340 pistons

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KB9GIB

KB9GIB

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Looking to see if anyone can tell me anything about these pistons I don’t see a name on them. Would they work for a street motor on pump gas going to use a set of cast iron heads from Indy cylinder head. Thanks for all your help. KB9GIB southern Illinois

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Sealed Power I believe 13:1 pistons, not for a a street engine build! Google search the number...
 
Look to be high compression 0.030 over. Definitely, not for a street build! 65'
 
I don't know those pistons exactly but looking at the design and size of the dome, a no go for a street motor, I find the minute any piston starts having a dome you start being in 12+ on compression (yes exceptions when piston is left in the hole or big chamber heads) if I had to make an assumption those are 13 or more just based on design. There is no hard fast rule for street compression limits but for all street most will stick with 9.5 as a safe number, can go higher (or Less) based a any number of factors (heads, quench, tune, fuel, etc.). These are likely high compression pistons with fairly large chamber heads. I am sure others may have more knowledge about that exact piston.
 
If financially feasible, I would cut the domes off to make it a true flattop. Those domes may have been cut down already. Yours look like something I had done years ago. That will bring compression down to a more reasonable level and save some weight. Speed Pro and TRW made some pretty heavy pistons. Couldn't hurt to take a little weight out underneath as well. Mopar use to sell similar units with their own P-# for 340s & 360s. I've seen all 3 brands "advertised" at anything from 11.5-1 to 13-1 with the full dome.

If you can't get a deal on machining, a different set might be worth considering.
 
the big issue is what is the pin height compared to stock piston you can change compression by lowering pin height witch raises piston in the bore I did that by using Chevy piston but the pin height was 30th lower witch raised the piston by that much in the bore raising compression and were a lot cheaper than dodge talk to you local machine shop
 
I wouldn't cut them down, they are not made anymore and could be valuable to someone who needs them. In fact, the ONLY bigger bore pistons you can get nowadays are of the hypereutectic variety.
 
if you were closer I would do it for free . I did a set for myself in 96 and they are still running . mine were 12.5 to 1 trw they are boat anchors by todays pistons but darn near indestructible .
 
Those are Speed Pro 7035P forged pistons. I would not run those on the street unless you want to buy racing gas.
The indy cast iron heads aka Indy LA-X heads are close chambers and would not work with these pistons.

As said they weight a ton, I have a set in a 340 that was cut down, still weighted a ton...
Compression height is going be around 1.82-1.84.
Actually ran a set in a 340 for many years on the drag strip until the STOCK connecting rod got tired of swing that heavy chunk of aluminum and broke.

340 MOPAR CHRYSLER DOME FORGED PISTONS L2322F STANDARD BORE SET OF 8 NOS | eBay

similar pistons for sale on ebay...shows the compression ratio with various head cc...
 
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I use a set that's been trimmed 3 times over the years as fuel got worse. They started at 13/1, down to about 10.5 now, still running today..
 
inertia said:
I use a set that's been trimmed 3 times over the years as fuel got worse. They started at 13/1, down to about 10.5 now, still running today..
Click to expand...
Thanks for all your help I will just put them on the shelf and look for some flat tops. Thanks KB9GIB. Southern Illinois
 
with domes removed they weigh 610 grams-not heavy for a 340 piston. and they are the good 1/16" top and second rings. if u can get the domes machined off for a decent cost run them, I do. and forget chevy pistons-they are only fair with a small cam cuz valve notch locations are different
 
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