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Discussion Starter #1
Hello all, I have a 91 GT full weight, stock suspension with 26x9x15 hoosier slicks in the back at 14 psi on this pass. I am running the wrong torque converter I know, but I am looking for suggestions on what to buy to improve my times and any tips at all, as well as gears. Trans is a 4r70w currently running a 4000 stall, footbraking at 2000 on the tree. I am running 3.73 gears. I just feel it's a little slower than it should be and I'm probably losing a lot of my midrange powerband with this converter. Still want it streetable just want to pick some time up. See image attached for slip. Thank you :)

Engine setup is:
336 CI (.060 overbore 331)
Trickflow 170 heads
Trickflow Track Heat Intake
Trickflow Stage 2 Cam
1.6 Rockers
75mm TB and 80mm MAF
42lb injectors
BBK shorty 1 5/8 headers with offroad x pipe and mac pro dumps for exhaust

Stock computer tuned with Moates Quarterhorse
TCI Trans controller
 

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theres alot of voodoo that goes into converters... i just called and ordered mine from Andre at Edge, fast friendly service. just remember, cheap aint good and good aint cheap.
 

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What's the shift fallback on the converter? Where does it flash to on the leave? What rpm are you shifting at? What kind of converter (size, stator if you know, brand)? Do you have traction problems or does it hit soft?
 

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Discussion Starter #5
I say it may be the wrong converter due to missing the meat of my powerband possibly? Looking for any pointers or advice. It flashes right to 4K when I leave(only can footbrake to about 2200 before it wants to go) and I have it shifting at about 6200 rpm right now. It launches pretty hard off the line and I dont feel like I have any traction issues at all really. I dont have a ton of details on the converter itself as I got it used, but it flashes to 4k on launch and driving on street it also flashes to 4k when flooring it. After each shift its right around there for rpm as well.

Thank you for the replies
 

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What does the converter fall back to on the shift?
 
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Discussion Starter #8
going off the cluster tach that wasnt 100% accurate if memory serves right was falling back to somewhere around 4200 or so. also pretty sure i was going thru the trap right around 5000 also. my tuner told me not to pay so much attention to the tach cus it would say 7k when it was hitting rev limiter so i would let off... but then he really only had it set at 6300 lol. but this pass I am not letting off anywhere at all
 

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Here is some additional information which will help us help you. What does your car weigh when you race it? Does the current converter have lockup? Are there any future plans to change any of the hardware in the current combo (change heads, cam, or intake)? Are you shooting for a specific number (11.99)? Are you having any traction issues getting off the starting line? Make sure to answer Alex's question too ;-)
 

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Discussion Starter #10
I am hoping to get this thing on a scale ASAP. its basically just a full weight gt with slicks on the turbines for wheels so nothing fancy yet. my specific goal is to get this thing to see the 11s, even if it means 11.999. I would have no problem changing up some things, but would like to keep my ac and power steering, but im not opposed to start ripping a little bit of the interior apart and racestars or weld wheels etc for weight reduction. I got the motor assembled from a horse trade deal so I would like to keep it together how it is but i would change things if necessary to break high 11 passes next season. No traction issues as far as I can tell. i was cutting 1.6x 60 foots all day as well but slower MPH and ET, this pass was my fastest MPH and ET. Current converter does have lockup btw.
 

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Discussion Starter #11
BTW, what did it take to get to your 3080lb race weight? :) I have no problem like I said stripping some things out to get some weight savings in
 

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Thanks for the additional information. If 11.99 is the goal then you can start looking at this from "how much HP do I need" and how efficient you are willing to make the car. In rough numbers, with a car that is very efficient with the power, you need to be able to run 110/111 MPH to run an 11.99. The less efficient your car is the more MPH (HP) you will need to offset the lack of efficiency.

