340 build

[1930]

Here's how to check the compression of your engine components:

How to Check Compression

Man thats alot of math, Ill have to go thru it more carefully, I must have missed where you mentioned what to do as far as filling the cylinder if you have pistons that sit above the deck surface, Im sure its there.

If it don't say 340 cast only then its a 360. either way it's NOT for a forged crank. Aka internal balanced.
Man no wonder you got this 340 for a song. .....vibrates, like a MO FO, over reved it and now it has a miss due to leaking bent valves.........
You might want to roll them push rod on a flat surface and see if you have any bent ones.

360 would make sense, from what I see on the net the connecting rods appear to be 360 as well according to the part number on them unless Im mistaken

I already threw the pushrods in the oil pan, I figured I better just go ahead and replace them.

I dont see any leaks though around the valve seats so Im assuming the heads are fine

 

[Moparman1806]

They are 340 rods that you have, I just double checked a set of mine- same number. I would have your shop check the valves anyway, I have seen valves somewhat seal, but hang at lift from a very slightly bent stem causing scars to the guides

 

[1930]

They are 340 rods that you have, I just double checked a set of mine- same number. I would have your shop check the valves anyway, I have seen valves somewhat seal, but hang at lift from a very slightly bent stem causing scars to the guides

Thanks for doing that, for some reason that does make me feel a little better, I just read here on this forum that 340 rods are forged and are lighter than 360 rods, any truth to that?

Do you have a known good dampner that you would sell or can you recomend an aftermarket one? Id rather have an original but I am worried about the rubber being dried out and brittle, whats your opinion?

I will have them check the valves

 

[Cudafever]

I think the only thing different between a 340 rod and a 360 rod is the bushing in the small end, for the wrist pin.
340 has a floating pin and a snap ring in piston. 360 the wrist pin is pressed into the rod.

 

[1930]

Any chance I can check the valves myself, I have the tool to remove them, Id like to do everything I can myself just for the experience.

 

[Cudafever]

sure why not. Just mark them so they go back into the right hole. or the guide it was in. then you can take a wire wheel to the valve head area and decarbon them, check guide play......maybe even clean up the port a little while your there

 

[Moparman1806]

Any chance I can check the valves myself, I have the tool to remove them, Id like to do everything I can myself just for the experience.

You can remove the springs, open the valve off the seat a little, spin valve to see if there is any binding. After that remove valve, place stem on flat surface and roll to see if there is any wobble. I will look to see if I have another balancer, I have to make sure I have an extra for the 72 Duster I just got. If I have one I will be happy to sell

 

[1930]

sure why not. Just mark them so they go back into the right hole. or the guide it was in. then you can take a wire wheel to the valve head area and decarbon them, check guide play......maybe even clean up the port a little while your there

Any way to check for bent stems or is it safe to assume that if they ride in the hole nice and smooth that they are fine?

I dont know if you noticed it or not but someone has already done some porting work, I dont know the extent. Maybe it was just a gasket matching, hopefully it was at least for this engine.

 

[1930]

You can remove the springs, open the valve off the seat a little, spin valve to see if there is any binding. After that remove valve, place stem on flat surface and roll to see if there is any wobble. I will look to see if I have another balancer, I have to make sure I have an extra for the 72 Duster I just got. If I have one I will be happy to sell

Ok that about answers my question, thanks. Let me know on the balancer. Id also like to find a decent set of original 340 manifolds, Im not a fan of headers.

 

[Cudafever]

One word to the wise, when you remove the retainer and locks off the valves. make sure there is not burs on the valve stem lock of the stem. if there is, (Real common on two and three grooved valve stems) remove it with a file. If you DON'T, the guide will have to be replace because of a great Big scare now, down the middle of if!!!!!!!

 

[nm9stheham]

You're 'saving' it from a certain death, I hope.

