La318 cylinder head question

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Señor Ding Dong

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Hey all, this might be a question with a really elementary answer, but I just want to make sure. I have a 1974 la318 with a set of 587 360 heads. I’m not sure the build on the engine, I believe .030 over and possibly a very mild cam. I have a stuck intake valve on cylinder 3. If it’s not just a broken valve spring and it needs a valve job, am I okay to put stock 1971 318 heads on it? Specifically, if the pistons are a higher compression piston and the cam matches it, will I still be able to run regular pump gas?

I’m assuming it wouldn’t bump the CR enough to be a concern, but I’d hate to make that mistake if it would.

The 318 heads would likely only be temporary, unless the pistons and cam turn out to be closer to stock, in which case I might stick to them rather than rebuild the 587’s.

Thank you!
 
The early closed chamber heads
should be about 10 or more cc's smaller than the low-compression smoggers on your 74 engine. This will bump your compression up from a true 8/1 to a true 8.8. and your cylinder pressure up to 158psi@sea-level.
Even if your cam is stock, The Dcr on this new combination is just 7/1, so it should run on 87E10 at full timing.
If your cam is not stock, the later ICA will only reduce the pressure, reduce the Dcr, and that means for sure it will run on 87E10
If you are at higher than sealevel, the pressure will again be reduced.
All-in-all, I would rip the bad head off and have a look-see.
If your pistons are where they're supposed to be, down in the holes around .157 inch, you should be good to go, AND
if you find 020 steel headgaskets, that would be a good indicator that the engine is still original. If it was mine, I would install the thinnest headgaskets that I could find.

However, in the event that your 71 heads have 60cc chambers; this will increase your Dcr to 9.14, the Dcr to 8.1 and with the stock 48*Ica, the Pressure jumps to 166 at sealevel. This will require Premium gas, for WOT operation; but the reward is excellent power.
I would still do this build, but with a thicker head gasket.

The bottom line is, that you won't know for sure until you get the heads off, and do some measuring.
And before any calculations are done, we need to know your local elevation, at which this vehicle will be operated at, and the Ica (Intake Closing Angle).
As for the Ica, without taking the front of the engine off, and degreeing the cam, here is a pretty good approximation;
With the engine fully assembled;
1) take all the spark plugs out, and using either #1 or #6 cylinder, whichever does NOT have a bent valve, roll that Piston up to TDC on the compression stroke, then back it up a half a turn.
2) we are gonna need to find fairly accurately, at what degree your intake closes, which is gonna be somewhere between 45 *After bottom dead center, and not more than about 70* ABDC; so to accomplish this, your balancer will need to to be calibrated. The best way to do this is to install a timing tape.
But, there is another way, that is accurate enough.
3) Install a fitting in the selected cylinder hole, 1 or 6, and inject about 20 psi into the cylinder. Then put a bar on the crank, and begin to rotate the Crank Clockwise, until you get resistance and most if not all, of the hissing stops. Find the exact spot of transition, then put a mark on the balance, with a sharpie, adjacent to the TDC Timing mark. If 20psi is too hard to work with, crank the regulator back until you can manage.
4) Rotate the crank back to TDC Compression of the cylinder you have selected, either 1 or 6, then measure the exact distance from TDC back to the mark you made with the Sharpie.
5) finally, measure the diameter of the balancer to the nearest 1/16 inch.

From this work you have done, I can easily back-calculate the Ica, within a couple of degrees.
If you cannot do this work, or areunwilling to make the effort, no worries;
just do it the old-fashioned way, namely, bolt it together and see if it detonates, on Regular gas. If it does, then try best gas. If it still detonates, take it apart and start over.
But if it does not detonate on best gas, try next lower octane.
The point is, that this swap that you are contemplating is or could be borderline for regular gas.
But if it works, you'll have a real powerhouse of a 318.
 
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The early closed chamber heads
should be about 10cc smaller than the low-compression smoggers on your 74 engine. This will bump your compression up from a true 8/1 to a true 8.8. and your cylinder pressure up to 158psi@sea-level.
Even if your cam is stock, The Dcr on this new combination is just 7/1, so it should run on 87E10 at full timing.
If your cam is not stock, the later ICA will only reduce the pressure, reduce the Dcr, and that means for sure it will run on 87E10
If you are at higher than sealevel, the pressure will again be reduced.
All-in-all, I would rip the bad head off and have a look-see.
If your pistons are where they're supposed to be, down in the holes around .157 inch, you should be good to go, AND
if you find 020 steel headgaskets, that would be a good indicator that the engine is still original. If it was mine, I would install the thinnest headgaskets that I could find.
The engine isn’t original, it has the 587 casting la360 heads, and I’m pretty sure a .030 overbore.
 
