I have had a valve train noise all year at about 8000rpm, everyone I talked to said "valve bounce" or "valve hitting piston"

But at Rally Aus I though well one thing I have change this year was to put on Yellow Terra roller rockers with Crow crome-molly push rods. So I change it all back to standard rockers and push rods, problem gone. set the limiter to 8200rpm no problems.

Has any one else had this problem. (I do check gap and end float setting before every rally)

No issues with mine
Pushrods the right length ?

yes i have had problems with these rockers, the rollers inside flatten out over time and become noisy in operation can't say this is your problem though as i havent seen your engine, plus mine was on a v8 but same setup, personally on datsun engines the standard rockers are nearly bullet proof, stick with em!

The push rods are the same as yours [Dattoman 1000] but are only 6.050 long x .080 I use the A12 block. but the tappet gaps are good.

The roller rockers come in 1.54 to 1 ratio & 1.65 to 1 while the stockers are 1.44 to 1. This means that at maximum opening, the valves are a whisker further down the bore than with the stockers.

Is it even remotely possible that you were having issues with either valve to piston clearance, or with clearance in the valve spring/collet/spring seat area that no longer exists now that the valve opens less than before?
This seems to be a more logical explanation under the circumstances, and we all know that sometimes even a few thou can make all the difference.

Which ratio rockers were you using & how much lift do you have at the cam? Were you using lash caps?
Yes, I have a set of 1.54 to 1 rockers to use on my humble street engine, so I'd love to find out what your actual problem was & its cause.

I do have lash caps and i have a JTS 247A CAM with .430 lift the rockers are the 1.54 ones. when i built the engine i checked and i had .040" clearance at full lift.

Quote:Quote: With .430 lift at the cam, you would have a nominal .662 lift at the valve.
Man, thats a LOT. This would translate to a nominal .619 lift with the stock rockers.
Doesn't look like a big difference, but in practical terms, it just might be enough.

Those figures look wrong

Maybe it is valves hitting.

I have tons of valve clearance. You should sell them rockers to me!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Quote:

.430" must surely be the lift at the valve, not the cam lobe. Also 40 thou clearance sounds a bit close, when I built mine I was told to have 80 minimum especially on the exhaust valve as it grows more as it gets a lot hotter.