Technical Poly head engine help

Hi everyone. I am looking for a little help with the engine in my 55 Dodge truck. I have been searching the threads for some good info on my poly head, but can’t seem to find what I am looking for, and hopefully someone has had experience with the valve train. (Where I think the issue lies) I have had it for about 12 years, and bought it from the son of the original owner. According to him, the engine had never been out, and is original to the truck. I have been driving it during the summer, and it has been running great. All of the sudden, it developed a marked power loss, with some backfiring and noisy ticking in the top end. (I believe) I pulled it into the garage and pulled off the intake, valve covers, and valley pan, looking for a possible bent push rod. They all look ok, and spin freely on the lifters, except the drivers side very front of the engine lifter. It looks as if it is protruding from the block about 1/4 to a half inch further then all the others, and the push rod has pressure on it. Question being, as I am slightly unfamiliar with the poly, should the lifter be more into the block? I don’t see anything else that could point me in the direction. I believe it is a 241 poly engine, i have some pics of it. Thanks for any help with the ol fella.

 

Sounds like the cams flat. look at the lobe under the lifter that's up...

 

That PR also looks to be at quite an angle. Is it sitting in the rocker arm properly? Might be the angle of pic?

 

what happens when you turn the crankshaft? Does the lifter eventually go down, and another one or two move up?

like what happens in any engine when it's all working right?

 

Beat me to it!

I don't see anything obviously wrong. I would replace the valley and intake then start it. Clicking in the valve train would then be obvious, as would the offending cylinder. Sticky lifter wouldn't surprise me at all in that vintage.

 

Skipped timing chain?

 

How about a pic of the rocker arms and valve springs.

 

Hi, thanks to everyone who took a sec to give me some info. I don’t think the cam is flat, I had that thought myself, and although I just tore it down, I have not spun the motor over yet. I had a little time last night after work to get at it for a little bit, and hopefully can make some more time this weekend. The push rod seems to be seated correctly, but I will have to look again to see if the lifter drops and another comes up. But it is the only one in the whole valve train sticking up. The problem started out of the blue. In early December, a friend that is a photographer asked if she could borrow it for the day for a Christmas shoot, and I trailered it there because the roads were slick, and it started when I pulled it off the trailer. Otherwise, it leaks all over the place, smells like gas and oil, leaks from the diff and trans like a damn near 70 year old truck should! I will find some time this weekend after work, but should it need pushrods or possibly a lifter or two, anyone have a decent parts source? Or leftovers from making a hemi from a poly? Thanks again for your help!

 

I also will take and post more pics.

 

Have you checked the oil to see if it looked diluted or smelled noticably of gasoline?

 

You might want to backtrack a little, and see if you can figure out what the problem is, before taking stuff all apart.

You can't really tell much about the valvetrain without turning the engine, unless you find an obvious problem like a loose rocker (which can have several causes), or see a broken spring, or something. Turning the engine while you watch the valves and rockers can let you see possible problems.

A compression test is always a good first step in diagnosing problems.

 

Good replies by all - that P-29 code bothers me a little - think trucks were all VT #'s - have to get out my book....

 

What about the valve spring or is the valve stuck?

 

Aren't the Poly's of that vintage solid lifters? Maybe it needs a valve adjustment.

Also, as Squirrel mentioned, it is always a good idea to diagnose the problem before tearing everything apart.

 

Hey everyone. Got out to the garage today, and spent some time with the poly. Honestly can’t see anything at all wrong. Spun the motor over with the starter quite a few times, absolutely nothing looks amiss. As I spin it over I can see the lifters getting oil in the valley, but not so much up to the valve train, although it’s 15 degrees here and that oil is thick. Put the valley cover back in, gonna order some intake gaskets and run it again with the valve covers off and see what she does. The power loss stumps me, really thought I would find a valve issue. Keep ya posted….

 

The book says P 29 is a 1956 Plymouth poly

 

That pushrod area in the first pic looks dry as a bone.

