340/422 clearances?

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wigsplitter74

wigsplitter74

The Mopar Kid
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So I've got a 70 340 block that was at .030 and needs to go .060 it was kinda hard finding decent pistons at the 4.1" bore so my machinist and I got to talking and I'm thinking a scat 4" cast stroker kit will do just fine, my rods are good bushed stockers and it should end up with 9.5:1 Diamond forged pistons. IDK anyone personally that's stroked an LA that I can ask so here I am to learn what some of you had to grind away inside to make room for the 4" crank? Thanks much, I'm just shootin for 11's here and maybe a 125hp boost later on 8)
 
as far as i know the LA's handle the 4" crank without any clearancing at all, atleast thats what i thought...is this 340 going in your duster? should be a blast if it is!
 
You don't need to clearance for the crank..but if you go with h-beam rods you need to clearance for them,I-beams you do not..60 over deffinately have that block sonic checked..
 
mshred said:
as far as i know the LA's handle the 4" crank without any clearancing at all, atleast thats what i thought...is this 340 going in your duster? should be a blast if it is!
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Yes, it is 8) I'm pretty excited to start on it and hopefully charge somewhere into the 11's. Hearing a tech guy say "nope, not til it has a roll bar" would be music to my ears lol

stroked 340 said:
You don't need to clearance for the crank..but if you go with h-beam rods you need to clearance for them,I-beams you do not..60 over deffinately have that block sonic checked..
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That's just been taken care of and this puppy is crazy thick even at the current bore.
 
You will need to clearance the bores for the stock rods. Not much, but a bit.
 
A .060 over 340 block is not a good foundation for a built stroker + a 125 shot . Find yourself a decent 360 block that is good at .020-.030 over. Thicker walls = less flex and the 360 has more piston choices.
 
what did it sonic check at?
Did you have it done in Wisconsin? Sure took me a while to find someone around here (SE Wi) that has a sonic checker!
 
Actually .060 over is no big deal, providing the block was actually sonic tested. I've done a couple that way and their fine... But I ended up sleeving at least one hole on each build due to thin walls somewhere.
 
wigsplitter74 said:
So I've got a 70 340 block that was at .030 and needs to go .060 it was kinda hard finding decent pistons at the 4.1" bore so my machinist and I got to talking and I'm thinking a scat 4" cast stroker kit will do just fine, my rods are good bushed stockers and it should end up with 9.5:1 Diamond forged pistons. IDK anyone personally that's stroked an LA that I can ask so here I am to learn what some of you had to grind away inside to make room for the 4" crank? Thanks much, I'm just shootin for 11's here and maybe a 125hp boost later on 8)
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I had a 425W5 motor and I had to grind not much for rod clearance.If you have an old 340 crank and rods so you can mark where the rod bolts on the bottom of the cylinder walls and just grind about .100-.125.

IMG_0443.JPG


IMG_0441.JPG
 
It'sa little more than what is shown. A little wider and deeper for the factory rods and nuts.

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stroked 340 said:
On my 416 the block DID NOT need to be clearanced...:-D
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all depends on the rods...........

scat/eagle I beams no clearance required...

anyones H rods...clearance needed...

stock rods....clearance needed...

BUT check any rod used before you go to bed at night....
 
if your shooting for mid to low 11's and a 125hp boost down the road i would seriously think about dumping another $400 into your engine and going to a forged crank, and maybe another few $$ for better rods.
 
kielbasa said:
what did it sonic check at?
Did you have it done in Wisconsin? Sure took me a while to find someone around here (SE Wi) that has a sonic checker!
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I apologize, but I can't remeber what the results were off the top of my head, I just remember my machinist being impressed by how thick it was, so that's probably a good sign. My friend/machinist actually just bought the equipment a couple days after I handed over the block, so it's new to the area I guess.
 
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