L71 Rebuild
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Joined: Jun 2025
Posts: 84
Likes: 13
From: Will County, Illinois
L71 Rebuild
Once again, I appreciate all you guys and the knowledge you share on this forum.
So I’m rebuilding this thing to be somewhere around 550-600hp… the question for you guys that have a similar setup, did you do anything to beef up the M21 tranny or the rear end in these cars? It’s a ‘68.
Thanks guys!
So I’m rebuilding this thing to be somewhere around 550-600hp… the question for you guys that have a similar setup, did you do anything to beef up the M21 tranny or the rear end in these cars? It’s a ‘68.
Thanks guys!
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Joined: Dec 2024
Posts: 77
Likes: 38
From: The Plains, VA
2025 C3 of the Year Finalist - Modified
Well, for a start does your M21 have a drain plug? It didn't from the factory, and it does have a magnet glued to the bottom of the case which is probably covered in a significant amount of sludge. I'm replacing mine right now and planning a rebuild with upgrades for strength and reliability. I'm expecting that running dirty oil through it over the years will have taken a toll. You might want to check out Paul Cangialosi's Super661 site and videos for some good information. I know there are others, but I find his most useful for me.
Race Director
Joined: Mar 2016
Posts: 14,347
Likes: 8,155
From: Napa Valley California
If you are building the engine to 500-600 hp, then figure in that you’ll need to up grade everything from the flywheel back to the rear wheels.
If you can do all the work yourself add $5k to $7k to your project.
If you can’t do all the work, then add $7k to $10k to your project.
One of the biggest issues you’ll run into is that all the quality components for the rear differential and axles are no longer available and the people who do have them know their value.
Gary Ramadei GTR1999 is the best at building rear differentials.
If you contact Gary, he can help you.
If you can do all the work yourself add $5k to $7k to your project.
If you can’t do all the work, then add $7k to $10k to your project.
One of the biggest issues you’ll run into is that all the quality components for the rear differential and axles are no longer available and the people who do have them know their value.
Gary Ramadei GTR1999 is the best at building rear differentials.
If you contact Gary, he can help you.
