Engine woes

[69gmachine]

I've built several SBFs in my life, but this is not one of them. Everything I had built before was a mild performance hop up with a stock bottom end. This was a high dolllar, high performance engine I didn't trust myself to do. My mistake. I only made two runs on a road course and bent 6 of the intake pushrods when making a pass and revving the engine well over my intended 6k limit. Now here is the kicker: there is absolutley no evidence of any valve hitting any piston! I used a custom grind reduced base circle Comp cam, OEM used hyd roller lifters, the stock springs on the AFR 205 heads, 1.6 Comp magnum roller rockers, and what was supposed to be hardend pushrods. They are stock small Chevy lengths. They are cheap 5/16s tubes with pressed in balls. Most of the balls came out of the ones that bent. Since there is no evidence of physical contact, my question is this; is it possible that the pushrods were simply not strong enough to handle the revs? Has anyone else ever had this happen to them? My engine revved like crazy for a big 4" stroke, due to the aluminum flywheel.

 

[MitchGT]

I know the oem lifters don't like to rev all that high. They might have compressed with all that rpm, leaving too much lash so that the pressed in ends got pounded out. It's interesting that it only happened on the intakes. It could be that the intake valves are heavier and pounded the valvetrain harder, or that the valves have more diameter and did end up tapping the pistons a little.

 

[rbohm]

two things to check, coil bind and rocker arm to stud interference. you may have too much lift causing the springs to bind fully. it is interesting that only the intakes suffered bent pushrods though. perhaps the installed height of the springs on those valves was enough to allow coil bind. remember that the stock springs dont like valve lifts much over .460".

also even though the cam companies make the rocker arm slots longer to allow for more clearance between the rocker arm and the stud, it is possible that the rockers on those valve may have slots that were not properly machined.