Cam Install Question
Rule of thumb used to be , min. of .080 on intakes , and minimum of .100 on exhaust for drag engines , where the driver was careful in controlling his rpm`s . Was even recommended by cam maufacturers and Tom Hoover at Chrysler--------
NO VALVE FLOAT!
Yeah, I know that ROT. The problem is, especially with the intakes is that you are making the valve pockets way deeper than they need to.
For the intakes, you can run piston to head clearance and that's plenty.
For example, if you have .040 piston to head clearance and the piston doesn't hit the head, that's all you need for P/V on the intake side. As the intake valve opens, it's following the piston down the hole. They can't hit. Of course, u less I'm doing the machine work and assembly I'm telling anyone to go that tight. You have no control over other people's work.
The exhaust is different. As the exhaust valve is opening, the piston is coming up. Because stuff moves around, and guys still think the timing chain is all that, you need to give some extra room for that. Any time you have two objects moving towards each other, you need to have a bit of fudge room.
And, since most guys still love timing chains, which retard dynamically, and retard with wear, you need to give the exhaust extra room. As the cam retards, it loses exhaust P/V. So give the exhaust valve extra room.
I've run as tight as .040/.060 and never had an issue. But I don't run timing chains and I trust my machine work and my ability to read measuring equipment to the 4th digit if need be.
