72 LeMans project... what to do next? - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 5 (permalink) Old 11-18-2017, 02:45 PM Thread Starter
 
M070552's Avatar
 
Join Date: Mar 2016
Location: CT
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
72 LeMans project... what to do next?

I have a 72 LeMans that I put back on the road a few years ago. It's got a Pontiac 400 with mild cam, Edelbrock Performer intake, Holley street avenger 670 carb, aluminum radiator with electric fans, TH400 auto with 2.78 gears in a GM 8.5" rear axle. I also put a Hotchkis spring and swaybar kit into it, which tightened up the suspension a lot.

There are three major mechanical things I want to do the car still, all will cost in the same ballpark $ wise: 1) getting functioning AC 2) installing the TH200-4R that's in my garage 3) Ditching the carb for EFI.

I have some of the AC parts, and intend to use the factory setup inside the car, while converting to a modern style compressor and R134a, I estimate I need about another $1000 worth of parts to get it working.

I have a TH200-4R (BQ code) that I'm going to put in place of the TH400, but I will need to at minimum change the rear axle ratio from 2.78, probably to 3.55. While I'm at it I'll also put in an Eaton Truetrac, and potentially new axles and aluminum driveshaft, estimate $1500 total.

Also thinking of going the EFI route. The carb has a couple spots where it goes lean, and chasing it is driving me nuts. (I have a wideband O2 sensor installed to help in carb tuning). Looking at a Fitech setup, and will need to upgrade the fuel system. Estimate $1500 total.

Looking for thoughts on which should be the next priority?
M070552 is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 11-19-2017, 12:23 PM
 
1968gto421's Avatar
 
Join Date: Mar 2014
Location: Travelers Rest, South Carolina
Posts: 765
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 72 Post(s)
My thinking is that the A/C could be put off awhile since winter is upon us in many places and you have time before you need it. Likewise if the Holley is doing OK, the EFI could be pended.

I believe in doing the TH200-R4 and the ring and pinion/Eaton next. I'm sure others will advise differently but based on my experience I think this would be the best route.

(If you want to read some real life Pontiac experiences with FITech, you could check out this PY forum thread........ New self learning EFI at half the price.... - PY Online Forums

Best of luck with your Pontiac...and welcome to the forum.
1968gto421 is online now  
post #3 of 5 (permalink) Old 11-19-2017, 12:56 PM
 
Join Date: Jul 2016
Location: North Louisiana
Posts: 626
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
"...2.78 gears in a GM 8.5" rear axle...change the rear axle ratio from 2.78, probably to 3.55. While I'm at it I'll also put in an Eaton Truetrac, and potentially new axles and aluminum driveshaft, estimate $1500 total..."


Before you spend any $$$$ on it, make sure you have an 8.5. I say this because I think the '72 came with an 8.2. But, if you already know for sure you have an 8.5, please just ignore this.

Also, good luck on doing all that for only $1500.

"...The carb has a couple spots where it goes lean, and chasing it is driving me nuts.Looking at a Fitech setup, and will need to upgrade the fuel system. Estimate $1500 total..."

SMI can build you a good Q-jet for 1/3 that cost.

https://www.smicarburetor.com/produc...D2/9/sfID3/100

There's even a good Q-jet guy right there in your home state.

http://www.everyday-performance.com/

Last edited by bigD; 11-19-2017 at 01:21 PM.
bigD is online now  
 
post #4 of 5 (permalink) Old 11-19-2017, 01:45 PM
 
Join Date: Jul 2016
Location: North Louisiana
Posts: 626
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Just wondering exactly why you are considering going with the OD trans. Is it for lower rpm cruising ? Is it for more acceleration, from the combination of the 1st gear ratio plus the numerically higher gear ratio ?

Just curious. Some make the change, for different reasons.

I'd probably stay with a 3-speed trans, a good, efficient, stall converter, and no more than 3.08 gears. You can even have a 2.75 ratio 1st gear built into the 3-speed trans, if you want more low gear. Lots of class racers are running TH350's with a 2.75 ratio 1st gear. These are available for the TH350 & TH400.

This also prevents having to deal with the TV cable of the OD trans.

Hey, these are just other options. As has been said many times on many car forums, "It's your car & your money, so build it like you want it.".
bigD is online now  
post #5 of 5 (permalink) Old 11-20-2017, 12:07 AM Thread Starter
 
M070552's Avatar
 
Join Date: Mar 2016
Location: CT
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks all for the feedback.

BigD, I will check the rear axle before I buy anything to make sure I get the correct parts. As
far as why I want the overdrive trans, it's a combination of the two reasons you stated. The cruise RPM isnt terrible with 2.78 gears, but acceleration is. So I'm looking to improve on both with the OD, so that means picking rear gears just right. The math says 3.42 or 3.55 will accomplish that, and I break even at 3.73 on cruise RPM. So I think I will go with 3.55.

I already have the trans, it's been in my garage for about two years. So what I need to buy is rear axle upgrade stuff. Summit has the Eaton truetrac for ~$500, a couple hundred for ring & pinion, and another few hundred for axles plus some misc stuff puts it in the ballpark of $1500.

I have considered going to a Qjet, you make a sound argument about the $. I'm sure I could sell the Holley for a couple hundred and then only be into the Qjet for a couple hundred more. I don't mind tuning the carb to dial it in, but getting the transfer from idle circuit to main jets to be smooth has eluded me to date. Then I wouldn't have to do any fuel system mods, save for getting the gas gauge to work properly (when full it reads 3/8 of a tank, goes down proportionally from there, been like that since I first bought the car in 2001, and yes I have replaced the sending unit).
M070552 is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
71 Lemans driver project hondarider2289 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions 5 10-16-2017 10:26 PM
1967 LeMans project omnidrift 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions 27 09-11-2017 10:23 PM
My new project 65 Lemans SDGoat619 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions 2 03-27-2011 10:11 PM
1968 LeMans project xcmac26 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions 3 03-05-2009 10:07 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome