Model A engine overbore 125+?

[colin1928]

Rich as others have said 4.000 is fine it will come down to how much and have large you pitting is at that size
a rule my old boss taught me was the width of the compression rings should be double any pit or mark in a bore

 

[TerryNJ]

Those are my calculations! I would never say they're gospel. I've been wrong about too many things lately (Gettin' old) But that what I came up with.
Terry

Thanks Terry

215cu, great!
I did calculate it to roughly 207 or 8 but more use to working in the metric system.
We changed to metric for everything in between 1970 to 1975, they were still teaching imperial measurements in my first year in school in 75 then changed mid year to full metric.
I don't remember it but my parents reminded me of it years later.

 

[31Tudor]

I have run .125 bored block in a car for about 8,000 miles. Run it in 90 degree heat, long runs, and mountains. I have never had an overheating issue. The cylinder bore will not be the reason for overheating.

 

[George Miller]

Thanks everyone, all good advice.
Thinking I will just have it taken to .125 for now and not worry about a few pits left behind.
I guess the small pits left behind will just fill up with carbon with use.
I also like the idea of forged pistons too, don't know if I can purchase as sets of 4?
This engine will be running a performance high torque regrind cam but non counterbalanced crank (early beaver tail style)
Full insert, standard oiling system.

I hope your crank grinder puts the right radius on the journals when he grinds the crank.

I would not worry about the pits to much. Of course we would rather not have them, but they should not be a problem.

 

[Richie R]

I hope your crank grinder puts the right radius on the journals when he grinds the crank.

I would not worry about the pits to much. Of course we would rather not have them, but they should not be a problem.

Hi George
The machinist I have this engine with is highly regarded in early engine rebuilds, but this will be his first insert Model A engine he has done.

Any advice on crank radius angles advice? I have read many stories of crank failure due to incorrect radius but nothing on the best way to finish it.

I will be doing all the rotational assy

 

[TerryNJ]

My exact calculations with a machine are 2 squared X 3.141 =53.407 X 4 (Cyls) = 213.628 Cubic Inches or for shorthand, 214 Cu.In, Not 215 as I said
4" Bore = 2.000 R 2 X 3.141 = !2.566 X 4.250 Stroke. The old rule of thumb is that for every percent of displacement increase (214-200 = 7%) the HP goes up by and equal amount. Is this wrong? Our bigger bored engines are about 3 more HP than a stock bore.
Terry