MTFCA Forum

Working on a custom piston and was looking for suggestion on what is a recommended distance from the top of the top ring to the deck? Thanks

All modern automotive type pistons I've ever seen have around 3/8" above the top ring, probably to give some protection from heat and facilitate keeping some lube available to the ring. Reducing the dimension could improve efficiency, but would most likely place the top ring in a more stressful environment.

I have seen rings go just below the top edge of the deck. I believe my 292 pistons over an A crank rajo head are this way. Not had an issue & the motor has been in operation since the late 60's. Extra heat could be something to consider, but in such a motor, they tend to run rich. I might consider 1 ring width from the top as extra safe.

Antique wide rings can go to the top. I'd be cautious about pushing a modern, narrow ring too near the top.

The block in my Touring had the top deck milled .060" The top ring comes just about even with the deck. Been running that way for 45 years now.

If you are ordering pistons from Ross... I would trust their guidance. They have basic designs on file for both Model T and A pistons, and they are experts in this field.

I ordered pistons from Ross years ago before they had a T piston on file... simply told them to build an A piston with specific bore dimension, pin to deck height, and dome dimensions. They decided the skirt type and ring pack details. Still running strong 10+ years later

Can also depend on who did the machining of the rod bearings, not all have the center to center spot on.

Thanks everyone for the help. The issue I'm facing is that the crank (Model B) has been stroked giving the engine a 4 5/8" stroke, so the new aluminum version of the model T piston will have the top ring pop out above the deck.

Maybe you need short rods and slipper skirts.

henryford2 wrote: ↑

Fri Sep 24, 2021 7:17 am

Thanks everyone for the help. The issue I'm facing is that the crank (Model B) has been stroked giving the engine a 4 5/8" stroke, so the new aluminum version of the model T piston will have the top ring pop out above the deck.

In the day, there were other make pistons used. Olds possibly. 292 ford. My rajo T has 292's. A crank & rods. With the stroke you may be forced to custom made. Does Scat have any input. He is a real friendly resource.

The rod I'm using is 7" the same as the Model T

henryford2 wrote: ↑

Fri Sep 24, 2021 2:35 pm

The rod I'm using is 7" the same as the Model T

Look into the 292. the top is square but can come up from the bore to the top ring. That's how mine fits.
I dont know the exact dimension differences you are working with.