LS1 to Muncie M21
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On The Tree
Joined: Feb 2013
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LS1 to Muncie M21 Hi Guys, this my 1st post into this forum, but I've been around for a while, just its my first LS build, so you'll hear from me a lot! 
I'm trying to install a Muncie M21 transmission to a 2000 LS1, I already have the Sachs NFW 1050 flywheel that has the LS1 crank bolt pattern and the old style pressure plate bolt pattern, 1st problem I faced is that it uses (the flywheel) metric pressure plate bolts, and what I have are the shouldered 3/8 bolts, so I believe I need a different pressure plate that uses the two locating pins in the flywheel. The other problem is that I noticed that the flywheel friction surface is larger than the clutch disk surface, so it misses around 30% of the disk surface, which I think will affect the clamping force. I have searched a lot and found that it should use a 12 in. clutch instead of the 11 in., now my questions are :
1- what type of a pressure plate that I need to use? it should use metric bolts and dowel pins.
2- will a 12 in. clutch fit the normal 621 bellhousing?
I'm trying to install a Muncie M21 transmission to a 2000 LS1, I already have the Sachs NFW 1050 flywheel that has the LS1 crank bolt pattern and the old style pressure plate bolt pattern, 1st problem I faced is that it uses (the flywheel) metric pressure plate bolts, and what I have are the shouldered 3/8 bolts, so I believe I need a different pressure plate that uses the two locating pins in the flywheel. The other problem is that I noticed that the flywheel friction surface is larger than the clutch disk surface, so it misses around 30% of the disk surface, which I think will affect the clamping force. I have searched a lot and found that it should use a 12 in. clutch instead of the 11 in., now my questions are :
1- what type of a pressure plate that I need to use? it should use metric bolts and dowel pins.
2- will a 12 in. clutch fit the normal 621 bellhousing?
I dont know if the 12" clutch will fit in the 621 bell. The trucks use a much bigger bell with a larger cutout for the bearing retainer. You can use a truck bell with an adapter ring to fit the smaller Muncie bearing retainer.
If you try the 12" clutch, let us know if it fits in the 621 bell.
I used the metric clutch bolts made for the flywheel application. They're the right length but 3 are too large to fit in the 11" clutch. I removed the locating pins and only enlarged the holes big enough to tightly fit the bolts. I didn't balance it before bolting up, but would if I did it again. BTW, Pace sells a kit that looks very similar to this combo.
http://paceperformance.com/i-5146180...rsion-kit.html
The disc only contacts the flywheel partially due to the center cutout on the flywheel. Clamping force is based on the pressure plate springs not clutch surface area. The disc might wear a little faster though. More than a few running that way, although probably wouldnt do it on a 500hp engine.
If you try the 12" clutch, let us know if it fits in the 621 bell.
I used the metric clutch bolts made for the flywheel application. They're the right length but 3 are too large to fit in the 11" clutch. I removed the locating pins and only enlarged the holes big enough to tightly fit the bolts. I didn't balance it before bolting up, but would if I did it again. BTW, Pace sells a kit that looks very similar to this combo.
http://paceperformance.com/i-5146180...rsion-kit.html
The disc only contacts the flywheel partially due to the center cutout on the flywheel. Clamping force is based on the pressure plate springs not clutch surface area. The disc might wear a little faster though. More than a few running that way, although probably wouldnt do it on a 500hp engine.
