Dustys Svt

went to the track this past Friday and was not pleased at all it is a 98z with ms3 cam pat stage 2.5 heads 36 pound injectors on stock throttle body intake and 2.73 gears best pass was 12.60 at 110 on a 2.0 60ft time 1/8 mile was a 8.2 whats wrong with this thing the front o2 sensors were bad and a little vaccum leak what would cause it to be that slow I figured with the crappy gears it would still go 11.80s or better around 118 or so the tranny is a built th350 with a 3800 stall!!!! Help ASAP !!!!!

Dustys Svt

I was on Mt et street radials 17 inch feels like a dog down low barely getting out of second before the finish line!

thunderstruck507

iTrader: (18)

You answered your own question. Fix the problems and try again, but if you're leaving that soft it's not going to run 11 anything even downhill with a tailwind.

Dustys Svt

I plan on it but with bad o2s still should not run that bad cause at wide open throttle the o2s should not matter right ?

A.R. Shale Targa

iTrader: (2)

Big cam = power band of 4000-7200
THM350 first gear of 2.52 times 2.73 = dogshit
F bodies that run hard with 2.73s have the 3.06 first gear of the 4l60trans,
3600-3800 stall and the stock or a small (224 deg) cam
put some 4.56s in that rig and repost...............

LIL SS

iTrader: (9)

I personally think he would go faster with a bigger stall vs more gear. Put the motor at peak tq or even slightly after with the stall.

Also, I believe a TH350 is geared the same as a 4L60E. The 80E is geared like a 400 with the 2.48 1st gear. Heck, I have a 1.78 1st gear and my junk moves ok.

But.. There are lots of other problems to fix first.

Dustys Svt

I agree the gears are horrible I'm going with 3.73 before I go back but my concern is the slow trap speed 110 is what my old bolt on car would go!

thunderstruck507

iTrader: (18)

Nope the 4l60e is geared like a TH700r4 (aka 4l60). When I swapped from a TH350 to a 700r4 back when the car was a 355sbc car, it made it feel like a monster because of the low first gear.


I have seen cars with bad o2 sensors run like **** before. While it's true they are not used at WOT, if the car develops positive fuel trims they will affect WOT. I'm not sure what else causes it, but my friends car went from 7.6s to low 8s in the 1/8th then replaced the faulty o2 and went back to running 7.6s

Maybe it was voodoo, but either way the sensor needs replaced and it certainly won't hurt the car. After it's done pull the battery cables long enough to reset the pcm so it will relearn the fuel trims.

I also agree the TH350 and high gear combo isn't helping. A local guy did something worse and put a powerglide in his car and it runs slow as hell. If you're going to ruin a street car with a non-overdrive trans, ruin it all the way and match the rear gears and converter to the combo...otherwise you will still be slow and have nothing to show but shitty gas mileage. Gear it to cross the finish line near redline.

Dustys Svt

Thanks for the help guys from now on it's going to just be a strip car so would 3.73 or 4.10 be a better fit I think 4.56 would be to much I would try leaving on the stall too it would start chopping up when stalling up and would not spin but still run a 2.0 60 ft

thunderstruck507

iTrader: (18)

When you say chopping up do you mean the engine was breaking up? Does it do that any other time? Could be some ignition issues. If so check the plugs and wires for cracks/burns. Check with a scanner for knock retard. Depending on the vacuum leak it could also be a lean pop maybe?

LIL SS

iTrader: (9)

Not sure if this will help you work your gear change backwards but, I have a 4.56 with 30" Drag radial and turn to 6,900ish and am out of gear about 1,200-1,250 feet at 122-123ish mph.

I am also running a glide with too tight of a verter for motor. It is only flashing to 4,600 off the 2-step/trans brake. Probsbly good for bottle, but motor would probably like closer to 5,500-5,700.

I promise you, 3,800 is not enough stall for your combo if your car is going to be mostly track only. I would guess a 5,000ish stall with the MS3. Do you know where it makes peak TQ and what rpm hp falls off?

Gear will help sure, but not as much as the proper converter. Case in point, my truck picked up .35-.4 with a converter swap (3,600 to 4,500) when I had the 347 ci motor and Trex combo. When I did the verter I also went from a 3.73 26" tall tire to a 3.73 30" tire. Going from a 26" to a 30" tire is a big gear change. Something like a 4.30-4.56 going to a 3.73.. 60's went from a best of 1.89 to 1.67's

When I did eventually change gear from the 3.73 to a 4.56 keeping the 30" tire. I only picked up .1-.15.. 60's went from 1.67 to 1.60 and that was dead hooking. The truck was also a hundred pounds lighter. So the question I ask is, how much of it was the gear change vs weight?



I am not saying a gear change can't help, but I would change the verter first. Get the right one in it! Run it, get an idea of what your MPH will be through the traps and gear it accordingly.

Dustys Svt

Changed the plugs right before yes it breaking up the wires are stock but no scrapes or cuts on wires the fuel is ok it holds a steady 57psi on idle or wot and as for stall it will hold up to right at 4k but when I stall that high it runs worse! The stall was in it when I got it guy told me it was a monster 3800 not sure he knew though either.

thunderstruck507

iTrader: (18)

You might have cracked one of the new plugs putting them in. It happens a lot. I would check them to be sure before spending money on anything.

It's always better to get the car running in top shape to get a good baseline before further mods. That way you know what's really working and what is masking other issues.