• Welcome to For E Bodies Only !

    We are a community of Plymouth Cuda and Dodge Challenger owners. Join now! Its Free!

340 Piston Selection

B5Mopar

Member
Joined
Oct 14, 2022
Messages
8
Reaction score
1
Location
Kingsport, TN
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.
 

Steve340

Well-Known Member
Joined
Sep 19, 2016
Messages
946
Reaction score
357
Location
New Zealand
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

Member
Joined
Oct 14, 2022
Messages
8
Reaction score
1
Location
Kingsport, TN
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

Well-Known Member
Joined
Sep 19, 2016
Messages
946
Reaction score
357
Location
New Zealand
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

Member
Joined
Oct 14, 2022
Messages
8
Reaction score
1
Location
Kingsport, TN
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

Well-Known Member
Joined
Dec 28, 2008
Messages
4,524
Reaction score
2,159
Location
Panama
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

Member
Joined
Jun 23, 2021
Messages
23
Reaction score
4
Location
Mount Albert, Ontario, Canada
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

Member
Joined
May 9, 2011
Messages
8
Reaction score
0
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

Member
Joined
Oct 14, 2022
Messages
8
Reaction score
1
Location
Kingsport, TN
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.
 
Back
Top