Last Friday I went to the track for the first time after the cam swap and ran a 15.02 but I needed a lot of tuning. I upped my psi to 12.5, adjusted to timing slightly, and removed the back seats. MY best time this friday night was a 14.83 and all my mphs were in the high 92's.

I'm still not getting a good launch. My traction sucks! I know it is mostly because of my open rear (still looking for a one to swap in), but I'm having problems with wheelhop too. If any one has some good traction upgrades that helped them out please let me know. You guys that are running 3.73's, it is too much for highway driving/good mpg? Also are the Lakewood traction action lift bars any good?

Thanks

Matt

 

pretty good times for whats done...supposedly a good 3.42 or 3.73 posi rear with take 5 tenths off that time...posi will help your launch alot

 

Knocked another .2 off the time, nice It had to feel nice to finally see 14 on your slip!

 

Buy posi unit from slp for 85 bucks.

 

What was your E.T. before the cam swap?

 

The traction action lift bars are junk.....Lakewood was looking into redesigning it.

 

You bet it was nice to see 14's. The first time I ever ran the car it ran a 17.4...timing was really screwed up. Running 14's is a great feeling, but running 13's would be even better

My fastest time before was 15.307 @ 88.4 if I remember correctly. So the cam gave me 5 tenths and 4 mph after a little tuning (higher fuel pressure helped a lot). Car still runs great but mpg suffered some.

I know about the SLP take-off posi units but are they any good? I mean Eaton posi's are $435 and these are $85, something has to be different. Anyone using one right now? Any complaints? Also, would it be easier/cheaper to look for a new rear to swap in or buy the new gears and posi and have it done?

Anybody heard about the PowerTrax no-slip traction system? It's on pg. 147 of the most recent Jeg's catolog. They say it is fully streetable and can be installed without disturbing the existing gears and with hand tools. What do you guys think? Buy an open 3.73 rear out of a V6 and drop one of these in it? Just a thought...

Hmmm...four tenths for a rear swap...14.4 is getting kinda close to 13. We'll have to see

 

The SLP unit is good enough for new Z28s runnin 12s, and then 11s till the 10 bolt takes a dump.

It'd prolly be easier to get the gears changed, but prolly more expensive. $100 for the posi (shipping), $100 for the gears used, and $150-200 labor. But you just drop the car off with the parts and come back the next day to 3.73 posi The advantage to the new rear is discs, yum!

 

I've heard 3.73 is a little high for a 700-R4 because of the numerically high 1st gear ratio. I think I've heard at WOT you are only in first for about 1.5 secs. Any thoughts?

 

This is true.
I did a project in one of my classes about 1/4 mile performance and my concept (out of 8 others) was to just redesign the tranny. We wrote a program in Fortran (runs in MS-DOS and Unix) and it spits out the shift points, tranny gears, rear gear, and more just from input of the cars weight, horsepower, RPM at max hp, and tire diameter.
Anyways, you want a first gear ratio (rear gear multiplied by first gear in tranny) to be 13.5 or greater in drag racing applications. It just so happens that with a 3.73 rear and a 13.5 ratio you would actually want to have a 3.62 first gear. The TH700 (4L60) has a 3.06 first gear which is better than the TH200. If you raise the first gear ratio you'll need a higher first gear so long as the rear gear is left constant.
It just so happens that with 3.73 gears and a 3.06 first gear, your first gear ratio is only a 11.4 while using 4.50 rear gears and the TH700 yield a nice 13.8 first gear ratio. This is only the optimal tranny and rear gear combo if your tranny stays in 3rd and your engine can pull to 5000rpm. I'm working on making the program more user friendly with a windows interface, then I'll have it on my website.
I guess what really matters is not the time spent in a gear because if anything you want to spend the least amount of time in any gear. You want to keep the engine in it's powerband and for this reason transmissions, rear gear, tire diameter, and a dyno of your engine is the ONLY way to tell what is best for you application.
So I guess it needs to be said that the TH700 is a very good tranny for the weekend warrior. You not only have the awesome first gear, you also have overdrive .
I might end up moving this to the tranny board but I'm sure some of you are going to talk about the TBI and it's problems with breathing to 5000rpm.

edit: If I had to design a transmission for speed and had only 3 forward gears to do it with. I'd have made a 3.62/2.17/1.3 1st/2nd/3rd gear tranny for my car. It would allow for a 13.5 first gear ratio, be made specifically for my car which weighs 3550lb with me, has 330hp at 5400rpm and 3.73 rear gears. The 4th gear would of course be something around .7 so as to keep my gas milage above 20mpg. With those gears I would shift at 5500rpm and cross the 1/4 at 5400rpm in 3rd gear. The powerband would be only 2204rpm wide and the lowest my engine would ever have to drop would be 3296rpm. That's just about where my peak torque is .
For a street vehicle it's probably a good idea to keep the first gear ratio closer to 11:1 so with 3.73, 26" tires, and the TH700 you'd be near perfect .
Keep in mind that none of these calculations are exact and that they were actually designed with no torque converter slip. So you'd most likely want less than 4.50 rear gears.