No need for an OEM damper; the heads and pistons aren't. BTW, that crank COULD have been balanced to work with that damper and a 360 type flexplate or TC. It would end up with some pretty big holes in the 2 large end counterweights. I think I see one pretty deep hole in the rear large counter weight but dunno if it stock or not. Sounds like some prelimnary balance work is in order, to find out what the balance is set up for, before turning the crank. It is not hard to work up a bobweight with the parts you have so the shop can just test spin it with a close bobweight to see if the crank is basically in balance with no external balance parts. Stock early 340 bobweight should be in the area of 2326 grams, and the pistons and all the other parts that effect bobweight which you have should be close to stock weights. (If you have access to a gram scale, you can tell if this is so. Weigh one piston-rod-pin assembly; stock ought to be around 1635 grams (if my notes are right), maybe a bit more since the pistons are oversized. Weigh this WITHOUT rings and bearing shells.)

Have the shop look at the bores and pistons first, get some basic bore and piston diameter measurements to see where the piston-to-bore clearance is right now. And then see what the shop thinks of how the bores will hone out and what the piston-to-bore clearance will end up with hone job. Then make a judgement on being able to use the block. Do that before working the crank. The head work can go on independently as the heads can be used on any 318-340-360.

If worse comes to worst, then you can put the heads on a 360. Crank and block and rods and pistons are needed. Sell the rods and crank unless you want to run down a 340 block.

And a good calculator for CR is adequate if you don't want to do the measurements. All the part dimensions well known and you have the measurements to do it. I use the Pat Kelley calculator. (We aren't just pulling CR numbers out of thin air...)

 

[nm9stheham]

Any way to check for bent stems or is it safe to assume that if they ride in the hole nice and smooth that they are fine?

Riding in the hole smoothly does not verify a straight valve; the stem can be bent below the guide area, right above the valve head.

 

[Cudafever]

Riding in the hole smoothly does not verify a straight valve; the stem can be bent below the guide area, right above the valve head.

But, then it would leak fluid thru the valve right???

 

[Cudafever]

I guess if the valve was only bent slightly, the pressure of the valve spring,,,,,May flex the head on to the seat.
just kind a thinking out loud here.

 

[nm9stheham]

But, then it would leak fluid thru the valve right???

I would expect so.... it don't take much to leak a thin fluid like alcohol. Unless.....

I guess if the valve was only bent slightly, the pressure of the valve spring,,,,,May flex the head on to the seat. just kind a thinking out loud here.

I don't know that answer to that: I often wondered if that would happen. But the OP could pull the valves, put a light spring in, and THEN test with liquid.

I know for me, I would have them checked at a shop and I do all sorts of things myself if I can; this one is beyond my tooling. At a shop, they would spin them in their valve machine, and know right away. (But those are really precise and super steady, and I would not expect something like a drill press to be precise and steady enough.)

 

[nm9stheham]

And FWIW I almost asked if the heads had been ported from your pix, but I figured it was may imagination...... other things need tending first.

 

[1930]

One word to the wise, when you remove the retainer and locks off the valves. make sure there is not burs on the valve stem lock of the stem. if there is, (Real common on two and three grooved valve stems) remove it with a file. If you DON'T, the guide will have to be replace because of a great Big scare now, down the middle of if!!!!!!!

Good advice and makes sense

And FWIW I almost asked if the heads had been ported from your pix, but I figured it was may imagination...... other things need tending first.

So let me ask you a few questions

1 - I know when tearing down and engine and assuming parts were gonna be re-used that that you want to keep pushrods, lifters and maybe the rocker arms in the order they were removed so they could be put back in the same location but what about piston/connecting rod combo?

I have them now sitting on top of my bench in a specific fashion but Im guessing that theres no need. That when I go to put this thing back together ( and it will go back together, Im a sucker for this kind of stuff ) that yes they need to go a certain way but that that way is pretty evident by some telltale signs on the parts?

Also do rocker arms need to go back on the same side of the head?

I planned to replace the pushrods, maybe I dont need too, I should roll them on a piece of glass to check for straightness. Since Im obviously replacing lifters can I re-use the pushrods if they are straight?

2- Can you comment on post # 61. Sounds like a good idea to me but no-one seemed to notice the post.

3- The 340 is neutral balance.....that sounds like internal balance, not sure on the difference.......the counterweights are what are modified so that internal balance is independent of outside bolt on items.

So what does that mean in relation to dampner and whatever is mounted on the back of the crank?

