LT1 TDC Hub Position
Thread Starter
Teching In
Joined: Oct 2013
Posts: 15
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LT1 TDC Hub Position My car is a 1993 Firebird Formula LT1 and I'm working on installing an LE2 head and cam package.
I've been reading some posts saying that lining up the the crankshaft hub and pulley does not matter.
Looking at the picture of mine, you can tell that hub was not lined up correctly at TDC. The mark on the hub that should be in the 12:00 position is in the 7:00 position in the picture. The white mark is just there for my reference of how the pulley came off the hub.
In the picture of the pulley, I circle what looks like a weight. If it doesn't matter how the hub and pulley are oriented, why would there be a weight in the pulley? When I reinstall the hub and pulley I would like to orient them so they are at the 12:00 position at TDC, but the thing that looks like a weight is making me hesitant to do so. Does anybody have any input on this?
Thanks,
I've been reading some posts saying that lining up the the crankshaft hub and pulley does not matter.
Looking at the picture of mine, you can tell that hub was not lined up correctly at TDC. The mark on the hub that should be in the 12:00 position is in the 7:00 position in the picture. The white mark is just there for my reference of how the pulley came off the hub.
In the picture of the pulley, I circle what looks like a weight. If it doesn't matter how the hub and pulley are oriented, why would there be a weight in the pulley? When I reinstall the hub and pulley I would like to orient them so they are at the 12:00 position at TDC, but the thing that looks like a weight is making me hesitant to do so. Does anybody have any input on this?
Thanks,
The damper is zero balanced. There is no heavy side. The LT1 engine is internally balanced in the front therefore it does not matter how it goes on. In the 15+ years I've dealt with these cars and internet message boards I have never encountered a LT1 4th gen f-body owner claim their engine seemed "out of balance" by not installing the damper at TDC. The weight you see is nothing more than the damper itself being at a neutral or zero balance.
TECH Veteran
Joined: Apr 2008
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OP
the pin weight on the balancer would be to make the balancer itself neutral. It would appear the hub was reinstalled with no thought as to replacing it so the "pointer" was on top with #1 piston at TDC on compression stroke.
I would/do put the hub back on in correct position but since the LT1 balancer is neutral and motor is externally balanced from the rear with a weighted flexplate or flywheel you would be "OK" leaving it the way it is. IMHO better to have the pointer in correct position.
the pin weight on the balancer would be to make the balancer itself neutral. It would appear the hub was reinstalled with no thought as to replacing it so the "pointer" was on top with #1 piston at TDC on compression stroke.
I would/do put the hub back on in correct position but since the LT1 balancer is neutral and motor is externally balanced from the rear with a weighted flexplate or flywheel you would be "OK" leaving it the way it is. IMHO better to have the pointer in correct position.
TECH Veteran
Joined: Apr 2008
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from an engine balance standpoint it doesn't matter
I have a ATI with keyed hub so it always goes on right but as we all know the stock LT1 hub is not keyed
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I would never trust a non-keyed hub to maintain TDC and use it as a reference. I have a much easier, very accurate way of finding TDC. It involves a 5/8" socket, wrench and a McDonald's straw.
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Brett Foote TECH Veteran
Joined: Apr 2008
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nor would I Mr SS
my point is/was, jusk like Rob's, is the hub should be installed with pointer at 12 o clock as the factory put them on with # 1 or 6 @ TDC on compression stroke. It is more of a visual reference more than anything, not to determine 'dead nuts" TDC. Will the Op's world end if it isn't, no.
watching the rocker position as motor is rotated by hand, yes 5/8" socket :-), and visually refrenceing a pointer (that I know is positioned correctly) or in my case detailed marking on ATI balancer, is what I do.
Your "straw" tool is also a way.
Again in th eOp's ? I believe he was asking thinking the pin in his balancer was for "motor" balance and he knows the pointer is not in the correct position when he is at TDC
I think we have covered his ?
my point is/was, jusk like Rob's, is the hub should be installed with pointer at 12 o clock as the factory put them on with # 1 or 6 @ TDC on compression stroke. It is more of a visual reference more than anything, not to determine 'dead nuts" TDC. Will the Op's world end if it isn't, no.
watching the rocker position as motor is rotated by hand, yes 5/8" socket :-), and visually refrenceing a pointer (that I know is positioned correctly) or in my case detailed marking on ATI balancer, is what I do.
Your "straw" tool is also a way.
Again in th eOp's ? I believe he was asking thinking the pin in his balancer was for "motor" balance and he knows the pointer is not in the correct position when he is at TDC
I think we have covered his ?
Fortunately with these engines you really do not need a visual aid. If one wants to adjust valves using the damper as a reference then the most accurate way is to use a straw to find TDC and note the position of the pointer and go from there. That's about all it's good for other than piece of mind for those that a are a little OCD overboard and to claim the damper is correctly referenced. Basically what I'm getting at is it should serve no function other than to claim, "Hey bro, the pointer is true!"
Teching In
Joined: Dec 2023
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Tdc My car is a 1993 Firebird Formula LT1 and I'm working on installing an LE2 head and cam package.
I've been reading some posts saying that lining up the the crankshaft hub and pulley does not matter.
Looking at the picture of mine, you can tell that hub was not lined up correctly at TDC. The mark on the hub that should be in the 12:00 position is in the 7:00 position in the picture. The white mark is just there for my reference of how the pulley came off the hub.
In the picture of the pulley, I circle what looks like a weight. If it doesn't matter how the hub and pulley are oriented, why would there be a weight in the pulley? When I reinstall the hub and pulley I would like to orient them so they are at the 12:00 position at TDC, but the thing that looks like a weight is making me hesitant to do so. Does anybody have any input on this?
Thanks,
I've been reading some posts saying that lining up the the crankshaft hub and pulley does not matter.
Looking at the picture of mine, you can tell that hub was not lined up correctly at TDC. The mark on the hub that should be in the 12:00 position is in the 7:00 position in the picture. The white mark is just there for my reference of how the pulley came off the hub.
In the picture of the pulley, I circle what looks like a weight. If it doesn't matter how the hub and pulley are oriented, why would there be a weight in the pulley? When I reinstall the hub and pulley I would like to orient them so they are at the 12:00 position at TDC, but the thing that looks like a weight is making me hesitant to do so. Does anybody have any input on this?
Thanks,
