Rocker arm problems

duke96_old · April 29, 2009 at 9:59 PM

I seem to have a problem with my rocker arms in my motor. I have broken two rocker in half. the car idled great and only when i got on it did i have a problem. i have solid lifters, stock rocker arms, stock springs with a higher lift cam (not sure how much lift, it was installed before I bought the car). This past winter I replaced the heads because i was having problems with my rocker studs backing out of the head. i replaced them with 302 heads off a 347 stroker which was pro built and ran very well. I'm looking for all suggestions on what I should do. having the motor rebuilt at a machine shop is not an option for me at the time because I just bought a house. thanks again

Duke

RalphJr · April 30, 2009 at 6:42 AM

I haven't experienced this on my Fords, but did on a .....dare I say...a 396 and 454 Bowtie! Yikes - I just said the C word!<img src=images/icon_smile_big.gif border=0 align=middle><img src=images/icon_smile_big.gif border=0 align=middle><img src=images/icon_smile_big.gif border=0 align=middle>

My brother is a big Chevy guy - go figure - but did result in some great Bench racing as teens.

Using stock valve train with a high lift cam commenly causes the issue you are seeing - especially if all the parts are not brand new.

Here is what I would recommend - use at your own discretion....

1) you definitely need screw in studs - if you don't have them the high lift on the cam will pull the pressed in ones out. 2) get some good aftermarket roller tip rocker arms - WELL worth the money. 3) swap out the stock springs - you can do it with the heads on the car - find the correct tool at the local AutoZone - put the piston at TDB - and you will be fine swaping out the springs. 4) USE HARDENED push rods and retainers - don't scrimp here and don't assume what you have is good. If you have broken an arm it is very likely you have bent a push rod (probably most of them are bent by now).

OR you could go the other way and pull out the cam and swap it for a more reasonable one. Most novices make the mistake of putting a wild cam in to get the lumpity/lump and forget that all the other pieces need to match for it to work reliably.

It will definetly be worth the money in the long run - and doesn;t require a machine shop (except thescrew in studs) or full motor rebuild. Plus it will be a great weekend project - maybe two.

Good luck.

C6ZZKGT · April 30, 2009 at 8:19 AM Official Post

Duke, Ralph is sending you down the right path on this. Here is another food for thought on your problem and I believe that this fits your scenario perfectly. If you are using stock springs with a high lift cam, you might be experiencing coil bind on the springs. This will be more of a problem at high RPMs which is where you are having your problem. You can check this also with the heads on the car by having your valve at its most open point. At that point you need to be able to compress another .100" more before coil bind or your setup will continue to give you problems. If the springs do coil bind then change the springs as Ralph suggests. Be aware of proper seat pressures for the new springs so have them checked to see what height you will need to set the springs at when installing them. The height is adjusted with the spring shims. You might also check to see if you have spring shims already as if there are and they are too thick, that will cause coil bind. Just a side note here, I have been running a 427 bowtie for 40 years with a ZL1 .600" lift cam. I have stock 3/8" pushrods and stock rockers arms. I have had the engine to 8,300 RPM many times and have never had a rocker arm or push rod failure.

-Fred-

Mu5tanggt_old · April 30, 2009 at 8:43 AM

I had the same problem on a cleveland and it ended up being some weak valve springs. Car ran fine as long as I kept it below 4,000 RPM, as soon as I went above it bent the pushrods.

duke96_old · May 1, 2009 at 4:28 PM

I thank all you guys for the info. It is def spring binding that I am having a problem with. I am going to replace everything with a full matched cam, lifters, springs, retainers, ect... Hopefully this will fix my problems and I can enjoy my pony the rest of the year trouble free. I'll keep you all posted on how I miake out. Thanks again.

Duke

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