Cutting valve reliefs into early pistons
 

Does anyone know how deep valve reliefs can be cut into late 70's flat top 302 pistons? Just how thick do you think the tops of the pistons are? Thanks.

Some of the different cam companies make a kit to do such a thing., Installs in place of a valve, then you install the head, put the end of the tool in a drill and start cuttin.. Other than that I dont know what is involved. I know that you need .100 thickness on the top of the piston to be able to cut reliefs.

Bradley

how big of a cam are you trying to make clearance for?

Comp cams 292H (.534 lift, 244 duration at .050 lift)

Flat tappet hydraulic if it makes any difference. Thanks.

have you clayed them to see how close they are, you shouldnt have probs going deeper if you need too.. I cut a set of TRW flat tops .090 deeper to clear a .640 lift cam.. so you shouldnt have to cut much.. if any...

I know they're not early pistons, but I cut my reliefs in my 87-92 pistons with a dremel. Not hard to do, but go slowly. I had to clear for a TFS Stage 2. (.542/.563)

Cool, thanks guys. I figured you should be able to cut about .050 - .090 or so but wasn't sure. I've got a couple griding wheels that are right at 2" diameter so they should work good to cut out for a valve. Thanks again.

I'd clay them 1st... you shouldnt need to cut that much...

Oh, i forgot, the heads are GT-40P heads which have slightly larger valves. I guess I'll just clay them and see. Or maybe I'll go ahead and put a .070 cut in them or so. Does anyone know how deep the stock HO pistons are cut? And what size of cam they can handle? Thanks.

it's not so much the lift as it is the duration that causes the problem.. the piston starts to get close to the valve on the way up.. so the longer you hold it open, the more chance of hitting..

clay it and see..

here's a link for you

http://66.96.130.106/archives/1999/10/ptov/index.shtml

When you use the clay to check clearance do the lifters not compress since there is no oil pressure? I guess I could remove two valve springs. Anyway. Thanks for the help guys.

quantum , it funny that you posted this thread because I just bought the same exact cam for my 351w I'm building. I'm a little bit worried about clearance too. The valve relieves in my new pistons seem pretty deep(not sure exactly).
I was thinking about getting them flycut before I put it together and not have to worry about getting it together and finding out that I need to tear it apart to get the pistons cut.

Competition Cams recommends that you use a solid lifter when checking piston/valve with a hydraulic cam because hydraulic lifters bleed down and give a false reading.