's.)
If you DO use the standard Felpro head gaskets (PN 8553PT, like came off of the engine) then they are nominally .051" compressed. I bet you can swap a few of the pistons around and get that tallest one down a bit. With the 8553PT head gaskets, then your pistons should be .005" to .015" above deck to keep the quench gap in the .035" to .045" range. If you use the 1008's then the number is different. If you use the Cometics, you don't need to touch anything.
Do you mean that the block will be square decked? Or do you mean that the piston tops will be milled down to equal clearance over the deck? If you ARE going to square deck the block, then count on as much as an extra .005"-010" coming off of the deck to all over to get things trued up. So, if you are indeed going to have the block square decked, you HAVE to wait on the piston work to see where things end up. Then you put things back together temporarily, (block, crank, and all pistons) and re-measure the piston to deck clearance; only then do you cut the pistons.
A few more parameters before you act; what do you mean bay 'standard head gasket'? The standard ones out of the Felpro gakset sets are NOMINALLY .051" thick. I don't think their thickness is all that well controlled so for tight clearance use, I would not use them personally. (Someone has reported the 8553PT's as thin as .046" thick compressed.) The Felpro 1008 gaskets are .039" thick and I think that thickness is better controlled. You have to buy them in addition to the standard gasket set.
(BTW, you can but a lower end gasket set and an intake set and save a few $$ to put towards the Cometics or Felpro 1008's.)
If you DO use the standard Felpro head gaskets (PN 8553PT, like came off of the engine) then they are nominally .051" compressed. I bet you can swap a few of the pistons around and get that tallest one down a bit. With the 8553PT head gaskets, then your pistons should be .005" to .015" above deck to keep the quench gap in the .035" to .045" range. If you use the 1008's then the number is different. If you use the Cometics, you don't need to touch anything.
Do you mean that the block will be square decked? Or do you mean that the piston tops will be milled down to equal clearance over the deck? If you ARE going to square deck the block, then count on as much as an extra .005"-010" coming off of the deck to all over to get things trued up. So, if you are indeed going to have the block square decked, you HAVE to wait on the piston work to see where things end up. Then you put things back together temporarily, (block, crank, and all pistons) and re-measure the piston to deck clearance; only then do you cut the pistons.
Glad you asked, I called federal mogul today and they told me that I could easily/safely remove 100.000 from the top of the piston if I chose, he also told me 7.6 for valve relief CC ( if I remember correctly, I left the exact info at the shop )
Bore diam I dont know yet cause I guess I have to decide on a head gasket first. I need to go thru this thread, look at my options as far as head gasket goes and then figure out what the bore diam is for that gasket.
Im assuming I need to figure out how much exactly the machine shop has to remove from the decks, then do my setup and decide how far down in the hole or above the deck Id like to be and with the chosen head gasket where I can get the compression.
I talked again with the machine shop today and the guy cutting the pistons, what came out of that was too get all the machine work done to the block first then Ill take everything back and set my pistons back up to re-measure how high they are out of the hole after they have cut and squared the deck.
Bring the pistons back to Matt and let him cut them down and then return them to the machine shop for balancing.
I didnt get the friends and family discount on the cutting of the pistons and so its not gonna be 50 for all 8 but 80. He said he does it quite often for guys that have mismatched engine components, his name is Matt Mercer, he is a fairly famous local sprint car builder/driver ect.
He also says he does it quite often for the diesel truck guys, something about there being a limited choice of head gaskets.
Pictured below is is milling machine and the fairly simple device to hold the piston
1930 said
I called federal mogul today and they told me that I could easily/safely remove 100.000 from the top of the piston
You mean 100 thousand aka .100"
Like i said before, while you're doing you measurements keep quench in mind.
You can check the bore diameter on the head gasket you took of for reference.
With a .060 over bore 340 (4.100) i think you need to stay with a 4.180 bore gasket. i don't think a 4.04 bore gasket is a good idea. WHAT SAY YOU ALL...............
Now onto the valve reliefs. that tells you how much to subtract from a .018 pop up flat top right? You need more math to so see how many cc a flat top piston would be .018 out of the hole........or .020 out of the hole for you tallest piston......Make sence?
I will try and dig it up and lay it out for you.
I called federal mogul today and they told me that I could easily/safely remove 100.000 from the top of the piston
You mean 100 thousand aka .100"
Like i said before, while you're doing you measurements keep quench in mind.
