46 UL Badly pitted cylinder head gasket surface

[AZ pan]

Thanks Doug, will look more into it.

[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.

[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.

[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!

[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

[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]

Thanks Rub greatly appreciated...

[Rubone]

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

[AZ pan]

I set cylinder up in the mill and indicated it, .015 will clean up the gasket surface and .020 will clean up the whole top. It isnt going to do any thing with the valve seats but am concernd about piston height, but then I guess I could always make up for that at the base gasket. Still can anyone tell me if its safe to take that much off the cylinder top?
Thanks

[AZ pan]

Photobucket is down, will post some pics hen its back up, thanks...

[39 UL]

What Kerry says is right on. The area between the valves and bore can also be "relieved". This would clean up the pitted area, and provide better flow. Lightly grind the path between the valves and bore. This will lower the compression slightly, but will improve power at higher RPMs. Just make sure you stay away from the gasket area. Put a gasket on and scribe around it first. I'm sure a search will turn up "how tos" on relieving.

[kg993]

I wouldn't be concerned about pitts between the cyl. and the valve area, as that is not a sealing surface. Only the perimiter around the bolt or stud holes need to be in good shape.
Kerry

[sirhrmechanic]

Rub: Thanks for pointing that out. I read Cylinders and Head Gaskets in the same line... and the visual that popped into my head was all wrong! My mistake... sorry!

On cast iron... possible, but you have to be very careful! If you overheat the cast iron, you can get a crack (likely a pair of cracks) at the "heat joint." But silver solder will stick nicely and if you use a low-enough melting alloy and are careful with heat, no problem! So Bob's solution is definitely one with potential. But make sure the welder knows his stuff! I know people re-weld fins and repair these cylinders all the time, so I am betting that it would be no problem.

As an aside, we try and avoid cast-iron welding (or silver-soldering) at almost all cost. Too much risk. But when we do have it done, we use a company in Oh called Columbus ColWeld. They will strip a part and then heat it up in a furnace to high black/low red temperature. Then weld it in an inert gas environment. The part is then cooled down over 24 - 48 hours, depending on the size, and remachined to true. Not cheap, but sometimes the only alternative. Once the parts are welded by some skeeziks with a stick and, as a result, are all cracked and contaminated... part is basically ruined. But done right, cast iron can be saved.

If you ever need to call Columbus ColWeld, ask for Maynard Stumph. Great guy and lavishes a lot of care on vintage parts.

Back before new Ghost cylinder blocks were available (at $9K each), we used to fix eroded/thin/weeping blocks by milling out the bad area with a thin flange, then by pinning in new plates to restore thin/rusted through areas. We would then soft-solder the joint. This was only at water jackets, so low temperature. Nothing near combustion areas. And it was only intended to be a 'temporary' repair until new blocks were available. Yet some of those blocks are still in service more than 30 years later. But we don't do those sorts of repairs any more. Again, too much risk (and time and labor) when new parts are available.

The good news with the UL cylinders is that if you don't solder, you can almost certainly mill enough off the top to clean up the damage and then add a spacer plate at the bottom of the cylinder to restore the height. That way you can maintain both compression and the pushrod lengths, etc. Even if you go a bit below 'factory' minimum, the factory set those minimums with the idea that once the minimum was reached, you would bin the part and get a new one from the shelf. There is probably some 'material to spare.' Remember that few of these old car/bike companies built vehicles with ANY concept that we would be cherishing them and restoring them and riding them 65 years later!

Depending on how much gets cut from the top of the cylinder jugs, valve seats may have to be recut and that could be a concern... How deep you can go with the seat??? That may be your limiting factor for depth. Just thinking out loud on that one...

Cheers,

Sirhr

PS. If you call Dave "Rat" Sherk at Harbor Vintage, he almost certainly has a number. And Steve Slocombe who is active on this forum will also probably have some outstanding experience here. You can find him easily on the forum. I'd be surprised if he didn't respond by morning... being in the UK, he is likely kipping some Z's right now.

[AZ pan]

Sirhr, you understand exactly what I am after but, its not the head, head is in great shape. Its the top of the cylinder surface I am talking about. Also, the heads are cast iron not aluminum. will add some pics tomarrow when I am at the shop. I can figure all this out my self but would have to put just about the whole motor together to see what clearances I have to work with, was just hopeing that someone has been through this and could save me some time.
Thanks, Bob and Sirhr any help is always appreciated.

[Rubone]

Good thought, but those are aluminum heads. Silver wouldn't stick and the heat would be enough to warp them if you tried to weld.

Go back and read the original post. Cylinders, not heads, therefore cast iron!
Bob's solution is a possibility.