The early closed chamber heads
should be about 10 or more cc's smaller than the low-compression smoggers on your 74 engine. This will bump your compression up from a true 8/1 to a true 8.8. and your cylinder pressure up to 158psi@sea-level.
Even if your cam is stock, The Dcr on this new combination is just 7/1, so it should run on 87E10 at full timing.
If your cam is not stock, the later ICA will only reduce the pressure, reduce the Dcr, and that means for sure it will run on 87E10
If you are at higher than sealevel, the pressure will again be reduced.
All-in-all, I would rip the bad head off and have a look-see.
If your pistons are where they're supposed to be, down in the holes around .157 inch, you should be good to go, AND
if you find 020 steel headgaskets, that would be a good indicator that the engine is still original. If it was mine, I would install the thinnest headgaskets that I could find.

However, in the event that your 71 heads have 60cc chambers; this will increase your Dcr to 9.14, the Dcr to 8.1 and with the stock 48*Ica, the Pressure jumps to 166 at sealevel. This will require Premium gas, for WOT operation; but the reward is excellent power.
I would still do this build, but with a thicker head gasket.

The bottom line is, that you won't know for sure until you get the heads off, and do some measuring.
And before any calculations are done, we need to know your local elevation, at which this vehicle will be operated at, and the Ica (Intake Closing Angle).
As for the Ica, without taking the front of the engine off, and degreeing the cam, here is a pretty good approximation;
With the engine fully assembled;
1) take all the spark plugs out, and using either #1 or #6 cylinder, whichever does NOT have a bent valve, roll that Piston up to TDC on the compression stroke, then back it up a half a turn.
2) we are gonna need to find fairly accurately, at what degree your intake closes, which is gonna be somewhere between 45 *After bottom dead center, and not more than about 70* ABDC; so to accomplish this, your balancer will need to to be calibrated. The best way to do this is to install a timing tape.
But, there is another way, that is accurate enough.
3) Install a fitting in the selected cylinder hole, 1 or 6, and inject about 20 psi into the cylinder. Then put a bar on the crank, and begin to rotate the Crank Clockwise, until you get resistance and most if not all, of the hissing stops. Find the exact spot of transition, then put a mark on the balance, with a sharpie, adjacent to the TDC Timing mark. If 20psi is too hard to work with, crank the regulator back until you can manage.
4) Rotate the crank back to TDC Compression of the cylinder you have selected, either 1 or 6, then measure the exact distance from TDC back to the mark you made with the Sharpie.
5) finally, measure the diameter of the balancer to the nearest 1/16 inch.

From this work you have done, I can easily back-calculate the Ica, within a couple of degrees.
If you cannot do this work, or areunwilling to make the effort, no worries;
just do it the old-fashioned way, namely, bolt it together and see if it detonates, on Regular gas. If it does, then try best gas. If it still detonates, take it apart and start over.
But if it does not detonate on best gas, try next lower octane.

Oh dear lord just answer the question AJ.

Yes you can swap heads, it’ll run, may ping, if so, reduce timing and/or use the next grade up octane until knock disappears.

Fix the 360 head and swap heads to keep it balanced.
 
Not sure if AJ went here or not, but......

If it's not disassembled yet, do a compression test on the other cylinders. Might give a indication of what your working with.
 
Not sure if AJ went here or not, but......

If it's not disassembled yet, do a compression test on the other cylinders. Might give a indication of what your working with.
What kind of numbers would I be looking for? I did compression test on the left bank where the valve issue is and on the three good ones got around 120 on each. (Not an expensive tester, so who knows if it’s accurate though)
 
They don’t have to be expensive just give repeatable results.
 
Being in the 120lb range, i think you may be happy with the 318 heads. If you have a big port intake currently, don't let that discourage you, it will be fine with the right gaskets.
 
Ok, thanks for that everyone. I’m hoping it’s a valve spring and this is all moot, but if not it sounds like I’ll be fine to run the stock 318 heads. They’ll need a cleanup, but other than that they’ll do for the time being.

I appreciate all the feedback, you guys are great! I love having this forum to learn from.
 
