What flywheel do i need to work with my 2 piece rear main seal 383/T5 ?I'm using a centerforce dual friction clutch. I didn't realize the difference between internal/external balancing and im having bad vibrations right now , any help would be appreciated

internal balancing is all balancing is done on the crank, that means u need a neutral harmonic balancer and flywheel. external balancing is that the crank is set for the balancing weights to be used on the harmonic balancer and flywheel. wats even more complicated is my setup... 383 HSR with internal balance front of the crank and external balance for the rear of the crank. means i needed a neutral balance harmonic balancer and an external balance flexplate.

u need to find out what your rotating assembly was set up for... if its internal balance then u need neutrual balance harmonic balancer and flywheel. if its externally balanced then u need the opposite.

just so u kno... most 383s are external balanced. are u sure the engine is running right? no dead cylinders? or anything

The motor is running good . but i have an internal balance flywheel . I am fairly confident now that it is an externally balanced .

also the vibrations start at about 1800 rpm .

Centerforce 700102 how about this one ?

bump

anyone ?

Surely somebody knows the answer to this !!

idk bout manuals much... but you need to figure out what yours is set up for. whether it be external or internal balanace. anyway u can find out?

is the vibrations when the car is in park? or driving? if driving i would think it could be a driveshaft balance issue.

it vibrates at 1800 rpm or above when driving and in neutral , the vibration is worse when driving though cause the vibration is transferred to the trans .

You need to make 1000&10% sure you have all the right matched parts.

front balancer, crank, flywheel.

They all should be for internal or external.

Call summit tech line

Odds are that you require both an externally balanced flywheel and an externally balanced damper. Recall that a 383 is based on a 400 crank. Which has both of the above two pieces different then all other 2-pc RMS SBC engines.

Once you start swapping new parts in be sure to 'test' them before bolting the clutch & tranny up. Up can change the damper and test it in neutral at MILD RPM levels.

Same for the flywheel. Can even borrow these pieces and try them out first.

The reason for all of this is that unless the engine builder TOLD you how the engine is balanced, it could be any number of combination's. Which is what customblackbird is saying.

RBob.

Well originally this was an automatic . And i bought i flywheel for 2 piece rear main seal , 350 internally balanced . Because of my lack of knowledge of 400 cranks being externally balanced most of the time . I looked at my old flex plate and it has a weight offset on it . Doesn't that mean it was externally balanced ?

If the old flexplate is from the '92, then no, it isn't really an external balance flexplate. That small weight is to make up for the lack of counter weight on the tail end of the crankshaft. With the 1-pc RMS engines the rear of the crank is round.

Where a 2-pc RMS internally balanced crank has a small counter weight on the tail end of it.

Where the 1-PC RMS crank GM moved that small counter weight to the flywheel/flexplate.

RBob.

well the only thing i did to the motor is swap the flexplate to the flywheel . And now it vibrates , it did not do this before .

Then it goes back to having the builder who balanced the engine tell you how it is balanced. Which has been mentioned a couple of times already in this thread.

You need to go back to your engine builder and ask him what is required. Because evidently you have a mix & match on the balance. We can only give so much information on the various ways to balance an engine.

What we can see from here is how it is actually balanced and what is required to eliminate the vibration.

Question:

Which brings up how did you bolt the '92 flexplate onto the current engine (with the 2-pc RMS crank)? To know that it didn't vibrate? A 1-pc RMS crank and a 2-pc RMS crank have different bolt patterns.

RBob.

Well the thing is the engine builder has moved away , and i have no way of contacting him .

The flexplate was not off of a 92 , im assuming because it had no modifications in the bolt pattern .

Is it possible to run the part # off the flexplate ?

Take the old flexplate and the new flywheel to a reliable engine shop. They may be able to check the balance on the old flexplate, and get the new flywheel balanced close. It's not perfect, but beats pulling the motor for a complete re-balance.

can i ask
whats the crank from. or .who made it?

Stock GM 400 crank = extrnl bal

after market Cast 98% of the time extrnl Bal
(use stock 400 bal and fly/flexplat)/aftermarket parts for same.
IE.extrn bal sbc

forged crank aftermarket 98% of the time intrnl bal

2 piece rear = use Bal. fly/flex plate 86 and up 350's (intrnl bal)
1 piece rear = all other 350 bal/flex/flywheels. (intrnl bal)
(aftermarket parts for same)

the other 2% from ea is why i ask who made the Crank

you say it's a 383..

so it's a 350 block with a 3.75 stoke crank.
we just need to know what crank it is..

stock GM
OR
aftermarket
we get this info
we get it Fixed
see how easy

what parts are you using
block year ?
crank ?

if eng is externally bal all parts need to be externally BAL

See how easy it is..

the flywheel should always be bal..
and if it is.. i would look at the Damper make sure it matches the Crank.. extrnl OR Inturnl
see my first post just above..who made crank?

Not really sure at this point what crank it is actually using , i know its a 383 because i measured the bore and stroke when the heads were off . This motor never vibrated like this till i swapped it to manuel and put this flyweel on .

I can check my block numbers later today .

then take a look at the damper

is a a 350 or a 400.

get some photos of the damper
post them we can tell you from that if it's a Intrnl or exturnl.

Alright i will as soon as i get a chance .

Thanks for all the help
I looked at the balencer and it was a stock external balance for a 400 .
Already ordered my new ex balance flywheel

hi , i just had a an almost the same issue....i went from a 700r4 14' 168 tooth flexplate/flywheel on my camaro 1985 with a 1978 350 ...i wanted to swap a T5 , but T5's use a 13' flywheel with 153 teeth and 1 piece REar seal...mine has a 2 piece rear seal...so what do i do now?...well some poeple said move over your starter and get a new 153 tooth flywheel for a 2 piece rear b seal...can't because my starter has the offset bolts and no other holes were drilled in the block to have any other type(old style 350 )..so my starter would never catch this smaller flywheel...well i want a manual trans ...so i got a 168 tooth 14' flywheel for a 2 piece rBseal for V8 85 and down with a 2 bolt pattern for a 10.4' or 11' pressure plate/clutch...my starter would now catch the flywheel to crank the engine,,,but the bell housing on a T5 only can take a 13' flywheel...well i bought a new bellhousing that takes 13- or 14' flywheels..it should arrive this week ,,,it should all fit nicely i hope!!!...but sometimes it pays to research (which i did a lot)...hope this helps anyone with my type of setup...i'll post results soon ...