I am at my wit's end.*
To recap, I'm building a stock 1970 GTO RAIV engine (614 heads, ww block, etc).* The heads were originally assembled by a local "Pontiac" machine shop 10+ years ago but final assembly was done 1 year ago.*
It had a RAIV replacement cam and Comp Cam roller tip rockers.* Everything*else stock.The machine shop messed up and did not machine the valve stem bosses, so the inner aftermarket springs did not seat and sat too high, creating too much pressure.* On first start up it broke a few pushrods at the top ball.* I did not know the springs were too high and thought maybe I over tightened the rocker nuts.* Same thing happened with pushrod set #2 (all 9.2", 11/32) obviously.*
Out came the engine, off came the heads and I had the bosses machined.* Heads and engine reassembled with Butler Performance *RAIV kit (still using the 1.65 Comp Cams roller rockers), this time with poly lock rocker nuts.* Valves were measured and lapped in, correct original valves.* Valve springs installed height was 1.84" (only one needed a tiny shim) and seat pressure measured between 118 and 120 lbs.I rechecked this twice.**The roller tips on all valves sit squarely on the middle of the valve stem top.* Geometry looks perfect.* I used the Butler RAIV equivalent cam and lifters and pushrods.* All pushrods mic'd just for fun and dead*on.* Engine primed and each valve adjusted to zero lash plus 1/2 turn.* *ZDDP added, new filter, engine fired up and run at 2000 RPM for 15 minutes and shut off when it began to get a bit noisy.*
I took the valve covers off and there are two broken pushrods.* Same type of break as all the others, at the rocker end, ball is pushed down into the shaft, causing it to flare out.What am I doing wrong?* What else can I check?* Are these modern pushrods prone to failure?* I checked for spring bind but there is plenty of clearance between coils.* I am very frustrated.* I hope someone out there can provide some insight.**
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