46 UL Badly pitted cylinder head gasket surface

[sirhrmechanic]

Taking .015-.020 off the cylinder will not affect it at all. The difference in compression will be small, like about 1/4 of a point! The only thing to look at is top of piston to head clearance in the squish area. All the racing flatheads popped the pistons up and had a pocket relieved in the heads for better squish. If you needed more clearance that is where to get it!
Robbie

Completely agree with this. .015" is 5 sheets of typing paper. You can make that up with a thick base gasket or if you are concerned about rigidity of the jugs, make a thin (.010") spacer from shim stock and use a thin paper gasket on each side at the base of the cylinder.

I like the idea from earlier about relieving the flow areas between valves and cylinder, too. There are probably some good old articles about how to do that/what to do if you dig around. Lots of people hotrodded flatheads back in the day.

Please post some pictures as you proceed. We can all learn something new! I know I've picked up a lot from folks here.

Cheers,

Sirhr

[AZ pan]

I milled .020 off cylinders yesterday and everything cleaned up nice, thanks again for your input. I'm always up for improving performance so will look into some relieving and blending for flow. Have built many motors but this is my first total rebuild on a flathead, so am sure there will be more questions asked.100_0595.jpg

[37ul]

Looks nice! I had to "finish" the relieve job on my cylinders someone started with a rough grinding stone and an uneven eye. It was a lot of work by hand to try and even it out! i cleaned up the intake and exhaust port runners while i was at it. I even evened out the core shift in the intake manifold. Be careful grinding on the cast iron, nasty stuff if you breath it in!

[Sargehere]

... I like the idea from earlier about relieving the flow areas between valves and cylinder, too. There are probably some good old articles about how to do that/what to do if you dig around. Lots of people hotrodded flatheads back in the day...

Cheers,

Sirhr

Here's one of the most complete books you'll find on Harley Big Twin hop up "secrets:"
http://victorylibrary.com/80PER.htm
They also do one on 45s, and one on Linkerts, and on, and on.

[D.Mac]

Here's a couple diagrams from a Harley Davidson publication titled "Competition Racer", although they are intended for KRs, I'm sure they would be of use for your U. Those cylinders look like they could really use some work between the valves and pistons. I haven't looked at the info Sarge linked to, it may have the same or similar diagrams.
Doug.

[AZ pan]

Thanks Doug, will look more into it.