Engine balance ???
Thread Starter
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
Engine balance ???
I'm picking up a shortblock this weekend. It is a 4 bolt (1996 LT1) , with Ross forged pistons and Eagle rods. The seller says his machine shop balanced the motor, internal balance. I have a 92 6 speed so what do I need to do to make it work? Have my flywheel neutral balanced? What about the harmonic balancer? 
BTW it's getting topped off with P/P heads, 2" intake valves, beehive springs, crane gold 1.6 RR, custom matched cam, ported intake, 30lb injectors, hooker LT's no cats, yada yada yada. almost forgot 150 shot of N2O.
BTW it's getting topped off with P/P heads, 2" intake valves, beehive springs, crane gold 1.6 RR, custom matched cam, ported intake, 30lb injectors, hooker LT's no cats, yada yada yada. almost forgot 150 shot of N2O.
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by RUBYREDVETTECARD
The harmonic balancer is neutral balanced already, I would have the flywheel balanced (or checked for balance) and you will be fine. Sounds like it is going to be a beast
She ought to really storm! 
Le Mans Master
Joined: Jul 2001
Posts: 8,183
Likes: 3
From: Santa Maria, CA
Without knowing what kind of harmonic balancer you have, we don't know.
I don't really know anyone that would re-use a old balancer on a new motor. Check what ever you use anyway. You want it neutral.
On your flywheel. You have a ZF6. That FW is a dual mass and has external weight permanently cast into it. I guess a guy could machine off the weight, or grind it off to get it to neutral. Never heard of that being done tho. You might consider doing the single mass conversion right now if you are so inclined. It would mean a steel flywheel (cut .090 down) from a F-body car and a clutch disc with a sprung hub (something like a McLeod).
Otherwise you have to get that dual mass to neutral one way or another. Your motor will not like it if you bolt it on as-is. Will vibrate bad and ruin the main bearings. Let us know what you think.
I don't really know anyone that would re-use a old balancer on a new motor. Check what ever you use anyway. You want it neutral.
On your flywheel. You have a ZF6. That FW is a dual mass and has external weight permanently cast into it. I guess a guy could machine off the weight, or grind it off to get it to neutral. Never heard of that being done tho. You might consider doing the single mass conversion right now if you are so inclined. It would mean a steel flywheel (cut .090 down) from a F-body car and a clutch disc with a sprung hub (something like a McLeod).
Otherwise you have to get that dual mass to neutral one way or another. Your motor will not like it if you bolt it on as-is. Will vibrate bad and ruin the main bearings. Let us know what you think.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by SPEED750
The seller says his machine shop balanced the motor, internal balance.
RACE ON!!!
Safety Car
Joined: Sep 2003
Posts: 3,599
Likes: 24
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
Originally Posted by CFI-EFI
The question is whether it was a true, neutral, internal balance that would take a true, neutrally, balanced flywheel? Or whether it was internally balanced to 1 piece seal specs for your existing flywheel? Unless the machine shop has someone on this forum, you won't likely get an authoritative answer, here. You will have to check as to how it was internally balanced.
RACE ON!!!
RACE ON!!!
you want to be sure before you bolt everything back up. talk to that machine shop. a mis-matched rotating assembly / flywheel configuration will not make you happy... 
