LT1 Manifold/GenI Block Conversion Checklist
Melting Slicks
Joined: Aug 2004
Posts: 2,914
Likes: 229
From: Oakbank Manitoba
It is the difference in distributors that is the main reason you can't retrofit the Lt1 computer/harness to your HEI setup. The optispark setup has nothing in common with the HEI.
Vats...is the anti theft system. It can be removed by whoever rewrites your programing on the memcal (chip). I recommend "PCM For Less".
Vats...is the anti theft system. It can be removed by whoever rewrites your programing on the memcal (chip). I recommend "PCM For Less".
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I just got off the phone with a guy named Dana, in PA, that does exactly what I need. He says I can use the LT1 harness and computer. They can alter the harness to fit my needs on this engine including early HEI style. He can then reprogram the chip specifically for my 400 and cam, and delete what I don't need. Deleting VATS, smog, and altering for use of a TH200R4. It'll be converted to OBD1, a '94/'95 LT4 cal. It's just a little pricey but he allows me to do it all with what I have already.
Racer
Joined: Mar 2004
Posts: 292
Likes: 2
From: Plumas Lake CA
The 96 Impala (and other 96 LT1's) was the only one that used a crank sensor and OBDII. I believe the computer can be fooled to ignore the crank sensor if you have an OBDII, but a lot of 96 guys just convert to OBDI anyway - it makes tuning easier and makes more power.
Vats is the vehicle anti-theft system. It uses a coded key in the ignition to protect the vehicle from being stolen.
I think the Optispark ignition can be deleted and a distributor can be made to work. Maybe it requires the TPI type of distributor? Does that LT1 manifold conversion site talk about which distributor to run?
edit: I just saw DB's last thread. You're good to go!
Vats is the vehicle anti-theft system. It uses a coded key in the ignition to protect the vehicle from being stolen.
I think the Optispark ignition can be deleted and a distributor can be made to work. Maybe it requires the TPI type of distributor? Does that LT1 manifold conversion site talk about which distributor to run?
edit: I just saw DB's last thread. You're good to go!
Last edited by 1mpalss; Nov 8, 2006 at 04:18 PM.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by 1mpalss
edit: I just saw DB's last thread. You're good to go!
Sweet. Does all that sound like good spending?
$200 to have the manifold converted to Gen1 block and HEI dist.
$325 to have the LT1 harness modified for my '77 Vette and HEI dist.
$125 to have a custom chip programmed for the 405 and cam, deleting unused programs.
Looks good to me.
Melting Slicks
Joined: Aug 2004
Posts: 2,914
Likes: 229
From: Oakbank Manitoba
Good to hear of harness problem being solved. Don't forget to tell them to add the correct connectors for a small cap HEI distributor. They are different then the large cap HEI setup. Other items to consider are the fuel return line upgrade and high pressure (43psi) electric fuel pump mounting location. The minimum size of return line needed is 5/16. Your cars original line is 1/4. Also needing thought is the MAF location (sensor in front of the throttle body in the air inlet stream).
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by KENS80V
Good to hear of harness problem being solved. Don't forget to tell them to add the correct connectors for a small cap HEI distributor. They are different then the large cap HEI setup. Other items to consider are the fuel return line upgrade and high pressure (43psi) electric fuel pump mounting location. The minimum size of return line needed is 5/16. Your cars original line is 1/4. Also needing thought is the MAF location (sensor in front of the throttle body in the air inlet stream).
Good thinking. I didn't know the return line was insufficient. That'll be tricky to replace. I'm still looking for the fuel pump I want.
Does the '94 Impala LT1 have a MAF sensor? I wonder why it hasn't been mentioned to me before by anyone. What options do I have? I was just gonna run a cone filter at the throttle body.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by KENS80V
Impalss would be the best guy to ask that...but I think the 94 ImpallaSS uses both a map and maf sensor. I can see in your pictures that a map sensor is present.
I'll figure it out somehow. I always do. By the way, Kens80V - Where did you get the cone filter on the TPI throttle body on your avatar? That's the kind I'm gonna want to find.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Originally Posted by Durango_boy
Good thinking. I didn't know the return line was insufficient. That'll be tricky to replace. I'm still looking for the fuel pump I want.
Does the '94 Impala LT1 have a MAF sensor? I wonder why it hasn't been mentioned to me before by anyone. What options do I have? I was just gonna run a cone filter at the throttle body.
