Thread: pistons 3.480 or 3.750

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does it really matter what if you buy pistons for a 383 that are for a stroke of 3.480 but still have the same bore diameter?

what is your current stroke?

I'm not a chebbie guy, but I would imagine the pin location is going to be different.... Not sure, Eric will know, he builds a bunch of them.

Originally Posted by #1firebird

does it really matter what if you buy pistons for a 383 that are for a stroke of 3.480 but still have the same bore diameter?

You need to look at the compression distance.
You may find pistons that have the same compression distance but they will also have different rod lengths.

well my current stroke is 3.480 and want to stroke it out to a 383 but want to know if i can use my same pistons

Think about it....

Your current stroke is 3.48 (standard 350 chev stroke)
You want to change the crankshaft to a 3.75 stroke

This means that the piston will travel 3.75 - 3.48 = 0.270
further; half of it up and half of it down. SO 0.270 divided
by 2 equals 0.135 which is how much further up your existing
piston would travel.....you aint got room at the top for this!!!

So...you must either get a shorter rod (mucho expensive) or
buy new pistons for the stroker.....buy a stroker kit which
includes the crankshaft and the pistons matched for the application.
You'll be better off in the long run than trying to piece together
a mismatch of parts.

mike in tucson

yeah i didnt know what the difference was thats why i asked

Oh well,,,,, Hey Bird, if it was cheap and easy then everybody would have a fast car, right???? Situations like this separate Hot Rods from "Normal" cars!!!!!

Some of the early KB 383 pistons were the same part number as their 350 pistons using the shorter 400 5.45 rods.
the difference in stroke is the same as the difference in rod length.

I used a set of their 383 pistons in my sons 350.

You can use stock 350 pistons in a 383 if you use 400 rods. The pin height is the same on 400 and 350 pistons. The 400 rods are shorter to compensate. Also, the rod bolts are countersunk on the 400 rods to help eliminate bolt to cam clearance issues.

The 383 in my 46 was built this way. It went together almost as easy as a stock engine. the only clearance problems was on the bottom of the piston skirt, none in the block.

If you're not going for high RPM's the short rods do OK. I had ARP rod bolts installed just for a little extra strength. I have my rev limiter set a 6000.

Mike

well yeah i would like to achieve high 6's to low 7 thou. rpm. now when building this mtr i would like to run about 11.5:1 comp would cast pistons and stock 350 crank work ok or should i get some hypereutic's and forged crank? also how would stock rods work in something like this.

but in other words the 350 pistons and 383 pistons are the same

Ok, now I'm confused. Didn't you say you wanted to make your 350 into a 383? If so you will need a 400 crank.

If you are asking whether stock 350 cast pistons and a cast crank will take 6K rpm. Yes they will. Stock car claimer motors were all built with cast internals.

Most of us have wanged cast pistons way farther than the factory ever intended.

I have blown up my share of engines but I have never broken a cast crank. I have spit stock rods out the side of blocks, burned holes in cast pistons, but never have seen a cast crank "broken".

right well i do but dont want to convert it. i just kinda wanted to know what the most a stock bottom end can take and if the 350 pistons will work in a 383

I think I should add that my cam and intake combo is all done by 5500. Really noses over about 5300. I don't think it's ever seen then high side of 5500.

If you want to run over 6000 I think you would better off with the longer 350 rods.

Just my 2 cents.

Mike

like 6in rods