please help/ wicked vibration
Thread Starter
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
please help/ wicked vibration
I have a 92 lt1 6 speed. Just did a complete engine rebuild and now it vibrates to bad to even drive it.
4 bolt main block
forged steel eagle crank
forged steel eagle I beam rods
Mahle forged pistons .40 over
LE 1 camshaft
LE 2 heads
Its a problem with the harmonic balancer/flywheel
Anybody else ever have this problem after a rebuild ?
How did you fix it? Maybe have the harmonic and flywheel
balanced? I didn't have the motor balanced because the eagle sight
says its an internal balanced crank.
4 bolt main block
forged steel eagle crank
forged steel eagle I beam rods
Mahle forged pistons .40 over
LE 1 camshaft
LE 2 heads
Its a problem with the harmonic balancer/flywheel
Anybody else ever have this problem after a rebuild ?
How did you fix it? Maybe have the harmonic and flywheel
balanced? I didn't have the motor balanced because the eagle sight
says its an internal balanced crank.
Le Mans Master
Joined: Feb 2005
Posts: 6,479
Likes: 565
From: Clearwater Florida
........... You may need to change the flywheel ........ One piece main engines have a small counterweight on the FW to compensate for the metal removed from the rear crank flange to accommodate the seal ... your new crank is internally balanced ......... check with Eagle tech to verify ...............
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
Something is out of ballance.
I can tell you driving it like that is gonna kill your motor
Most important question was your motor really internal balanced?
Did you have the flywheel neutral balanced?
Is the front balancer neutral balanced?
Somewhere on the Internet I saw a procedure for balancing the DMF in the car. It was some sort of TSB because some of the LTx cars were exhibiting an issue and some had to be re-balanced by the dealer. You may want to track that down if the answer to the three questions above is yes and if anyone of them is no.
I can tell you driving it like that is gonna kill your motor
Most important question was your motor really internal balanced?
Did you have the flywheel neutral balanced?
Is the front balancer neutral balanced?
Somewhere on the Internet I saw a procedure for balancing the DMF in the car. It was some sort of TSB because some of the LTx cars were exhibiting an issue and some had to be re-balanced by the dealer. You may want to track that down if the answer to the three questions above is yes and if anyone of them is no.
Cruising
Joined: Nov 2011
Posts: 11
Likes: 1
Since you have mahle pistons, this wasn't a rotating assembly kit from eagle right? The rods pistons and crank were bought separately. The rotating assembly has to be balanced. Eagle stating the crank is "internally balanced" means the harmonic balancer should be a standard sbc non-weighted type as opposed to a 400 balancer which has a separate weight added. Basically your stock balancer is what you should use or new equivalent. As for the flywheel, your stock one is the correct one to use. Again, your rotating assembly, balancer and flywheel need to be sent to a machine shop for balancing. Even though the machine shop shouldn't have to touch the balancer or flywheel it's always best that they have them as well. I hope all that made sense.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Since you have mahle pistons, this wasn't a rotating assembly kit from eagle right? The rods pistons and crank were bought separately. The rotating assembly has to be balanced. Eagle stating the crank is "internally balanced" means the harmonic balancer should be a standard sbc non-weighted type as opposed to a 400 balancer which has a separate weight added. Basically your stock balancer is what you should use or new equivalent. As for the flywheel, your stock one is the correct one to use. Again, your rotating assembly, balancer and flywheel need to be sent to a machine shop for balancing. Even though the machine shop shouldn't have to touch the balancer or flywheel it's always best that they have them as well. I hope all that made sense.
Gotta pull the motor and have everything, balancer to flywheel balanced.
Thread Starter
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
Something is out of ballance.
I can tell you driving it like that is gonna kill your motor
Most important question was your motor really internal balanced?
Did you have the flywheel neutral balanced?
Is the front balancer neutral balanced?
Somewhere on the Internet I saw a procedure for balancing the DMF in the car. It was some sort of TSB because some of the LTx cars were exhibiting an issue and some had to be re-balanced by the dealer. You may want to track that down if the answer to the three questions above is yes and if anyone of them is no.
I can tell you driving it like that is gonna kill your motor
Most important question was your motor really internal balanced?
Did you have the flywheel neutral balanced?
Is the front balancer neutral balanced?
Somewhere on the Internet I saw a procedure for balancing the DMF in the car. It was some sort of TSB because some of the LTx cars were exhibiting an issue and some had to be re-balanced by the dealer. You may want to track that down if the answer to the three questions above is yes and if anyone of them is no.
I'm useing the stock dualmass FW that came in the car and the same lt1 balancer that was on the car. I put about 80K miles on these stock parts with no issues.
The new motor isn't designed for high rpm where a full balance is most critical. It should have a decent powerband from 1900-6500rpm.
