Flywheel options
Thread Starter
Le Mans Master
Joined: Aug 2010
Posts: 8,508
Likes: 501
From: Bussey, IA
Flywheel options
Not there yet, but sneaking up on flywheel. I have two that came from Dad and one that came from Skids with the engine. One from Skids is smaller. Ones from Dad have an M11 cast on them What size flywheel did my 68 327/350 come with? Trying to think for the future, what will be best for my son when he inherits it and the starter goes bad and he has to replace it. Car is not numbers matching, so just trying to be practical. What words of advice say y’all?
Race Director
Joined: Oct 2000
Posts: 12,640
Likes: 3,103
From: Shamong, NJ
What year car do you have, what bellhousing do you have and what engine is in it? Different flywheels were used with different engines in different years, and the bellhousing you have will determine which flywheel/clutch you need.
63 Corvettes all used the "421" (last three digits of the part number) and used 12" flywheel and the 10 1/2" clutch. This bellhousing can only be used with 63 Borg-Warner T-10 and Muncie transmissions, and not later Muncies or Super T-10's.
If you have the 64-72 "403" bellhousing it also uses the 12" flywheel and the 10 1/2" clutch (the "403" is identical to the "421" except it has a larger front bearing hole).
If you have the "621" bellhousing that came with 66-72 big blocks and all 73-81 small blocks it uses the 14" flywheel and 11" clutch.
Finally, there was also a "444" bellhousing used only on 65 and early 66 (I think) big blocks, that is basically the same bellhousing as the "621" and also uses the 14" flywheel and 11" clutch.
63 Corvettes all used the "421" (last three digits of the part number) and used 12" flywheel and the 10 1/2" clutch. This bellhousing can only be used with 63 Borg-Warner T-10 and Muncie transmissions, and not later Muncies or Super T-10's.
If you have the 64-72 "403" bellhousing it also uses the 12" flywheel and the 10 1/2" clutch (the "403" is identical to the "421" except it has a larger front bearing hole).
If you have the "621" bellhousing that came with 66-72 big blocks and all 73-81 small blocks it uses the 14" flywheel and 11" clutch.
Finally, there was also a "444" bellhousing used only on 65 and early 66 (I think) big blocks, that is basically the same bellhousing as the "621" and also uses the 14" flywheel and 11" clutch.
Last edited by gbvette62; Jul 17, 2025 at 03:50 PM. Reason: put bellhousing where I had previously mistakenly said flywheel
Drifting
Joined: Jun 2025
Posts: 1,635
Likes: 575
sbc or BBC
Typically, flywheel or flexplate's either 153 teeth (straight-across starter bolt pattern, One short bolt + One long) OR
OR 168 teeth (staggered-diagonal starter bolt pattern, Both bolts long).
Light flywheel-clutch = Quicker Accel and Quicker Decel; but easier to stall when leaving a traffic light/stop sign. Easier to "steer" car with throttle when driveline has lighter rotating mass. Practice makes perfect.
Heavier flywheel-clutch = somewhat smoother running at low rpm + less likelihood of stalling.
Typically, flywheel or flexplate's either 153 teeth (straight-across starter bolt pattern, One short bolt + One long) OR
OR 168 teeth (staggered-diagonal starter bolt pattern, Both bolts long).
Light flywheel-clutch = Quicker Accel and Quicker Decel; but easier to stall when leaving a traffic light/stop sign. Easier to "steer" car with throttle when driveline has lighter rotating mass. Practice makes perfect.
Heavier flywheel-clutch = somewhat smoother running at low rpm + less likelihood of stalling.
Thread Starter
Le Mans Master
Joined: Aug 2010
Posts: 8,508
Likes: 501
From: Bussey, IA
sbc or BBC
Typically, flywheel or flexplate's either 153 teeth (straight-across starter bolt pattern, One short bolt + One long) OR
OR 168 teeth (staggered-diagonal starter bolt pattern, Both bolts long).
Light flywheel-clutch = Quicker Accel and Quicker Decel; but easier to stall when leaving a traffic light/stop sign. Easier to "steer" car with throttle when driveline has lighter rotating mass. Practice makes perfect.
Heavier flywheel-clutch = somewhat smoother running at low rpm + less likelihood of stalling.
Typically, flywheel or flexplate's either 153 teeth (straight-across starter bolt pattern, One short bolt + One long) OR
OR 168 teeth (staggered-diagonal starter bolt pattern, Both bolts long).
Light flywheel-clutch = Quicker Accel and Quicker Decel; but easier to stall when leaving a traffic light/stop sign. Easier to "steer" car with throttle when driveline has lighter rotating mass. Practice makes perfect.
Heavier flywheel-clutch = somewhat smoother running at low rpm + less likelihood of stalling.
Drifting
Joined: Jun 2025
Posts: 1,635
Likes: 575
Great information! Never heard that before! I have quite bit of experience with a stick so I will see how I do with the 153 tooth set-up. Trusting starter will be easy as well. Since everything was in baskets it is all a guess on what is what, what came from what and what is needed to work! Thanks again!