Ok, so I’ve pulled the valve cover and rocker shaft. No sign of broken spring, valve seems to move fine when using pry bar to lever it down. Obvious marks on piston from valve contact. I don’t get it. Stuck lifter maybe?

I assume I’m going to have to pull the head to inspect the valve for damage, so my next question is, how the hell do you get the head off a 318 in a 1966 Dart? I can’t get the exhaust manifolds out of the way enough to get the bottom bolts, especially on the drivers side, and I can’t get to both flange bolts at the bottom of the exhaust manifold in order to remove it entirely. Is there a trick or tool I’m missing? I’d really rather not pull the whole engine again just to remove the heads, ya know?
 
I have a stuck intake valve on cylinder 3
You said that you had a stuck valve.
now you say it's not stuck.
How did you diagnose this?
a cylinder balance test?
a Compression test?
a Leak-down test?
The sound the pistons make when they hit the hung-open valve?
The 12.5% powerloss?

Maybe it's time to back up the us and start over?
Edit, back up the bus.
 
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You said that you had a stuck valve.
now you say it's not stuck.
How did you diagnose this?
a cylinder balance test?
a Compression test?
a Leak-down test?
The sound the pistons make when they hit the hung-open valve?
The 12.5% powerloss?

Maybe it's time to back up the us and start over?
I diagnosed it by:
1-Loud ticking noise from drivers side
2-rough running
3-power loss
4-compression test showing 60psi on that cylinder, only improving to 65 with a wet test, while all the rest are 115-120psi
5-valve marks on the piston top
6-backfire through carb on acceleration
7-burning oil from that side of wngine

Now, looking at the piston top with borescope, it looks more like the exhaust valve, based on the position of the valve marks on the piston. Which seems odd with the backfire through the carb, but I’ll see for sure once I get the head off.

Edit: definitely the exhaust valve. Not sure why it hit, lifter is moving freely, pushrods aren’t bent, I’ll pull the valves later this week and see if any are bent?

Any ideas on what else would cause just one valve, in just one cylinder to hit the piston a few times, and that cylinder to have super low compression on a wet and dry compression test?
 
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Which seems odd with the backfire through the carb, but I’ll see for sure once I get the head off.
Not snarky.

If a cylinder has a leaking exhaust valve, then;
On the intake stroke, with the carb at idle, that cylinder may find it easier to pull air in from the exhaust manifold, than from the plenum. So it idles rough cuz that cylinder does not have a combustible mixture in it.
If you whack the throttle open, then atmpspheric pressure, being higher than exhaust pressure for at least part of the induction cycle, stuffs some intake charge into the cylinder.
But The Log manifolds are now full of hot expanding gasses and not all of them have finished burning.
If the pressure in the log is higher than the pressure in the cylinder, then the fire can enter the cylinder with the bad valve, set that charge on fire before the intake closes, and Blam, you get a "backfire" in the intake.

If you have witness marks on the piston then yes the head has to come off, and the reason for it to be found and eliminated.
If you find witness marks in other cylinders, my guess is that your spring pressure is inadequate to keep the valve train together, and that the lifters pumped up, trying to do what they're supposed to do.
But if ONLY one valve hit a piston, then there could be other reasons, such as;
a bad lifter
a bad rod bearing,
A jumped timing chain,
A pushrod not sitting in the lifter-cup,
or, yes, a valve stuck open in the guide.
 
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Not snarky.

If a cylinder has a leaking exhaust valve, then;
On the intake stroke, with the carb at idle, that cylinder may find it easier to pull air in from the exhaust manifold, than from the plenum. So it idles rough cuz that cylinder does not have a combustible mixture in it.
If you whack the throttle open, then atmpspheric pressure, being higher than exhaust pressure for at least part of the induction cycle, stuffs some intake charge into the cylinder.
But The Log manifolds are now full of hot expanding gasses and not all of them have finished burning.
If the pressure in the log is higher than the pressure in the cylinder, then the fire can enter the cylinder with the bad valve, set that charge on fire before the intake closes, and Blam, you get a "backfire" in the intake.
Yeah sorry, I edited my post. Thanks for clarifying, and thanks for the answer. I just have to figure out why the valve isn’t closing.

So much for my goal of being on the road by this weekend!
 
Not snarky.