Does the '94 Impala LT1 have a MAF sensor? I wonder why it hasn't been mentioned to me before by anyone. What options do I have? I was just gonna run a cone filter at the throttle body.
Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
A little background on MAF sensor usage. The '94 Camaro didn't use an MAF but the '95 Camaro did. I think the '94 Corvette had an MAF, though. So it would be logical to assume that an MAF wasn't used on a '94 Impala if it wasn't even used on the Camaro.
Melting Slicks
Joined: Aug 2004
Posts: 2,914
Likes: 229
From: Oakbank Manitoba
93 Corvette was map, 94 Corvette was maf and map, 95 Corvette was maf and map. David Koldos has modified two of my throttle bodies now. He rebuilds them by boring it out to 52mm and he installs needle bearings for the throttle shaft. Do a search on the C4 site to get his address and phone...or I can give it to you. He doesn't have a website.
The air cleaner on my throttle body is the K&N RC5050. This one is the larger of the two offered by K&N and flows 1000cfm. You have to grind away a bit of the filter at the throttle position sensor otherwise you will never get the harness connector on.
The air cleaner on my throttle body is the K&N RC5050. This one is the larger of the two offered by K&N and flows 1000cfm. You have to grind away a bit of the filter at the throttle position sensor otherwise you will never get the harness connector on.
Last edited by KENS80V; Nov 9, 2006 at 06:24 PM.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by KENS80V
93 Corvette was map, 94 Corvette was maf and map, 95 Corvette was maf and map. David Koldos has modified two of my throttle bodies now. He rebuilds them by boring it out to 52mm and he installs needle bearings for the throttle shaft. Do a search on the C4 site to get his address and phone...or I can give it to you. He doesn't have a website.
Yeah, it'd be great if you could PM me his info. Do you remember how much he charged fro the work?
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Originally Posted by KENS80V
... Other items to consider are the fuel return line upgrade and high pressure (43psi) electric fuel pump mounting location. The minimum size of return line needed is 5/16. Your cars original line is 1/4. ...
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by markdtn
I am running the 1/4 return line on my TPI conversion and I know of at least 4 more C3s like that with no issues at all (3 TPI, 1 LT1).
And your return line would bet eh same as the one in my '77 right? That's good news. I was hoping for an easy solution. I really didn't want to lift the body just for a fuel line.
Racer
Joined: Mar 2004
Posts: 292
Likes: 2
From: Plumas Lake CA
All the '94 - '96 Impala's used the same MAF. A lot of Impala guys (myself included) go to the larger Camaro MAF. It's .25 or .5 inches bigger than the stock Impala unit, and it uses the same plug. I'd have to guess all the Vette and Camaro LT-1's used MAF sensors (as well as the same PCM boxes), except for maybe the first Vettes. I don't reccommend any aftermarket MAF, as their "tables" are not as common as the factory stuff, making them difficult to tune properly. Make sure you tell the programer about all your components and mods so he can set up the tune accordingly.
I've got the Koldos 52mm on my car now. Quality work. If you go any bigger, be sure to bore the two intake manifold holes to match, as they are only about 54mm. Definitely bore the manifold to match if you go to the larger 58mm throttle body.
Something else I just thought about, the 94 and 95 Impalas used 2 O2 sensors, 1 in each exhaust pipe just before the cats. The 96 used 4 O2's, 1 before and 1 after each cat.
I've got the Koldos 52mm on my car now. Quality work. If you go any bigger, be sure to bore the two intake manifold holes to match, as they are only about 54mm. Definitely bore the manifold to match if you go to the larger 58mm throttle body.
Something else I just thought about, the 94 and 95 Impalas used 2 O2 sensors, 1 in each exhaust pipe just before the cats. The 96 used 4 O2's, 1 before and 1 after each cat.
Last edited by 1mpalss; Nov 10, 2006 at 05:36 PM.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by 1mpalss
Something else I just thought about, the 94 and 95 Impalas used 2 O2 sensors, 1 in each exhaust pipe just before the cats. The 96 used 4 O2's, 1 before and 1 after each cat.
The programmer said he will easily convert it from 2 to 1, O2 sensors. That part's covered. Thanks.
Racer
Joined: Mar 2004
Posts: 292
Likes: 2
From: Plumas Lake CA
I tend to agree. If the MAF fails, the car defaults to a preset table so you can get the car home. I've had an O2 sensor become loose. The car started running really bad until the check engine light came on and the computer stopped utilizing the closed loop system and went into open loop which utilized the pre-set tables. The car ran pretty decent then.