4 - Ok so it sounds like one way or another I can use the dampner I have and just have the machine shop make it work assuming it dosent already. I guess Id rather do this to eliminate having to buy one ( prob. cost about the same as shop cost to make it work ) and it would eliminate that pesky rubber ring.

I think I got everything else. Thanks

 

[1930]

One more question, is there a bore dial indicator ( bore gauge ) I can buy myself that would be fairly affordable ( maybe off E-bay ) Id like to have one cause Ive had call for one more than once. What should I look for specifically.

 

[1930]

These are the only balance holes I could find on the damper

 

[1930]

I received good news this morning in that the battle with the guy that sold me the truck appears to be over, he is sending me 300 dollars ( the amount we agreed upon ) to cover some of the costs of the engine muck-up.

Ill use that of course toward the repairs

I feel better cause although the truck is rough rough Im sure I can pull 500 out of it somehow by selling parts. It is 4WD.

 

[Moparman1806]

Good advice and makes sense


So let me ask you a few questions

1 - I know when tearing down and engine and assuming parts were gonna be re-used that that you want to keep pushrods, lifters and maybe the rocker arms in the order they were removed so they could be put back in the same location but what about piston/connecting rod combo?

I have them now sitting on top of my bench in a specific fashion but Im guessing that theres no need. That when I go to put this thing back together ( and it will go back together, Im a sucker for this kind of stuff ) that yes they need to go a certain way but that that way is pretty evident by some telltale signs on the parts?

Also do rocker arms need to go back on the same side of the head?

I planned to replace the pushrods, maybe I dont need too, I should roll them on a piece of glass to check for straightness. Since Im obviously replacing lifters can I re-use the pushrods if they are straight?

2- Can you comment on post # 61. Sounds like a good idea to me but no-one seemed to notice the post.

3- The 340 is neutral balance.....that sounds like internal balance, not sure on the difference.......the counterweights are what are modified so that internal balance is independent of outside bolt on items.

So what does that mean in relation to dampner and whatever is mounted on the back of the crank?

4 - Ok so it sounds like one way or another I can use the dampner I have and just have the machine shop make it work assuming it dosent already. I guess Id rather do this to eliminate having to buy one ( prob. cost about the same as shop cost to make it work ) and it would eliminate that pesky rubber ring.

I think I got everything else. Thanks

I will address these in order
#1. Yes, it is good practice to keep the parts in order, especially the lifters, as they wear to the cam.
As for the pushrods, they can be reused, check for galling and roll them as you stated, the pushrods and the stamped rockers are not as critical in placement as the lifters, but be aware of wear, with adjustable rockers- much more critical

#2. As for milling the pistons, yes, it can be done, but be aware that you would be taking quite a bit of metal from the piston face, it has been quite some time since I had those Trw/ Sealed Power pistons in my hand, but I don't know how much metal there is to play with, let alone the expense, as this would have to be done prior to balancing. Go with the thicker gaskets or get open chamber heads. I am sure you could easily sell those Eddies to offset a good amount of the price of the proper ones
#3. The forged crank 340 is internally balanced, meaning the parts are weighed and metal is taken away or added to compensate for proper balance. The cast crank 340 and other externally balanced engines have special balancers , flywheels, converters to counteract the vibrations and balance issues. As for using the externally balanced balancer on the forged crank and trying to balance internally to compensate, don't even ponder it. The can of worms you would open for a 175 dollar part is not worth it. The amount of weight that would have to be removed or even added( really expensive) to make up for hanging that counterweight on the nose of the crank would be ridiculous.

IMO, for the type of use you are looking for, along with reliability, if you really want the 340, get the proper balancer, heads( to avoid the alignment issues from the thicker head gaskets), have the machine shop check and freshen the short block. Or sell the 340 to someone who really needs the date code and buy yourself a crate stroker motor and have a warranty and real torque without the headaches

 

[Moparman1806]

Just to show the difference in balancers- the shiny one with the counterweight is external and the other is internally balanced

 

[1930]

I will address these in order
#1. Yes, it is good practice to keep the parts in order, especially the lifters, as they wear to the cam.
As for the pushrods, they can be reused, check for galling and roll them as you stated, the pushrods and the stamped rockers are not as critical in placement as the lifters, but be aware of wear, with adjustable rockers- much more critical

Ok got it, at this point the lifters are mixed up, im gonna do my best to make sure they are straight and prob. re-use them. The rocker arms...Im assuming theres a right and left and only go on the one way.