You can check the bore diameter on the head gasket you took of for reference.
With a .060 over bore 340 (4.100) i think you need to stay with a 4.180 bore gasket. i don't think a 4.04 bore gasket is a good idea. WHAT SAY YOU ALL...............
Now onto the valve reliefs. that tells you how much to subtract from a .018 pop up flat top right? You need more math to so see how many cc a flat top piston would be .018 out of the hole........or .020 out of the hole for you tallest piston......Make sence?
I will try and dig it up and lay it out for you.
OK here is the math. you don't have to understand the math to use it!
.7854 X bore X bore(4.100 x 4.100) x stroke aka piston pop up(.018") = 0.2376463(cubic inch) X 16.387(converts it to CC)=3.8943099 or 3.89CC
So your piston sticking out of the hole as a flat top(no valve reliefs)=3.89 cc
Your Valve reliefs are 7.6 CC, Sooo, 3.89 CC (Minus) -7.6 valve relief CC equals a minus (-)3.70569 or 3.71 CC in the hole.
So when you use that calculator and it says (Input a positive number for valve reliefs.
Input a negative number if it has a dome. )
It has a .018" dome or pop up but it is actually in the hole 3.71 CC not 7.6 CC aka you us "positive number" on the calculator, not a negative number. Even though the math we just did cam up with a negative number.
compression is volume below piston (stroke)+ volume above piston, divided by volume above piston.
You add 3.71 cc to the head volume. if it had a dome that stuck into the combustion chamber, then there would be less space in the combustion chamber causing you to us a negative number.
If i lost you anywhere, let me know and i will try to explain better.
Note: I used the .018" pop up or above deck because what's what the piston manufacturer said it is.
.7854 X bore X bore(4.100 x 4.100) x stroke aka piston pop up(.018") = 0.2376463(cubic inch) X 16.387(converts it to CC)=3.8943099 or 3.89CC
So your piston sticking out of the hole as a flat top(no valve reliefs)=3.89 cc
Your Valve reliefs are 7.6 CC, Sooo, 3.89 CC (Minus) -7.6 valve relief CC equals a minus (-)3.70569 or 3.71 CC in the hole.
So when you use that calculator and it says (Input a positive number for valve reliefs.
Input a negative number if it has a dome. )
It has a .018" dome or pop up but it is actually in the hole 3.71 CC not 7.6 CC aka you us "positive number" on the calculator, not a negative number. Even though the math we just did cam up with a negative number.
compression is volume below piston (stroke)+ volume above piston, divided by volume above piston.
You add 3.71 cc to the head volume. if it had a dome that stuck into the combustion chamber, then there would be less space in the combustion chamber causing you to us a negative number.
If i lost you anywhere, let me know and i will try to explain better.
Note: I used the .018" pop up or above deck because what's what the piston manufacturer said it is.
I just when and played with that compression calculator.
didn't realize it had deck height on it.
compression come out the same if you use 7.6 and deck height -.018"
or if u use my math above and input 3.71 and then .000 deck height.
Wow that was a lot of hot air for nothing
didn't realize it had deck height on it.
compression come out the same if you use 7.6 and deck height -.018"
or if u use my math above and input 3.71 and then .000 deck height.
Wow that was a lot of hot air for nothing
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Stop!
back up the bus.
This has already been mentioned, but it is worth repeating; Your deck height may vary because the rods vary. Or because the crank is not the same stroke on every throw.Or because one deck is shorter than the other, or because one or both decks is not running parallel to the crank. If you square deck it you have paid a lot of money, possibly to not correct anything at all. Before spending money, you have to prove whats what.
Here's how to prove it in your garage;
Drop the crank in with just the front and back main-bearings,snug up the bolts to like 80% torque, no big deal. Get a Sharpie. Grab any piston and rod assembly.Drop into #1 hole with a new top-half bearing. Set it just below the deck. Lay a STRAIGHT square rod across the hole on it's centerline in the fore/aft direction, on the wrist pin axis. I use a 1/4sq by about 8" length of keystock. Set your dial indicator up on it, set to zero. Now roll the crank over to push the piston up out of the hole. The piston will raise the bar and the indicator will read the deck-height. When it peaks, stop. Rock the piston and record the MINIMUM height.Write it on the deck with the Sharpie on the valley side of the hole.
Repeat in every hole with this same piston assembly.
Now you have a picture of where the decks and crank-throws really are! You will find some tall deck heights and some short heights.
