SM465 to 5.7 vortec flywheel/clutch - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Chilly178 · 05-01-2018, 10:07 PM

Hey I'm looking to replace my old 168 tooth flywheel off my 72 C20 and replace it with a externally balanced one for the new engine, which is a L31-r/5.7 vortec. I would like to change the clutch while everything is apart. I have a 12" clutch that was pulled out of it. I'm wanting to go with a cast iron flywheel because I don't really need a steel one I don't think. The only flywheel I really found that is to these requirements is the perfection flywheel. https://www.summitracing.com/parts/z...make/chevrolet Does anyone have any experience with this brand? I found a GM one which I would prefer but it's only good for 11.85" clutch I guess. https://www.summitracing.com/parts/n...make/chevrolet Now for clutch selection, I pulled out a borg clutch out of the truck. I want to go to the diapram type. Do I have to swap anything on the trans to accept this type of clutch? I narrowed it down to two different clutches, RAM https://www.summitracing.com/parts/r...make/chevrolet and LuK https://www.summitracing.com/parts/l...rview/make/gmc Any opinion on which one I should go for? I just want something that I will put in once and not have any issues, thanks.

**'68OrangeSunshine** · 05-02-2018, 12:11 AM

Probably uses a different throw-out bearing between Borg & Beck and diaphragm types.

**kwmech** · 05-02-2018, 01:03 AM

If you measure your clutch you may find out that it actually measures 11-7/8 and will bolt directly to the flywheel mentioned

Chilly178 · 05-02-2018, 08:07 AM

Yep I measured it it’s 11 and 7/8. Went to autozone and had them pull out a new 12” for the truck just to compare and that one too measured under 12”. So i’m guessing all 12” clutches measure a little short. So are you saying a 12” (11 7/8”) clutch will work with the GM one for sure that lists the clutch diameter 11.85” max?

**kwmech** · 05-02-2018, 10:28 AM

Sure looks like it according to the measurements. Looks like all the bolt holes are there also, just like a factory flywheel. Will take 10, 11, or 12'' disc

Chilly178 · 05-02-2018, 12:43 PM

Thank you it gets confusing when people start rounding up. I’m gonna go ahead and get the GM flywheel. Now I just gotta decide what 12” clutch kit to get.

05-01-2018, 10:07 PM	#1
Chilly178 Registered User Join Date: May 2016 Location: Green Bay, WI Posts: 129	SM465 to 5.7 vortec flywheel/clutch Hey I'm looking to replace my old 168 tooth flywheel off my 72 C20 and replace it with a externally balanced one for the new engine, which is a L31-r/5.7 vortec. I would like to change the clutch while everything is apart. I have a 12" clutch that was pulled out of it. I'm wanting to go with a cast iron flywheel because I don't really need a steel one I don't think. The only flywheel I really found that is to these requirements is the perfection flywheel. https://www.summitracing.com/parts/z...make/chevrolet Does anyone have any experience with this brand? I found a GM one which I would prefer but it's only good for 11.85" clutch I guess. https://www.summitracing.com/parts/n...make/chevrolet Now for clutch selection, I pulled out a borg clutch out of the truck. I want to go to the diapram type. Do I have to swap anything on the trans to accept this type of clutch? I narrowed it down to two different clutches, RAM https://www.summitracing.com/parts/r...make/chevrolet and LuK https://www.summitracing.com/parts/l...rview/make/gmc Any opinion on which one I should go for? I just want something that I will put in once and not have any issues, thanks.

05-02-2018, 12:11 AM	#2
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,047	Re: SM465 to 5.7 vortec flywheel/clutch Probably uses a different throw-out bearing between Borg & Beck and diaphragm types. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

05-02-2018, 01:03 AM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,390	Re: SM465 to 5.7 vortec flywheel/clutch If you measure your clutch you may find out that it actually measures 11-7/8 and will bolt directly to the flywheel mentioned

05-02-2018, 08:07 AM	#4
Chilly178 Registered User Join Date: May 2016 Location: Green Bay, WI Posts: 129	Re: SM465 to 5.7 vortec flywheel/clutch Yep I measured it it’s 11 and 7/8. Went to autozone and had them pull out a new 12” for the truck just to compare and that one too measured under 12”. So i’m guessing all 12” clutches measure a little short. So are you saying a 12” (11 7/8”) clutch will work with the GM one for sure that lists the clutch diameter 11.85” max?

05-02-2018, 10:28 AM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,390	Re: SM465 to 5.7 vortec flywheel/clutch Sure looks like it according to the measurements. Looks like all the bolt holes are there also, just like a factory flywheel. Will take 10, 11, or 12'' disc

05-02-2018, 12:43 PM	#6
Chilly178 Registered User Join Date: May 2016 Location: Green Bay, WI Posts: 129	Re: SM465 to 5.7 vortec flywheel/clutch Thank you it gets confusing when people start rounding up. I’m gonna go ahead and get the GM flywheel. Now I just gotta decide what 12” clutch kit to get.



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