Thomas Aquinas

iTrader: (14)

Alright, I hope someone can clear this up for me. I have been looking around for used parts to start my 383 and I came across someone selling new cola cranks. He is selling one that is designed for the new GM 383 shortblock with a 3.800" stroke. What's going on here? I was under the impression that 383's used 3.750" stroke? I know I'm right there. So I went to Scoggin-Dickey's site and sure enough they list the new 383 shortblock as having a 3.800" stroke. So now I kinda have raised my eyebrows.

How are they doing this on a typical 9.025" deck height? Are they still keeping the piston 0.025" down the bore? More importantly the block? What kind of clearances issues are there?

Could one use that crank, 5.7 or 6.0 in rods, with corresponding pistons and not have to deck the block??

What would this do to power numbers?

Would this be something to look into?

Thanks guys
-Brent

MrDude_1

4.000"x3.750 = 3.77

4.030"x3.750 = 382.7 aka a 383

4.000"x3.800= 382

so you could leave the bores stock, and just drop a 3.800" stroke in there and get somthing close enough to call and sell as a 383.

Thomas Aquinas

iTrader: (14)

Thanks Mr. Dude,

They probably went that route, but wouldn't they need to clearance the bottom of the bores for the bigger stroke?

Here is the link:
383 shortblock

I guess I'm still wondering about the rod length and piston comp. height, so that the stack up will work out?

If my calc. are right, it works on to be an extra 5.1 ci. ? I wonder if that is even worth trying?

-Brent

Thomas Aquinas

iTrader: (14)

Sorry, that number was worked out with a 4.030" bore.

Kandied91z

iTrader: (7)

my gm 383 from Sd that was ruined by tpis was measured off the crank rather then a bore....had alot of work to do when i modified it to a 388.

Thomas Aquinas

iTrader: (14)

Kandied -

So you are running the new 383? Are you saying you used that crank (3.800") and there was lots of work to make it fit with usual 383 bores, rods and pistons. What was your final deck height on the block?

I'm wonding if using that crank with typical 383 rods and pistons and not decking the block, would work? So you have the typical bore of 4.030" but the stroker crank of 3.800" and keeping the deck height at 9.025"?

Thanks

MrDude_1

care to elaborate?

CamaroMike

MR. Dude,

Improper fuel table cause fuel wash of the rings. See Kandied I do pay attention.

Kandied91z

iTrader: (7)

lol.......yeah you do, thanks for making it easy for me.




i "was" running gm's crate 383 from SD but it was ruined. so the only thing i was able to save was the crank. picked up a truck 350 block and turned it into a 388. the odd thing with the gm parts was the crank really determined the c.i unlike most things where there are other factors.

guy1138

The new factory GM 383 motor is a longer stroke smaller bore engine than the typical .30 over 350 w/ a 400 crank. This was so they could use stanard bore small blocks, and get the same cubes for less $$. The motor was originally designed as a truck motor, which explains the long stroke. It'll give you better torque down low for towing with highway size gears in.

However, the deep cylinders have filling problems at high RPM unless you've got a really free flowing induction system.

Generally, conventional hotrodder wisdom says that bore is better for horsepower than stroke, but stroke is better for low end torque, but like previously mentioned, it'll run out of gas on the top end. This is why with similar big block and small block 396 cu motors, the big block will spank the small block. It's got bigger cylinders. Please nobody start a whole small block is better than big block flame. Yes, SBCs can make awsome power with high comp aluminum heads, roller valve train, huge cam, etc. and be lighter by a lot than a big block (unless it's a Caddy BB, but I won't even get into that), but big blocks make easy, streetable power.

This is all rule of thumb stuff of course.