Motor running over the converter

Reggie West

Well-Known Member
TurboBuick.Com Supporter!
May 28, 2001
OK guys here is a good one for you.

This is my Dads car.
Stage 2 block. M&A heads. 72 turbo. DFI with a VIC controller. MSD DIS 4.
Trans is a built TH 400
Rear end is a Detroit locker with 3.50 gears in it.

We ran this thing at Palmdale last night. This is the fun part.
We turned up the boost on every run and the car ran 10.9 to 11.0.
Boost started at 18 psi on the first run to 23 psi on the last run.

MPH stayed between 123 and 124. We have noticed that at half track the motor is hitting the rev limiter at 6500 rpms.

Cam is said to have max rpms at 5800. That is the powerband.
Duration on the cam is 224 intake and exhaust. 112 degrees lobe separation.

I believe the converter has way too much slippage in it and that is what is causing us to redline. It is a new Art Carr ( from the real Art with a beard). Stall speed is 4000 rpm. This car just runs on the track.

What do you guys think is going on?
Have you data logged RPM on the laptop? If it looks like a solid line and you can't see where it shifts, time for a tighter converter. :D

Ask Neal Whyte about that one..he was in about exactly your shoes 2 years ago. I saw the data log of one run and couldn't tell where it shifted...he was running 10.xx @125ish. Got a better matched converter, now he's in the 9s at 140+ where the car should be.

What are you shifting at? What is the rpm drop on the shifts? What are you crossing the finish line at? Also that 224 cam should not be running out at 5800. Unless its a totaly different grind than most turbo V6 224 duration sticks.
The trans shifts at 5500.

The rev limit on the cam is what ken duttweiler told us. I know the motor will rev to 6500 rpms without a problem.

The drop on the shifts is about 1000 rpms. So from what I have been told that is about right.

The more I am talking to people the more I believe the problem has been the torque converter all along. We had just changed the gears in the rear from a 3.88 to a 3.50. That may have helped a little but the problem still exists.
If its dropping 1000 rpm and your shifting into 3rd at 5500 then your RPM would be 4500 into 3rd gear. So your saying your climbing from 4500 to 6500 at half track??? I think you would be close to half track on the 2-3 shift. Also the change to a 3.50 from a 3.88 will generally cause your converter to have more load and thus more stall.

I've got the same cam and I can tell you that it will run to around 6200 RPM before it's out of wind. My trans had been set up to shift at 6400 before and it just goes flat at that point

I've got to think form what you've said that the convertor is too loose. Convertors are sort of a black art really. Stall speed is completely undefined and every combo is different.

I know your Dad is running a turbo 400 so lock up or 4th gear is of out of the question. Since the the car has a T-72 I'd see about tightening up the convertor to bring the RPM down. After that a taller tire might be in order.

Let me know if I can help.


P.S. What was the 1/8th mile E.T. and M.P.H.?
I'd get it tightened up.
We went from 9.6 @ 134 to 9.0 @ 150 with a "good" converter on the race truck..
We fought it for 2 years before we finally went with our gut feeling and quit listening to the vendors..

Thanks Neal.

His 1/8th time is 7.0 @ 102 mph.

He is using a 28 inch slick now.

So we will be talking to Art Carr.
After my son got this post going and I read all the replies and I got to thinking does this thing really drop a 1000 rpms when it shifts.Well I took it out for a run found out that it shifts at 5800 and it only drops 600 rpms.I think the converter is to loose. What do you think?


I'm fighting the same thing. Converter was not right from the git go. didn't know the "vendor" had no clue what he was doing!! Virtually NO drop.. like 50 in all shifts.. Back to the conv. guy.. then it's 400-500. Then on the 3rd he tells me too bad, this is it, need to change shells as this 1 won't get any tighter.
Car has a T-400, 3.42 gears, 28 x 10.5 MT slicks.
After the first change, the ET went from 11.25 to 10.27. MPH went from 122+ to 132+. Temps on the street went down to 170-180 from 375!!
All runs made at the same track, same 20psi boost, same 8 psi leave, same driver.
During all this BS, I'm getting an education in fuel systems:mad:

Got that right, got an AC converter, got a TE-49,:D , some 95# inj's and a set of Champion iron heads.;)

The part I don't understand: The 60' times never changed much. All were in the mid 1.40's. May see some 1.30's IF the converter and the new turbo and inj's work!!:eek: :eek:

Originally posted by Chuck Leeper
The part I don't understand: The 60' times never changed much. All were in the mid 1.40's. May see some 1.30's IF the converter and the new turbo and inj's work!!:eek: :eek:

The first converter that we had in the truck would flash to 6000+ when the Tbrake let go and the N2O hit. The shift point was 6500 and with the powerglide he was shifting into 2nd before the 60' mark. The 60's were 1.27's. After the converter was tightened up to flash to 5500 when the N2O hit the 60's went to 1.30-1.33 on the same amount of N2O. The looser converter launched the truck alot harder through the 60' but just never locked up enough in high gear to pull the truck for any ET/MPH. Now with an additional 75hp of N2O the 60's dropped to 1.26 and the suspension works a lot better the harder we hit it.

Loose conv.

I think the thing that kept me from seeing better 60' times was the harder hit on the tires was turning into tire spin at the first 20-30 ft out. This was due to the shocks being too soft. [HALS@2 clicks off soft] I am now starting at mid point. [6 clicks off soft]

Getting 3700# of slug to move is a torture no converter should have to endure!! About 850# of torque doesn't help the tire spin either!!:D
Re: Loose conv.

Originally posted by Chuck Leeper
Getting 3700# of slug to move is a torture no converter should have to endure!!


I couldn't imagine the R&D that converters went through before someone said "I got one that can handle it!"

Motor running over convertor.

REG. I have a AC9"-Turbo400 convertor, it's what I call a excellent match for my combo, here are some numbers from the time slips and the Fel-Pro logs. The car has 29x11" slicks and 3.42 gears.
On the brake at 4000- about 10psi of boost.
Over the line at 135-6 mph- 6050 rpm.
Over the line at 145-6 mph-6450 rpm.

What stall is your conveter? Did you they get it right the first time or did you have to pull it in and out a hafe dozen times?

Motor running over the convertor

I never could figure how they rate a convertor on a turbo motor, anyway this ones just starts to lift the boost gague at 3200rpm, at 3500 it's about 5-6lbs of boost and that's what i told them I wanted when I ordered the convertor, I was luckey and they got it right the first time, i shift at 6500 and it will drop back to about 5700rpm, if I short shift it at 6000 it will drop to about 5500 . I did run a 224-224 pte cam with solid roller lifters, it was on 110 lobe seperation and would pull to 6500 with good 1.48" springs.
The motor is a 276" Champion heads and a T76-4bolt.


Thanks for the info your combination is about the same as mine.I talked to Art Carr today and 3500 stall was what we agreed on to change to.This conveter stuff is Black Magic I guess.


You have too see when the converter got changed in stall if the torque multiplication ratio changed as well. One with a higher ratio will hit the tires harder. Its a combination of both things stall speed which gets it into an optimal rpm for where your motor makes power and torque mutiplication ratio. They effect each other.