The Ford Barn

Matts30coupe · 03-09-2020, 09:34 PM

Looking to buy a performance head for my model A build. Motor has been freshly rebuilt yrs ago. It was an old guys spare. I will be taking it down to check it all out before building it back up.

Question is that I am looking at getting a performance head for it.

I would like to shoot for a 7:1 compression ratio. I like Dan Prince aluminum Thomas repos. Thing is, that there is no flycuts... My pistons come above deck .010" now. Gasket looks to be cold .055". (Maybe add .005" for compression of head gasket.) So, I am looking at .045"-.040" of a squish band. I have heard for a model A driver you want your "squish" to be around .060"+- maybe .005"?

So I am wondering my options. I can pull the pistons out and cut some off the top in the lathe, or have a machine shop fly cut the new head. Wondering what people have done in the past. I am worried that my setup now is too tight, and want to avoid my pistons kissing the new head when the cylinder grows.

Anything will help, thank you!
Matt

Jack Shaft · 03-09-2020, 10:26 PM

Ideal quench (what you call squish band) is .040,so it appears you are good.The best 509c copper gasket is pretty thick as well.Measure 5 times fit once,be dead on in your factor,you can use a piece of modeling clay to squeeze and measure as a test.Its not expensive to have your head flycut to achieve the desired clearance and it doesn't lower the compression ratio measurably...maybe a few cc's. Be sure and use a waste metal with your aluminum head..I'm pulling my aluminum,got a cast iron one.

Matts30coupe · 03-10-2020, 07:30 AM

Thank you jack! One question with your info above. What is waste Metal?

Jack Shaft · 03-10-2020, 07:50 AM

Waste metal is a cathode (or anode heard it both ways) to accept the electrolysis effect on aluminum parts in a cast iron engine,The aluminum will erode from this effect.

https://www.snydersantiqueauto.com/P...MM-PLUGS-18-27

Nosetime · 03-10-2020, 09:11 AM

Sacraficial anode. I had a threaded bung installed in radiator top. You can get threaded pencil anodes from boat supply, makes a really easy way to change them. I was able to get away with a Super Winfield with no fly cut. Test with clay balls or balls of aluminum foil. I did it without the gasket and with, as told to me by an old flathead racer. Do the test a couple times to be sure. i use the Best 509 graphite.

Matts30coupe · 03-10-2020, 10:37 AM

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Thanks! I figured it was something to help will corrosion. Nosetime, do you remember your specs. Or distance from piston to head? How did it run?
Matt

Nosetime · 03-12-2020, 09:51 AM

I will look for the info. I took pics of my piston protrusion above the block and mic of my balls of foil. Give me a bit. PM for easier info

03-09-2020, 09:34 PM	#1
Matts30coupe Member Join Date: Sep 2019 Location: Chicago Burbs Posts: 46	Safe "Squish band" for a model a head Looking to buy a performance head for my model A build. Motor has been freshly rebuilt yrs ago. It was an old guys spare. I will be taking it down to check it all out before building it back up. Question is that I am looking at getting a performance head for it. I would like to shoot for a 7:1 compression ratio. I like Dan Prince aluminum Thomas repos. Thing is, that there is no flycuts... My pistons come above deck .010" now. Gasket looks to be cold .055". (Maybe add .005" for compression of head gasket.) So, I am looking at .045"-.040" of a squish band. I have heard for a model A driver you want your "squish" to be around .060"+- maybe .005"? So I am wondering my options. I can pull the pistons out and cut some off the top in the lathe, or have a machine shop fly cut the new head. Wondering what people have done in the past. I am worried that my setup now is too tight, and want to avoid my pistons kissing the new head when the cylinder grows. Anything will help, thank you! Matt

03-09-2020, 10:26 PM	#2
Jack Shaft BANNED Join Date: Dec 2019 Posts: 1,196	Re: Safe "Squish band" for a model a head Ideal quench (what you call squish band) is .040,so it appears you are good.The best 509c copper gasket is pretty thick as well.Measure 5 times fit once,be dead on in your factor,you can use a piece of modeling clay to squeeze and measure as a test.Its not expensive to have your head flycut to achieve the desired clearance and it doesn't lower the compression ratio measurably...maybe a few cc's. Be sure and use a waste metal with your aluminum head..I'm pulling my aluminum,got a cast iron one. Last edited by Jack Shaft; 03-09-2020 at 10:36 PM.

03-10-2020, 07:30 AM	#3
Matts30coupe Member Join Date: Sep 2019 Location: Chicago Burbs Posts: 46	Re: Safe "Squish band" for a model a head Thank you jack! One question with your info above. What is waste Metal?

03-10-2020, 07:50 AM	#4
Jack Shaft BANNED Join Date: Dec 2019 Posts: 1,196	Re: Safe "Squish band" for a model a head Waste metal is a cathode (or anode heard it both ways) to accept the electrolysis effect on aluminum parts in a cast iron engine,The aluminum will erode from this effect. https://www.snydersantiqueauto.com/P...MM-PLUGS-18-27

03-10-2020, 09:11 AM	#5
Nosetime Senior Member Join Date: May 2017 Location: Huntington Beach, Calif Posts: 330	Re: Safe "Squish band" for a model a head Sacraficial anode. I had a threaded bung installed in radiator top. You can get threaded pencil anodes from boat supply, makes a really easy way to change them. I was able to get away with a Super Winfield with no fly cut. Test with clay balls or balls of aluminum foil. I did it without the gasket and with, as told to me by an old flathead racer. Do the test a couple times to be sure. i use the Best 509 graphite.

03-10-2020, 10:37 AM	#6
Matts30coupe Member Join Date: Sep 2019 Location: Chicago Burbs Posts: 46	Re: Safe "Squish band" for a model a head Sponsored Links (Register now to hide all advertisements) Thanks! I figured it was something to help will corrosion. Nosetime, do you remember your specs. Or distance from piston to head? How did it run? Matt

03-12-2020, 09:51 AM	#7
Nosetime Senior Member Join Date: May 2017 Location: Huntington Beach, Calif Posts: 330	Re: Safe "Squish band" for a model a head I will look for the info. I took pics of my piston protrusion above the block and mic of my balls of foil. Give me a bit. PM for easier info