318 Poly HELP!

[clocktowersniper]

A while back I posted about an engine shop rebuilding my poly for my 65 Coronet. Well in the past few weeks I got everything together. We ran the car and it ran but not well. We changed out just about everything so we were starting fresh and it still runs like crap. The car rebuilt engine (maybe 20 miles on it) new cap,rotor,wires,plugs,distributor,pertronics module,coil,carburator,radiator,water pump, etc. Everything new. At idle she idles with a slight miss. Under acceleration it feels like it has a dead cylendar. Timing is set right as is mixture and valves. What else could it be?? I am stumped! Someone told me to check for vacuum leaks and I couldnt find any. Maybe they put in a bum cam?? I checked all ignition sources and ran a timing light on each wire to check for smooth firing and its fine, so it must be internal engine right???

[turbovanman²]

Maybe do a compression test.

[clocktowersniper]

I did one already. Compression good across the board. The engine has pep, you can just rap the gas and it will spin the tires, but you can fell that its not hitting on all 8.

[Clay]

sounds like an ignition thing to me, maybe. Do you have a stock ignition you can try out to eliminate the pertronics?

[clocktowersniper]

Not ignition, see comment from above:
Maybe they put in a bum cam?? I checked all ignition sources and ran a timing light on each wire to check for smooth firing and its fine, so it must be internal engine right???
Has to be engine related.

[clocktowersniper]

And yes I went back to points to check.

[turbokid]

maybe time to switch to electronic ignition.

[Clay]

the petronics is an electronic ignition

[Clay]

Not ignition, see comment from above:
Maybe they put in a bum cam?? I checked all ignition sources and ran a timing light on each wire to check for smooth firing and its fine, so it must be internal engine right???
Has to be engine related.

I would say its probably not internal to the engine. If the engine is running, those crappily, and you have good compression across the board, then I would say the internals are fine.

Granted, the cam could be out of time I guess, or if it has hyd. lifters maybe thats an issue. Ive never worked on a poly block, so I'm not sure what they have for lifters or rocker arms, but if it has solid lifters then it probably has adjustable rockers. If so are they adjusted correctly?

other than that it would probably be a fueling or ignition problem. Get some kind of temperature gun if you have access to on, and while the engine is running shoot the temps of each exhaust port (or header pipe if it has them). This will tell you right away if you have fuel or ignition problems as one/two/three/etc exhaust pipes/ports may be low/high on temperature compared to everything else.

[BIGBRUDDA]

"At idle she idles with a slight miss. Under acceleration it feels like it has a dead cylendar. "

That sounds like the age old chrysler problem ,of a crack in the exh crossover port.:nod: Rythmic miss, or "thump...............thump" at idle. Under power high press leakage between 2-4 or 3-5 ehx ports.
Were the heads re done? By a "KNOWLEDGEABLE" poly guy? :thumb:

[clocktowersniper]

Well they call themselves reputable! However I do not. The engine ran fine before being redone, when I got it back, it wouldnt even run at all. I sent it back, they said it was a distributor problem and they changed the points. They didnt cuz it didnt have points! I suspect they changed the cam because there was copper gasket spray around the intake and timing cover.

[BIGBRUDDA]

Ya may want to check wit da 318 poly owners. I've seen a site similar to this one. But can't say where.:nod:
Poly go fast parts were super rare, and expensive , even" back in the day", especially heads .:eek: If you had a"good" set of heads originaly. ya may have gotten back an "exchange set". :evil:

[turbovanman²]

Ya may want to check wit da 318 poly owners. I've seen a site similar to this one. But can't say where.:nod:
Poly go fast parts were super rare, and expensive , even" back in the day", especially heads .:eek: If you had a"good" set of heads originaly. ya may have gotten back an "exchange set". :evil:

Why can't you say where?

[BIGBRUDDA]

Why can't you say where?

Actually ....it's a closely guarded secret. Can't let you canucks know everthing. We don't want all the scrap iron migrating north!:D

[moparman76_69]

Is it a hydraulic lifter setup? If so you may have a lifter that won't pump up therefore not opening the valve on that cylinder.

[shadow88]

Vacuum gage readings? any fluttering at idle or light accel?
Will removing each ignition wire cause a noticable difference?
Plug readings?
Is this ignition system anything like the mopar electronic conversion?
Just so you know, an inductive pick-up timing light will flash even with a very weak spark- just saying.
Do you have a leakdown tester?

Just some thoughts

[clocktowersniper]

Vac 122 inches
miss-both
plugs-!!!!
Ingition-no
leakdown tester-no

You guesses it!
I had a bad plug on the #3 cyl.
It took a while to show up
My bud said keep running it. He is a NAPA fossil, knows his chit. He said I bet its a bad plug, even though its new. He said keep running it and it should get progressively worse. Then keep checking the plugs. Well this time #3 showed up totally gas fouled. DEAD HOLE!
Changed plugs, full speed ahead!

[The Pope]

most buy 318 regular plugs for a poly and smack the pistons. You have to use 440 or 383 plugs. The poly is a great engine normally, better than the later engines. One poly had dual quads and was rated at 290 HP:thumb:

[SpiritedShelbys]

the 290 versions were 1957-1958 Plymouth Fury motor. Definitely a hot motor and extremely torquey but the 4v IMO runs better, I've had both. The dual 4's are just too much gas for the engine. I've heard the 3x2's runs the best but VERY few are around.

[moparzrule]

The poly should be a solid lifter cam. Although I see you got your problem solved with the spark plug, just so you know have you checked the valve clearances? You'll need to check them atleast every other oil change.