model A head gasket question

M

minerman1

New member
I have a blown head gasket in my '30 model "A". I have read that if the pistons rise above the surface of the block, I need a thicker head gasket. I have searched the parts catalogs I have, but there is no mention of thicker gaskets. Does anyone know who supplies these.
Thanks
 
It depends on how much sticks above the block surface. Most model A pistons stick up about 30 thousandts. Unless you have had the block deck considerably lower a nice copper head gasket should do the trick for you.
 
The FelPro 7013 copper gasket should work fine. The gasket area around the top of the cylinder is large enough to accomodtate a piston at least 125 overbore. Most pistons that size are chamfered at the top to make sure it does not interfere with the gasket. Put the gasket in place and turn the engine over with the crank to see if there is any interference.
 
Take the head off and see what's what before worrying about the gasket. See what brand of gasket you have now. Measure its thickness.

More than likely the head will have to be resurfaced. If so, (or even if not) scrape or clean the carbon out of the way and measure the depth of the recess in the head above the pistons (assuming of course you have a head with a recess; like most of the stock heads for example). Add this to the measurement of the gasket thickness.

Subtract the distance that the pistons rise above the block (clean the carbon off the tops) and you will know the approximate clearance.

.035" clearance is the minimum practical to run without engine damage on an engine with steel rods, tight bearings and pistons and modest RPM.

You will have to allow a little for the compression of the head gasket when it's installed, i.e., its measured thickness will be less than what it is before installation. It won't be much. A Fel-Pro 7013 C compresses from about .080 to about .065 or .070.

If things look like they're going to be close, you can insert a piece of soft solder through the spark plug hole after you put things back together and rotate the engine until the piston comes up and mashes the solder against the head in the flat area above the piston. Continue to rotate the engine a bit so you can remove the solder. Then remove it and mic its thickness.


Larry B.
 
What does btt mean? I figure since forever4 said what he said about btt it has to be degrading...I like Larry's idea about the soft solder. Also the advice about modest rpm, tight bearings, and steel rods.

Q. Can a guy remove say 0.030 off of the top of the pistons without terrible problems?

Model 'T' Monty had a post in the old Ford Barn about a guy who hand lapped the 'T' head to the 'T' block with no gasket and no leaks. Said she had more power.


skip.
 
btt= back to the top, in other words they are asking moderator to bring the message to top of the messages.
Paul in CT There is a whole thread on abbreviations
 
Q. Can a guy remove say 0.030 off of the top of the pistons without terrible problems?


skip.[/QUOTE]

Yes you can remove that much. This past winter I had .030 taken off the top of "Model A" style pistons to allow a Thomas head without a flycut proper clearances. The engine shop had "custom" jaws to clamp the pistons that aligned from the piston grooves. I don't think the custom jaws on the three jaw chuck are important to the process other than the setup was very quick. It only took about 10 minutes to complete all 4 pistons.
Good Day!
Dave in MN
 
Dave is correct, you can remove .030 and probably more. I have a Weiand with no flycut and took .025 off the piston tops, no problem. The Best gasket torques down to .050. One guru I know says piston tops need be about .200 think. My pistons were about 3/8" thick on top, .375. More than enough to remove any pop-up. I agree with Larry that .035 is sufficient clearance for average driving, I would go .040-.050 if you are going to run it fast, and if you have an HC head you will probably wind it up sometime just for fun. Also, you can get solder from Radio Shack in different thicknesses, it says the thickness on the side of the spool. Get some that is around the thickness you want and if it is not compressed per Larry's method, you know you have at least that much clearance and no problem. Measure it if it is compressed, you then have a starting point and go from there.
 
JoeWay: Composition gasket. The tech guy at Best said they torqued to about .057, but others I have taken off were at .050, 60lbs torque. Maybe someone who knows how to do it could set up a survey site to collect actual thicknesses from different gaskets guys have used.
Larry: Dunno the weight either before or after.
 
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