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so i'm putting everything back together does anyone know the torque specs for the harmonic balancer not the HUB
i found some where its 63 lb ft does that sound right???
But where is your dampener??? That's an underdrive pulley, right? The dampener should go on over that. Sorry to tell you now, but they do very little for an LT1 and have been known to cause charging problems at idle unless you also change the alternator pulley.
Yes. Shoebox is pointing out that what is shown in your picture in post #4 does not appear to be a harmonic damper. It appears to by an aftermarket underdrive pulley, that is intended to be sandwiched between the hub and the factory damper. Without the damper, you are stressing the crankshaft with harmonic vibrations, and can damage it.
He is also pointing out that since the water pump is not belt driven, there is very little if anything to be gained with an underdrive pulley, and it can also lead to charging problems. This dyno test shows that an underdrive pulley netted a peak gain of 0.7 HP.
What a really stupid design. Thank you Shoebox and Injuneer. I will have that fixed after a trip to the hardware store for longer bolts.
I guess I’m used to Ford type of underdrive pulleys.
Good advice. Im going to go an extra 1/2” on the bolts. The threads won’t even catch right now. ASP says to torque 45-50 but Shoebox’s guide says 63. What would the best route to go?
ASP makes a full replacement underdrive damper... or at least they did in 1995 when I bought a set. It came with an option for an overdrive (speeds the alternator back up) or an underdrive (slows the alternator down even more). alternator pulley. I had the U/D alternator pulley, for a full 40% reduction, and it barely kept the battery charged at idle, even with the M6's 800 RPM stock idle speed.
Definitely more problems than they are worth. The big gains with an U/D pulley are from slowing down the water pump. But on the LT!, the pulley is only turning the alternator, PS pump, A/C compressor and the idler pulley. When you want to make a pass at the track, you aren't using the PS or the A/C, so there is not much to gain.
I bought my car brand new in 1994, and tried all the "bolt on" gimmicks, because I didn't know any better.... the only stuff that was really worth anything - at least based on track times - was the Borla 3" catback and a Moroso cold air intake. Even the JBA 1-5/8" stepped shorty headers gained nothing.
I don't think the torque on the bolts makes too much difference, but I would opt for the higher value.
this is what i just took off my 95, it was on there when i got the car and didn't know why even the over drive pulley i put on the alternator wasn't doing the trick. my battery was going dead in the winter with all the stop and go traffic.
I even bought a $300 200 amp alternator just to make up the difference. never installed it, now i don't have to.
Im about to intstall a bbk underdrive pully tomorrow, i have not touched mine, its still stock and does not look like that with the second piece......its just a one piece harmonic stock and then the 3 bolt crankshaft thing on the end. Mines a 1994 though, not sure if thats different? Ill let you know if i feel any power, im sure it will make some diff but not insane obviously its just a few lbs off the crank.
09-04-2019, 04:12 PM
