Hey guys, I finished up my auto to manual conversion and here's the results.

Auto
1.9 60'
13.25 1/4mi
101 mph


Manual
2.3 60'
13.75 1/4mi
106 mph


The day I did the auto it was cold and rainy and the manual was hot, but still humid. The auto was in WI, not sure of the elevation, but the manual was in TX at 500ft altitude.

The manual obviously gave me more HP, and if I learn to launch it I should have a slighly better ET. Just thought you guys would like to see this info.

The ONLY change done to this car was the transmission change.

Mods to the car:
Stock buick LT1 longblock, 350ci with iron heads
230/236 cam with better spring
58mm TB
Mez water pump
MSD Digital 6
Accel Gen 7 DFI with dual sync dist
custom fuel setup
D44 3.45 gears

700r4 with manual valve body and 2800 stall converter
to a
Stock used clutch and zf6 setup

 

interesting....

 

but the 6-speed is more fun, huh???

 

The MPH is way up so the ET will come.

 

Sorry, but the auto will always be more consistant. And a manual tranny isn't gonna ad 1 HP. you don't get HP from a tranny.

 

Ah, but you do get more gears to stay in the power band and horsepower that used to run the converter. 5 MPH is a lot. I'll give you the automatic being more consistent if set up right. In my drag racing years I migrated from 4 speed to 5 speed to 400 turbo to powerglide. The latter with a trans brake being the most successful. ET was 2 tenth slower and mph was off 4 but 60' was about the same in the 1.32-35 range. Sorry, rambling and I miss racing. Still love pulling those gears and that's why I have a 6 speed Corvette and a 4 speed Chevelle. If this is the normal difference between a 6 speed and automatic I'm so glad I didn't compromise when I was looking for a C4.

 

Are you sure you got the numbers right? How can you go faster when the numbers are higher? Shouldn't your 106 MPH be with the 13.25!!??

 

Looking at the 60' I'd say he was spinning.

 

with all the goodies that motor has it should be running 110+ and in the 12's either way.

 

No, you don't get HP from a tranny, but you can lose HP through a tranny. The automatic is more consistent, but takes more HP to drive it because of the pump and fluid pressure it has to maintain, so you wind up with a little less at the rear wheels.

 

I agree. My cam is smaller at 224/224 and I'm running 12.7s on a cool day at 114mph with a 1.1 or 1.2 60' time.

 

it all depends on the driver. Not to say he's bad or anything, but maybe you guys are just a little more experienced. I've never been on a 1/4 mile before and I bet i'd run like 14+ second runs with my Vette cause i'm not experienced.

 

With a full manual auto it should be easy and consistent to get down the 1/4. I think there may be some tuning issues with the motor. plus the car shouldn't pick up 5 mph in a trans swap especially when the auto was on a cold day and the 6 speed was on a hot. I suspect 7-8mph difference on sim. D.A. days.

To be losing 50-60 hp with the auto seems excessive. I would expect 3-4 mph max. Especially because the auto was hooking and appying power the whole way down the 1/4. 101 on a 13.25 still dont seem right either. only if the car stopped pulling once it got in 3rd maybe.

 

The times seem about right. due to the 60 foot the 1/4 et is increased. thats all driver/tire/suspension. 5 mph might be 60 hp or so but also remember his first times were in cold but RAINY weather. moisture plays a big part. The swap no doubt freed up a little hp and having shorter gears definitely helped the motor accelerate.

its funny that someone said 3-4 mph maaaybe... the difference is 5


Out of curiousity.. why the gen 7 with a dual sync? I went that route so the motor would pull clean to 7500+. just curious is all.

 

My engine is similiar, other than a few cubes more , and I run 11.6's at 119mph.
What tires are you using? Tuned? heads Ported? LT's

 

Switching from the 4+3 to the zf6 got me 2 tenths in the 1/8th mile, consistently, with no other changes. If anything, the clutch slipped more.

 

hm... iron heads?? Which are they? off the Impala SS?

 

A manual will always MPH higher by 3-4MPH over an auto of the same combo. This is in part due to the efficiency of the manual over an auto. You have basic direct coupling of the drivetrain, whereas with an auto you have fluid coupling through the torque converter which is not as efficient.

HOWEVER, you will never be as consistant with an manual as an auto, nor will you recoupe the most critical of intervals on the track as the 60ft time. So what you gained in MPH, you have lost 2 fold in ET. You have also put your rear differential if you continue launching it hard trying to recoupe the 60' times at a HUGE risk of failure. I have yet to see a manual trans/rear hold up with repeated track use. You will go through a minimum of 2+ clutches per year, and rear component dealers/suppiers will know you by first name and be on your speed dial.

Manuals are fun to drive, but are tough to keep alive on the strip, which is why 99% of the drag cars are autos, with manual capability shifting. Just like shifting a manual, just straight line motions with no clutch. And when properly built, and setup; perform time and time again with zero problems.

 

Is that motor out of a Buick Roadmaster Wagon?? If so it has lower compression than a Vette LT1 I believe.

all I was saying earlier was that he should have had way better traction on the hot day (which he trapped 5 mph higher) which should have taken him into the low 13's easily. There is major tuning issues with this car.
A good running stock LT1 will run 101 with an auto - the cam, exhuast, and DFI should have picked up at least 50 hp with no other changes at all provided the tuning is right. With that conveter and manual valve auto I would have expected 12.9ish@106+. The Manual trapped that on a hot day which leads me to believe it could have gone 110+ at the same et.
Check all sensors and tuning. I think it may be a bit lean (making less power when cold more when hot).
When My old setup was untuned it always ran rich and ran 4 mph higher when it was cold out. 108 mph hot summer and 112+ in fall. Higher Barometric pressure makes more power and I always ran my best time and MPH on my first run of the day. When it was most damp.
Good luck and enjoy 106+ mph is no slouch.

 

One of the HUGE things that I'm contributing the mph change to is the cam. Just look at the cam specs. What rpm range is that good for? on a 350ci its probably well past the redline of the motor. Just staying in that rpm range more often with the manual will help it alot. With the auto I'm shifting down to 3500 each time and about 4500 with the manual.


Yes the engine is out of a buick roadmaster. I rebuilt it and threw it in there as my spare engine. These are stock unported heads which is the big bottle neck in this engine. The cam is definatly too much for the heads, but its what I had lying around. And I'm running it with stock buick manifolds(because of the strait plugs) and stock exhaust which wouldn't help it breath.


The reason that I went with the gen7 DFI setup is because my origional engine is a low compression 383ci with a turbo kit I built. Lets just say that its a little hard to do factory speed density with 12psi going into the engine. She made just shy of 600hp and 650tq on the dyno with a turbo that was to small.


An auto tranny is defitly the way to go if its a track car only but mine is not and I kept going to through auto trannies like they were nothing. People just say you need to find someone that knows how to do them right, well, I've tried several people and I decided to go with something that I KNOW will work, I'm tired of the gambling at $1,500 a pop. $2k for something that I knew would work is a good choice.


Oh yeah, and the problem at the track didn't seem to be spinning the tires, it was more of the car bogging. That lack of low end torque isn't all its cracked up to be. I'm having issues getting comfortable reving the thing and popping the clutch. I'll get the launch down, hopefully soon, and then get the et's back down to where they should be.