Pic request: stock lt1 flywheel
08-21-2011, 07:33 PM
#1
On The Tree
Thread Starter
iTrader: (2)
Join Date: Aug 2008
Posts: 163
Likes: 0
Received 0 Likes
on
0 Posts
Pic request: stock lt1 flywheel I need a pic of the backside of a factory lt1 flywheel the side where the counterweight is. Reason I'm asking is because my machine shop was supposed to internally balence my motor and I'm replacing the clutch now and the factory flywheel stillhastheweighton it. Just want to comparethepic you guys give me to what I have thanks
08-21-2011, 09:25 PM
#2
The factory LT1 and any '86-up 305 / 350 / LT1 / LT4 / L99 cranks lack a rear counterweight on the crank. Therefore on any '86-up, the weight is on the flywheel from the factory.
This is due to the rear main seal one-piece design which eliminated the rear mounted offset weight that was on all 2-piece seal '85 down cranks. All neutral-balance (no flywheel weight) SBC (all but 400 cid and BBC (all 427 & smaller) cranks take the no-weight flywheel which has absolutely nothing to do w/ anything '86-up SBC.
Your shop would have balanced the crank to the new rod and piston assembly weights and the difference between those and the originals would affect how much weight they needed to add.
It doesn't mean the weight is eliminated from the flywheel. Having to custom-balance a flywheel everytime it's service or replaced is pointless for a street car. Being able to buy one off the shelf makes sense.
There are exceptions to any of these and a machinist could theoretically put the weights where he wants but yes your LT1 flywheel is supposed to have a weight on it's backside. Google pics of any '86-up flywheel; they'll have a weight just like yours.
This is due to the rear main seal one-piece design which eliminated the rear mounted offset weight that was on all 2-piece seal '85 down cranks. All neutral-balance (no flywheel weight) SBC (all but 400 cid and BBC (all 427 & smaller) cranks take the no-weight flywheel which has absolutely nothing to do w/ anything '86-up SBC.
Your shop would have balanced the crank to the new rod and piston assembly weights and the difference between those and the originals would affect how much weight they needed to add.
It doesn't mean the weight is eliminated from the flywheel. Having to custom-balance a flywheel everytime it's service or replaced is pointless for a street car. Being able to buy one off the shelf makes sense.
There are exceptions to any of these and a machinist could theoretically put the weights where he wants but yes your LT1 flywheel is supposed to have a weight on it's backside. Google pics of any '86-up flywheel; they'll have a weight just like yours.
08-22-2011, 10:31 AM
#4
you want to take your stock LT1 FW to a machine shop and have them "neutral" balance it. The weight is cast into the FW. It is about 1/2" wide x 2" long. They typically grind that off then ad pins to the outer holes in FW to balance it further to "zero".
you can also buy a zero balance FW from SPEC but it is $300+
below on my pic you can see the pins the machine shop used to neutral balance the FW. You can then have the FW resurfaced in the future on clutch swaps.
FWIW I also bring in my PP and after the neutral balance the FW they put on PP and address any issues with it. In some PP they have removed multiple gr of material. Since I went with a internal balanced motor I have had a zero balance stock FW
note: the pic showing FW/PP/disc shows the areas on PP where material was removed and pins on FW were used to balance. The "blue" paint mark is where they actually line up on assembly but I rotated to show balance areas for the pic
08-22-2011, 05:11 PM
#6
your motor was internally balanced...so you need a "neutral" aka zero balanced FW. The weight needs to be ground off the stock FW BUT this does not mean it will be zero balanced without further balanceing by either drilling out some material and/or adding pins to the outer holes. The machine shop can do this for $40-$50
If you start the motor now with a non neutral balanced FW it will shake like a dog shiating razor blades
If you start the motor now with a non neutral balanced FW it will shake like a dog shiating razor blades
08-22-2011, 06:12 PM
#7
On The Tree
Thread Starter
iTrader: (2)
Join Date: Aug 2008
Posts: 163
Likes: 0
Received 0 Likes
on
0 Posts
Okay I don't think I'm being clear sorry. My motor is supposed to be internally balenced. When my machine shop built the motor I gave them the whole rotating assembly/fw/ harmonic balencer the whole 9. so when I got everything back from them with the motor assembled I put it in the car. The clutch went bad so now I'm doing a clutch in the car and the flywheel I gave them is no good now from the clutch slipping bad. When I took off the flywheel I noticed the weight still there so I'm assuming they didn't balence the motor internally correct?
Trending Topics
08-23-2011, 01:32 AM
#8
you can have your current FW resurfaced if it is not cracked or has already been resurfaced 3 times and just put it back on.
most "internal" balanced motors rotateing assemblys are not balanced with a FW. Since yours was you now need to replace it with what you have now which sounds like a stock weighted FW.
One thing that could be going on is the machine shop that balanced your deal could have drilled or removed material without actually grinding off the "weight". Only a guess.
Might want to take your current FW to a machine shop and have them check to see if it is "neutral" or not.
most "internal" balanced motors rotateing assemblys are not balanced with a FW. Since yours was you now need to replace it with what you have now which sounds like a stock weighted FW.
One thing that could be going on is the machine shop that balanced your deal could have drilled or removed material without actually grinding off the "weight". Only a guess.
Might want to take your current FW to a machine shop and have them check to see if it is "neutral" or not.
