Another oddity...the upper main cap from a 1961 Plymouth aluminum block Slant Six.
Most engines back then had a lower cap only, but these sat above the crank and let you avoid having to try to directly seat the bearing shell in an aluminum block.
In any case, a guy wants me to consider making him some out of steel (these are also steel as best I can tell).
I can figure it all out easily except for the top OD 'curve'. It's a machined finish made to a tight tolerance, just like the ID. The ID I can cut in a lathe. But the top's shoulder prevent me from making it in a lathe...so how did they make this in 1961? I've looked for tooling marks and there are very few. The few I do see suggest they used a shaper but I'm not sure on that. Could a shaper cut this profile? I'd guess they'd need to have some sort of holding fixture that allowed the cap to be clocked around a little bit per pass?
Most engines back then had a lower cap only, but these sat above the crank and let you avoid having to try to directly seat the bearing shell in an aluminum block.
In any case, a guy wants me to consider making him some out of steel (these are also steel as best I can tell).
I can figure it all out easily except for the top OD 'curve'. It's a machined finish made to a tight tolerance, just like the ID. The ID I can cut in a lathe. But the top's shoulder prevent me from making it in a lathe...so how did they make this in 1961? I've looked for tooling marks and there are very few. The few I do see suggest they used a shaper but I'm not sure on that. Could a shaper cut this profile? I'd guess they'd need to have some sort of holding fixture that allowed the cap to be clocked around a little bit per pass?