MTFCA Forum

Thinking of installing a Prus head on 24 engine that is stock except for aluminum flat top piston’s - also running a Warford w/ standard gearing at rear. My vehicle is slightly heavier than most, extra power would help on hills but I don’t want to shoot my self in the foot here. Crankshaft & lower end issues ? Head gasket availability also a thought. Any info would be helpful.
Thanks for your help!

Re flat top pistons, do you mean stock or the later V8 type?

Re: flat top pistons…
Aluminum modern piston (350 ci Chevy)

Please excuse my ignorance here.
I know of running 292 ford & Oldsmobile pistons, but have not heard of using 350 chevy's. Do the chevy pistons come out above the deck & how much? Are the tops notched for stock valve clearance? Are these pistons starting you off with a lower compression ratio?
Got a picture with a piston on top dead center?

If the pistons come straight out of the cyl's, you could have some head/gasket clearance issues. Replacement aluminum pistons have a large bevel that makes for good clearance.

The 350 c.i. has a bore of 4.00 inches. The piston size seems extreme for a model t block.
Maybe a 327 Chev piston. 3.875 inch diameter
Or a 265 Chev piston. 3 750 inch diameter.

Art Mirtes

I was told Chevy piston’s… maybe not the case, but they are modern aluminum flat piston’s. Don’t know if the bore diameter has been changed, but I can check it.

I am very pleased with a Waukesha Ricardo head and a mildly advanced Stipe 280 cam

lots of combustion improvement without the pounding that lots of extra compression can give

My mistake in previous posting.
327 cu in 4.00 in diameter.
283 cu in 3.875
265. 3.75.

Art Mirtes

A flat top piston will dramatically lower the compression in a stock bore engine (3.750”). Would probably have to overbore to 4.000” just to correct the compression back to stock (3.75:1). Any mainstream high compression head would be a good addition to this motor, and would doubtfully raise the compression above 5:1. I would not be concerned about hardware failure at this compression ratio, especially with a stock carburetor

I'm running two Prus heads. Both cars have aluminum pistons, Chevy valves. I work them hard here in the mountains and they run strong with no lower end problems. They are a good product.

Thanks for all the replies, I have made up my mind and decided to leave my engine stock. “ Don’t fix it if it ain’t broke “

Assuming you have flat top pistons as discussed, that would increase the combustion chamber volume by nearly 4 cubic inches. The stock compression ratio is 3.75:1, and this additional volume would decrease the ratio to somewhere around 2.9:1. Theory suggests that an engine will not draw sufficient vacuum to operate if below 3:1 compression. A Prus head sized at 5.5:1 compression, would increase your flat top piston engines compression to right around the stock 3.75:1.

Your car’s performance is normal to you, but most likely is not as designed...

Or, he has the "flat top" aluminum piston sold by every supplier for the last 50+ years (not domed/high compression)...I am going to go with that...

I'm with Scott,
The amount of work to fit skinny block cheby pistons and the lack of compression I don't think the term If it isn't broke don't fix it would apply. Unless there is a A crank in the engine. I have seen Y block pistons in a A crank engine but the stroke would make up for the piston only coming up to the top of the block.( Kind of defeats the install of a A crank ) other than the strength of the crank. I would talk to some friends & see if any of them have a bore scope. Pull a plug and look then you will know what pistons you have. As far as the concern about the bottom end there are heads that are not real high compression but will improve low end some when it comes to hills and not stress the bottom end real bad. Keep in mind Ford only made two cranks for the Model T those that have broke & those that will. Bad driving habits break as many cranks as anything else.
Craig.