When I had 2:73s, stock cat-back (flowmaster muffler), a burnt plug wire and slipping tranny I ran a best of 15.41 at 93mph with the G-Tech. Now I have upgraded to 3:73s posi, Hooker cat-back, and new plugs. Also the tranny shifts a lot better now, but still could use some work. Anyway, I ran the car on the same stretch of road 2 times. I ran a horrible 15.32 at 95 mph. Now I gained 2 mph and only a 1/10, with the mods I did and the tune up. I know G-Techs aren't exact but are good for testing mods. First of all how come I only gained that little with what I did. I did only run the car twice shifting at the same rpm 4700rpm, maybe I should up it a little, but still what gives. And second, say the G-Techs are close to what you really run, I know there will be an error if the road is a little up and down, but how about if the road has a bend to it, even though I don't slow down can that affect the reading as well?

 

In my experience g-techs are right on the money if you use them correctly. With those gears you definitely should have run a better time, but are you sure you used the g-tech correctly both times? Turning won't have much affect, just vertical changes in the road.

 

Yeah, the G-Tech was used properly, it said go and I went. Now I didn't bother trying to bring the rpms up a little since I do have 3:73s and my redline is only 5200rpms. I may have let up a little on the last run which was my best, but nothing that would help me get in to the 14s. I was hoping I'd be between 14.4 and 14.6. I don't get it, I figured the gears didn't help as much as they should have or at least what I paid for them but geesh. And the car felt like it pulled a lot harder in 3rd as compared to when I had 2:xx.

 

I really doubt those gears and exhaust would knock off a full second. From what I've seen 2:7# to 3:2# is worth about two tenths in a 15 second car, and exhaust may be worth less than a tenth. I don't know about the plug wire or the tranny. The mph increase shows an increase in power.. but the time doesn't show much. I'd guess you're having a bit of a traction problem with those gears and that may be why your time didn't improve all that much.

 

Well, the tranny before I had to let off the gas for a quicker 1-2 shift, I don't have to do that any longer but it still needs work. So I figured about .6 for the gears, .1 for the exhaust, and I was hoping for about .2 from the plug wire and tranny. For one on the tranny I was able to knock .2 off by letting off the gas and shifting as opposed to staying on the gas. But now that is a lot better too, maybe I should still try to let off the gas just a bit.
And I had very little wheel spin. Guess, I'll try it another nite. I don't like doing it too many times because I don't want the neighbors waking and calling the cops and the fact that it is a public back road.
Could it be the fact that my peak torque is around 3500rpms and peak HP is around 4200 rpms, maybe the 2:73s kept me in that rpm range better.

 

Mark,
I found my car had the best 1/4 mile performance when I let her scream up to 6000rpm in 1st gear, and shift again at 5300-5500rpm. With a 700r4 you kind of have to "overrev" 1st a little because 2nd is much deeper. How are you launching? That can make a big difference too. You kind of need to play with everything and see what happens. Last time I was at the track (oct 2000) My first run was a 15.5. By the end of the day I pulled a 15.0 @ 91.5. I'm sure I could do better now (mods)...the key is to try everything. Also keep in mind that things like temp, humidity, wind, and condition of road come into play too. The Gtech is a good tool to see improvement (which you did), but for getting the absolute best time for you car you should go to a track.

-peace

 

the 3.73s you have would work much better if you had a bigger cam. Trust me. When I had the old cam and 3.73s I was running 10.0s in the 1/8 but with the cam I ran low nines and thats with tire spin. 3.73 are meant for cars with high rpm ranges. Spend a hundred bucks and slap a crane cam in. You will be amazed.

 

With the motor being under warranty there won't be any internal mods. I'm putting on a new intake I have in Spring and the other other mod I might get would be a TC. But that's doubtful as I'm looking into an SS hood and a paint job. Oh, and I can't rev my motor to 6k, my redline is only 5200rpms. Maybe I should have went with 3:42s. Besides my tranny is kind of messed up too, I'll probably have some more work done to that too.

