urban_cowboy

I was thinking the pre-detonation might be slapping the valve shut. Since I am running 3/8" pushrods, they do not bend easily so I figured it was sending the push rod through the rocker...maybe not.

The springs are the AFR solid roller springs. I think they are 210 seat 520 open and bind at .670 valve lift.

I had not thought about the pistons slapping the valves. The pistons and valve heads looked pristine when we pulled the heads after the valve stem wear issue. I did have the heads machined .005 to true them up and had o-rings put in them to help eliminate head gasket issues. I did not recheck the clearance after that. I guess it could interfere now...

67mustang302

It could be, and even very VERY minor contact could be enough to either hammer the rockers, or it could be creating vibration, but without bending the valves badly enough to lose compression(not all of it anyway). The general rule of thumb is that you want .080" ptv clearance on the intake and around .100" on the exhaust, to account for thermal expansion of the valve/rod/piston, as well as piston/rod stretch at high rpm and valvetrain motion expansion. And those are minimums. Which are at least .030" larger with aluminum rods.

fakesnakes

You've already spent the price of a Jesel set, so bite the bullet and you will never have another problem! Just to temp you, here is the Jesel set up on my GT40. Aren't they purdy?!

urban_cowboy

Shwing...they are very nice. I have thought for a long time about upgrading to Jesel. Some of the racers I spoke with had concerns about running them on the street b/c they are still aluminum...

Are those 1.6s or 1.7s? How many rpm do you spin it? How many miles have you put on them? And how much valve lift are you running?

I have ordered CC Hi-Tech SS rockers, but I can always return them and get some Jesels coming. Fake, you should change your name to the Devil on UC's Shoulder .

67mustang302

Jesel is the undisputed master of the valvetrain. You pay a pretty penny for their hardware, but it's simply the best out there.

fakesnakes

I run a 7500 redline and shift at 6800. They are 1.6 ratio on a Comp Cams 31-760-8 solid roller cam (.586/.586, 243/243 @ .050). Very sweet!

You could always go for the new steel ones:

urban_cowboy

I spoke with my racing buddy who helped me with the finer points of engine building tonight. He did check the piston to valve clearance early on in the process to make sure I did not screw something up. It said clearance was .125+. I had the heads decked .005 to sure them up. That still puts me .120+ valve to piston clearance. He agrees that piston to valve interference is not an issue.

There could be something to the valve shock and/or vibration thing. I am not sure what to do about it...I plan to replace the valves with Ferrea SS valves and new springs during a refresh, but I hope that is a couple of years off.

I saw those new steel ones, but they do not show up on the price list...I am guessing $1500+ since the pro rockers are $1400.

urban_cowboy

Double post.

valley firearms

How is your geometry? Jim could be onto something. If the geometry is off your rocker arms may be interfering with the studs. Id check the rocker interference in the slot while at max lift and see if your coming close.

cprstreetmachines

Asked asked about the tips because it looks like one thing could be valve float. It's very hard on valve train. If you look at your valve stems, and you've seen valve float, the tops will look like little stars.
Solids break rockers on the street because of the lack of rebound in the spring under normal driving. It's hard to explain, especially when just typing it. But when it happens, it puts slack in the valve train, kinda like valve float. But every person I've seen break rockers on the street has been while normal driving.
I'll be getting the T&D or jesel for the same reason. Going to have a solid of the street. FWIW, those Harland sharps would have broken as well. Even some CM comps would do you good.