RAMM
Well-Known Member
Grab 'em, a +10cc gasket ain't gonna do it. J.Rob
Help on 408 build
- Thread starter Mopar204
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Grab 'em, a +10cc gasket ain't gonna do it. J.Rob
nm9stheham
Well-Known Member
With a Felpro 8553PT head gasket (standard kit gasket, like it appears you have now), I am coming up with 9.7 for the SCR for those Wiseco's. With your cam, installed at an ICL of 108 degrees, I get DCR of 7.9. So that gets you to manageable/tunable point on the DCR number.
The Wiseco catalog says 527-530 grams for piston weight, and a pin weight of 126 grams for a piston+pin total weight of 654 grams +/-. That is almost 30 grams heavier than what is in there now IF IF IF you presently have the Icon IC744's in the present. So IF that is the case, then a re-balance is needed... 30 grams piston weight change is too much to ignore IMHO.
But: Please call SCAT to verify the pistons that you have or see if you have that in your paperwork. No need to go down the wrong road again based on anyone's 'best guesses' on what pistons you have.
Also, look to see if those Wiseco's are the same oversize as your present piston if you decide to use them. But I personally would not.... I'd go with ICON 745's and probably decide to live with the 10 gram weight change, since this is a street engine, not a full race engine. Again, this matter on piston weight assumes you now have Icon IC744's....please verify.
The Wiseco catalog says 527-530 grams for piston weight, and a pin weight of 126 grams for a piston+pin total weight of 654 grams +/-. That is almost 30 grams heavier than what is in there now IF IF IF you presently have the Icon IC744's in the present. So IF that is the case, then a re-balance is needed... 30 grams piston weight change is too much to ignore IMHO.
But: Please call SCAT to verify the pistons that you have or see if you have that in your paperwork. No need to go down the wrong road again based on anyone's 'best guesses' on what pistons you have.
Also, look to see if those Wiseco's are the same oversize as your present piston if you decide to use them. But I personally would not.... I'd go with ICON 745's and probably decide to live with the 10 gram weight change, since this is a street engine, not a full race engine. Again, this matter on piston weight assumes you now have Icon IC744's....please verify.
RAMM
Well-Known Member
Look, either way I would pull it apart and have it re-balanced. While its apart order a nice set of rings with a Napier THG 2nd ring gapped accordingly. Have your fave shop de-glaze the cylinders and re-assemble. Enjoy your "Street" engine with aplomb as it is now easy and fun to tune and live with. Oh and it will make a ton of power. J.Rob
nm9stheham
Well-Known Member
For a professional engine builder like yourself, I am sure it is bing-bang-boom-done, without a 2nd thought. It's just the matter of the extra $300-400 for the re-balance work, and the need in this application; factory engine ran how many miles with a balance tolerance of +/- 20 to 30 grams? With info, the OP can 'weigh' that part of the cost/benefit situation IMHO.
And, yes, I would for sure have the cylinders re-honed lightly for some set of new rings. All in all, it is not any major re-work, and there's no re-working cylinder/block surface to insure the best seal with thick Cometics, or ARP bolts to try to stabilize a thick head gasket (which I would do for a .125" thick gasket).
And, yes, I would for sure have the cylinders re-honed lightly for some set of new rings. All in all, it is not any major re-work, and there's no re-working cylinder/block surface to insure the best seal with thick Cometics, or ARP bolts to try to stabilize a thick head gasket (which I would do for a .125" thick gasket).
67autocross
A new iron curtain drawn across the 49th parallel
Just make sure you get the guy selling the pistons to send you the spec sheet first just in case they were ordered with any custom modifications that don’t work for you.( if I recall he lives about 4 hours from Winnipeg)
I’m surprised that he still has not sold them yet, I talked to him last fall about them when I started gathering parts for a 340 stroker build.
I’m surprised that he still has not sold them yet, I talked to him last fall about them when I started gathering parts for a 340 stroker build.
