MTFCA Forum

Anyone know the maximum amount of material that can, or has been removed from the late model cyl head?

I am contemplating installing a set of 265 chev pistons into a T block to accomodate the chevy crankshaft I will be installing.
It seems the chevy pistons are a pretty close match for the chevy rods, this will require a bushing for the wrist pin, a relatively simple fix.

The one concern is with the compression height of the pistons, the 265 pistons will be lower, basically flush with the surface of the block. this will lower the compression ratio....which is extremely low to start with, at around the 4-1 ratio.
Planing the head will help. I would think you would have to remove ALOT of material due to the huge combustion chamber in the T head.

Anyone have experience with this ?

Dave Eddie

Its a bad idea to chop a bunch off late heads. It weakens the combustion chamber & they crack from the flexing.
Some heads are better than others. I know of Montana racers that used to remove 3/16". They typically failed quickly. Usually in break in, before a race. You will run into valve head clearance issues also.
Your use of chevy pistons is going to get you less than stock compression. You should do some CC work & math to see how low your compression will be. I would think, at the very least, you need a high compression head like a Prus just to meet or beat a little a stock 4-1 ratio.
Talk to the zoom zoom guys like Dan McEachern.

Dave I can wrap my head around cost and the doing it yourself part, what I can't is, going to all this work and wanting to use a Model T head. Because of core shift, not all heads are the same thickness where you would be wanting to cut it back, ballpark would be around 1/8" maybe a little more and still have the needed strength. You might want to contact Les Schubert or Kevin Prus.

I have a set of pistons that I was told came out of a T engine, the wrist pins are too big for A rods so thought may be chev, so just checking on that, may be questionable, chev at .850"? These come in at 910"

Core shift, corrosion, sand inclusions, original manufacturing tolerances.... how much you could take off would be trial and error. At some point, shaving the head will shroud the valves. With a flat top piston or anything near it, you'd still have a poorly shaped combustion chamber.

Kerry, The chevy pins are .850" dia.

TXGOAT2, relatively simple to check for valve clearance to the combustion chamber, place a spot of putty on one intake and exhaust valve,install the head with out a head gasket, turn the engine over a couple of revolutions. Remove the head and measure the thickness of the compressed putty.

Have you read this thread? Look at the postings on 3/11 at 7:06AM & 11:08AM.

viewtopic.php?f=2&t=35219

Valve clearance aside, shaving the head will reduce the area of the passage between the cylinder and the valve pockets.

Personally I think I would purchase a high compression cyl head before I would modify the Chevy pistons by adding a dome to them. It may work just fine but I would likely loose sleep worrying about it.

Dave Eddie

In regards to the bolted on piston tops.
Yes I have done it on a first generation Fordson tractor. NO I wouldn’t do it on the engine you are building.
I would certainly consider welding the rods using the approach that Kevin is doing.
I would also consider casting custom pistons. Easy for me to say because I have spent a career doing things like this!!

A member of the Houston MTFCA club says he has shaved high heads .150 with success. Someone on this forum has posted that they have shaved low heads .125, with success. Either way, to see any compression gain, the engine would have to have high compression pistons.