what needs to be done to make this work properly and balanced? I asking for the exact precedures here not just some guesses!
Do I need a new balancer and flexplate along with having the whole assembly balanced? or just have the whole assembly balanced with the stock flywheel and balancer?
The crank I bought is a 3.75 stroke/ 1 piece rear main / internally balanced crank but they say you cannot use it in an LT1...??? whats the differences? other than internal and external balancing? the main journals are the same the rod journals are the same, what else could be different?

 

You have two choices. Internal (zero) balance: This means you will need a new, neutral (zero) balance flywheel (the harmonic damper is already neutral balanced). External balance: In this case, you can use your existing flywheel. In both cases, the balance shop will want the crank, flywheel, and one piston/rod/wrist pin/ring package assembly. They will use this to calcualte the "bob weight" needed to performance the balancing procedure.

Who is "they"? "They" are wrong or you are misunderstanding what you are being told.

Rich

 

"they" are the ones that I bought the crank from. even if the crank was not internally balanced (which it was advertised as one). I can use it, right? just have the machine shop balance it however I want? I would prefer the internally balanced so I can use the stock balancer and just have a new flywheel neutral balanced?
Thanks rich for your input. This is my first stroker motor.
Les

 

If it is a 1-piece rear seal SBC crank with standard journal sizes, you can use it after it has been balanced.

Rich

 

I've put a number of early crankshafts (2-piece main seal) in LT1 blocks. An adaptor is necessary to make the seal work but it's really a no-brainer. I personally prefer using the early crankshaft with an unweighted flexplate right out of the box and an ATI balancer on an aluminum hub designed to fit an LT1 front cover. The non-metric bolts on the rear flange and the wide selection of SFI-approved flex plates are both a plus.

 

Thanks rich and cnorton for your valuable input! I really appreciate it!

 

I have that crankshaft with 2-piece main seal in my new LT1 block.
It has worked fine with an adaptor

 

Ok so if i were to use this with my current flywheel, would that cause problems? I thought the LT1 was a neutral internal balance motor meaning the flywheel was a neutral balance already or am i misunderstanding and the LT1 stock flywheel is a balanced flywheel.
having this knowledge (or lack of knowledge). I had already installed the crank and ran the motor a little, idle to 1000 wasn't too bad (big cam shakes the car anyway and solid motor mounts) but 1500 up to 4000 was an earthquake! I have alread started to disassemble and plan to take everything apart and check everything to make sure I havn't damaged anything, I will be putting in new rod and main bearings! and tossing the others.
So if I want an internal balance I have to get a "neutral" flywheel? (assuming the LT1 is not as I originally thought). what are the pros and cons of internal vs external balancing?
What will they do to my stock flywheel if choose external balance and will I need a new damper if I do?
Thanks,
Les

 

The crank I have is for the one piece rear main. what I believe is wrong is the balance of it.

 

Stock LT1: harmonic damper (at front) is neutral blance (i.e. "neutral balance at front"). Flywheel/flexplate (at rear) has a counterweight (i.e. "externally balanced at rear"). There is no way to tell you how your RA is balanced without dismantling the motor. All else is just guessing.

As far as adapted 2-piece rear main seal cranks goes, they are prone to leaking. This is what the switch to a 1-piece design was intended to cure, it's potentially even worse with an adapater. But if yours doesn't leak, that's great.

Back to balance: a crank cannot be internally balanced in isolation. It must be balanced against a specified bob weight. The bob weight consists of the weight of the rod small end plus the piston, rings, and wrist pin. It as not as critical as some suggest that it be exactly right, as long as it is not "underbalanced". Some balancers deliberately "overbalance". Meaning that the weight of the crank counterweights is more than the bobweight by a couple of percent. Some people think this smooths out the motor at high rpm. Underblance is always bad though.

Rich

 

This is all making sense now! so more than likely my "shakes" after putting it all together is due to my stock flywheel being balanced to a stock crank. (instead of a stroker crank).
Thanks again for all the info...

 

I'd fix that problem before driving the car much more.

Steve

 

Read all the post...#8 to be exact!
I have already starting tearing the motor apart and I never actually drove the car! I only idle'd it and reved it a little!