I don't know him either, but I did give him advice based on his inquiry, not what I think is the perfect solution, but I thought he wanted to drive his car. If you can't get a Cometic gasket to seal, by all means, don't use them.
Every engine builder has his own preferences and methods, but the engineering math does not change. The same applies to rocker geometry, and there are a whole lot of people who get that wrong, because they took advice from the wrong sources, without applying the math and pure simple logic.
Take good care of him. We need more young people in the Mopar hobby.
These won't give you any quench unless you buy aftermarket heads to go with them, so you still won't please everyone giving advice here. Whatever you decide, best of luck to you. I hope you get the results you are looking for without breaking the bank.
Wyrmrider
Well-Known Member
so
dbl check the piston and deck clearance stack, gasket, head cc yourself
see if a lighter pin is available to save the re-balance
if you do have to rebalanced with those pistons then check if any other pistons are available that do not require re balance
what do the kb quench domes weigh? heavier pins are easy to come by,
sometimes the lighter ones get pricey
If the block was honed professionally last build just hit it with a bottle brush yourself
grit depends on the ring selection,
you can eyeball the heads and block deck yourself
check the depth each end of the heads just in case someone belt sanded them somewhere along the line unless you are sure of their history
you can inspect the edge of your rings - if from the face side the wear mark is real narrow then they do not many miles on them and you can reuse
(trying to save some $$$ here) If they are worn all across the face they are junk
(but depends on if they have a taper or are barrel shaped)
I'm easy to please
just avoid "do it fast, do it wrong, do it over"
remember no scotchbright or discs for clean up of old gaskets- they will kill your new build
glad you have some help up there
dbl check the piston and deck clearance stack, gasket, head cc yourself
see if a lighter pin is available to save the re-balance
if you do have to rebalanced with those pistons then check if any other pistons are available that do not require re balance
what do the kb quench domes weigh? heavier pins are easy to come by,
sometimes the lighter ones get pricey
If the block was honed professionally last build just hit it with a bottle brush yourself
grit depends on the ring selection,
you can eyeball the heads and block deck yourself
check the depth each end of the heads just in case someone belt sanded them somewhere along the line unless you are sure of their history
you can inspect the edge of your rings - if from the face side the wear mark is real narrow then they do not many miles on them and you can reuse
(trying to save some $$$ here) If they are worn all across the face they are junk
(but depends on if they have a taper or are barrel shaped)
I'm easy to please
just avoid "do it fast, do it wrong, do it over"
remember no scotchbright or discs for clean up of old gaskets- they will kill your new build
glad you have some help up there
I’ve run so options with an engine shop a couple days ago and I think I’ve decided to go the heads and cam route since I wanted to go with aluminum heads in the future anyways. Not sure on cam yet maybe you guys can help me out a little bit more than you already have. Here are the heads I plan of going with (Promaxx shocker 185 CNC)
Shocker 185 Mopar CNC (Sold in Pairs) - PROMAXX Performance Products
What do you guys think of these heads?
Shocker 185 Mopar CNC (Sold in Pairs) - PROMAXX Performance Products
What do you guys think of these heads?
nm9stheham
Well-Known Member
Nice heads, but not the main question IMHO. Chamber size is hardly changing so your static CR is not going down. That means you have to go with a 20 degree or so larger cam (for advertised duration) to get the dynamic CR down to the low to mid 8's.
That moves the engine operation away from 'smooth' idling street operation, but that being good or bad is a very subjective thing. Rougher idle, but with that DCR ought to still have good mid-range torque for the street. Quite workable IMHO, but just beware that idle/off-idle operation will be rough-er. Lots more power from mid range on up. That outcome might just be A-OK with you.
AL heads are an aid to stay away from detonation so that is good. With your present head gaskets, any anti-detonation aid from quench/squish is probably on the margin of being useful, based on common thinking. Tune will have to be done well and maintained well with this DCR level.
The plan is less invasive into the engine too; that certainly has its merits.
