.273 to .373 swap

**guitarjay76** · 03-02-2007, 12:36 PM

Im going to change my gears to .373s in my 2000 auto Z. I was wondering how much I should gain in my quarter mile time as well as how much I'll lose on the gas milage. Any input is appreciated.

**juiced99ws6** · 03-02-2007, 01:51 PM

you should see roughly .5 second difference and only a few mpg difference in fuel economy..

**juiced99ws6** · 03-02-2007, 04:59 PM

i dont have any lag but I dont remember having any in the first place to be honest with you. I did have 323s stock though so that may be the difference, that and i have had these gears and 12 bolt rear for almost 2 years now

**guitarjay76** · 03-02-2007, 06:21 PM

What was your main reason for going with the 12 bolt? Also, how much of a difference did you notice when you went to .373s?

**juiced99ws6** · 03-02-2007, 06:37 PM

Originally Posted by guitarjay76

What was your main reason for going with the 12 bolt? Also, how much of a difference did you notice when you went to .373s?

because I have a high stall+ 150 shot+ drag radials. The 10 bolt woulda shit on me pretty quick. I know I gained a few tenths and it just pulls harder all through my RPM range and people say you sacrifice high end power but if you dont mind not driving above 140 or so then you will be just fine

**guitarjay76** · 03-02-2007, 06:46 PM

What tuning did you have to do? How much should the gear swap cost me if I keep the stock rearend?

**juiced99ws6** · 03-02-2007, 06:48 PM

you just need your speedo recalibrated. are you planning on doing the install yourself?

**guitarjay76** · 03-02-2007, 06:50 PM

My hypertech III should handle that right? I'm trying to make a solid quarter mile car / daily driver on a pretty limited budget. What should my est. E.T. be after the gear swap?

**juiced99ws6** · 03-02-2007, 06:53 PM

the gears should be around 200$ for a nice set of richmond gears. The speedo racalibration you would just have to talk to a local tuner on that one and the replacement shouldnt be that big of a job

**guitarjay76** · 03-02-2007, 06:56 PM

I'm currently a consistent 112 / 115 mph.

**guitarjay76** · 03-02-2007, 06:58 PM

Can my local GM dealer do a dynotune for me or does it have to be a high-performance shop? I live up north in the boonies- so it kinda sucks ass!

**juiced99ws6** · 03-02-2007, 07:05 PM

Originally Posted by guitarjay76

I'm currently a consistent 112 / 115 mph.

wow.. what are your mods.

I am not sure if the dealership can do it for you or not. You do not need a full dyno tune though for that just the speedo recalibrated or any handheld programmer should do it as well

**guitarjay76** · 03-02-2007, 07:24 PM

If I add headers would a full dynotune benefit me?

**juiced99ws6** · 03-02-2007, 07:30 PM

OHHHH that makes things alot better.. lol you can reflash your computer for the 373 gears with your hypertech so the swap if you do your one work will only be around 200$

A dynotune would benefit you at anytime however with headers it is still not needed. I would get some o2 sims so you arent throwing a code all the time for your o2 sensors. You will run richer with a set of longtubes but you will still be happy with your gain. For me, I never did the dyno tune because I have always had plans to get a cam and then I would need one anyways so I figured I would just wait. If you are just going to leave it as a bolt on car for a while and have the money for a tune then you would definatly get a little more out of it

**juiced99ws6** · 03-02-2007, 07:32 PM

Originally Posted by guitarjay76

My hypertech III should handle that right? I'm trying to make a solid quarter mile car / daily driver on a pretty limited budget. What should my est. E.T. be after the gear swap?

sorry i didnt see this qoute before but yes it will do it. as for the ET. I dunno man, all cars are different. Depends on alot of factors

**juiced99ws6** · 03-02-2007, 07:33 PM

I can tell you that I trap about 114 and run low 12's with my current setup. that is mainly because of traction I should be more in the mid to upper 11's on a better track

**guitarjay76** · 03-02-2007, 07:36 PM

What about a cam / intake swap? What would that cost me, and how much performance, mainly quarter mile would I gain?

**juiced99ws6** · 03-02-2007, 07:47 PM

you can buy an LS6 manifold now for about 375$. A cam swap will end up costing you a little over a 1000$ if you do all the work yourself because there are some supporting mods you need with it like new valve springs and a dyno tune would be a must. On top of that you should also get a stall because an auto car without a stall isnt the best thing to cam. For now, on your application and being on a limited budget I would stay away from the cam route. Do a stall and your 373s first. Go to fuddleracing.com and look at converters. John is very helpful. Then get yourself some gears and find a friend to help you do the work yourself. That will be around 600$ and will get you almost a full second off your ET providing you get traction. Then look into some LT headers. You can pick them up for about 500$ with a Y pipe I believe (been a while since I priced them) and then will be good for another couple of tenths as well as help out any further mods that you do.