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Racer
Joined: Oct 2011
Posts: 312
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From: state of insanity
I have a 92 lt1 6 speed. Just did a complete engine rebuild and now it vibrates to bad to even drive it.
4 bolt main block
forged steel eagle crank
forged steel eagle I beam rods
Mahle forged pistons .40 over
LE 1 camshaft
LE 2 heads
Its a problem with the harmonic balancer/flywheel
Anybody else ever have this problem after a rebuild ?
How did you fix it? Maybe have the harmonic and flywheel
balanced? I didn't have the motor balanced because the eagle sight
says its an internal balanced crank.
4 bolt main block
forged steel eagle crank
forged steel eagle I beam rods
Mahle forged pistons .40 over
LE 1 camshaft
LE 2 heads
Its a problem with the harmonic balancer/flywheel
Anybody else ever have this problem after a rebuild ?
How did you fix it? Maybe have the harmonic and flywheel
balanced? I didn't have the motor balanced because the eagle sight
says its an internal balanced crank.
Thread Starter
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
Well it's not in the drivetrain. It has the problem just sitting still so it has to be the motor balance. I got the info about the crank off the Eagle website.
I think I'm getting closer to an answer. Did some forum grave digging and found a member that did a zero balance on his DM FW. Looks like they have weights on the back that he had to remove to make it a zero balance. I sent him a pm , just waiting on an answer. HELLO "SlickFX3" hit me up !
I think I'm getting closer to an answer. Did some forum grave digging and found a member that did a zero balance on his DM FW. Looks like they have weights on the back that he had to remove to make it a zero balance. I sent him a pm , just waiting on an answer. HELLO "SlickFX3" hit me up !
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
You need go pull the engine and have it balanced. An internally balanced crank does not mean you do not have to balance the assembly. What it means is you need a neutral balanced flywheel and harmonic balancer. The entire assy still needs to be balanced and you need a new flywheel.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
something is out of balance reving/driving it is gonna kill your the bearings/motor quick.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
I think I'm getting closer to an answer. Did some forum grave digging and found a member that did a zero balance on his DM FW. Looks like they have weights on the back that he had to remove to make it a zero balance. I sent him a pm , just waiting on an answer. HELLO "SlickFX3" hit me up !
It's an expensive lesson in engine rebuilding 101, but it'll get more expensive if you don't pull the engine and balance it correctly.
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
Doesn't apply in your case. You have a new crank, rods, and pistons. Even if you put on a neutrally balanced flywheel, you'll still need to pull the engine and balance the rotating assembly.
It's an expensive lesson in engine rebuilding 101, but it'll get more expensive if you don't pull the engine and balance it correctly.
It's an expensive lesson in engine rebuilding 101, but it'll get more expensive if you don't pull the engine and balance it correctly.
I now have it all apart, the crank needs polished - so guess what - I get to balance it all again. Mine lives above 3500 rpm all the time its on the race course so it has to be as close to perfect as possible.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Somebody didn't do their homework!
If you put the stock (imbalanced) flywheel on your new internally balanced motor, the motor will vibrate/shake at idle. Late gen1 and gen2 stock engines are imbalanced at the rear. They have a 30g imbalance that's offset by a 30g weight in the flywheel. Take away (only) one of those weights and you have crapola.
Slick isn't going to solve your problem. You and/or your builder screwed up.
BTW...the perimeter weights on the DMF are 1oz/hole IIRC. Filling all of them up (on one half) won't really cure the problem. You're going to need a neutral-balanced flywheel and a sprung-hub clutch. Slick didn't even get that one right.
I agree that disassembling the motor and balancing the rotating assembly is also the right thing to do. (Technically should be done with the flywheel -- as a group.)
Depending on your labor costs, getting the flywheel and transmission "right" might (sufficiently) cure your problem -- if the pistons are a perfect match to the RA and each other. If not...you're F'd.
If you put the stock (imbalanced) flywheel on your new internally balanced motor, the motor will vibrate/shake at idle. Late gen1 and gen2 stock engines are imbalanced at the rear. They have a 30g imbalance that's offset by a 30g weight in the flywheel. Take away (only) one of those weights and you have crapola.
Slick isn't going to solve your problem. You and/or your builder screwed up.
BTW...the perimeter weights on the DMF are 1oz/hole IIRC. Filling all of them up (on one half) won't really cure the problem. You're going to need a neutral-balanced flywheel and a sprung-hub clutch. Slick didn't even get that one right.
I agree that disassembling the motor and balancing the rotating assembly is also the right thing to do. (Technically should be done with the flywheel -- as a group.)
Depending on your labor costs, getting the flywheel and transmission "right" might (sufficiently) cure your problem -- if the pistons are a perfect match to the RA and each other. If not...you're F'd.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Oh yeah...get ready for ZF6 rattle after you're all done. If that'll bug ya, maybe do a transmission conversion while you're at it.
Or, have it sent for modification.
Or, have it sent for modification.
