Folks Of Interest HELP

Got a blown 354 Hemi it was a marine engine anyway took it apart to check it (its new to me) while apart re ring ect then hit a problem pistons are flat top Bohnalite part number 1639222 ? cant find a reference anywhere as to what they are please help if you know or point me in the right direction

 

I have no direct knowledge of your pistons but I can tell you that Bohnalite was a firm that did much casting of aluminum BITD, both OEM and aftermarket automotive parts.
The pistons may be nothing more than OEM items, I cannot say for sure, but your mention of a “blown 354” has me wondering. Are you describing a supercharged engine or one that has internal damage?
If doing a re-ring check the bores for excessive taper and also check for wear in the ring grooves using feeler gauges to determine vertical clearance. Too much clearance in the ring lands will kill the rings in short order.

 

you should add "Hemi" to your thread title for more reactions.

 

^^^^. We have hemi experts on here.

 

It might help if you stopped creating a new thread with each thought that you have. Keep it to one thread that way we can respond to all of the issues at once.

 

This won't help you much but interesting none the less

https://theoldmotor.com/?p=67095

 

The page that themoose posted in post 6 pretty well tells the story. That's pretty interesting reading though. I found a crusty set with rusty rods that seemed highly overpriced on Ebay but that only means they made them for a lot of different applications
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Just thinking, depending on the size of the blower and the drive ratio it may or may not be putting out all that much boost and may be more show than go. If it is blower on top rather than blown up that is.

 

Low compression pistons for blown hemis such as blown fuel were measured by "down in the hole". 426 style was out of the hole. So a flat top piston could have been such a piston.

 

It sounds like you already know all you need to know. They are Bohnalite pistons, flat top, the only variable is the deck height. Since Bohnalite was primarily a "rebuilder piston" they are most likely cast. If they are zero deck or .010-.030 down, they are probably stock replacement pistons and are probably close to the stock compression ratio unless the heads have been cut a bunch. What more would you like to know?
The 392 that came in my vintage flatbottom had flat top TRW forged pistons listed at 9:1 in one catalog and 10:1 in another for the same part number. I added a Mooneyham 6-71 at 10% over and never had any problems with pump premium and an octane booster additive.
The old Hemis are pretty forgiving unless you are racing them.