MOPAROFFICIAL
Oogliboogli
I have two sets of trw 4.070.
I don't think I'll ever run them again.
I don't think I'll ever run them again.
Best piston for street/strip 340?
- Thread starter Captainkirk
- Start date
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Captainkirk
Old School Mopar Warrior
Man, what a bunch of buzzkills...
Seems no matter what I do, somebody's gonna clean my clock over it...
This car...and the motor...are only slightly "less older" than me. I don't give a rat's *** if the motor is noisy. Not gonna hear it over the exhaust anyway. If it moves anything like it did 40 years ago I'm gonna be a happy camper. I'll let my descendants worry about the latest and greatest mods after I'm gone. Me; I just want to hear it run again.
mderoy340
Well-Known Member
Here's an option from SRP.
I don't know your budget but build what you want. To many of these cars sit in garages as pipe dreams. I'm using the heavy slugs, eagle forged crank and I beam rods. My rev limit is 6400 and I shift at 6000 with no issues.
I won't use a hyper piston. I dropped an exhaust valve on my 360 magnum and when the piston shattered the motor was toast; wrist pin punched 2 holes in the cylinder.
Here's an option from SRP.
SRP 142068 Forged Flat Top Pistons 4.070 Bore
I don't know your budget but build what you want. To many of these cars sit in garages as pipe dreams. I'm using the heavy slugs, eagle forged crank and I beam rods. My rev limit is 6400 and I shift at 6000 with no issues.
I won't use a hyper piston. I dropped an exhaust valve on my 360 magnum and when the piston shattered the motor was toast; wrist pin punched 2 holes in the cylinder.
Here's an option from SRP.
SRP 142068 Forged Flat Top Pistons 4.070 Bore
MOPAROFFICIAL
Oogliboogli
Nah, not really. I personally think you got scared or the machinist over horror stories of hyper pistons.... So you go with heavier cheaper of the bunch forged pistons like it was 1978. I have those pistons too, on a shelf hung on rods...4 brows.
I don't really care, they might make a little noise cold...oh well...its just me giving you gas over using an old *** heavier piston.
I mean hey.... lets point out for such a simple mild build...theres much worry over piston strength etc... unnecessarily considered.imo
Captainkirk
Old School Mopar Warrior
I heard the horror stories on the 'net...many of them here, actually. I discussed it with my machinist and he confirmed he had experienced the same issues on engines he had built for people several years back. This guy knows how to gap rings and read directions, trust me. He actually tried to steer me toward Ross pistons but they were a bit too pricey for me for a street motor. The SP's fit nicely in my budget and albeit "heavy", are forged and tough as nails. This car is nearly 50 years old and left the assembly line when Nixon was in the White House. I don't see the need to re-invent the wheel; other than fuel concerns (octane vs compression, which I have addressed) and valve issues (hardened seats, etc, which I will address when I do the heads); has that much really changed? 12 seconds is still 12 seconds whether it's today or 4 decades ago and it really doesn't matter to me how I get there, the cheapest route is the best. I don't intend to race this thing, it's for my own jollies and maybe a car show or two.
I see nothing wrong with using a hyper KB if you've had success with them (you obviously have) and want to shave every second off the ET you can. It's not that important to me. I'd prefer to have a bulletproof bottom end and never have to tear it down again; that's what I'm shooting for. I think I made the right choice based on those facts.
QuickDart360
Well-Known Member
I have kb pistons in a 360. They have been terrific!! Just follow the ring gap instructions. The ring gap for top ring is very important!! Mine have been in the motor for 8 1/2 years now. Some abuse from time to time. Still going.
Piston failures with the KB pistons are pretty much always from incorrect ring gaps. People simply will NOT follow instructions.
Bighead440
Well-Known Member
A little off topic, but when a friend wanted his '70 Challenger 340 convertible rebuilt, we found '72-up 340 replacement TRW forged (8.5:1) inside with the X-heads, which was really holding it back. The deck clearance was close to zero, so we did a Magnum conversion on it to get the compression up and get some better flow (velocity). He said it felt like it gained 100hp-LOL-but regardless, we did get some quench. Another buddy has a '69 340 Dart running the positive-deck KB hypers with "J" heads and has countless trouble free miles. I have run the KB-107s in 360s and some BB KB's with good results, so I wouldn't hesitate to run them in a 340. FOLLOW THE RING GAP INSTRUCTIONS!!
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NC Engine Builder
Grumpy Old Man
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For all the original posters endless over thinking, he should have just bought some cast replacement stockers.
Captainkirk
Old School Mopar Warrior
Overthinking? Really?
I asked for some suggestions then chose what sounded best for my application.
Next time I'll flip a coin.
I asked for some suggestions then chose what sounded best for my application.
Next time I'll flip a coin.
Forged pistons have worked great for what.......60 plus years? I think you did fine.
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