 

Make sure the exhaust is not plugged. Mice nest in pipe etc. I have seen it in the past

 

Hi. Update to a few questions…. Basement.. the lifter I was concerned with, does move as normal, and they are hydraulic lifters I believe. Valve covers are off, and with the valve covers off and the valley pan off, I turned the engine over quite a bit to confirm everything looked ok in the valve train, and it seems to be ok. The engine has not been sitting for any real amount of time though, I drive it about 500-1000 miles a year, and the problem started right out of the blue. I wonder if possibly a lifter lost its hydraulics? I put the valley pan back on, I plan on ordering some intake gaskets, but as far as the valley, I really can’t see anything amiss. It’s definitely a mechanical ticking, it’s not fuel or ignition, and with lost power, I certainly would have expected a collapsed lifter, or bent push rod, but didn’t see either. The engine numbers I was wondering about also. I thought the p also denoted a Plymouth, but I find conflicting info on it, but the original owner swore that it had never been out, or rebuilt. It has 101,000 miles on it. I appreciate the help, and apologize if I don’t get right back on the thread, I work two jobs, and time to wrench on ol blue gets limited ✌️✌️

 

I'll add my 2 cents.
There is no oem rocker adjustment on a P29 or any other EarlyHemi/Poly except for the Chrysler 300, some Marine and the A series engines.
How long since the last oil change? The interior looks very clean so I won't suggest that sludge is the culprit. The clean interior and the P29 code also says the engine was swapped and your engine may have been rebuilt which is a plus. An EarlyHemi/poly with 101K miles will not be that clean......
A 'tick-tick-tick' can be caused by things as simple as an exhaust manifold gasket leak so the search needs to start over when you put it back together. As mentioned, I would verify condition of the electrical to eliminate an errant spark.
I have Dodge poly gaskets in the discount bin if you need them.

 

Check for blocked exhaust or possibly a piece of carbon broke off and is hitting the head , nothing to worry about ,but it can make a noise .
See if you can push the lifter side of the rocker arm down , check each rocker and if you have one real easy to push , look into that further after cranking again and recheck .

 

You might consider doing a leak down test or a least a compression test (as Squirrel suggested). Maybe it's a burnt valve?

 

There were several aftermarket pieces available back in the 60's but highly unlikely that they would be found on an engine like this.
In my decades of working with and selling parts for these engines I have only had 4, maybe 5, requests for adjustable conversions for the Dodge poly. Very little interest.

 

Thanks.

 

Did this sudden power loss happen while the engine was running? If so you most likely have a timing chain that jumped a tooth.

 

Hey all. Definitely had a mechanical metallic Ticking/tapping, that did definitely start out of the blue. And I do believe it to be in the top end of the motor, which I determined by listening to it run, and primitive yardstick to the ear listening. From Basement, who implies that all of the sudden I heard a noise I wasn’t sure was there, and immediately parked the truck in the garage, got out some harbor freight sockets and blindly started ripping the engine apart, that’s not correct. I’ve had the truck a long time, I brought it back from the dead myself, and again, the original owner claimed the engine has not been out or rebuilt. He also was 96, and had no reason to be “full of crap, or lying “. He was just an old guy happy to see someone take an interest in his old truck. That being said, sure the engine could have been changed, and apparently has been. Maybe the guy didn’t remember. It’s almost 70 years old. I wondered myself about the P29 prefix. I pulled the intake off after listening to it, and running it. There was definitely something wrong internally, the timing having jumped a tooth is definitely possible, I have the top end gaskets ordered, and then I can run it a bit more with the valve covers off, and of course do a leak down test. Thanks again everyone.

 

There's also the casting number that can be checked.

 

LOL. I concede, you know exactly what you're doing diagnosing the problem, obvious from you assuming a valvetrain issue and pulling the intake and valley pan to diagnose a bent pushrod or stuck lifter you could have easily checked by pulling only the valve covers. I also concede that the "happy 96-year-old guy" who sold you the truck was totally truthful and knowledgeable when he promised you the 1956 Plymouth engine was original to the 1955 Dodge truck. You get on a public forum asking for help diagnosing what you cannot, and when I take the time to write up some detailed diagnostic steps and get out my manuals to identify your engine code, you get offended and accuse me of saying thing I never said (Harbor Freight tools?) rather than objectively considering that input. You'll never learn anything about diagnostics with that attitude, so you might as well pay a mechanic to resolve the issue for you. Best of luck catching your tail.

 

So, basement, you seem pretty condescending, but glad to see that you went back and edited your reply, (twice! Lol) must be eating you up. Thanks anyway bud. ✌️