If you don't want to change up the engine combo then you would have to "attack" the 60 ft times and plan on a large weight reduction program. Right now you are close to running 108 MPH, so to reach the 110/111 target MPH you would need to lose roughly 200-300 lbs. You can employ the usual tactics, run with 1/4 tank of fuel, remove the spare tire, jack, and wheel well cover and insulation, rear lower seat cushion, and the passenger seat. That will net you close to 150 lbs. Weight reduction gets tougher from here, but some typical bolt-offs are removing the rear seatbacks, rear seat belts, console armrest (this thing is freakishly heavy), Weld Racing 3.5" wheels with a 155 smartcar tire on it only weighs 12 lbs and then there is the front sway bar and end links. That should net you another 100lbs Still need more? Replace the battery with a small gel cell battery that only weighs 13 lbs. Mount it in the same location after removing the existing battery tray and it should sit right on top of the frame rail and you can make some aluminum brackets to hold it down and be NHRA legal. Next on the hit parade is the coolant overflow tank. The tank isn't all that heavy but the fluid in it is. The replacement is a lightweight, 16 oz, plastic, soda bottle. Next on the hit parade is the windshield washer bottle. Same story, the bottle isn't all that heavy, but the contents are. Depending on how much fluids you carry in the tanks, that should net you another 40 lbs.

At this point you should be seeing the 110/111 MPH (or more), but you might be hung up in the low 12s. I would swap to a 4.10 gear. You need to get the 60ft down into the 1.56-1.58 range. If your 60ft is hung up in the low 1.60s then it is time to call Andre at Edge and have him build you a nice 9.5" converter. He will want more information than the IRS on your combination like dyno numbers, shift points, and race weight. After the converter change you will be solidly in the 11s and will be back here asking what it will take to run 11.50s ;-)
 
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If you're dropping back on the shift from 6,200 all the way to 4,200 rpm (assuming non-lockup), then that indicates the converter's too tight. But if it's flashing to 4,000 rpm on the leave, then that's about right. I'd say something's off. With a glide, they typically say 1,200 rpm is about the max drop off you want. With a 3 speed (which is effectively what you're running), a little less because there's less spread between gears. If I read you correctly, you also say you're going through the traps at only 5,000 rpm? I'm going to assume a little over if it's locked up in 3rd, and maybe another couple hundred rpm if it's not.

I'd have to say I'd be surprised if that thing made peak hp above 5,500-5,600 rpm with that induction. 6,200 rpm might be a bit high to shift.

I think you're probably right to look into the converter. As has already been said, a good converter's not cheap. My first "good" converter was a PI Stallion 3,200 rpm 9.5" lockout for my AOD. I wouldn't do lockup for drag racing - the rpm drop on the 2-3rd shift is too severe. But that converter cost me $750 in the '90's yet. I currently run a custom BTE 10" converter set to full tight with a steel "C" stator. That one cost me over $1,000 and I had to send it back once to get it dialed in. But I'm putting that converter through hell - 1.80 low gear, 3.08 rear gear, 3,500 lbs and a 3,200 rpm transbrake leave at 13.5 psi. That's a lot of stress on the converter - they even told me not to use the brake with that low (numerically) of a rear gear ratio. Getting it to minimize slip at the stripe and only 6,200 rpm is tough. You'll probably want a smaller diameter converter. BTE doesn't make 4r70w converters that I know of. Edge (as mentioned) is a good source, so is PTE or Lenny at Ultimate Converter Concepts - maybe one of them will make you a converter for that trans.

But again, getting a converter that flashes decently with a good k factor (tq multiplication) behind your motor and still locks up decently down track is going to be tough with that low of an rpm ceiling. You'll really be better off letting that thing spin to at least 6,500 rpm, which means a new intake at least (that's where I'd start anyway). You'll probably end up with an 8" or 9.5" converter.

Oh, one more thing - don't get hung up on slippage while driving around. Yes, it does happen, but with a good converter it's not bad at all and hardly noticeable. Until you hammer it, anyway. Here's me tooling around with my converter on the street (stalls at 3,200 rpm on the transbrake/two step and flashes to 4,200 rpm and falls back to about 5,200 on the shift):

The only time I get into it a little is at 2:48 in.

Sorry for the long post. Hopefully all this helps.
 
