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Old 10-09-2020, 10:18 AM   #1
Cadillac Bill
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Default Shave or not to shave?

I have a 1926 T Speedster. Have some overheating. I ran the engine and in a few minutes (At the correct water level) I saw bubbles coming up in the radiator neck.

I pulled the head and the head gasket showed no issues. Before reinstalling, I decided to have the head shaved. I have flat top pistons.

I did a test on the head to see if it had been shaved beore. No stampings from a machine shop. I did a test to see the amount of space in the combustion chambers in the head. I have 275cc which indicated the head not been shaved before.

I think I can shave 35 Thousands and the valves should not hit it.

I have been told about diametric opinions ranging from much greater power, to none.

Suggestions?
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Old 10-09-2020, 01:13 PM   #2
J Franklin
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Default Re: Shave or not to shave?

Starting with around 20 HP you won't notice too much. I would just make sure it was a flat surface.
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Old 10-09-2020, 02:26 PM   #3
Cadillac Bill
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Default Re: Shave or not to shave?

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Starting with around 20 HP you won't notice too much. I would just make sure it was a flat surface.
Thank you for your response.

I have heard that 1926-27 Model T somehow it was about 4 to one compression ratio, less than than 4.5 in earlier models. I have heard that a shave of 1/8th maybe up to 1/25th inches. I could get up to about 5 or 5.5 to one.

I have heard that I take a lump of clay on the tops of some valves, torque the head down, rotate the engine and see how much extra clearance will clear as it is, but still have a question that I could get the water jacket too thin?

Back to your question, about "a flat surface"?
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Old 10-09-2020, 03:28 PM   #4
J Franklin
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Default Re: Shave or not to shave?

High compression heads are available at most T parts suppliers. I was just saying shave to a flat surface for good gasket sealing.
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Old 10-10-2020, 01:18 AM   #5
Dodge
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Default Re: Shave or not to shave?

You can feel the difference with .125 off the head. You need to find someone with an
old rotary broach type of machine, the new machines give a much finer surface
but they can't remove a whole lot of metal in one pass.
My old rotary broach can take off as much as .050 in one pass.
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Old 10-10-2020, 09:56 AM   #6
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Default Re: Shave or not to shave?

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If and when you do this. Stamp along outside edge, how much was taken off for the next person.
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Old 10-10-2020, 11:24 AM   #7
Cadillac Bill
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Default Re: Shave or not to shave?

Quote:
Originally Posted by Dodge View Post
You can feel the difference with .125 off the head. You need to find someone with an
old rotary broach type of machine, the new machines give a much finer surface
but they can't remove a whole lot of metal in one pass.
My old rotary broach can take off as much as .050 in one pass.
I have heard that .25" Could be shaved. A local machine shop tells me they can do at .125, or even at ,25 for $100.
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Old 10-10-2020, 04:07 PM   #8
Dodge
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Default Re: Shave or not to shave?

Spend the extra and get a real higher compression head from Snyder’s or one of those places.
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Old 10-10-2020, 09:35 PM   #9
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Default Re: Shave or not to shave?

I guess it was when i was young and dumb I, took my head to the local parts jobber with a machine shop. I spoke with the machinist to say I wanted it cut. He looked it over and turned to his assistant and said, "You can really cut a lot off of these with no problem".

Upon my return I was informed that he noticed a lot of rust flakes which he hosed out with water and air. If told me how much he removed, my brain was busy processing the cooling issues.

Bottom line it performed much better. Hills became less of a problem.
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