first time out with 393w

finally got out with my 393w, car is a 1979 mercury zephyr, weight it at the track ,2800 lbs  still tons of tuning to do, bone stock 1979 suspension, tach was bouncing around and was reading 500 rpm difference then my digital timing light, so not 100% sure what rpm i shifted at, first pass went 11.50 in  1/4 mile then put 2 degrees timing in it and think i shifted around 6000 and went 11.12@121, then a 11.21 and then this happened the 4th pass, word of advise don't try to use a 393w and a 7.5 rear end, i thought it would last at least 1/2 season ..nope 3 passes

Get the rear end problem fixed and you should be able to tune it and run 10's.My buddy had a 7.5 in his Mustang with 3.42 gears and welded up spider gears car ran 10.90's with a 466 BBF in it.He never broke the 7.5 and sold the car with it still intact.

Mark Miller wrote:Get the rear end problem fixed and you should be able to tune it and run 10's.My buddy had a 7.5 in his Mustang with 3.42 gears and welded up spider gears car ran 10.90's with a 466 BBF in it.He never broke the 7.5 and sold the car with it still intact.  

im putting a 8.8 in it with 4.10 gears and try some 28-10 slicks , and want to try a bigger carb , just using a 750 carb, it is not 60ft very well, its spinning bad, currently on 26-8.5 slicks

Looks like you got a little day light under the tire ! sorry for the bad luck ,but you are going in the right direction ! Stay with it

You get a rearend under that thing and it will be .... on...

60ft-1.60
1/8 mile--7.08 @97mph
1/4---11.12@121

It was coming alive after the 1/8

im running in a class called the stock block class, i was number 1 qualifier then broke in the finals, im sure it needs more carb, just has a 750 on it

What gear ratio did you have in the 7.5"? Nice ride by the way.

supervel45 wrote:What gear ratio did you have in the 7.5"? Nice ride by the way.

3.73, guess i will spend the $ and get some good axles, and clip elimators and a spool

Those are some nice E/T's. My friends 408W Fox, liked the Holley 950HP he had on it. He had 4.10's also, and I can't remember the tire size, but I think they were 28's. Stock 31 spline Axles are pretty strong, but if you can afford after market go for it.

i got tranny out of car and tore apart, not a single broken part inside, it was prefect, converter has to be broken , its a brand new freak-show, i spoke with him and said he will warranty it..

Keep us posted on the out come of the converter , and the progress of the car ! Good luck !

i had the converter sent out the first time for a refresh and re-stall, tranny was brand new too,i paid shipping both ways on converter ,after i had issues ,it would not even try to move in any gear , so i pulled tranny and converter ,i tore apart the tyranny-resassembled it, then had it tore apart again by someone else to check it , nothing is wrong with tranny, other then it had .250-.500 inch of shaft play, we fixed that , so i called converter guy and it was under warranty ,so i paid to ship it back, i got converter back and he paid shipping and said nothing was broke in converter so i dont know what the deal was

I have a buddy in Broken Arrow that has an 8.8 in his car currently but he needs to step up to a 9".  It is set up with good axles, spool, etc... if you are interested in a complete rear.  It also already has good lower brackets on it.

We've been begging him to move to a 9" for gear life but he just keeps beating on that thing.  It's in an X car.


You must have a bunch of wheel hop with your stock setup. That kills C4 transmissions. There is not much to go wrong inside of one of those converters, nothing like you describe. I was wondering why after giving you prices for stuff you never messaged or called back, you bought straight from him.

I broke my stock 85 Mustang's 7.5" rear on bfg regular ol' radials on the street like 20 years ago. I'm surprised yours lasted 3 passes.

whatbumper wrote:I have a buddy in Broken Arrow that has an 8.8 in his car currently but he needs to step up to a 9".  It is set up with good axles, spool, etc... if you are interested in a complete rear.  It also already has good lower brackets on it.

We've been begging him to move to a 9" for gear life but he just keeps beating on that thing.  It's in an X car.


You must have a bunch of wheel hop with your stock setup.  That kills C4 transmissions.  There is not much to go wrong inside of one of those converters, nothing like you describe.  I was wondering why after giving you prices for stuff you never messaged or called back, you bought straight from him.  

that is all it was ..a price quote, i already had the tranny and converter i was just looking at other options is all, i decided to stay with my c4 and have converter re-stalled -fresh and sprag removed, i put a 8.8 and 4.10 gears in already, i am worried what my issue was to begin with, there was not a single broken part in my tranny and freakshow said there was nothing wrong with converter