If a cylinder has a leaking exhaust valve, then;
On the intake stroke, with the carb at idle, that cylinder may find it easier to pull air in from the exhaust manifold, than from the plenum. So it idles rough cuz that cylinder does not have a combustible mixture in it.
If you whack the throttle open, then atmpspheric pressure, being higher than exhaust pressure for at least part of the induction cycle, stuffs some intake charge into the cylinder.
But The Log manifolds are now full of hot expanding gasses and not all of them have finished burning.
If the pressure in the log is higher than the pressure in the cylinder, then the fire can enter the cylinder with the bad valve, set that charge on fire before the intake closes, and Blam, you get a "backfire" in the intake.

If you have witness marks on the piston then yes the head has to come off, and the reason for it to be found and eliminated.
If you find witness marks in other cylinders, my guess is that your spring pressure is inadequate to keep the valve train together, and that the lifters pumped up, trying to do what they're supposed to do.
But if ONLY one valve hit a piston, then there could be other reasons, such as;
a bad lifter
a bad rod bearing,
A jumped timing chain,
A pushrod not sitting in the lifter-cup,
or, yes, a valve stuck open in the guide.
If it was cam timing, with only the exhaust hitting, wouldn’t I still have decent compression on that cylinder? Exhaust would be staying open too long and getting hit, that would mean intake would still be closed on compression, maybe just closing partway through compression stroke? I’m only getting 60psi on that cylinder, if it was closing super late on compression, wouldn’t I be having valves hitting on at least cyl 6 too, if not all of them?

Trying to wrap my brain around the timing on all the cylinders. I’ve got the head off, I’ll turn it by hand tonight and see if it looks like valves are opening way off from when they should be.
 
You may be thinking in terms of just one problem; whereas I'm thinking in terms of any combination of problems.

In my experience, with a 318, there is easily room in the P/V clearance for the cam-chain to jump several teeth, and, the 318engine will keep running with retarded cam-timing. Obviously the cylinder pressure changes and the engine loses idle-rpm, as well as power, the more teeth it has jumped.
I've never had a 318 @120 psi
All my smogger 318s have run 135 at least, usually 140 or a little better.


Normally;
On the exhaust stroke, with the Piston at the bottom;
the valve has already begun to open. As the piston rises the valve is coming down to meet it.
When the piston is about half way up, the valve is about full open. After that, the valve begins to close, as the piston chases after it.
IF
the valve is very late to close, maybe the piston catches up to it.
if the lifter is pumped up, or the valve sticks in the guide, this is a very real possibility.

If it's a hard hit, the valve stem bends, and it no longer seals, and you get no compression. A light tap, could produce a light loss in pressure.
I have never seen a valve in a 318 stick, in normal use. Every stuck one that I have seen, was on a long unused engine in storage. If it only stuck part way open, likely the pushrod is bent, and the running engine immediately develops a tic-tic, until the pushrod falls out of the socket. If one stuck open, there is almost always a Second one.
But if several pistons show witness marks, that almost has to point to a jumped timing chain or pumped up lifters, or perhaps, a combination.

BTW
In have, at various times in the past, installed well-used 340 timing chains and sprockets onto a 318. In two cases, I remember that in order to get the cam-timing close, I had to advance the cam one tooth. It ran fine.
 
Ok, so turning everything by hand, it looks like the exhaust is closing exactly as the piston hits the top, and on compression, the intake isn’t fully closed until at least 20-30° past when the piston starts to come up. (A rough estimate using grease pencil marks on the balancer). Is that normal, or does that tell you the timing is way off?

There is a small mark on piston 6 as well. Just one tiny one, I didn’t pull that head as there was no ticking from that side, I thought it was drivers side only initially. The #3 exhaust valve has no visible damage, could there still be enough to drop compression that much, or is that explained by the intake valve closing late on compression stroke?
 
Is that normal, or does that tell you the timing is way off?
Using your method, it's hard to say.
I have never used your method.
And I can't get sense of how you wrote it;
In the same sentence, the piston is at the top, then it is coming up. So, wth stroke is it on at what time?
Looking at the factory 318 cam specs, with the cam installed 4* advanced, the intake should be opening at about 12* before TDC and closing 48* After Bottom dead center.
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The usual method for estimating cam timing, is to set the cam at split overlap, then read the balancer.
This is done with the piston at TDC-EXHAUST. Normally I rotate the crank until both lifters have risen to the same height, using numbers one or six. Then read the TDC mark on the balancer, having previously proved the TDC mark.
That reading should be in the window of 8* advanced to 4* retarded. The engine will run quite well anywhere in the window.
The more advanced the cam is, within the window, the more low-rpm power it will have. As the cam is retarded in the window, it will trade away that bottom end power to get some operating rpm at the top.
If it is outside the norm, that would be grounds for digging deeper.
 