 

Mark....I'm pretty sure you have the exact same 350 I do. Anyway my crate engine came with a 3 year warranty and I bought it only a year ago. Too bad I already voided the warranty. Oh well! If I break it i'll fix it. As for your gears you will probably get more out of 3.42s.

 

Mark,
Sorry I thought you still had the 305 in there.

Keep in mind that a bad auto trans eats even more power than a brand new one that'll eat up 18% of your ponies.

Were you hooking up well? Are you sure the road was flat? Will the warranty let you change to 1.6 rockers?

 

If he has the same one I do then Changing anything below the valve covers will void the warranty. Actually...technically if you take the valve covers off and don't put them back on using the right torque specs it will void the warranty. Sucks huh!

 

Really, cause I changed out the valve covers when the engine was installed. Anyways, the road is the flattest I can find and the straightest and even if it does have a minor bump or 2, I've tested my car on the same road all the time, so at least I should have some consistent results.

 

We have very similar mods and engine wise, except you do have a better cam, I was wondering what that 1/8 converts to in the 1/4 in your signature.

Just checked the converstion, comes out to around 14.4. I'm sure the mods you have over me, don't equal to a full second difference. Guess, I'll have to wait for some tranny work.

 

I had to go back and reread your sig to make sure you have a 350. My first question is are we talking about a TPI car,or a TBI? I've seen many try endlessly to tweak a tbi with no luck. Not having exact figures on what mod will yield what kind of direct result on the track,or if your using the Gtech correctly,I'd certainly agree that sounds slow. I mean a well tuned car should only get you so far...my current Iroc is a more or less a stock 305tpi(see sig)which has screemed ever since I got it. I post faster times than yours every time...which is very confusing to me.

Either way,if you feel it's not the GTech,driving,or traction that's the problem,then I'd restart with the basics. First place I would look after the standard tune-up and timing is the FPR and fuel filter especially if it's TPI. I have also had luck by replacing sensors the ecm directly relied on even though they were still in range,namely the cts,o2,and tps. Another SOTP boost was removing the baffels in the airboxes...yet all of those things are quickly nullified by a small thing like a vacuum leak,and those ba**ards are hard to find.

Good luck,
Niko

 

I have an Edelbrock 600cfm carb on there. Over the summer I replaced the fuel filter, the plug wires are about 4 months old. The car idles perfect with no missing. And I'm no longer using the ECM.

 

mark, I read an article in CHP a few years ago and it said the gear swap is only good for .2-.4 in the 1/4mi. I had swaped gears on a v8 chevy monza i had in highschool. It had 2.73 and i upgraded to 3.42's. The only difference I noticed was that the car had more rpm's on the freeway. I hated it! I'm sure gear swaps help, I would not trade my 3.23's and OD for anyother gear ratio. I use up first gear way too fast now anyway. I hope you do get some better times with your new mods That's a lot of hard work! I hope it was not for nothing.

 

Are you sure that was for 2:73 to 3:73. I recently read an article that for every :3 of gears you increase around 2/10 in the quarter, this was tested on a car. Which would be around 6/10 for me. I don't know maybe I need my tranny looked at. I know for one the governor is out of whack, if in D and I floor it rpms don't go over 3k before it shifts, I have to manually shift to reach higher rpms.

Could the timing be off on my car, I know my brother advanced it, not sure to what. But could a car run perfect other wise and the timing still be off?

 

The cam I have is perfectly matched for my carb and intake. As well as the exhuast system. I ran that time with MAJOR tire spin off the line. I had a 2.5 60 foot. Crappy huh!. Anyways Gears like 3.73s work better at high rpms. I still have the stock tranny with no rebuilds and stock TC. I need a 2500 rpm stall to get my car going high 13s. Your tranny is sucking a lot of power from you. If you get it rebuilt you might want to get a slightly higher stall speed. You should be running high 14s with the setup you currently have if not better. BTW nice car.... I love that pic!

 

I had the tranny rebuilt over the summer, no performance mods to it, I guess you get what you pay for. The TC is a non lock up, not sure on the stall though. I'm going to fool around with the governor, right now the car shifts at 3k rpms in D, so I just shift manually. Not sure if that will help anything though. Thanks for the compliment too.