That moves the engine operation away from 'smooth' idling street operation, but that being good or bad is a very subjective thing. Rougher idle, but with that DCR ought to still have good mid-range torque for the street. Quite workable IMHO, but just beware that idle/off-idle operation will be rough-er. Lots more power from mid range on up. That outcome might just be A-OK with you.
AL heads are an aid to stay away from detonation so that is good. With your present head gaskets, any anti-detonation aid from quench/squish is probably on the margin of being useful, based on common thinking. Tune will have to be done well and maintained well with this DCR level.
The plan is less invasive into the engine too; that certainly has its merits.
Wyrmrider
Well-Known Member
I'd run tight quench with the new heads, you can open them up around the valves for 5cc
I'd think solid cam and ask Mike Jones to run the numbers 4 U once you get the CR figured out- fill out his cam request card online
have your head flows handy he can make it work and advice on the resulting torque curve which may or may not be acceptable given converter and gears
do start the tune up conservatively
I'd think solid cam and ask Mike Jones to run the numbers 4 U once you get the CR figured out- fill out his cam request card online
have your head flows handy he can make it work and advice on the resulting torque curve which may or may not be acceptable given converter and gears
do start the tune up conservatively
67autocross
A new iron curtain drawn across the 49th parallel
They do flow close to what they are advertised at up to 500 lift when I watched one getting tested.
PRH
Well-Known Member
Imo, if the current plan ends up at something like 11.4:1cr, for a 99% street car to be driven on a diet of pump gas(where making the most power possible is not the primary objective)....... it’s not a very good plan.
Wyrmrider
Well-Known Member
yep 11:1 does not work
do the math
do the math
So this wouldn’t be a good idea unless I can get another 5ccs of of the chamber? Or it would and I wouldn’t be happy with the end result? Only reason I want to go this way is to stay away from touching the short block.
nm9stheham
Well-Known Member
IMHO.... it all depends on what he does with the cam and what he can accept in terms of operation, and how well he maintains tuning after build. DCR in the low 8's with AL heads, zero deck, and closed chambers would be OK in my book on 93 pump premium. Long duration, and older style slow ramps would be where I'd head if I chose to work with this SCR on pump premium.
Behavior I would expect with a cam that reduces SCR to DCR by 3 whole points with long duration:
- I'd expect it have good low RPM torque at that DCR and displacement.
- But I would expect the torque band to be somewhat 'peaky' up in the mid-range when a bigger cam is being used to reduce dynamic compression so much... i.e., not a very smooth torque curve for cruising.
- Economy is going to be pretty poor
PRH
Well-Known Member
I’m not going to argue with anyone about whether or not you might be able to come up with a specific combination of parts that will yield marginal operation with 93 octane gas and 11.4scr.
It’s absolutely not the path I would take for this application.
I would be shooting for low-10’s scr, and under 8:1 dcr, and be able to easily run a cam that is “right” for the application, rather than one that’s part of a band aid solution that isn’t exactly what the OP had in mind when he built the motor.
I don’t think you can really get where he wants to be without a piston change.
If I were the “project engineer”, it would get a piston change(Icon IC745’s, or any other quality forged 20cc inverted dome piston)....... and budget permitting, aluminum heads too.
I’d get the short block situation sorted out first....... you can always swap the heads in the car at a later date as the budget allows........ but “fix” the short block right the first time around.
Swapping the current pistons to something like an Icon IC745, and leaving everything else as is would put the scr at about 9.7:1.
Swapping to some new aluminum heads milled to 60cc would put you right at that 10:1 sweet spot.
Do it right........ or you’ll end up doing it over.
It’s absolutely not the path I would take for this application.
I would be shooting for low-10’s scr, and under 8:1 dcr, and be able to easily run a cam that is “right” for the application, rather than one that’s part of a band aid solution that isn’t exactly what the OP had in mind when he built the motor.
I don’t think you can really get where he wants to be without a piston change.