Now,number your cylinders 1 thru 7 on the drivers side and 2 thru 8 on the passenger side, in proper Moparese. Find the cylinder with the tallest deck height. What ever the number of that cylinder is, mark the top of this piston assembly with that number and the deck height in that hole,and set it aside.
Next grab another assy and stick it in this same hole. Measure it's deck height. Mark the top. Repeat with each of the other assys.
Now, line those assys up from tallest to shortest. You know where this is going right?
Take the longest assy and mark it with the number of the shortest hole. Then the next longest, gets the number of the next shortest hole and so on.
On a separate sheet of paper, right down all these things you have discovered, using the stamped number on the rod, as a reference. Record also the number of the tallest deck ht with what rod # was used, and what rod ended up in what hole. The important thing is to be able to identify the various deck-heights by the rod number, so that when the Sharpie IDs get erased, you can still find what assy goes in what hole.
Ok
Finally, stick each one in it's designated hole and measure it's deck height, in it's new hole. Erase all the old numbers. Mark it with the number of the HOLE on the top now, and the deck height in that hole.
Make a map like the one you earlier made but now with the holes correctly numbered in the Mopar way. Record all the final information, and what rod goes in which hole.
You might be concerned with what happens if you separate the pistons from the rods.And I was too. I found tho, that the piston tolerances are extremely well managed with differences in compression heights almost negligible.
So after you get this far, you will want to restamp your rods, to make it easier to correctly locate them at some future rebuild/freshening.
Now if you actually perform this exercise, you may find the deck-height variance to be acceptable. I got mine to within 002/003 IIRC.
If you get yours this close, then the block can be left alone.
At this point, you can shave the tops off the pistons equally to achieve your very-tight Q. I run .034 in my 367 with those same heads and rods but with KB hypers. The machine shop that I trusted, opened up the skirt clearance to .003/.004. Boy was I mad. This is partly why I run a minimum water temp of 205*, that's another story.
Now back to your post, above. If you square deck your engine, and it comes back perfect, but your crank is goofy and you have eight different length rods, you may actually be making things worse, cuz you have lost the opportunity to use the crooked block to your advantage. Only careful measuring can prove the block will or will not, work,......as is.
One more thing to think about;This is the best time to check the fit of your intake flanges to the heads to the decks. If it too is messed up, then the sq-decking is back on the table.
To do this, you can set the clean heads on the clean decks and snug down just the four corners, of each head, no gaskets. Drop the intake on. Measure the valley gap to the nearest 1/16 or so, and find some straight bar stock to lay on the china-wall to elevate the intake and produce a gap at the intake gasket surfaces. Drop the intake back on and skate it over to one side. Push it up tight and eyeball the fit where the gasket should be. If you see a gap, stick a feeler gauge in it. Check the front then the rear. Then slide it over to the other side and repeat. If there are gaps, you might be in trouble. If the gaps are on the bottom, it will never seal. The running engine will pull in oily crankcase vapors and fog the neighborhood, and it will run like crap. A slight gap at the top may be permissable, depending on how many corners are standing open, and how you are able to torque it down to average them all out.
So now you have, possibly, a second reason to SQ-deck.
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Thanks for all the input above, thats alot to take in, it was alot of time putting it there I know, I have to get to my shop now and get some customer work done so that I can pay the bills, I will read ( and re-read Im sure ) the posts above and comment the first chance I get. Thanks again.
Yes I meant .100
Ill check the bore diam of the one I took off, thats a great idea.
OK here is the math. you don't have to understand the math to use it!
.7854 X bore X bore(4.100 x 4.100) x stroke aka piston pop up(.018") = 0.2376463(cubic inch) X 16.387(converts it to CC)=3.8943099 or 3.89CC
So your piston sticking out of the hole as a flat top(no valve reliefs)=3.89 cc
Your Valve reliefs are 7.6 CC, Sooo, 3.89 CC (Minus) -7.6 valve relief CC equals a minus (-)3.70569 or 3.71 CC in the hole.
Good cause I do not understand it
So when you use that calculator and it says (Input a positive number for valve reliefs.
Input a negative number if it has a dome. )
It has a .018" dome or pop up but it is actually in the hole 3.71 CC not 7.6 CC aka you us "positive number" on the calculator, not a negative number. Even though the math we just did cam up with a negative number.
compression is volume below piston (stroke)+ volume above piston, divided by volume above piston.
