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Just like the subject says. How much HP can a stock 66-67 C4 transmission handle? Assuming it's in really good shape.
 

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I'd say at least 400 ponys as long as it is in good shape. The question is more about "How long will it last" to me. There are guys running C4's behind built 351C's at the strip but they are highly modified. A stocker IMHO will take a 400 HP street blast every once in a while without grenading. The same trans might not last a day at the strip making run after run. With a good shift kit and an external trans cooler the same trans would likely last a long time.
 

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I used to run a C-4 behind a well built 302..the tranny also was built to the hilt as the saying goes..for tough street use..I would get about 6 months out of it..for strip..it would self destruct..after about 25 runs..I was putting out about 400 HP
 

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Believe it or not I had a friend who had a 67 coupe with a 70 Boss 302 hooked to a C-4 until I found him a small blk. C-6 as he didn't to go the 4 speed route!
 

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I run a blueprinted stock early C4 in the race car....

It seems to hold up well...and likely has taken more hard use than most street cars can dish out...

Be aware that high torque at low rpm, combined with a heavy vehicle, can and will destroy a C4, even if it is built right (not modified, as in expensive racing trans).
 
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Ok... I'll be the spoiler. I have years of experience on this subject. I destroyed a C-6 every pass in my drag car. Decided to play with my '71 Grande, 365 horse 460, slicks, converter, C-4... yes C-4. Car ran low. LOW 13's all day long & after 5 years it still does, just a C-4 from a T-bird/400M. As far as power, my engine makes over 700 ponies on a real dyno & made close to 1100 on the bottle & a C-4 is the best thing I ever bought. I've had it many years & has never failed, trans brake & all. Car runs mid to low 1.20 60' times on a bad day. I have a ton of literature on how to make a C-4 live, it's eally simple. Ok... bring on the arguements /forums/images/icons/smile.gif
http://www.tulsahotrods.com/
66 Drag car
 

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You won't get arguments from me....I think they're great and I've seen enough of them in Super Gas cars to know they'll hold up, when modified for the job, in 2 hp/ci powertrains.

But, in the case of the poster here, he wanted to know how his stock 67 C4 would hold up. In that regard, I have much experience as I've only run OEM C4's in the race car. I do know at the peak power levels produced and in my particular combination of engine torque, torque converter and vehicle weight, that it does work fine and provide long life.

Add 50 hp or 300 lbs? Who knows...His early unit's weak point primarily is the input shaft, and, as I mentioned in my post, high torque at a low rpm (like my W produces) combined with a heavier car (he has about 600 lbs on me) could cause problems.

I think we would agree that C4's are a good transmission, better than many people give them credit for, but that doesn't keep me from running a scattershield on mine, eh?? *G*
 
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As you know from your racing experience I have the obligatory bellhousing & tranny shield. My S/C 'Stang I'm trying to slow down to S/G would have the shield nontheless. After what I saw this weekend, I'll be glad to keep the J&W b,housing too! Good cheap insurance.
 
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A "properly built" C-4 will handle anything a "street car" can throw at it. I have a friend that is running a C-4 in his 90LX with a 347 stroker and 225 shot of go juice with NO problems what so ever, and he's putting over 550HP to the wheels. I think C-4's are highly under rated trannys.
 
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