Most are around 30lbs, BUT there's an OE GM that's about 15-16 lbs.
Also, several aftermarket are 15-16lbs' even the cast iron (which is (cast) what L88 motor had). You can find an aftermarket cast 153T Light that's about 15-16lbs. If it's about $100, it IS cast & Asian. I ran local stock car and our primary sponsor supplied anything clutch/flywheel/pp - related. Ours ran 153T light cast iron.
There's another lighter option if you're flush w/ cash. Small diameter multi-plate clutchpak (looks alot like a motorcycle clutch assembly). The more common clutchpaks work in tandem with a 153T FlexPlate. In addition to light weight, the smaller the diameter, the quicker it reacts in both accel & decel; plain jane Newton physics.
Le Mans Master
Joined: Mar 2004
Posts: 7,458
Likes: 1,484
From: Little Rock AR
Remember to keep all the parts as a matching assembly. Flywheel, bell housing, clutch, starter nose cone, and starter support brace must all match. You can't mix and match. Small flywheel does not work with big bellhousing etc.
I would start with the bellhousing you have and go from there. You probably have a "403" casting number bellhousing and that works with the smaller 153 tooth flywheel, smaller 10.5" clutch, and the aluminum nose cone starter with the 2 holes in-line. One bolt short, one bolt long. Matching starter brace too.
if you have a "621" casting number bell housing, all the parts listed above will be different.
I would start with the bellhousing you have and go from there. You probably have a "403" casting number bellhousing and that works with the smaller 153 tooth flywheel, smaller 10.5" clutch, and the aluminum nose cone starter with the 2 holes in-line. One bolt short, one bolt long. Matching starter brace too.
if you have a "621" casting number bell housing, all the parts listed above will be different.
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Thread Starter
Le Mans Master
Joined: Aug 2010
Posts: 8,508
Likes: 501
From: Bussey, IA
Remember to keep all the parts as a matching assembly. Flywheel, bell housing, clutch, starter nose cone, and starter support brace must all match. You can't mix and match. Small flywheel does not work with big bellhousing etc.
I would start with the bellhousing you have and go from there. You probably have a "403" casting number bellhousing and that works with the smaller 153 tooth flywheel, smaller 10.5" clutch, and the aluminum nose cone starter with the 2 holes in-line. One bolt short, one bolt long. Matching starter brace too.
if you have a "621" casting number bell housing, all the parts listed above will be different.
I would start with the bellhousing you have and go from there. You probably have a "403" casting number bellhousing and that works with the smaller 153 tooth flywheel, smaller 10.5" clutch, and the aluminum nose cone starter with the 2 holes in-line. One bolt short, one bolt long. Matching starter brace too.
if you have a "621" casting number bell housing, all the parts listed above will be different.
Drifting
Joined: Jun 2025
Posts: 1,635
Likes: 575
suggest buy a NEW modern PMGR aka PG260 starter as found on 96-99 GM pickup with VIN R or VIN M and the correct bolts for same year.
Those starters are also diagonal mount AND they're so much lighter, that they neither need or require any "brace".
suggest download & save this 2-page TSB from REMY; it can help guide you when choosing to retrofit much improved PMGR
pay close attention to New starter bolts; It Matters A Lot.
https://autoprollc.com/wp-content/up...eb2016_web.pdf
Last edited by Rebelyell; Jul 22, 2025 at 10:20 PM.
Le Mans Master
Joined: Mar 2004
Posts: 7,458
Likes: 1,484
From: Little Rock AR
That Remy document is great but keep in mind that the part number you would buy for a '72 is discontinued. The solenoid with the "R" terminal bypass for the ignition is the issue if you do need it. If you run an electronic ignition, this will not matter so you can get the one in the Remy document without the "R" terminal.
The Remy numbers from this document are not listed for catalog purposes for any specific applications so don't expect them to show up in an online application lookup system. You need to search the part numbers listed.
The Remy numbers from this document are not listed for catalog purposes for any specific applications so don't expect them to show up in an online application lookup system. You need to search the part numbers listed.
Drifting
Joined: Jun 2025
Posts: 1,635
Likes: 575
That Remy document is great but keep in mind that the part number you would buy for a '72 is discontinued. The solenoid with the "R" terminal bypass for the ignition is the issue if you do need it. If you run an electronic ignition, this will not matter so you can get the one in the Remy document without the "R" terminal.
The Remy numbers from this document are not listed for catalog purposes for any specific applications so don't expect them to show up in an online application lookup system. You need to search the part numbers listed.
The Remy numbers from this document are not listed for catalog purposes for any specific applications so don't expect them to show up in an online application lookup system. You need to search the part numbers listed.
*add* the linked PMGR starter has diagonal-staggered bolt pattern AND has an R terminal: about $100 delivered
https://www.dbelectrical.com/product...sdr0031-m.html
Last edited by Rebelyell; Jul 23, 2025 at 10:17 AM.