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69projectKAOS
02-14-2011, 07:17 AM
im trying to order a flywheel that will mate my lt1 t56 to my pre-85 sbc ( 2 piece seal) but now the question is , how do i tell if my crank is a 400 or regular 350 crank. my dad says that the guy who built the engine about 2 years ago said it was a 383, but from what i can remeber he said it was a 355. i checked the receipt from the motor build and called the builder but the said it was too long ago and cant remember. i need to order this flywheel in order to get my transmission in and dont want to buy the wrong one. are there any things that will tell me the difference between a 400 and standard 350 crank without opening the motor up?

gEtyOpAPiOn
02-14-2011, 11:59 PM
does it matter on the stroke ? all it matters is how far out is the flange

MarkM66
02-15-2011, 07:04 AM
does it matter on the stroke ? all it matters is how far out is the flange

I think he just needs to know if it's internally or externally balanced.

MarkM66
02-15-2011, 07:07 AM
I don't know if there's a difference in external aesthetics of the cranks.

Is there a damper on the engine?

I would ask over on chevelles.com .

69projectKAOS
02-15-2011, 07:29 AM
from what i have read and been told is, that if there is a counter weight on my flexplate them my crank is ext. balanced and if there isnt a counter weight it in int. balanced. the question is, is there any marking or signs that i can look for when i get my auto tranny out to tell if i have a stock 350 crank or 400 crank without opening up the motor!? -Dom

JRComp
02-15-2011, 09:00 AM
The only way you will be able to tell without removing the oil pan is to look at the flywheel or damper. If it's a 383 using a 400 crankshaft, then most likely you will have an external weight on the flywheel. If it was built with an aftermarket 383 crankshaft, it could have been balanced either way. Take a look at the flywheel, it should have an external weight on it.

MonzaRacer
02-15-2011, 08:46 PM
ok big issue is if it was rebalanced for internal balance or is still external. if its a running engine and has the balancer on it look at the outside diameter of it, a stock 400 balancer will have a cast in space about 1/3 of the way around rather than being smooth all the way around, if the cast in area is on balancer you will need a flywheel for a 400sbc 2pc rear main for the appropriate starter, ie 153 tooth small diameter uses the straight bolt pattern and the 168 larger diameter flywheel will take a staggered or even a 3 bolt pattern starter. if you need a slim starter the autozone number is a DLG9990S and it is the exterior through bolt design, and you will need to go to GM dealer for bolts, ask for bolts for 94 k2500 350 eng. as this starter does take different bolts.
Oh yeah there is a counter balance on flexplate for a 400 over a 350, the crank flange is different if I remember correctly if a stock GM crank.
But I cant actually recall, Ill try to pull out a couple of cores.

69projectKAOS
02-15-2011, 09:11 PM
The only way you will be able to tell without removing the oil pan is to look at the flywheel or damper. If it's a 383 using a 400 crankshaft, then most likely you will have an external weight on the flywheel. If it was built with an aftermarket 383 crankshaft, it could have been balanced either way. Take a look at the flywheel, it should have an external weight on it.


ok big issue is if it was rebalanced for internal balance or is still external. if its a running engine and has the balancer on it look at the outside diameter of it, a stock 400 balancer will have a cast in space about 1/3 of the way around rather than being smooth all the way around, if the cast in area is on balancer you will need a flywheel for a 400sbc 2pc rear main for the appropriate starter, ie 153 tooth small diameter uses the straight bolt pattern and the 168 larger diameter flywheel will take a staggered or even a 3 bolt pattern starter. if you need a slim starter the autozone number is a DLG9990S and it is the exterior through bolt design, and you will need to go to GM dealer for bolts, ask for bolts for 94 k2500 350 eng. as this starter does take different bolts.
Oh yeah there is a counter balance on flexplate for a 400 over a 350, the crank flange is different if I remember correctly if a stock GM crank.
But I cant actually recall, Ill try to pull out a couple of cores.

thanks guys, i will hopefully be pulling the trans out tomorrow or the day after so i will have a look and report back for some more answers if needed. i really appreciate all the info and help! THANKS-Dom

taz
02-16-2011, 07:44 PM
Look at your harmonic balancer if its a 400 balancer there will be a weight taken out of the outer ring as its externally balanced . Here is a pic of 400 balancer.
Tim

69projectKAOS
02-17-2011, 03:11 PM
Look at your harmonic balancer if its a 400 balancer there will be a weight taken out of the outer ring as its externally balanced . Here is a pic of 400 balancer.
Tim

hey tim, i went out and looked at my harmonic balancer and it does not look like that at all. it completely round with no indentations on it.

i was also able to get my old th350 trans out in record time lol (1 1/2 hrs) in 45 degree weather non the less. and this is what the back of my crank looks like, and it has no numbers or anything on it unfortunately. my old flexplate that was on the motor has no counter weights on it either, which is making me think it is a stock 350 crank because a 400 crank would have to have a counter weight on it. the old flexplate was 168 tooth. i still need to know if this thing is internally balanced or not, this is the only thing holding me up from getting my t56 in !!!!!

MarkM66
02-19-2011, 05:07 AM
You could pull the pan and get the casting numbers off the crank, if it's a factory piece.

I could still be a internally balanced 383 if it has an aftermarket crank.

69projectKAOS
02-19-2011, 06:31 AM
so with having no counter weights on the olf flexplate i removed, and since my harmonic balancer doesnt look like the one in the picture another member posted , is it safe to say i should order a flywheel from keisler that internally balanced!? my dad called the guy who built the motor again and he said that he looked into his records and he thinks that i have a aftermarket 400 crank that was internally balanced, does that sound right? -Dom

taz
02-19-2011, 07:27 AM
A 400 crank externally balanced would have a counterweight on the flexplate . You could mesure the stroke remove a spark plug use a 1/4 drive extension run the piston to the lowest point that would give you a rough idea of stroke 3.48 for 350 3.75 for 400 you would have to guesstimatea little . Spin the engine by hand slow and to measure to avoid damage that will tell you what stroke you have . I built a 383 a couple of years ago and used an internally balanced crank . When in doubt measure . Oh and use a long enough extension please .
Tim

Steve68
02-20-2011, 08:00 AM
Looks like a 350 crank flange,

69projectKAOS
02-20-2011, 10:37 AM
Looks like a 350 crank flange,

the people that i have shown the picture said the same thing as well. -Dom

MarkM66
02-20-2011, 06:05 PM
my dad called the guy who built the motor again and he said that he looked into his records and he thinks that i have a aftermarket 400 crank that was internally balanced, does that sound right? -Dom

Yeah, it's possible, I just posted that above. ;) .

69projectKAOS
02-20-2011, 08:17 PM
so heres my question, if i order a flywheel from keisler tomorrow that is for a internally balanced motor, would it work if i have a 350 or 400 crank even though they both are internally balanced!?

shep
02-20-2011, 08:59 PM
As long as it is internally balanced and you match it to a fly wheel for an internally balanced engine it will work fine.