You add 3.71 cc to the head volume. if it had a dome that stuck into the combustion chamber, then there would be less space in the combustion chamber causing you to us a negative number.
If i lost you anywhere, let me know and i will try to explain better.
Note: I used the .018" pop up or above deck because what's what the piston manufacturer said it is.
I just when and played with that compression calculator.
didn't realize it had deck height on it.
compression come out the same if you use 7.6 and deck height -.018"
or if u use my math above and input 3.71 and then .000 deck height.
Wow that was a lot of hot air for nothing
Can you tell me what you input for
Bore - 4.10
Stroke - 3.75
Head Chamber CC - 63
Valve relief - 7.6
Gasket thickness - What did you input
Gasket bore diam - 4.180
Deck height - what did you input= unknown at this point
The block and everything are at the machine shop so this very informative post fell a couple of days late, I am going to do this though on a different engine and hopefully you can stay posted
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nm9stheham
Well-Known Member
To avoid confusion with the on-line calculator, do this:
- Just enter the valve relief in cc's as the piston manufacturer lists it (7.6 cc's in this case... which seems high but use what the mfr lists or what you measure... IF you measure the valve reliefs, which I don't.).
- You DON'T take off the above deck-volume of the pistons tops sticking above the deck from the valve relief; the math of the calculators do this automatically. Just enter the deck height of the piston, which will be a - number if it is a flat top sticking above the deck.
Numbers to use:
Bore: 4.100
Stroke: 3.31
Deck height: -.018 for the Wallace calculator or the Kelly calculator (for your TRW piston's standard deck height)
Valve relief: 7.6 cc
Gasket hole: 4.17" for Felpro 8553PT
(Gasket hole diameter will be as you order the head gasket made if you use Cometics; that is a custom order parameter in increments of .025" IIRC.)
Gasket thicknesses:
Felpro 8553PT = .051"
Felpro 1008 = .039
Mar Gasket 1121G = .028"
Cometic = thickness as ordered; increments are .005" in the .025' to .100" order range IIRC
FYI, I get 10.49 with both the Wallace and Kelley calculators for the above parameters.
- Just enter the valve relief in cc's as the piston manufacturer lists it (7.6 cc's in this case... which seems high but use what the mfr lists or what you measure... IF you measure the valve reliefs, which I don't.).
- You DON'T take off the above deck-volume of the pistons tops sticking above the deck from the valve relief; the math of the calculators do this automatically. Just enter the deck height of the piston, which will be a - number if it is a flat top sticking above the deck.
Numbers to use:
Bore: 4.100
Stroke: 3.31
Deck height: -.018 for the Wallace calculator or the Kelly calculator (for your TRW piston's standard deck height)
Valve relief: 7.6 cc
Gasket hole: 4.17" for Felpro 8553PT
(Gasket hole diameter will be as you order the head gasket made if you use Cometics; that is a custom order parameter in increments of .025" IIRC.)
Gasket thicknesses:
Felpro 8553PT = .051"
Felpro 1008 = .039
Mar Gasket 1121G = .028"
Cometic = thickness as ordered; increments are .005" in the .025' to .100" order range IIRC
FYI, I get 10.49 with both the Wallace and Kelley calculators for the above parameters.
nm9stheham
Well-Known Member
To clarify: The 10.49 number is with the .039" thick Felpro 1008.
Using the .051" thick Felpro 5883PT, I get 10.16 SCR. It also assumes the valve reliefs are actually 7.6 cc's volume.
I take these results to be close but not necessarily exact, but good enough for planning cams and predicting/planning overall performance. There are always variables in deck height an other things like as has been pointed out and you have measured.
Don't get hung up on .1 or .2 differences in CR computations; the cylinder pressure differences that result will be 1-3 psi. That's waaaay down in the noise for most builds. It would take a lot of precision machining to get under .1 variations in SCR, which does not make sense for you.
Using the .051" thick Felpro 5883PT, I get 10.16 SCR. It also assumes the valve reliefs are actually 7.6 cc's volume.
I take these results to be close but not necessarily exact, but good enough for planning cams and predicting/planning overall performance. There are always variables in deck height an other things like as has been pointed out and you have measured.
Don't get hung up on .1 or .2 differences in CR computations; the cylinder pressure differences that result will be 1-3 psi. That's waaaay down in the noise for most builds. It would take a lot of precision machining to get under .1 variations in SCR, which does not make sense for you.
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