I replaced my LT1 in my '97 with a new GM LT4 used in the '96 Vette. I had posted a few weeks ago about what need to be changed besides the manifold. I was informed that everything else changes over.

Well I have the new engine in there and I start it up. It seems to create a vibration through the body at differant RPM's. Both in park and on the road. I checked and found that there is a differant balancer for the LT4 on the Vette. I ordered it up and found that it has a huge weight on the backside of it. I tried bolting it up,but it would cause the serp belt to be WAY out of aliment. I checked my old balancer and it has several holes in it. I understand that weights possibly go in there. There were no weights in my old one.

What can I do to remedy the problem and also am I damaging the engine if the balancer is off?

 

The LT4 is internally balanced just like the LT1 is. I don't know about the wieght on the LT4 balancer but I know it is extended and you'll need spacers on the accecery bracket to keep the belt lined up properly.
I would try the LT4 balancer with the belt off and see if the vibration goes away, then you can fab up some spacers, think they're 16mm thick.

 

The Vette one I have is much heavier than the Camaro's. It seems to have some holes drilled in the back to balance it out. The Camaro's has holes all around that weights go into but there isn't any weights on mine.

Didn't SLP drop these LT4's into the SS in '97? The accessories are set up differant on the Vette. What did they do about it with those cars?

Could this problem not be balancer related? The car didn't have a vibration before the swap.

 

Fortunately for me there were no shaker problems when I put my LT1 hub on my LT4 motor. Use the LT1 hub assembly, but try rotating the assembly on the crank 90 degrees at a time to see if that will eliminate the shakes.

 

From http://www.grandsportregistry.com/lt1vslt4.htm

DUAL-MASS FRONT TORSIONAL DAMPER

Tuned for high engine speed, also helps reduce stress on the crankshaft. LT1 pt.# 10128489 and LT4 pt.# 12551486

And I'm pretty sure the SLP LT4 cars used the Vette dual-mass unit.

 

I purchased the 12551486. It won't line up with the rest of the accessories. It sticks out about 3/4 of an inch further than the stock LT1 I have. I can't image they used that on the SLP cars as the alt. and comp. mounting is setup differant. I'm totally lost on what to do. Maybe get a new LT1 unit and spin it 90 like carlos64030 said

 

No need to purchase a new LT1 hub if you still have the old one.

 

Yeah but maybe my old one is F'ed up? I'm not even sure this is the problem.

 

Well I took the old one off. I tried spinning it and also flipping it over to see if it was bolted up wrong. What I've discover is they made it fool proof. They have the holes drilled slightly uneven so there is NO WAY to put it on in any other way exept one postion and one side.

Anyone else know what I can do???

 

No-no-no dude! Pull the entire hub assembly off of the crank and rotate it 90 degrees...that means removing the center bolt in the snout and pulling the actual hub off with a puller.

 

'Weight' like in more mass to the dampner all around, or a weight that is just on a certain area of the circumference (as if to balance)?

I checked my old balancer and it has several holes in it. I understand that weights possibly go in there.

I believe you understand incorrectly. The balancing is done with the flywheel, not the dampner. The dampner is there to control harmonics, not to balance the rotating assembly, unlike the older 400 sbc.

What can I do to remedy the problem and also am I damaging the engine if the balancer is off?

The higher the rpm, the more the potential damage.

Actually, it is externally balanced just like the LT1.

....but I know it is extended and you'll need spacers on the accessory bracket to keep the belt lined up properly.

I believe the reason for the extention, is because of the dampner, and not the hub.

There is a procedure to properly position the dampner, on the crank, in the service manual.

Although the thread may generate ?s as well as answers, here is a link to a related thread in another forum:

http://www.impalassforum.com/cgi-bin...;f=33;t=002944

 

My LT4 SS has the Corvette balancer, but it's installed backwards, with the weight facing the front of the car. I'm not sure if it's just flipped around, or if there is a spacer between it and the hub for alignment.

 

I checked my old balancer and it has several holes in it. I understand that weights possibly go in there.

I believe you understand incorrectly. The balancing is done with the flywheel, not the dampner. The dampner is there to control harmonics, not to balance the rotating assembly, unlike the older 400 sbc.


Actually the radial holes on the LT1 balancer occasionally have weights in them... not very often, but I have seen this..

 

Well, if they are there occassionally, it's my belief they are there to balance the dampner itself, which is very possible, and may be sometimes necessary. That possibility/necessity had obviously, escaped me.

Edit: I narrowmindedly considered the balance statement above, by the original poster, to be focusing in on the rotating assembly in the block, and not the dampner itself. My error.

 

The thicker 'Y' body damper/balancer has the additional thickness/mass in rear of the pulley section, when installed in the vette.

Just a little info regarding different relevant engine components.

The 'F' bodies share crankshaft hubs with the LT1/4 'Y' bodies.
The 'B' body is separate, with the hub being .41" longer for the respective year.
The 'F' bodies share dampers with the 'B' bodies. They are both 1.34" thick.
The 'Y' body is separate, with a 2.08" thick damper (on an LT1). I do not know whether or not, the LT4 damper is a different thickness than the LT1, or for that matter, what the thickness of the second gen. LT1 #10128489 damper, or the second gen. LT4 #12551486 is. Any help/input?