Anybody recognize this style of pistons? I know the are 4" bore X 1.80" CompHt with full floating .927 pin bores. I think they are old Jahns. I need the 8 pins. Or source to get them. The pin length is 3.50" which is a rare length. Thanks
If they are Jahns the name will be cast in the skirt next to a pin boss, and also the underside of the crown will have a waffle pattern. What is the plan for this engine? Cast Jahns will be heavy, need a lot of clearance ( like .006-.008) and the first and second rings are 5/64 with a 3/16 oil ring. The big factor is the domes, you will have a high compression ratio. Lots of piston to wall clearance makes oil control more difficult and the weight makes the engine a bit less responsive. 5/64 rings are definitely available but if this is a performance build the thinner the ring the better. AHotRod gave a good lead for pins but you might consider aluminum buttons and no pin locks.
There is a trick you can do with solid skirt pistons. Fit to the recommended clearance then knurl them to prevent piston slap.
Venolia? That dingle in the top center of the dome and the reinforcing rib in the skirt means it is probably pressure cast and a good (if not heavy) piston.
Weird. I've seen some older Venolia pistons but they've always had the full name on the underside of the piston. Treb11 is the best guess so far ... Maybe newer than the older Venolia that I've seen ??
FWIW Venolia started making pistons in 1946, but their first forgings date to 1963. Could be Venolia’s but it doesn’t matter, they are heavy and high compression, dated for a performance application and of no use on the street. If the domes are not hollow they could be machined for lower compression but they will still need a lot of clearance.
X3 - piston and ring science has improved so much in the past few years, only run very old stock if you're flat broke and would be taking food out of your children's mouths to buy current production. jack vines
That reinforcing rib means it is cast, there is no way a forging die could get underneath that. If you want to be cheap, just use standard Chevy pins with press fit rods to locate them. [ OEM Chevy 265/283 wristpins are 3.1" long which will keep it .450" away from the cylinder walls]
There are a lot lighter pistons available today with thinner rings. They work though, I had a pretty stout 57 Corvette with a 301 with pistons like that in the 60s but but its yesterdays technology. They need like .006-.008 clearance and will sound like the pistons are swapping holes
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