Seanndogg

Well I am going to put my heads on and today I went to turn the crank bolt to put the #1 piston at TDC and so I put the timing mark straight up but the #1 piston was about an inch away from the top. I am pretty sure I put the hub on correctly so the timing mark would be right ...

Should I just bring the #1 piston as close as I can to top dead center by looking at it as I turn the crank ? I really don't want to take it off.

shoebox

If you are going to rely on the crank pointer, I would take this opportunity to remove it and make it correct. The point at which the piston is at the top and neither moving up or down is TDC.

Alternately, you could also just bring it up to TDC and make another mark straight up on the pulley or hub as your new reference. I would also look to be sure that you have no balancing weights in the holes in the pulley.

norcalstreet

If your harmonic balancer is off set it may cause vibrations. Check the balancer and see if there are weights in the drilled holes. If there are it's very important to get the TDC in correct.

Seanndogg

yeah , there are 2 weights in the balancer on the right hand side right next to eachother.

Why does this matter so much.? Why dont they all have weights?

shoebox

Because that is how it is balanced.
I would recommend you take it off and re-orient it or you might have some vibe problems. Most people don't find any weights in theirs (mine has none), but if there are some, you need to install it back like it was..

95 Z/28 LT1

I thought that the balancer was neutrally balanced? Isn't that why there is no keyway for it to be lined up to?

I was under the understanding that the engine was balanced from the factory solely by the flywheel.

shoebox

It is a fact that some have weights in the pulley. Seanndogg is proof. If you have no weights, it doesn't matter how it is put back on.
There have been others that have experienced vibes when theirs had weights and they did not line it up correctly on re-install. The vibes were corrected when they went back at re-oriented it. The weights are mentioned in the factory manual.

Seanndogg

I didn't get any vibration while my car was running last time I did major engine work... I am just think out loud but I would really hate to take off that damn timing cover again ! I may throw the heads and everything else on, adjust the valves and see what happens. Is that crazy ? It really doesn't seem like it would make a big difference.

shoebox

You don't have to remove the timing cover, just the hub.

norcalstreet

The position is extremely important. I have seen engines before which have had these installed incorrectly and there is extreme vibrations (I'm speaking about one which was off by 40 degrees or so). If you did pull it off before you must have put it on correctly before as well. You can stick a wire into the spark plug holes to feel when the number one piston is at TDC and you can then realign the hub as needed.

If your heads are off now it should be easy to tell where TDC is.

Blk94Z28LT1

has anybody bought the keyed hub from thunder racing?

kirschman

are u sure bout that Rob? I thought it doesnt matter bout how the hub goes on, its not balanced. The hub, seems to me, would have to be on in the correct position for finding TDC only, or wouldnt it be keyed?? Seems to me its the balancer that needs to be on it the correct position, since its, well, a balancer. I dont think the hub has weights in it, correct me if I'm wrong.

kirschman

one more thing, what if you cant tell which way it "was" on. My balancer has the 2 weights in it and I cant tell which way it was on!! I know, I know, I should have marked it but I was under the impression that it doesnt matter how it goes on. The t/c sprocket dots are lined up and I put the hub with the with the arrow pointed up, which should be no6 at TDC correct. I installed the balancer with the arrow lined up with the hub arrow, sound right. So tell me this, if i have any vibes can I just take the balancer off and spin it around one bolt hole and try it, or do i need to go 180 around.

norcalstreet

There's a few ways to determine TDC.

1. Pull your heads and actually see where the pistons are.
2. Pull your valve covers and watch the rocker/valve springs to see where TDC is.
3. Put a wire inside the spark plug hole and feel where the piston is.
4. You could pull the timing cover and determine where TDC is based on the timing chain.
5. I've also heard of using a compression tester but I'm not sure if that is accurate enough.

Don 97 SS

I am considering buying a keyed hub, but now I am wondering if I do get one will I need to have it balanced with the crank?

Is a keyed hub really necessary on a non-forced induction LT1? Would it be over kill? Who has one of these that can comment on their experience?