Last November I had a higher stall converter put in my car...I went to a 3200 stall, lock up, Vigilante...I have been drag racing the heck out of it since but only at the 1/8 mile track in anticipation of participating in the new Corvette Challenge at that same 1/8 mile track...no problems at all...

Segway to two days ago...I enter the Super Chevy event at Bradenton Motorsports Park which is a 1/4 mile track...on my first time shot on Saturday, I launch and all is good..the car shifts like always and goes into 3rd just before the 1/8 mile mark like always...

This is where it gets weird...at about 1000' the engine rpm drop, for a split second, by about 400 rpm then start to rise again...I get a second run later on and the same thing happens...

Yesterday morning I got another time shot before elims...same thing again but it didn't seem to be quite as bad...a cold front had come through on Saturday night and it was cold as heck (for Florida) yesterday morning...

This has never happened before with the stock converter or the 2400 stall I had before this one...a couple of guys said it sure sounded like the converter was locking up for a second, then unlocking again...seems to make sense but I thought the TC will not lock up at WOT...everything works fine at part throttle...any thoughts on this?

p.s. I did get my best time on that Sunday morning run...13.18 with a 1.79 short time on Nitto DR's...

 

I don't know if that's what's happening but you can wire in a switch to shut it off.

 

The converter is locking up most likely. That is why you see the 400rpm drop then it starts to climb again. What are your 1.4 mile MPHs? From what I remember your stock setting is around 79mph for lockup.

here is what I would do if you want quicker ETs, lock the converter by jumping the required pins in the ALDL so it locks as soon as it goes into 2nd gear. I did this for years on my vigilante and 406ci motor and it yielded nearly .1sec quicker ET in all conditions over letting it unlocked.

 

Jesse...I had four runs last weekend...
13.57 @ 97.71mph...1.81 short time
13.90 @ 69.63mph*..1.81 short time
13.18 @ 102.98mph..1.79 short time
13.27 @ 102.34mph..1.80 short time

*I lifted on this run...being sensitive to my problem on the first run, I thought my motor was reving so high at the 1/2 shift it was going to blow up...turns out it may have been my opponents motor screamin', not mine...lol

 

My converter locks up just after I hit third on the track, almost feels like bog but it isnt.

 

Interesting...mine never did before this new converter...I could live with it if it was the same every time since I bracket race but it's not...my short times were within .01 of each other too...

 

does it do it at the same RPM point, or randomly? Are you certain it couldn't be a fuel delivery problem? (just trying to cover all the bases here). Lock out the TCC, and see if it goes away.

 

Yep I would say its your TCC locking up. Nothing to worry about. Would try the lockup as soon as it hits 2nd though and you will get some better ETs. Make the Trans/converter more efficient, quicker into the run - hence better ET/MPHs. It will "feel" slower cause the RPMs of the motor will stay lower, but it will be quicker.

 

I never noticed it until I put a Hypertech chip in (after I fixed a fuel.lean problem), guess it has something to do with it from what I hear. Of course, prior to that Ive had a loss of power,especially on the top end so it may have done it with the stock one and I just didnt notice...

 

I would say yes, since it seemed to happen at the same point on the track...I'm not completely sure what it is yet but I'm working on it...see my post below..

 

I'm leaning that way as well...I am waiting to hear back from Mike Norris...he's trying to set up one of the only C4 tuners in central Florida to meet me at Mike's shop....then we can scan and dyno the car to see what's up...if it turns out to be a glitch in the computer we'll burn a new chip and set it up correctly for what I have...

I've got my fingers crossed and thanks to everyone for your thoughts...I'll let you know what the outcome is and hopefully I'll make the National event in South Carolina...

 

Ok guys, the car is fixed...turns out the stock computer setting had it locking up at 90 mph, even at WOT...I had a new chip burned which won't allow lock up at WOT until after 115 mph...we checked it on the dyno and, sure enough, it locked right at 115 at WOT....

I'm good to go for the National Event...WOOT!...it turns out I never noticed it before because the converter wasn't locking before...sheesh...when I had the 3200 stall put in last fall it wouldn't lock up...the brake switch was screwed up...they fixed it and I hadn't been to 90 mph at WOT...I've had 50 passes since but all at an 1/8 mile track so I was only trapping 82-84 mph...

If the Super Chevy show had been late last fall instead of two weeks ago I could have found out about this then...lol...the lesson for me is to make sure I take some 1/4 mile passes when I change something...