318 A Block Heads.

[Dick Koch]

Well, it looks like Charleen has come down with the vapors. She has a 318 A Block and I think is having trouble exhaling thru her exhaust valves. She runs badly at Idle with a popping sound coming out the passenger side exhaust, Cylinder #2. But at speed runs smoothly. A compression test showed 125 lbs. witch is the bottom limit. I have a complete 318 LA engine.

Question is? will 318 LA heads fit or work on a 318 A Block. If so I will have them rebuilt and updated.
Thanks,
Dick.

[Bernie B.]

Dick,

Check out this link for poly engine lovers - http://www.1962to1965mopar.ornocar.com/poly318.html

Most likely someone there will know for sure, but you will be going against the grain, they are dedicated to preserving and hopping up poly engines.

And even if you could do the head swap you're considering, it would likely be the only one in the world. Not sure but the head bolt pattern might be the same to put it on the block. Water passages might be different, manifolds and camshaft changes for sure, then there are the different pistons due to valve clearance considerations. Sounds like you want to reverse Chrysler's improvements of 1964 on the "A" engine.

Maybe as a first step try matching a 318 "A" head gasket against a 318"LA" and if identical, take the discussion further. If not, well, a can of Restore is cheap.

[big m]

Dick,

125 lbs of compression is not bad, a cylinder will still fire at 80 lbs of compression. A burnt exhaust valve generally will drop compression down to 40 psi or lower, from my experience.

Is it possible you haver another problem causing the misfire, such as a vacuum leak?

---John

[Dick Koch]

Well a local Mopar guru told me the switch won't work, the A heads are Poly and the LA heads are wedge. Bernie - I have used a can of restore already but I havent checked to see if it helped yet. I'm not into major conversions, just thinking I could save some money$. I did a dry compression test and got the 125 lbs. in #2 cylinder, then I did a wet test and got 195 lbs. All the other cylinders range from 135 to 150 lbs. John - I have had several friends suggest it could be a vacuum leak, I put a vacuum gauge on the intake manifold and at idle I'm getting 16 lbs. I rev it up a little and get 18 lbs. Where I tested it is at the small fitting that goes to the AC/Heater system, when I squeez that small hole off nothing changes, The Guru suggested I take the valve covers off and check for valve lash, he also suggested it could be a worn cam. All are options are to be explored.
Thanks for the help,
Dick.

[big m]

Your gauge reads a bit higher than most, but that is not the issue. All eight cylinders should be relatively close readings, no matter what the gauge reads, high or low.

A wet test that is substantially higher than a dry test shows worn piston rings. The oil will not improve the reading on a valve that is beginning to burn on the edge. I wish I was a bit closer to you, I'd be happy to help you. Over the internet is difficult, at best.

---John

[Dick Koch]

John F. - Thanks for the info. If you were driving the car, you would here a popping noise coming out the right tail pipe, at idle the car would be shaking pretty good, as you took off the engine would smooth out and stay smooth at speed. Unless you have another suggestion I thing I will rebuild the spare 318 A block engine I have and put it in Charleen along with the tranny I just had bebuilt. I was going to put that engine in the convertible anyway. What comes out of Charleen will be rebuilt and put in the convertible. That way I would be able to drive to California and pay you a visit, included would be a stop off to see Mr. John Q. in Arvada, Co. Yesterday I finally got the Convert. body epoxy primed.
Dick.

[rogerh]

Interesting reading! I will be very interested in any discoveries/remedies.
The wet test shows the rings are getting tired, pointing to a block re-build.
If the #2 cam lobe is worn, a new (re-ground?) cam is needed.
Doesn't seem like it could be a simple sparkplug wire or distributor issue.

[RICKYMOPAR]

The heads can be swapped, but require dowell pin check, intake and exhaust manifolds and camshaft replacement, being the valve arrangement. Not worth the effort! I highly suggest there is another problem, Tune up related. Fouled plug? poor spark plug wire? Vacuum leak? Valve lash? Cracked or dirty distributor cap?

[Dick Koch]

Thanks Ricky - Easier to rebuild the A engine than the swap of heads. Not plugs they are new, not spark, used a spark tester, BUT valve lash and cracked distributor cap worth a check. Thanks,
Dick.