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C6 Transmission question
#1
I have 73 Q Code with a newly built C6 transmission. I will take it back to the shop, but there seems to be something odd going on. I was told the torque converter was a 1900 rpm stall, but I have read that these came with a 2500 rpm stall. When I step on the gas, the tach runs to around 3000 and I don't really feel the power at the wheels.

It may be I'm expecting more torque than the 351C outputs. I know they have a high rpm torque max. It will do a great burn out, but it just feels "off" to me. I have 68 GTO and the two cars feel SO different it's a bit disconcerting. I do realize the GTO has a lot more low end torque and horsepower, but it seems odd that no matter what gear, if I am running at lower rpm's it slides up to 3k and then seems to fully engage.

Engine was recently rebuilt, but when I bought the car the trans was having serious issues. Since the rebuild it's much better, but that initial rev on acceleration just seems wrong.

Thoughts?

Mustang Bob
Burbank, CA

'73 Mustang "Q" Code Convertible
'68 Pontiac GTO
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#2
All I can tell you is the Cleavland wakes up a little past 3000 rpms so that might be your trouble. This engine was made as you say for high rpms and it does fell a little lacking lower than 3000. The 4 v was made to race in long track not drag racing so it might feel a little sluggish on the take off. there are way's to get better low end torque. Putting 2v heads or even Aussie heads or aftermarket heads will help in that situation. A shift kit in the trans will make the changing of gears quicker also. And yes you could use a bigger stall. My 351 isn't stock anymore but I put a 3000 rpm torque converter in it and it really gets the job done.

Eric


[Image: a58hgh.jpg]
DRIVE IT DON'T STORE IT!
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#3
72 and 73 C 6 Q codes came with a 2500 stall converter.


Ohio Mustang Supply
440-949-2556

[Image: oms_sig_banner.jpg]
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#4
the converter could be defective.
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#5
I'll take it back to the shop and have them check it out. I had a moderate shift kit installed with the rebuild, but I think I can go even more aggressive with it. Doesn't the 351C redline around 5500? Seems like a very short power band, but it does well at higher speeds under acceleration since it stays in the band.

What's the biggest difference between the 4v and 2v heads that gives the lower end torque?
Also, I haven't really driven higher stall converters in any of my other cars. The concept, as I recall, is to get the engine RPMs up to the power band by slipping the converter and not fully engaging until it hits x,xxx rpm. With the higher converters, does it feel like then engine "slips" a bit until the converter fully engages? And if you are driving under the stall, does it feel slightly sluggish to subtle acceleration?

Mustang Bob
Burbank, CA

'73 Mustang "Q" Code Convertible
'68 Pontiac GTO
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#6
Yes below the stall speed the car will feel sluggish.
Try standing on the brakes and slowly rev the engine with your other foot to see how much stall you can get. This should only be done for a couple seconds to avoid overheating the tranny/converter. then record the rpms reached.
High stall converters are usually a lot smaller diameter than standard ones.

[Image: mustangnight010.jpg]
1972 Mustang Convertible 351C 4V
1966 Ford Galaxie 7 litre-4speed

Jorge
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#7
I am not running stock but I have a C6 with a reverse valve body and a shift kit. My MSD box has a 7000rpm chip in it and I am going through the traps at 6450. X2 on the high end torque. I leave the line at about 2000rpm. As was said try fooot brakeing for a couple of seconds and see where you are at.
Jim

drive it like you stole it
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