 

1. You need a vFPR (Vacuum-compensated Fuel Pressure Regulator). That should help with the normal-driving fuel economy, and still give you the higher fuel pressure you need at the track. There is a long vFPR thread on this forum on that NotDadsW41 started that might be useful to read. I think Tom and his 400 CFI (dual small TBIs) got back 2-3 mpg after he installed the vFPR, and he didn't complain about any power loss.

2. ECM recal would optimize your engine + mods (incl the vFPR) but doing the recal yourself requires some hardware investment and some learning. - Ken

 

So, JPrevost, to summarize your last post....3.73's or maybe 4.10's, with the TH700, would be great for a daily driver that you enjoy taking to the track on the weekends? I do plan on modding my L03 to make it breath up to at least 5000-5500 RPM's.

 

I know that my car now pulls strong up to 5500 in 1st, but for some reason falls flat above 5000 in 2nd. Why is that? I've tried shifting early out of first at say 5000, but I lose about a tenth to a tenth and a half. I think that if I'm going to spend the money to do a complete rear swap or new posi/gears I would want the biggest bang for the buck (i.e. 3.73) It is good to know that someone understands the relationship inbetween rear ratio and tranny ratio because that is one thing that I just assumed numerically higher was better. Thanks for the info...

kdrolt....

I want to start to program my own chips but every time I look into buying the stuff to do it, I realize that I could get something else with the money that would make a bigger e.t. difference. I also realize that the closer I get this car to running like a "race car" the more the custom chip will be needed.

Is the VAFPR worth the swap..I guess with gas prices on the rise and the possibility of getting the 3.73's it couldn't hurt...anybody got a link to the site you buy it at?

Thanks

 

You always get more torque multiplication in 1st than 2nd, but if you are leaning out at WOT then the engine will run more sluggish as rpms increase and as the gear increases.

IMO you should get the bugs sorted out of the setup your have FIRST before you complicate matters with a rear end gear swap.

The more you modify the LO3 away from the factory 170 fwhp rating, the more you need ECM tuning... and at 15.0 sec range, you are now far away from the stock performance. You also run the risk of damage to the motor if you aren't running an air:fuel if around 12.5:1 at WOT.... So waiting on the ECM stuff may be false economy.

IMO yes. The cost is around $40 from a discount online GM parts dealer.

 

I have it, i love it ... best Mod I have ever done ......

 

Seriously, if you put a 3.73 posi rear in there, you'd get one HELL of a kick.


When you first ran your car bone stock it ran a 17.4? See, something must have been wrong with mine...with headers, cat-back, MSD ignition & wires, and a Ram Air setup (with K & N) the car only ran a best of 16.8@79. Even with my .515 reaction time and minimal wheelspin (hard to spin wheels on a 92 RS) I could only cut a 2.3 60 ft.

Maybe something was wrong with..uh...something?

 

Were you racing on top of Mt. Everest?

It had to have been in your tranny, or maybe you didnt have all 8 cylinders firing. I ran 16.4 bone stock and I thought that was a tad slower than what I'd like to have run.

 

2 things...
1. Reaction time has nothing to do w/ your ET or 60ft time (assuming you didn't know that from your post)
2. Somethin has got to be wrong....when my 89 RS had an LO3...I ran a 16.1 BONE STOCK w/ a 2.39 60ft time. So if your 60ft time was 2.3...then you're VERY slow up top, which makes no since. You're running on a stock rearend right? Where do you live? If you live in a high elevation area (such as mount everest haha), then that could explain it.

 

If your running 17.4 here's some things to consider:
Your fuel system is clogged. Run some injector cleaner
through your tank the next 2- or 3 times you fill up.
You maybe losing compression at the combustion chambers
and valves.

2) your tranny fluid probably needs to be changed.
3) You fuel pump/relay might be dying.

 

If you're going to do that, make sure you change your fuel filter after you run that stuff cause all it does is break up the carbon in your tank and put it in the fuel filter. Clogged fuel filter=less performance.

 

Carbon in the fuel tank??? Thats a new one

have a look inside your tank sometime youll be surprised. They tend to stay pretty darn clean.

 

and those over the counter injector cleaners tend to do one thing really well... I like to call it "nothing"

 

Gas isnt the cleanest substance I have ever seen...they do a real good job of getting it lookin clean when its ready for the pumps, but it isnt spotless and after like say 100k it starts to build.

 

Carbon deposits arent formed until after the fuel has been burned. I sure hope its not burning in the tank. The tank itself should be completely clean aside of some particles like sand or pebbles, and the screen itself will probably look like it spent a little time in a dirt storm, but nothing bad.

The 35 year old, 250k+ mile tank on my other car looks fine. I replaced the missing strainer and called it good.

I also agree about the injector cleaner. I've only found one that works much at all, and you have to use it all the time for it to do anything and prevent future deposits.

 

There must have been a little confusion here...

The first time I ever took my car to the track, about this time last year, I ran a 17.4. That is not what I'm running now. When I bought the car it had always felt pretty weak and after that dismal track preformance I installed my TES headers and found out that my timing had been set by the previous owner without disconecting the bypass connection so I was running about 14 deg. ATDC NOT COOL. Needless to say I fixed it and it ran in the 15.9-15.8 range after that with the new headers. Sorry for the confusion!