Hey all, this might be a question with a really elementary answer, but I just want to make sure. I have a 1974 la318 with a set of 587 360 heads. I’m not sure the build on the engine, I believe .030 over and possibly a very mild cam. I have a stuck intake valve on cylinder 3. If it’s not just a broken valve spring and it needs a valve job, am I okay to put stock 1971 318 heads on it? Specifically, if the pistons are a higher compression piston and the cam matches it, will I still be able to run regular pump gas?

I’m assuming it wouldn’t bump the CR enough to be a concern, but I’d hate to make that mistake if it would.

The 318 heads would likely only be temporary, unless the pistons and cam turn out to be closer to stock, in which case I might stick to them rather than rebuild the 587’s.

Thank you!
You can put regular 318 heads on it, just make sure the Springs are right for the cam if it's not stock. As for the stuck valve in the 360 heads if it didn't hit the Piston it should be okay but if it did it's bent. You'll want to clean that guide out and put a new valve in it and either touch the seat with a stone or see if you can lap it in. For what it's worth open chamber 318 heads of the open chamber variety around 1968 to 1970 one or two have 68 CC combustion Chambers
 
Using your method, it's hard to say.
I have never used your method.
And I can't get sense of how you wrote it;
In the same sentence, the piston is at the top, then it is coming up. So, wth stroke is it on at what time?
Looking at the factory 318 cam specs, with the cam installed 4* advanced, the intake should be opening at about 12* before TDC and closing 48* After Bottom dead center.
-----------------------------------------

The usual method for estimating cam timing, is to set the cam at split overlap, then read the balancer.
This is done with the piston at TDC-EXHAUST. Normally I rotate the crank until both lifters have risen to the same height, using numbers one or six. Then read the TDC mark on the balancer, having previously proved the TDC mark.
That reading should be in the window of 8* advanced to 4* retarded. The engine will run quite well anywhere in the window.
The more advanced the cam is, within the window, the more low-rpm power it will have. As the cam is retarded in the window, it will trade away that bottom end power to get some operating rpm at the top.
If it is outside the norm, that would be grounds for digging deeper.
Sorry if it wasn’t clear. The exhaust valve closing was on the exhaust stroke, and the intake valve was concerning the intake stroke and compression stroke.

I know it’s not the proper way, I was just hoping that it would give me a better idea if the timing is way off. I don’t want to pull the front of the engine apart if I don’t need to, but unfortunately I think that’s where I’m at. I don’t see any issues with any pushrods, lifters, valves or valve springs that would cause the valve to hit the piston, so I’m thinking I need to look at the cam timing and inspect the timing chain.
 
Using your method, it's hard to say.
I have never used your method.
And I can't get sense of how you wrote it;
In the same sentence, the piston is at the top, then it is coming up. So, wth stroke is it on at what time?
Looking at the factory 318 cam specs, with the cam installed 4* advanced, the intake should be opening at about 12* before TDC and closing 48* After Bottom dead center.
-----------------------------------------

The usual method for estimating cam timing, is to set the cam at split overlap, then read the balancer.
This is done with the piston at TDC-EXHAUST. Normally I rotate the crank until both lifters have risen to the same height, using numbers one or six. Then read the TDC mark on the balancer, having previously proved the TDC mark.
That reading should be in the window of 8* advanced to 4* retarded. The engine will run quite well anywhere in the window.
The more advanced the cam is, within the window, the more low-rpm power it will have. As the cam is retarded in the window, it will trade away that bottom end power to get some operating rpm at the top.
If it is outside the norm, that would be grounds for digging deeper.
When i do this to estimate cam timing, TDC is correct on the balancer, and with both lifters at exactly the same height it is reading about 1° advanced. So I assume this means it’s not the timing chain.

The exhaust valve on that cylinder is definitely leaking, using the carb cleaner test. The rest are not, on that side. The pushrods don’t look bent, unless one is off by a tiny fraction. What would I look for, for a pumped up lifter? I don’t know what that means.

The valve wasn’t stuck in the guide, and no valve springs are broken. The engine did sit for a long time before I got it, but I saw it running on a stand before I bought it, and the valve marks were not on the pistons when I got it. The lifters had bled down by the time I got it installed though.
 
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