I'm trying to help a buddy of mine put together a parts list for his LT1 Firebird that just spun a bearing and took the crank along with it. Figured this was easy enough for you guys to answer. :) Anything special to an LT1 crank or is it just your run of the mill 3.48" 1-piece rear SBC crank?

1997 Firebird
T-56 Tranny

 

Damn this account still works?:hurray:

Hey Brian thanks for posting this!

Yeah I ended up getting this Formula off a good deal from my Friends Dad.

If you're interested in seeing some pics, damage etc., they're in this thread here: http://www.corral.net/forums/showthr...5&pagenumber=1

But yeah, spun it pretty good. All in all I took out the crank (I can feel it w/ my fingers, I think it's a *tad* more than .030!), Camshaft, couple lifters, Possibly the connecting rod, we'll see if the block will clean up at .030/.040; and hopefully the head is OK, but I'm pretty sure the piston was smacking on it, based on the shinyness.

I really don't want to spend a whole grip of money on this engine, as I've got a Turbo 351W project I'm trying to get togother for an '87 Mustang Coupe that I have, but bad timing on this engine going out, since it's my Daily Driver! A standard rebuild w/ "standard" machining, assembled, pan to intake I was told ~$1200. Hard to resist throwing a few go-fast parts while I'm in there. :crazy:

Anyways, thanks for any insight you guys might be able to give on this.

Did this to 2 lobes on the camshaft:


Not only spun it, but split it too!


Coming out the top...not bad for a FORD guy :thumbs:


Here's a closeup of the crank. Couple more pics in that thread but I don't want to load up this thread with them.






[Modified by Dave88LX, 5:54 AM 4/18/2003]

 

Externally balanced! Just read this in Rebuilding the LT1/LT4 Engine. :)

 

yes... externally balanced.

you may wanna consider 383???

at the very least, I would get 4 bolt main caps!!!

 

There is some good info in these posts:

Getting conflicting info - does a new balancer for the LT4 need to have the old weights transferred?

Balancing a LT-1

 

I was told that when you balance them you have to have the flexplate or the flywheel on because the back of the crank is externally balanced but the front is nutral balanced (internally balanced) I was told that you have to do it like that because the big end on the cranks with one piece seal would take to much to balance.
I dont think the LT1 cranks are any different then other cranks.

Jay

 

Ok so to sum this up.

From the factory....

The crank is neutral.
The balancer is weighted but not keyed onto the crank?
The flywheel is weighted.

 

Problem is, I have guys (Ford guys mind you) telling me I need a 400 flywheel, and the right starter for that. Maybe "back in the day" that's how it was done to get a 383? I want to say "nowadays" they have the cranks that are designed for this setup? I've read a bunch of your threads on it, but I still can't find a definitive answer, and what exactly needs to be done.

Do I buy a "balanced" crank, or is it the crank/rods/pistons that are balanced? Then the machine shop balances just the flywheel to that?

<0-----Lost as all heck! :crazy:

 

Dear Dave,

It goes like this.

The pistons and rods are paired and weighed then the lightest one is found. The balance pads on the rods are then ground on the heavier rod/piston assemblies so that all assemblies weight the same as the lightest assembly.

They assemble an unbalanced crank with a flex plate or flywheel and neutral balancer. Bob weights equal to the weight of the piston/rod assemblies are then attached to the rod journals and the assembly is spun in a balancing machine.

The machine indicates where weight has to be added or removed from the crank counterbalance weights. Many of these machines have a drill press built in and the operator just drills the crank counterweights without removing the crank assembly from the machine.

Tungsten(mallory metal or heavy metal...weighs about twice as much as steel) can be added by press fitting it into holes drilled in the crank counterweights then permanently welded in place if wieght has to be added to your crank.

The assembly is then spun again to check to see if it is properly balanced.

Usually this is done a minimum of two times to come up with a perfect balance.

:party:


[Modified by 95BLKVette, 1:00 AM 4/18/2003]

 

:eek: Check ebay for some kits :thumbs:

:cheers:

 

Thanks! Great info!

I have another question. Do I want to buy a crank that is INTERNAL or EXTERNAL balanced...

Scorp said that Mallory is ~$50/slug...I'm not wanting to spend that.

 

As I believe was mentioned above; LT1's are "split balanced"...The rear is external while the front is neutral (internal). On the strokers we build we do complete neutral...Much simpler and better for rev's, smoother...
-Jeb Burnett

 

just got my rotating assembly back for my 383 LT-1 and had it internally balanced. If you just want to replace the stock parts i'll sell you my old rotating assembly if you want. Shoot me an email if you need any more info. Vetteman@bellsouth.net

 

You want to buy a stroker crank that can be internally balanced, otherwise they will need to sell you a non-neutral harmonic balancer or they will have to add mallory metal to the front crank balance weight (which is expensive), and also, that type of harmonic balancer won't work with an LT-1 since it doesn't have an integral drive pulley or extended shaft to clear the optispark unit. :smash: