Checking runout of QT Bellhousing
09-08-2012, 03:08 PM
#1
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Checking runout of QT Bellhousing I just want to make sure i'm doing this right and that my findings make sense. I'm checking to see if i need offset dowels on my Quicktime bellhousing. the car is a '01 SS with a T56. I marked the bellhousing where "0" is, the point closest to the crankshaft, and the furthest point from there was 0.014" away from the crank, thus requiring a 0.007" offset dowel. The spot that was 0.014" wasn't 180° from "0." I don't know that it needs to be, just seems logical that it would be, unless maybe the opening is egg shaped. Does it look like i did everything correctly?
Here's what i have:
Here's what i have:
09-10-2012, 05:52 PM
#2
I did this, bymyself at 1st so only checked a few spots like you did. But you need to set it up so you dont crash the indicator, going past the openings. And get 2 people and watch how it maps out 360* then you can see got round the hole is for sure, if its a steady 0-.014 wave, or how bad it is. I also noticed some paint runs, and orange peel in the ID of that 1/2 plate or whatever thickness it is. So went over that with some sand paper squarely. No to remove the paint but knock down any high spot that show up with a light scuff. Looks like you did that around the t56 mounts, but just a heads up for anyone doing thinks like this. But I was +.0055 or something on just the bell, then I did it what really matters. How your t56 bolts on. How centered the input shaft bearing bore is to the crank centerline. That bell roundness really dosnt mean anything, the t56 has thouse 2 dowels that locates on and repeats its placement.
Check my build thread on this, I did it a few weeks ago so it should be on the last 1-2 pages. The trans plate was withing like .005 just bolting it on and the bell with gravity pulling them down. I found giving them both a light tap with the rubber mallet, and pushing them the way to be more centerd, got them better. I should be within .003 .002. Not sure if you can make that up. But the offset dowls I think would be a pain to setup, that might help you get it alot better.
Check my build thread on this, I did it a few weeks ago so it should be on the last 1-2 pages. The trans plate was withing like .005 just bolting it on and the bell with gravity pulling them down. I found giving them both a light tap with the rubber mallet, and pushing them the way to be more centerd, got them better. I should be within .003 .002. Not sure if you can make that up. But the offset dowls I think would be a pain to setup, that might help you get it alot better.
09-10-2012, 05:54 PM
#3
https://ls1tech.com/forums/manual-tr...ht=Bellhousing
https://ls1tech.com/forums/drag-raci...h-diet-42.html
also test fit the bell on your trans and maybe sure you have slave line and bleeder room. I little 45* bevel made mine alot better for bleeding , glad I found it mockup.
https://ls1tech.com/forums/drag-raci...h-diet-42.html
also test fit the bell on your trans and maybe sure you have slave line and bleeder room. I little 45* bevel made mine alot better for bleeding , glad I found it mockup.
09-10-2012, 06:15 PM
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I did this, bymyself at 1st so only checked a few spots like you did. But you need to set it up so you dont crash the indicator, going past the openings. And get 2 people and watch how it maps out 360* then you can see got round the hole is for sure, if its a steady 0-.014 wave, or how bad it is. I also noticed some paint runs, and orange peel in the ID of that 1/2 plate or whatever thickness it is. So went over that with some sand paper squarely. No to remove the paint but knock down any high spot that show up with a light scuff. Looks like you did that around the t56 mounts, but just a heads up for anyone doing thinks like this. But I was +.0055 or something on just the bell, then I did it what really matters. How your t56 bolts on. How centered the input shaft bearing bore is to the crank centerline. That bell roundness really dosnt mean anything, the t56 has thouse 2 dowels that locates on and repeats its placement.
Check my build thread on this, I did it a few weeks ago so it should be on the last 1-2 pages. The trans plate was withing like .005 just bolting it on and the bell with gravity pulling them down. I found giving them both a light tap with the rubber mallet, and pushing them the way to be more centerd, got them better. I should be within .003 .002. Not sure if you can make that up. But the offset dowls I think would be a pain to setup, that might help you get it alot better.
Check my build thread on this, I did it a few weeks ago so it should be on the last 1-2 pages. The trans plate was withing like .005 just bolting it on and the bell with gravity pulling them down. I found giving them both a light tap with the rubber mallet, and pushing them the way to be more centerd, got them better. I should be within .003 .002. Not sure if you can make that up. But the offset dowls I think would be a pain to setup, that might help you get it alot better.
Yeah i pulled the spark plugs so it would rotate smoothly and had a buddy help me turn the motor while i watched the indicator.
From that "0" mark going counterclockwise to the .014" mark it ramps up pretty quick, but going the rest of the way from the 0.014" back around to zero, it slowly tapers backto nothing as you go around.
The bellhousing locates the CL of the gearbox since it attaches with tapped holes. The slop is in the blind holes on the bellhousing. Theoretically, the opening on the T56 side (round or not) should be symmetrical with the bolt pattern around it. The adjustment comes from the engine side of the bell, which can only be changed by the dowels.
correct?
All i know is i have .014" TIR and a broken clutch to prove it. i Think with a single or even twin disc, the offset is less of a concern, although still "wrong." Since i had a triple disc, the problem was exaggerated by the thickness of the clutch assembly. There was more material there to be affected by the offset in the input shaft, if that makes sense.
09-10-2012, 06:45 PM
#5
I think if u are gonna measure the runout, u either need to bolt it to trans and measure to make sure the round hole in the bell is centered or use a front plate bolted to the bell as studderin did. No thing says the the round part is cut correctly and the input shaft will be dead center. When I put mine in, I just used a metal alignment tool and a welders magnet and measured with calipers. Definitely not the best way, but I thought it was close enough for a single disk.
09-10-2012, 08:11 PM
#6
The slop is in the blind holes on the bellhousing. Theoretically, the opening on the T56 side (round or not) should be symmetrical with the bolt pattern around it. The adjustment comes from the engine side of the bell, which can only be changed by the dowels.
All i know is i have .014" TIR and a broken clutch to prove it. i Think with a single or even twin disc, the offset is less of a concern, although still "wrong." Since i had a triple disc, the problem was exaggerated by the thickness of the clutch assembly. There was more material there to be affected by the offset in the input shaft, if that makes sense.
09-10-2012, 09:24 PM
#7
Before I installed my QT I stumbled across studderins writeup about checking the runout but other guys say thats not necessary. So I didnt measure, a royal PITA to pull everything apart at work then push the car outside & wait for offset dowels to arrive. I got 7k on mine, handful of track outings & so far so good. I thought if this was so important some instructions wouldve been included with the QT but nothing but a few QT stickers in there unlike the monster clutch I got. All kinds of instructions for that. So who sells the offset dowels?
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09-10-2012, 09:36 PM
#8
lakewood sells them. But if you got 7k on it with no problems, I would say you are good.
When checking, you should also check to make sure that the mating surfaces of the bell to block and bell to trans are parallel.
When checking, you should also check to make sure that the mating surfaces of the bell to block and bell to trans are parallel.
09-10-2012, 09:40 PM
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Best deal i've found, and the ones i ordered, are from RobbMc. google it and you'll find their site. Those dowels are $28 + shipping. they're adjustable with a wrench, real simple operation. I've read the dowels from Moroso and the cheaper lakewood dowels are either too soft and can break or "mushroom" during installation OR they require a hole be drilled & tapped on the block for a set screw. You can't really do that with the engine in the car. The nicer dowels from Lakewood seem identical to the ones from RobbMc, but they're twice the price.
09-10-2012, 09:43 PM
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It sucks to pull it apart and check everything like this, but its worth it in the end. Its not just about meeting a certain tolerance. If you get it all dialed in really close, the tranny will shift a lot smoother and you may get a little more life out of everything.
