Surface head for a little more compression?

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jensenracing77
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Surface head for a little more compression?

Postby jensenracing77 » Mon Nov 08, 2021 5:18 pm

I have a broken head bolt that I found a couple years back and just now going to fix it. When I pull the head would it be a good idea to surface the head and gain a little compression? I didn't know if .010 would hurt or help any at all. My engine is still strong and don't need rebuilt but I have always felt these could use any help they could get. I am guessing these have enough valve clearance?

Gary Dotson
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Re: Surface head for a little more compression?

Postby Gary Dotson » Mon Nov 08, 2021 5:58 pm

.010 won’t be noticeable but you can go quite a bit more. You’ll want to measure the valve to head clearance but I’m pretty sure .050 - .060 should not be a problem. I have a couple heads, on the shelf, one is cut .100, the other angle milled .100. These aren’t mine and neither has been installed on an engine, the owner passed away. Chamber measurement shows there is no benefit to angle milling. Heavy milling can cause a port flow issue, on a flat head engine so some relieving the top of the block can help. Perhaps you’ve heard the old flat head term “ported and relieved”, block relief is what is referred to here. I think a little extra compression is a good thing.

Gary Dotson
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Re: Surface head for a little more compression?

Postby Gary Dotson » Mon Nov 08, 2021 6:01 pm

Oh yeah, if this is your 184, with domed pistons, you’ll probably need to clearance the head to clear the piston dome.

jensenracing77
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Re: Surface head for a little more compression?

Postby jensenracing77 » Mon Nov 08, 2021 8:47 pm

At one time there was an aftermarket head for them. Is it still available and is it any good?

Bob McCarty
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Re: Surface head for a little more compression?

Postby Bob McCarty » Mon Nov 08, 2021 9:29 pm

TM Tractor sells an import, but I can't speak to quality.
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we need to think differently."
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Re: Surface head for a little more compression?

Postby outdoors4evr » Tue Nov 09, 2021 6:24 am

A little modeling clay on the top of the pistons will tell you how much you can cut.
Since the head is flat, stick a ball of clay to the high point of the piston and put the head back on with the old gasket. Roll the engine through a revolution or two.
Pull the head back off and measure the thickness of the clay. The thinnest part of the clay is the most you can take off. Maybe mill a little less so there is room for heat expansion.

Make sure that the block is also flat. Maybe take .010 off the block and the remainder off the head.
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jensenracing77
Posts: 20
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Zip Code: 47834

Re: Surface head for a little more compression?

Postby jensenracing77 » Tue Nov 09, 2021 6:47 pm

My machine shop has done several of these engines. He said that clearance is not an issue on these heads. He said it is safe to go .100. We decided to go .050, with the stock compression at 7.5 I would think this has to help some.

Gary Dotson
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53 Cockshutt 20 restored (Shooter)
52 Cockshutt 20 unrestored
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49 Leader "D" (Princess)
49 Leader "D" very rough
48 Leader "D" unrestored
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Location: OH West Mansfield

Re: Surface head for a little more compression?

Postby Gary Dotson » Wed Nov 10, 2021 8:48 am

This being a 184, with (I presume) the domed pistons, you could, potentially, have a clearance issue at the point where the chamber meets the flat head surface. A quick hit with a die grinder will be all it takes.

jensenracing77
Posts: 20
Joined: Wed Jan 22, 2020 1:12 pm
Zip Code: 47834

Re: Surface head for a little more compression?

Postby jensenracing77 » Wed Nov 10, 2021 1:59 pm

I will check before assembly the clearance but it appears to be more than safe.


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