Surfacing Cylinder Heads With Sandpaper and Granite Surface Block...

If you look at the surface of the head or a block that's been decked at the machine shop, it's fairly rough unless you're using MLS head gaskets. From what I can tell from a fair amount of searching, 80 grit paper should give the correct Roughness Average (RA) for a non-MLS head gasket.

I agree with you on removing the taper; each head is lower on one end, so it will not necessarily be an easy task to get both heads completely flat. However, I plan to go slow and check often, and if it's not working the way I planned, I can always bring them to the machine shop to get a skim cut done. The heads appear to be untouched, so removing a bit of material is no big deal.

Thanks

 

I do a lot of motorcycle stuff, heads, manifolds etc. If I could only have one grit it'd be 80.

 

I'm reminded of an air compressor I once had. two cylinder two stage with a plate between the head and block. Said plate was where the reed valves resided. They are the first thing to fail in that compressor type. I bought it knowing it needed them. Bought the plate and the upper and lower gaskets. They were a fairly soft, graphite impregnated material. Put it together, worked fine, until a gasket blew. Rinse and repeat. Finally I examined the replacement plate carefully, die cast and really smooth surface.

Flattened and roughened with 80 on a piece of 1/2" plate gl*** and fixed the problem. The high pressure piston was pushing the gasket out of the thin area of the gasket. roughened surface gripped and held.

 

From GA also, my 283 block and heads took 2 months. They don't even have a hot tank.

 

Finally got started on this yesterday. I'm using a 12" x 9" x 2" granite surface plate with a sheet of 9" x 11" 80 grit sandpaper that's attached with some 3M adhesive spray.

The cylinder head is on the bench and I'm running the surface plate on top of it, front to back.

Using a Sharpie to help tell where I'm removing material, and checking frequently.

I didn't realize I only had one sheet of sandpaper, so I culminated after that got a bit worn out.

On this particular head, it was .0025" warped when I started and that's the same measurement I got after about 10 minutes of sanding.

I'll pick up more sandpaper and get after it again today, but if this is going to take 3 hours per cylinder head, I think we're going to end up at the machine shop for a skim cut.

FYI - the 80 grit is definitely not too rough.

More follow.

Scott

 

Being honest about it, I don't think I would worry about the .0025 as long as you have a good texture on the surfaces, both block and heads. Milling a surface doesn't create a perfect .0000 flat surface, thats why production parts have tolerances. Even a surface grinder (which is a lot more precise than a mill) has some tolerance.........
Have you checked the block for flatness as well?

 

I agree that .0025” is fine, especially since the block is less than .0015” warped. But the other head is .004” and that’s at the far end of the allowable spec of .001” per cylinder.

 

Well, I stopped admiring the problem today and got it done. It was surprisingly quick and effective. I don't think I spent more than 15 minutes sanding on each cylinder head and they're both less than .0015" warped now (that's the thinnest feeler gauge that I have).

The trick, in my opinion, was the sandpaper. Yesterday I was using regular box store sandpaper and someone pointed out to me that I needed something suited for working on cast iron, so I picked up some ceramic sandpaper from Harbor Freight and it worked great! I started with 60 grit - one sheet per cylinder head - and after removing some material and getting it close to being flat, I switched to 80 grit. I used 4 sheets of paper total.

Really pleased with how this worked out.

 

Traditional Hot Rodding- using what you have to get the job done. Looks good.
Dan

 

A friend of mine works at a machine shop and when I bring him heads in the morning he usually cuts them during his lunch break and I can pick them up later that day, even if I’m telling him that we are not in a hurry. If they need cutting valve seats too it may take a couple lunch breaks, so it never crossed my mind if I could do it myself. But good to know how it‘s done !

 

You're a lucky guy! The rest of us are waiting for weeks or months!

 

Shot a video of the process. Here's a link in case anyone is interested:

 

Yes , I probably am, more than I´m aware of.
Today I learned that our local Opel-dealership threw out a 25 year old cylinder head surfacing machine since they don´t do any in house machine work anymore. I was told it had been only used a couple of times since they got it new. I would have snagged it immediately had I known they ´d throw it away.

 

Hate hearing about someone throwing out perfectly good equipment. Surprised that one of the employees didn't grab it.

 

I glued a couple sheets of 80 grit to a 1 x 2 piece of flat gl*** and used it to surface some 215 Buick and V8 60 heads. Then used the same piece held with one of those double suction gl*** handles from Harbor Freight to clean up the the blocks.

 

I cleaned up the iron deck and the aluminum head surfaces of the 4.8 in my 55 buick with a sanding block and 400 wet dry paper, not to surface but clean up the old head gasket residue. Running 7 layer MLS head gaskets and reused TTY head bolts, holding up fine at 10 pounds boost so far.

 

You can always do it this way if sanding is to hard,

 

Damn, that's impressive!