If I were the “project engineer”, it would get a piston change(Icon IC745’s, or any other quality forged 20cc inverted dome piston)....... and budget permitting, aluminum heads too.
I’d get the short block situation sorted out first....... you can always swap the heads in the car at a later date as the budget allows........ but “fix” the short block right the first time around.
Swapping the current pistons to something like an Icon IC745, and leaving everything else as is would put the scr at about 9.7:1.
Swapping to some new aluminum heads milled to 60cc would put you right at that 10:1 sweet spot.
Do it right........ or you’ll end up doing it over.
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nm9stheham
Well-Known Member
As you say, it can be made to work, but the operation will be something like what I outlined above and is a setup that you may or may not enjoy. Getting down close to 10:1 static CR is the max CR you would want to be for a cam for 'smoother' street performance, pump fuel, etc.
The heads you show are really to achieve mid to high RPM flow and are more for high performance so great for making more high RPM HP on the drag strip. But you may be just as happy with smaller flowing heads for street use if you never get to the high RPM's much. Smaller heads are A-OK with me as I am more interested in good street operation and a smooth, wide torque curve than raw peak HP; I am not a drag racer.
Since the smaller heads have the same chamber sizes, the high static CR problem you have still does not change. Options to lower the CR:
- Different pistons as discussed
- Bigger head chambers, which none of the AL heads achieves. I am not aware of any AL heads with chambers larger than 65 cc.
Another choice to get larger chambers is to go with stock iron heads. Yours have been milled heavily and that is the main source of the small chambers and the high CR problem. Get some stock iron heads and have the chambers set to around 74-75 cc's (And you could go even bigger) and you are most of the way to managing this. You still need a slightly larger cam, but not a big cam change like for the AL heads so engine performance can be kept closer to street.. if that is what you want.
Not sure if this helps you or not!
67autocross
A new iron curtain drawn across the 49th parallel
Keep in mind most of our gas stations only carry 91 octane, we do have some Husky stations that have E94...
Wyrmrider
Well-Known Member
Let me be cleat
I said you might open new al heads up 5cc
in your case that might not be enough
determine how many cc's you need in the chambers before buying
do not put a thick gasket with your new heads just to get the right ccs unless for a short term bandaid
I also do not know of any 74 cc SBM al heads OTB
I said you might open new al heads up 5cc
in your case that might not be enough
determine how many cc's you need in the chambers before buying
do not put a thick gasket with your new heads just to get the right ccs unless for a short term bandaid
I also do not know of any 74 cc SBM al heads OTB
If I were to get the ic745’s which are 10 grams heavier and go with some pins I found that were 11grams lighter than the one I currently have. Just to avoid rebalancing. That one gram wouldn’t be anything to worry about? I apologize for going over what we probably already discussed but all of you guys keep making really good points.
PRH
Well-Known Member
I might get flamed...... but......
I wouldn’t even skip a beat over 10g of piston weight.
The old pistons would come out, the new ones would go in.
I wouldn’t pull the balancer, water pump, or timing cover off, or the crank out.
Rings would get transferred from the old pistons right on to the new ones.
You’ll get plenty of suggestions and opinions about how to go about reconfiguring your combo....... in the end, you have to decide what makes the most sense to you.
What I outlined above is how I’d go about it.
I wouldn’t even skip a beat over 10g of piston weight.
The old pistons would come out, the new ones would go in.
I wouldn’t pull the balancer, water pump, or timing cover off, or the crank out.
Rings would get transferred from the old pistons right on to the new ones.
You’ll get plenty of suggestions and opinions about how to go about reconfiguring your combo....... in the end, you have to decide what makes the most sense to you.
What I outlined above is how I’d go about it.
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Wyrmrider
Well-Known Member
That's if the Ics give you the right end up cc's show us the math
good find on the lighter pins
good find on the lighter pins
Wyrmrider
Well-Known Member
what say u NM
he did not show his inputs so hard for me to tell and I'm not going to look them all up
he did not show his inputs so hard for me to tell and I'm not going to look them all up
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