Grog

All -

I am installing a set of HP500 heads with 2.30" intake valves on a stock Gen VI 502. The old heads had 2.19" intake valves. I am running a stock cam and plan on using .040" head gaskets (Fel Pro 17048, I think)

Would you expect any valve to piston clearance issues???

Grog

Oh, and while I am here, does anybody have a copy of Dennis Moore's Marine BBC book that they want to sell.....rent.....lend?

jdnca1

You should have more than enough...but its still worth checking.

Griff

You won't have any issues. Pretty sure the engines use the same pistons. The cam you ar eusing is much smaller as well.

kennyo

Greg, I was pretty sure you would be okay. You sure you don't want to change the cam? I've got two "731 Cranes " on the shelf!

Grog

Stop that. Stop that right now!

mrhorsepower1

Those heads will work best with 2.250 int. dia. with the correct port work. If your already committed to the 2.300 you will still have to do pocket porting to benefit from the larger valve.

Grog

I appreciate everyone's input. I realize that I may not be optimized, but right now, my goal is to just get back on the water.......this spring.........without spending more money.

Kennyo - If you still have those 731s next fall, I may be interested in one.

Griff - Why would the cam matter? At TDC of the stroke the lifter should not be on the ramp of the camshaft, and the intake valve should be completely closed...right?

Still looking for, and counting votes. Will I have a problem when I bolt things back together and turn the key?

Thanks again.

Griff

Correct, but valve to piston clearance problems really don't happen at TDC, they happen when the cam and piston are moving. A bigger cam will open the valves farther during this process and they will get closer together as they move up and down. The distance also changes if you advance or retard the cam timing.

Grog

Understood. I would guess then that clearances would get even tighter at max rpm when/if the valves start to float and when the pistons see their greatest travel in the bore.