#2. As for milling the pistons, yes, it can be done, but be aware that you would be taking quite a bit of metal from the piston face, it has been quite some time since I had those Trw/ Sealed Power pistons in my hand, but I don't know how much metal there is to play with, let alone the expense, as this would have to be done prior to balancing. Go with the thicker gaskets or get open chamber heads. I am sure you could easily sell those Eddies to offset a good amount of the price of the proper ones

I dont know what its like where your at but here is crazy trying to sell something, all of my stuff is worthless and all of theirs is gold. Im not giving anything away and Id like to use what I have but I do understand.


#3. The forged crank 340 is internally balanced, meaning the parts are weighed and metal is taken away or added to compensate for proper balance. The cast crank 340 and other externally balanced engines have special balancers , flywheels, converters to counteract the vibrations and balance issues. As for using the externally balanced balancer on the forged crank and trying to balance internally to compensate, don't even ponder it. The can of worms you would open for a 175 dollar part is not worth it. The amount of weight that would have to be removed or even added( really expensive) to make up for hanging that counterweight on the nose of the crank would be ridiculous.

IMO, for the type of use you are looking for, along with reliability, if you really want the 340, get the proper balancer, heads( to avoid the alignment issues from the thicker head gaskets), have the machine shop check and freshen the short block. Or sell the 340 to someone who really needs the date code and buy yourself a crate stroker motor and have a warranty and real torque without the headaches

I dropped most everything off at the machine shop ( Im sure it will be there for several weeks.......I hope your a B.B guy to and frequent that forum ) They pointed out to me that the crankshaft had been drilled pretty darn extensively, several holes and very deep. Maybe the balancer has been matched to the crank? They will check it out and let me know.

Ive always wanted a real 340 ( no offense to anyone with a 73 engine ) and Ill prob. never have the chance to own another so Im gonna do everything I can to save this one.

I guess I have the two options on either the thicker head gasket or find out from machine shop about cost of shaving pistons.

BTW the crank is hopefully gonna be saveable. They checked it, said really bad, they told me that since its already been turned .020 that I can only go up one more to 30s.

Do you know of anything bigger?? On the mains

Just to show the difference in balancers- the shiny one with the counterweight is external and the other is internally balanced

View attachment 1715037459

ok thanks, I may still need one

 

[1930]

I replied within your quoted message, if you click expand I think you will see them

 

[Cudafever]

Ok i agree with Moparman on everything BUT tossing them EDDY heads, because it will cost some $$$ for a head gasket.
For that matter why can't he just reinstall the head gasket he had on there.
1930, I'M NOT RECOMMENDING THIS BUT....FOR THEARY...
The head gasket he used was 53 or .053 and the highest piston pop up was .020=.013 piston the head clearance.
That's a Loooong long way from the .035-.040 that is recommended.(EDIT MY MATH SUCKS!!!! = .033) BUT!!! He "did not" have piston to head contact, he had "valve" to piston contact. I'm vary confident that even if it wasn't valve float that caused the valve to piston contact, and there just wasn't enough piston to valve clearance. By the time he grind off that shelf in the valve relief, on the piston, there will be boatloads of clearance and become a non issue.
Now your issue with the thicker head gasket is that it might hold the head up to high and keep the manifold from bolting up. Wasn't a problem with .053" head gaskets.
If you don't want to worry bout any of this a just bolt it up and it works. Then by all means by the right head for 340, us any head gasket, use stock pushrod,(don't measure the will work) and throw it together. It will work you won't need to know why!
However if you want to learn something and make a better mouse trap, like all of us hot rodder do, then you need to press on.
Moparman, after re reading this, it sounds like I'm trying to pick a fight with you. TRUST ME THAT NOT THE CASE. Just getting some info out there.
1930 please tell me you mark the piston or the rod before you pulled them out..........