Olds flathead 6s

[B442adams]

I have a 28 coupe. My question is, what are the physical differences in olds flathead 6s from the 20s to the 40s era... if i decide to swap out my original motor to preserve it, will 215, 230, 238 etc be a direct bolt in or are there major differences between them? Thanks

[Rusty_OToole]

I wouldn't worry about it. Keep the original engine in good shape and it will outlast you. If not in good shape, rebuild the original.

[Graham Man]

If your oil pressure is good, I would drive it.   My 1928 runs like a top, engine has not been rebuilt, well in the last 50 years.  The last owner did plastic gauge the bearings, all checked good.

[Rusty_OToole]

Yes check your oil pressure and do a compression test, do not be too shocked if they are low, many engines back then did not have much oil pressure or compression to begin with. Maybe some Olds experts can tell us the recommended oil pressure and compression.

[nzcarnerd]

The compression ratio is probably not more than 5:1 - might even be less. Don't expect to see a compression pressure figure of more than 70 psi.

[chistech]

What I have found is Olds used two different Babbitt compounds in their engines at least in 31-32. While original mains have held up well, the original rod bearings have been a different story. The rod bearings have just crumbled when pulling the caps off. Simply go through you motor and use it. My 32 cost less than $4k for a rebuild including custom pistons. Unless you already have another motor, finding an appropriate one to use would probably be hard.

[chistech]

Forgot to mention, not sure of your engine but my 32’ is fully pressurized by gear pump and includes rifle drilled rods to pump oil to the wrist pins. That motor runs a steady 30 psi even when at temp. Compression ratio is at the 5 to 5.5 side in original configuration. After a modern rebuild one can expect a difference.