Thread: 360 w/broken rockers

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I'm not sure if this is the right spot for this or not....
I have a 350ci Chevy motor bored .060 over, 202 double humped heads w/screw in studs, supposedly a 513 Lunati cam....anything else I wasn't told. It was built by someone else and that's all they told me. When winter gets here...time for me to find out for sure. Anyhow...it keeps busting rockers. As far as I know they are stock rockers and pushrods.
Should I go a little longer with the push rods...will guide plates help.....???? Any ideas

This is the head in which the last of the four rockers had broken..they didn't break all at once.....just one here...one there...etc etc.

To me it looks like they used the stock (likely used) rockers and pushrods, and I bet what they did was adjust the nuts too tight so that the rockers were tight on the pushrods. What that will do is make the moving parts in there get peerrty hot and wear out real fast. Thus, breaking the rockers and you could be revvin her higher than those little rods are used to. Check for how much preload has been set on the lifters. Hmm, forgot to ask, what kind of lifters are they? I would assume just hydraulic units? In which case a good amount of preload is to tighten the rocker nut down while turning the pushrod between your fingers. When you feel a slight drag while turning the rod then stop tightening and go about 1/4 turn more. Some people say 1/2 a turn, some say never go half a turn. If you already knew all of this then I would just tell you to go out and buy some good rockers and pushrods. Not to mention that if the head is already machined for screw in studs then guide plates (the proper style!) would only be a quick bolt in thing, but make sure you adjust them for both rods at the same time, and make sure to put some sealer on the threads as they likely go into water jackets. Ask the guy if he ever milled the block or the heads if you can contact him. If he did you will have to shorten the pushrods to get proper geometry. I would just be thankful you didn't break retainers like I did yesterday...that cost me about 3-4 bent valves for sure. Another thing to keep in mind is that a excessively bored cylinder wall will not dissipate heat as well and you could generate some more heat issues with that beast. Hope this helps, good luck

Ahh yes, forgot about the binding springs or umm short slot rockers which is very possible with a high lift cam and stock rocker units.

Piston/valve collision is bad...I would know this as of yesterday. But oh well, I still have 2 BBs and a smally on the way to tinker and drive around with.

I'll second the coil bind, a stock sbc spring will bind at or about .490 from what I've run into, short slots I'll also second, since you say it "keeps" breaking em I don't believe your making piston/valve contact . just my $.02

Aye, I third the no piston to valve contact thing, but actually my small block still runs with 4 bent valves. YAAY!........Not that that is a good thing to do but it does move under its own power....I had to get it from the middle of the yard somehow and its ALL uphill to the garage. But yes I would imagine that either the springs are binding or those rockers (which I was warned about when I built my SBC) DO NOT have enough clearance for that much lift, they are likely hitting the stud which could screw up the stud too though. tech gave you good advice, check those things out real closely and decide what is binding.

I'll check into those....I've had the motor for a little over a year...it still runs like a bat out of hell.....it's just now and then you break a rocker...and it's not always the same number. It was running great....doing nice burnouts......then on the way home..."POP POP" messed up number one (a) rocker and number one (b) pushrod. Gets tiresome after awhile....was supposed to have been built by someone that knew what they were doing...but ya never know. Thanks for the input guys