Push rod bolts breaking

[Cudadrag]

I have just broke 2 more push rod bolts. (Rocker bolts for the push rods.) Cam lobes, Rockers and the push rods appear to be fine. The rods are 3/8" the cam is .590 lift and the lifters are solid running stock type rockers. .020 lash for intake. .030 for exhaust.

Are the bolts just getting old and tired? it started in the rear of motor and moving forward. I'm a little weary to start using stronger bolts. When they break oil pressure drops but nothing else breaks.

[cudabob496]

Correct ratio for the rocker arms? And are bolts that are breaking on the exhaust or intake valves? Getting any valve float while racing?

[Tarrbabe]

last forever. Even stock parts break but when you use higher pressures things are bound to happen. Replace ALL the units you are now using and look for stress points. All parts will fail with usage and when you consider thermal cycles, mileage, and possible mis-alignments the odds go way up. Then you need to consider that FEW of us use what worked in the past. I feel I should add my own opinion here. The MOST of the power/hp/toque are applied to the rear of the engine because that is where the power is transverse to the drive train. This should lead us to understand that the most thrust is applied to the rear part of the engine. This tells me that we should build the rear of the engines to a stronger standard or at least replace the parts at the rear of the engines more often. This is not true with all engines but if you look at it with this standard, then the rear section of the engine will require more attention than the rest.
This is not an expert opinion, but it seems most realistic to me.


Just thinking out loud.

[Cudadrag]

So far 2 intake 1 exhaust. Maybe it's just a strange coincidence. I am now going to replace the remainders. When one broke I thought nothing much of it. But now 3? Perhaps its time to lower the rev eliminator. I did miss a gear a month back and the r's shot up to max 7200. I will lower to 7000. But strange the effects would be this far delayed. Got to love the Pars. They do demand attention.

[Locomotion]

I take it you are talking about the adjusters in the rocker arms?

If so:
* Crane had a run of bad adjusters, but that was several years ago.

* Do the adjuster balls "fit" the pushrod cups properly? I believe there may be different sizes available.

* Some manufacturers do make stronger adjusters and use 12 point jam nuts.

* Are they adjusted so only about 1 thread shows on the underside of the rocker? If too many threads are showing, then your pushrods are too short for the application. The further the adjusters stick out, the more side-loads they get, mainly because the OEM Mopar valvetrain geometry is already wacky. It would just aggravate the situation.

* Perhaps some harmonics generated by the engine and/or valvetrain are stronger towards the rear of the engine. But that shouldn't be the main cause of the problem. Must be something else there too.

[cudabob496]

You must have some hefty valve springs. That 7200 overshot may be your culprit here. Maybe some valve float. Sometimes it takes a little time to realize and discover the damage from an rpm overshot.

[Cudadrag]

It is starting to look like it may have been the over rev. And if that is all that happened I guess I can thank my lucky stars. I will find out this week-end

[cudabob496]

One time I burped a lifter, and lost oil pressure. When we took it down, I had bent pushrods, then I remembered I overrved about a month before.

[Cudadrag]

Originally Posted by cudabob496

One time I burped a lifter, and lost oil pressure.

I too am chasing low oil pressure. After replacing the oil pump (which looked a little chewed with some shavings in pump and pan) I started car and pressure only went up from 5 to 10 lbs. I then took the valve covers off (again) and found the 2 more broken lifter adjuster screws. (One on each side.)

Question. Could this be the problem of low oil pressure and the bad pump just being a well timed coincidence? It appears to me the old pump would work just poorly. Being the 451 has solid lifters I didn't think of a push rod problem causing low oil pressure. The engine runs and remarkably sounded fine with a pump looking bad and 2 broke adjuster screws.

[pishta]

Are you binding? Did you factor in the .590 lift to the ratio rockers you have?

[pcrmike]

Same here on a 360 job I built for the street. THe guy calls me up about a month after getting it and says "come listen to it". I get there and it sounds like crap. Pull the covers, five bent pushrods. after talking to him, I find out he was used to the Chubby he used to have loading up with carbon and whatnot and he would every once in a while pop it in neutral and give it a "buhWHOOM" of the gas after slow driving. I promptly explained this is no Chubby and asked him what happenned. He said "I did like I always but there was no "buh" before "WHOOM", and it wrapped up 8K on the tach!!!!!! I sat there jawdropped at what he told me. I explained how the finish I put on the chamber of the head and piston crown required none of that, that is was not a dog-pie chevy and not to do that again. The characteristices of the engine are a super torquer at low revs while making almost 400 hp by 6K. He paid me to replace all the pushrods and rockers (lucky that was all) and got off with the stern warning that anything else would not be covered for hte next month, that he was lucky not to blow it. Try THAT with a 2-bolt chevy main set. :-)PCRMike