Low Compression on Stock 318

[nm9stheham]

Was this an older car that you just got running? If the fuel is old, then it can gum up and get on the intake valve stem as it flows into the cylinder, and then gum up the intake valve stem and jam the valve. I've had one do exactly what happened here with old gas. If the fuel is old, drop the gas tank and clean it all out (plus all the rust and crud) now before running the car again.

Also, the lifter could have pumped up or had the little clip break/fly out of the top and the lifter piston will pump way out and push the valve into the piston, with the above result. BTDT

If you replace the rocker and pushrod and lifter, then rerun the compression on that cylinder to see if the valve is bent. It only takes on hit on the piston to do all of this; you would not really hear it so don't make any assumptions.

 

[element303]

nah i just throw it away and order another one. dont want to take any risk. yeah its stuck in there pretty good. no other damage beside that as far as i can tell. also im pretty sure i got (hopefully) all the metal pieces. pretty interesting how they built the head so nothing gets in between the springs or falls further down into the head. i cleaned it by hand and later do the same on the other head and when the new parts are installed i will flush the engine first thing.

 

[318willrun]

^^^^ fuel gum'n up the intake valve is a good thought! I've never had a pushrod go through a rocker, but have seen it on others cars.

 

[element303]

Was this an older car that you just got running?

If you replace the rocker and pushrod and lifter, then rerun the compression on that cylinder to see if the valve is bent. It only takes on hit on the piston to do all of this; you would not really hear it so don't make any assumptions.

No, I was driving it for a few months.

Thats my plan. I will crank it first without sparks and test compression again before I fire it up just to be sure.

 

[Cudafever]

I don't think this damage was from, over revving, stuck lifter, exc. I think this rocker assembly has been on more than one eng(tones of miles) and is Flat Out, use up!!!! Bet you have Several more that are about to do the same thing. look for any kind of cracks on all the rest of them.
My buddy and i was at a race with his 68 dart and a 383 eng. this same problem happend and it made some noise for sure.
there was a wrecking yard close and we grabbed some push rods and two full set of rocker arms. We were glad we did as there was several other that had cracked and were very thin.
pulled other valve cover, installed two sets of rocker arms and a pushrod. was good for the weekend.

 

[Cudafever]

One more thing, you said you had low compression in two cyl? (5/7)but only one bad pushrod/rocker arm..........think you still need to do some more looking.

 

[element303]

Hello. Thank you! No turned out later that all other cyl were good, I just didnt turn it often enough to get a good reading. All within 130-150. So I went back to the guy I bought the car from and as expected he could help. We opened up another 318 he had in another Demon outside and I got a few rockers and the rod. I just need to clean it.

That Charger always breaks my heart when I see it... Too bad its already beyond worth fixing.

 

[element303]

Cleaned both heads, all rockers and little holes for the oil of which some were clogged and the covers as far as possible, installed the rocker I got and the pushrod was still straight so I used the same one because it was cleaner than the one I got from the other engine. Runs smooth as always again. Now I just need to change the oil twice.

Big thanks again to everyone.

 

[nm9stheham]

Runs smooth as always again. Now I just need to change the oil twice.

Good to hear!

Twice at least! Maybe throw a pint of kerosene 15 minutes before the next 2 oil changes, or a bottle of Seafoam or some Marvel mystery oil in each change. Keep and eye on your oil light, just in case the oil pan is full of sludge and it tries to clog the oil pickup.

The humidity down there in PR must be heck on cars.

 

[element303]

Actually the light is been on since a few weeks regardless on the level. I bought a can of engine flush. Just got to get the oil pan gasket first. Yes, humanity and salt in the air.

 

[nm9stheham]

Uh oh....Is it only on at idle or low RPM, and then goes out as it revs?

If so, time to pull the pan while you are doing the gasket, and clean out the crud. Then pull the oil pump and clean the screen on the pickup. Then I'd put the pickup onto a NEW stock pump. Who knows what crud has passed through it; the oil filter is AFTER the pump so all the crud scores and wears the pump.

It is also possible that the oil pressure relief valve is stuck open and killing the pressure.

If the light is on all the time, regardless of revs, then maybe the oil pressure sensor or the wire to it is shorted to ground. Pull the wire off of the sensor (on the back of the block beside the distributor) and if the light goes out, then either the sensor is shorted or the oiling system is reeeeally bad.

You had better figure out this oil light situation before the whole engine goes kablooie. That may be part of why the rocker failed.

 

[element303]

Yeah you could be right. I am planning to flush it before the first oil change and then take out the pan and replace the gasket too and im sure as hell there is quite a collection of dirt in the pan as well if the heads look like that. Other than that the engine itself runs so smooth its hard to believe its 40+ years old. Again, thx for your help guys. I love this forum.

 

[stixx]

"Yes, humanity ..... in the air.

Good one. Yes, in this forum there is also humanity in the air... most of the times.

 

[element303]

hahah oops I didnt see that. I wrote it on the phone haha