roughskinjrz

ok first off, im running trick flow twisted wedge heads, 3/8" studs with guide plates, and trick flow 1.60 roller rockers, and 7.900 comp cams hardended pushrods

now when the motor is running i get some tapping type of noises, so i stop it, i took off the roller rockers, and they all have little marks on them like hitting somthing, they are hitting the rocker studs, what would cause this?

pushrods too short?

i have a pushrod length checker but its from 6.800-7.800 and i dont know how to use it or maybe be too short. lol

Stekman

How does a rocker arm hit a rocker stud, when the studs are the pivot point?

Where are the marks?

roughskinjrz

never checked, they are on the bottom, on the inside of the rocker, here is a picture

http://img343.imageshack.us/img343/7...kers0088ph.jpg

im not sure what else they could be hitting, the guide plate?

AlkyIROC

It sounds like the pushrods are too short. This forces the rocker to sit lower on the stud.

Check the valve train geometry and buy the proper length pushrods. Comp Cams web site has instructions on how to use a checker pushrod. Don't crank the engine over with the checker in place. It will bend from the spring pressure unless you have the lightweight checking springs installed. Since you already have pushrods longer than the checker pushrod, you'll need a longer checker.

roughskinjrz

thanks, i guess ill get another pushrod length checker, and try that.

i read comp cams site twice, but still a little confused as to how they work, can anyone explain it to me?

AlkyIROC

The one that you have starts at 6.800. Factory SBC pushrods are 7.800 so your checker can't even be used because the high end is at the factory length.

Using a 7.800 to 8.800 checker, Start by adjusting it to it's smallest setting. This will now be the same length as a factory pushrod. Each full turn is equal to .050. Two full turns will make it .100" longer which will be 7.900 and the same length as the pushrods that you currently use.

You need to see where the rocker tip sits on the valve stem to know the proper length. When the lifter is on the base circle of the cam, the rocker tip should be on the inward side of the valve stem (towards the rocker stud). When the cam lobe forces the valve to open, the rocker tip will walk to the outside of the valve stem.

We're not talking about a huge distance. Use a black felt marker to mark the valve tip. Put the rocker on and wiggle it back and forth. It will leave a register mark in the ink where the rocker tip is sitting.

If you divide the valve stem into quarters, the rocker should only travel inside the middle 2 quarters from fully open to fully closed. To get 100% geometry, you need to use lightweight checking valve springs and rotate the engine through a cam rotation to see exactly it's full travel. For most of us, a simple base circle measurement is close enough. At least it will give you an idea if the geometry is close enough.

Worst case if the geometry is correct is that you try a different set of rockers and/or studs. My old SBC engine had Crane Gold rockers that hit the studs. .100" longer pushrods fixed the problem. I was also using 7/16" SBC studs and rockers instead of the factory's 3/8" size.

I currently use Comp Pro Magnum rockers in my BBC and have never had a contact problem. My pushrods are also .200+ longer than stock to get the proper geometry.

Cam grind (small base circle etc), head/block decking, valve length will all change the required pushrod length. Whenever any custom work is done, pushrod length should always be checked.

roughskinjrz

yeah i was told to change to pro magnum or magnum rockers, is there a big difference between the 2?

these trick flows roller rockers are huge

none of that made sense to me, i will get someone over to help with that, ill just have to get the pushrod checker, thanks for everything also.