Opinions on maximum horsepower to a C4 and 8" rear end

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Holubs

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All,

Starting on my journey for the 1973 convertible that will be dubbed "Kiki" after the widow of the original owner. The drive train needs to be gone through, rebuild the C4 transmission, the 8" differential, and the 302 2V engine. I could replace the entire drive train with heavier duty parts, but would prefer to keep the car mostly original.

I plan to up the horsepower on the 302 from stock when it is rebuilt, how much power can the C4 and 8" safely handle?

 

Hemikiller

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C4 can be built to handle 1000+ hp. Obviously, you're not going there, but it is a very good transmission. A stock rebuild with good clutches, a larger intermediate servo and a shift reprogramming kit will be all you should need, along with a torque converter to match the power characteristics of your rebuilt engine. 

8" is plenty strong, it only becomes an issue when you have traction and are launching hard. 

 
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+1 on what Hemikiller said.  I had my c-4 built probably 14-15 years ago. It has been behind a stock 302, mildly built 351C with 400hp, and a 408C stroker with close to 600hp.  I got all my parts from Broader Transmissions. https://broaderperformance.com/  They are top notch guys. Highly recommend their valve bodies. I got my torque converter from B&M. Its a 3,000 stall unit.  Works great.  

As far as the 8" rear end goes I ran mine for a couple years behind my 302 and 351C. It seemed to do just fine. Mine was only 3.00 gears. So instead of doing a gear swap, I swapped in a ford 8.8"  for less money than it would of took to do a gear change on the 8".  My 8.8 also came with 3.73 gears, factory disc brakes, and 31 spline axles. I have had that rearend in there for probably 12-13 years and have had 0 issues. If your interested in that route, look at some older Ford Explorers for the rearends. I believe mine came from a 2005. 

 

Holubs

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Thank you for the information, that is helpful! I was looking at around 300hp after the engine build. Not planning on a lot of hard hole shots or drag racing with this car, is would be nice to have the option to light up the tires on occasion without breaking anything!  :)

Did you rebuild your transmissions or have them done professionally?

 
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