340 High Compression Pistons

-
70sublime340 said:
My machinist recommended the high compression with an aggressive cam profile to achieve the 450hp were looking for without using a stroker kit. I know it makes more sense to stroke it and use different heads but I want to keep the stockish head outward appearance. We're aiming for more of an old school type build. Looking at the mopar muscle 340 build I don't think 450hp is out of line with the right combination
Click to expand...


It sounds like the engine builder is on the right track. I'm running 11.08:1 on pump gas with iron heads.

It can be done.
 
70sublime340 said:
Yellow...that's exactly what we're after. What's your combination?
Click to expand...

I just used a production 340 head and did the port work to it and a new valve job I want to try on the street. I think it's reliable. Most don't. I would have to pull the engine file and look at the head CC's but IIRC they were 73. I used the TRW L2322 piston and milled the dome down until I had about a net 6 CC dome, IIRC.

The cam is a custom Racer Brown grind that Jim and I talked about for a long time. I'll post the grind number later but it's 255/255 @ .050 and 283/283 at lash. .620/.620 gross lift. It lashes at .014/.018 hot. It's ground on a 105 LSA and installed at 105. There is a start up video on line somewhere. Damn if I know how to find it.
 
Sounds very similar to what we were talking about. Machinist was talking around a ..550-.600 cam and the lax heads from Hughes have a port job done to them. Did you run a factory rod and crank? I have a fresh 70 steel crank and am going to run a Manley or scat connecting rod. Car is also 4 speed with billet flywheel short tires and 3.55. How do you like the trw slugs? I've been told they're bullet proof just really heavy
 
70sublime340 said:
Sounds very similar to what we were talking about. Machinist was talking around a ..550-.600 cam and the lax heads from Hughes have a port job done to them. Did you run a factory rod and crank? I have a fresh 70 steel crank and am going to run a Manley or scat connecting rod. Car is also 4 speed with billet flywheel short tires and 3.55. How do you like the trw slugs? I've been told they're bullet proof just really heavy
Click to expand...

Factory crank, scat rod. The Pistons are a bit heavy but I don't get my nuts out of joint on Bob weight like I used to. Not a big fan of your flywheel unless you mean billet aluminum and not steel. Steel will just beat the tire up.

Run a good damper. I used a Fluidamper on mine, but if you fear the rumors, use an Innovaters West and your crank will love you for it.

Your on the right track. As much lift as you can squeeze in there. I wanted to net .600 and made it. The W2 heads I have I want to net .750 but that's down the road a bit.
 
yellow rose said:
Factory crank, scat rod. The Pistons are a bit heavy but I don't get my nuts out of joint on Bob weight like I used to. Not a big fan of your flywheel unless you mean billet aluminum and not steel. Steel will just beat the tire up.

Run a good damper. I used a Fluidamper on mine, but if you fear the rumors, use an Innovaters West and your crank will love you for it.

Your on the right track. As much lift as you can squeeze in there. I wanted to net .600 and made it. The W2 heads I have I want to net .750 but that's down the road a bit.
Click to expand...


Edit: you will also want to contact B3 racing engines. Give him some simple measurements and he will hook you up with the CORRECT shims to correct your rocker arm geometry. There is no other way to do it, that I know of, except to mill the rocker stands off and use blocks. That is a giant PITA when you can buy the shims from B3. And they won't bust the stands off like the cheap little shims other people sell.
 
Last edited:
Correct, billet ALUMINIM not steel. And thanks for the tip on the rockers, I haven't thought that far ahead. I know big lift usually is a bear when it comes to he geometry. What rockers are you using? And which scat rod?
 
70sublime340 said:
Correct, billet ALUMINIM not steel. And thanks for the tip on the rockers, I haven't thought that far ahead. I know big lift usually is a bear when it comes to he geometry. What rockers are you using? And which scat rod?
Click to expand...

4340 H beam
PRW stainless 1.6 rockers
 
dodgedude said:
I have an NOS TRW set. .030, never ran. $400 shipped. The tops have been slightly flycut for valve clearance, but the dome is untouched. They will still be around 11.5:1 compression with

factory J or X heads. I probably wont ever use them. Let me know if you want some pictures. Thanks
Click to expand...

U still have pistons
 
70sublime340 said:
Can anyone direct me to a 34 piston in the 11-12:1 range? Prefer domed, I have looked and can't come up with anything besides sets that are $1500 or custom made. Thanks!!
Click to expand...

I know your pain Im going thru the same dilemma I
if u 30 over I have a good part # for ya !!!
My 69 model block needs to be bored to 4.080 and options are thin for 40 over in high compression.
 
1Badcolt said:
I know your pain Im going thru the same dilemma I
if u 30 over I have a good part # for ya !!!
My 69 model block needs to be bored to 4.080 and options are thin for 40 over in high compression.
Click to expand...


You can buy a TRW piston with a dome on it that you can cut down and set the compression where you want it. I can't think of the part number now but I used them in my last build. The weight means little to me.
 
speed pro 7035...

not sure if they are still available...do not remember them being available with a 4.080 bore
 
I wish my block was 30 over these are sweet and almost 12.1 just what I wanted !!

Screenshot_2018-07-04-11-28-31.png
 
why fart around ? spend the money on a set of custom pistons. it's only money !
A 340 in a Henry J screams 8000 rpm all day. get it to rev and quickly.
 
...watching. I posted about my hydraulic lock issue that has turned into a broken 340x head issue. It has the trw 12.6:1 pistons also. Not a stroker and dyno'd 450+. When I pull the heads this weekend, I'll probably find myself in the same boat needing a new 340x head and pistons. If I can't find replacements for both I'll be chasing a new high compression piston / high flowing head combo and needing the same help finding something fairly straight forward to use. The indys and eddys were my first thoughts too because the magnums won't fit my intake and TTI headers.
 
dont think they would be close chamber for more than a stroke or two...
 
fishmens67 said:
why fart around ? spend the money on a set of custom pistons. it's only money !
A 340 in a Henry J screams 8000 rpm all day. get it to rev and quickly.
Click to expand...
Odering custom set net week from Cambell performance they have responded to every email I sent unlike some other piston manufacturers.
 
You must log in or register to reply here.
-

Back
Top