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Discussion Starter #14
If you're dropping back on the shift from 6,200 all the way to 4,200 rpm (assuming non-lockup), then that indicates the converter's too tight. But if it's flashing to 4,000 rpm on the leave, then that's about right. I'd say something's off. With a glide, they typically say 1,200 rpm is about the max drop off you want. With a 3 speed (which is effectively what you're running), a little less because there's less spread between gears. If I read you correctly, you also say you're going through the traps at only 5,000 rpm? I'm going to assume a little over if it's locked up in 3rd, and maybe another couple hundred rpm if it's not.

I'd have to say I'd be surprised if that thing made peak hp above 5,500-5,600 rpm with that induction. 6,200 rpm might be a bit high to shift.

I think you're probably right to look into the converter. As has already been said, a good converter's not cheap. My first "good" converter was a PI Stallion 3,200 rpm 9.5" lockout for my AOD. I wouldn't do lockup for drag racing - the rpm drop on the 2-3rd shift is too severe. But that converter cost me $750 in the '90's yet. I currently run a custom BTE 10" converter set to full tight with a steel "C" stator. That one cost me over $1,000 and I had to send it back once to get it dialed in. But I'm putting that converter through hell - 1.80 low gear, 3.08 rear gear, 3,500 lbs and a 3,200 rpm transbrake leave at 13.5 psi. That's a lot of stress on the converter - they even told me not to use the brake with that low (numerically) of a rear gear ratio. Getting it to minimize slip at the stripe and only 6,200 rpm is tough. You'll probably want a smaller diameter converter. BTE doesn't make 4r70w converters that I know of. Edge (as mentioned) is a good source, so is PTE or Lenny at Ultimate Converter Concepts - maybe one of them will make you a converter for that trans.

But again, getting a converter that flashes decently with a good k factor (tq multiplication) behind your motor and still locks up decently down track is going to be tough with that low of an rpm ceiling. You'll really be better off letting that thing spin to at least 6,500 rpm, which means a new intake at least (that's where I'd start anyway). You'll probably end up with an 8" or 9.5" converter.

Oh, one more thing - don't get hung up on slippage while driving around. Yes, it does happen, but with a good converter it's not bad at all and hardly noticeable. Until you hammer it, anyway. Here's me tooling around with my converter on the street (stalls at 3,200 rpm on the transbrake/two step and flashes to 4,200 rpm and falls back to about 5,200 on the shift):
https://youtu.be/j8SNo7kpcxw

The only time I get into it a little is at 2:48 in.

Sorry for the long post. Hopefully all this helps.
Hey man. It's been awhile but I've decided I'm not happy with 12s out of my stroker anymore. I pulled the trigger on a set of trickflow 11R 190 heads, holley systemax II intake, and more than likely a custom cam from Ed. I'll be putting a tube k member, manual rack, and dropping weight here and there on the car as well. Converter fall back was more like 1,200 rpm actually. My tach was really wacky at the time. I ran some actual logs and installed a tach to determine that. Thanks for the advice I finally am starting to make the push forward. Looking forward to some better time slips late spring time! :grin2:
 

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You are going to need 4.10:1 gears.
 
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Hey man. It's been awhile but I've decided I'm not happy with 12s out of my stroker anymore. I pulled the trigger on a set of trickflow 11R 190 heads, holley systemax II intake, and more than likely a custom cam from Ed. I'll be putting a tube k member, manual rack, and dropping weight here and there on the car as well. Converter fall back was more like 1,200 rpm actually. My tach was really wacky at the time. I ran some actual logs and installed a tach to determine that. Thanks for the advice I finally am starting to make the push forward. Looking forward to some better time slips late spring time! :grin2:
Talk to Ed about your complete combo. Also where were you truly shifting since you said your tach wasn't accurate?
 

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Discussion Starter #17
Talk to Ed about your complete combo. Also where were you truly shifting since you said your tach wasn't accurate?
i have a trans controller with my 4r70w and the tach signal was coming directly from the coil. we had it shifting around 6,200rpm
 

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I have to figure why my tach is off. It is a 30 year old car...lol
 

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All of the factory Fox tachs were off. at low rpm's they are close, but the higher the rpm the further out of wack they get.
 
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My tach has a mind of it's own. I'd like to send my gauges out to be rebuilt. I prefer the stock look.
 
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