RickR

What is the absolute minimum piston to valve clearance for a nearly stock 454 Mag that will see 5200RPMs max?

Thanks!

tahoez71

Im not to sure what the tolerance is but if your going to run the minimum run a trust worthy rev limiter
P.S I think it's around .100" but dont take my word for it and what does nererly stock stock mean, what has been done.

formula31

I lived with .060 once and limited rpm to 5000 with a good rev limiter. Also had a real good valve train with good springs and dampers. Worked OK but I was never comfortable with it. Watch cam timing, too much advanced and intake will be close (if I remember right)

RickR

Thanks for the info
Decked block .010, milled head .035, using GM .030 (Compressed) head gaskets

I am at .068 clearance on the intake valve with 110 Intake Lobe Centerline, over .100 clearance on the exhaust.
I am using a MSD with Soft Touch and good springs and dampers on a flat tappet hyd Bullett Cam.

[ 02-05-2002: Message edited by: RickR ]

formula31

Hopefully Bruce will chime in soon. I think your Ok. Thats about where I ended up with flat tops and angle cut heads with .018 head gaskets.

Griff

Rick, you could use a Felpro marine gasket #1037 to add a little more clearance. They are .039 compressed thickness.

bobl

I would consider .080 the bare minimum. You could try retarding the cam 1-2 degrees from where it is and you'd probably gain the clearance you need. I ran into the same situation on a 454 Magnum. I flycut the pistons to gain enough clearance.

RickR

Why do you need more than a few thousanths clearance on the intake valve? It is opening @ TDC so valve float wouldn't be a problem?

"Chevorlet Big Block Parts Interchange Manual" says .045 on a stock engine, .080 Intake .100 Exhaust on a high RPM engine.
I would consider 5200 RPMs a stock, max RPM.

Bruce

RickR, for an added margin of safety I would install titainium retainers to reduce the recipricating weight. In a perfect world your logic applies, in the real world a valve train is somewhat unstable at WOT. The valves are rotating and bouncing, the pushrods are flexing, the lifters are rotating and collapsing, etc. My rule of thumb is .080 minimum. In your application I would retard the cam 3-4 degrees, that will carry the torque peak higher in rpm range anyway. This should get you the clearance for a safety factor. If in doubt, "run it like you stole it!"

RickR

FYI
GM says .045 if run within recommended RPM range on their sight
http://www.gmgoodwrench.com/crate_en...big/torq2.html

[ 02-07-2002: Message edited by: RickR ]