340 Piston Selection

[B5Mopar]

Working on a stock stroke 340 with factory iron heads. Does anyone know of a piston with an above deck quench pad (around 0.100" above deck) that will give around a 10:1 compression? Bore is 4.07 or 4.08. Lots of piston options out there for aftermarket closed chamber aluminum heads, but I want to stay with the stock head.

 

[Chryco Psycho]

Check with Diamond

 

[Steve340]

You are asking for pistons that have a positive deck height of 100 thousands?
Is this a mistake I think you mean 10 thousands.
I think Keith Black are positive 18 thousands (0.018")
I believe they are the only one with off the shelf positive flat top piston.

 

[B5Mopar]

I probably wasn't specific enough. The 100 thousandths area is only on the quench pad area. Icon Pistons call it a step dish style piston. The quench area on 340/360 heads is about 0.100" deep, so with a 0.040 gasket, the quench distance would be about right. The rest of the piston would need to be zero deck or slightly dished to get the compression right.

 

[Steve340]

OK sounds like Icon might be the way to go for you. I know they are made by KB but I have never heard of "step dish style"
Good info I will take a look when I get a chance - sounds interesting.

 

[B5Mopar]

Look at page 3 of the ICON Premium catalog. Problem is, I don't know that they make them for Mopar. Probably custom. I am hoping someone knows of a stock/standard option. This topic has been discussed (somewhat) in prior threads about welding up the quench pad to get it down to deck height, or milling 0.100" off the heads. Both of those options have real downsides.

Catalogs | UEM Pistons

 

[Chryco Psycho]

Probably need to have them custom made , often it is not much more though , I know Diamond specializes in Mopar , Others can custom make them also.
2 other points stay away from Hyperutectic , pay a bit more & get forged .
If you are doing custom pistons you might want to add the stroker crank to 412 CI .

 

[Monty's 340]

Look into the Speed Pro L2316F 30 pistons from Summit, based on the older TRW forged pistons, Ran them in my Challenger with Iron heads with excellent results. Still using them in the motor I am currently building. Old school rings at 5/64 to and second ring. Good solid piston, available off the shelf.

 

[mrbill426]

I installed a set of those Speed Pros and after doing all the measurements (CCs etc) with stock '72 J heads I came in right at 9.5 to 1 using a Fel Pro gasket.

 

[B5Mopar]

Thanks for the responses. The TRW/Speed Pro has been a good 340 piston for years. That's the same piston that's been in my engine since the mid 80s. I'm hoping to achieve a couple of other benefits from a different piston. First, weight savings. My current pistons + pin + rings weigh in at 943 grams. That's pretty heavy for today's standards. The other objective is to create a proper quench dimension (around 0.040") with a quench 'dome' on the piston. That's the small section that woud have to come about 0.100" above deck.

I talked with Diamond and they were very knowledgeable about this situation. They have made custom pistons like this for a 383, but not a 340. Really easy company to communicate with. I may just have to go the custom route.

 

[B5Mopar]

My mistake. My pistons are Sealed Power 233P. May be the same thing as the TRW?