LT1 Manifold/GenI Block Conversion Checklist
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Team Owner
Joined: Aug 2006
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From: Columbia Missouri
LT1 Manifold/GenI Block Conversion Checklist
This weekend I am making a short drive to pick up a complete '94 Impala SS LT1.
I know very little about fuel injection. I'm basically looking for a good map, or checklist of things I will have to do or buy to swap the LT1 intake onto my 400/'89 heads.
I already have a link, to send the manifold off for machine work.
I have lots of questions, but I can't seem to get them organized in my head, and I was hoping for some groundwork to get me straighted up.
I also have a H200R4 to use when I do the swap, but it's a vacuum operated trans, and I don't know if the computer can be alerted to use that trans. Do I have to use the LT1 computer or is there a better tunable option?
All ideas and suggestions welcome. Pics and links. Experiences are welcome. Thanks so much.
I know very little about fuel injection. I'm basically looking for a good map, or checklist of things I will have to do or buy to swap the LT1 intake onto my 400/'89 heads.
I already have a link, to send the manifold off for machine work.
I have lots of questions, but I can't seem to get them organized in my head, and I was hoping for some groundwork to get me straighted up.
I also have a H200R4 to use when I do the swap, but it's a vacuum operated trans, and I don't know if the computer can be alerted to use that trans. Do I have to use the LT1 computer or is there a better tunable option?
All ideas and suggestions welcome. Pics and links. Experiences are welcome. Thanks so much.
Racer
Joined: Mar 2005
Posts: 473
Likes: 2
From: Champlin Minnesota
Curious, I never knew that there was a way to fit a LT1 intake onto gen 1 block and heads. What machining is involved, is the distributor in the same location. I do know that you will have to upgrade your fuel system (which is the hardest part of my EFI struggle), add either a intank pump or an external pump, add another fuel line as the supply and use the stock supply line as a return, and think about adding a sump and baffles.
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Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by davidm_comp
Curious, I never knew that there was a way to fit a LT1 intake onto gen 1 block and heads. What machining is involved, is the distributor in the same location. I do know that you will have to upgrade your fuel system (which is the hardest part of my EFI struggle), add either a intank pump or an external pump, add another fuel line as the supply and use the stock supply line as a return, and think about adding a sump and baffles.
Well the heads I'm using are actually '89 heads similar to those used on TBI and TPI manifolds. From what I undersand, the manifold will bolt up to the heads just fine. The site LT1intakes will machine the dist. hole and provide a shim to make up the height difference. I will have to use the earlier smaller dist. with an external coil.
There was something I read about only needing a single line, but I seem to remember having a return so that won't be a problem to plumb. I'll likely add an external TPI style pump.
Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
Originally Posted by davidm_comp
Curious, I never knew that there was a way to fit a LT1 intake onto gen 1 block and heads. What machining is involved, is the distributor in the same location. I do know that you will have to upgrade your fuel system (which is the hardest part of my EFI struggle), add either a intank pump or an external pump, add another fuel line as the supply and use the stock supply line as a return, and think about adding a sump and baffles.
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by I'm Batman
Great site but they offer no help to a swap on an earlier carbed Gen1 motor.
Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
I'd use the TPI harness that you have and a 7727 weather-sealed computer (might have to modifiy the harness a bit for the WeatherPak plugs. I can get an adapter to make chip changes easy on the P4-style memcal (I've already assembled two).
http://gmecm.mine.nu/ is a great forum for EFI stuff.
I'll dig up and send you some save pages I have on converting from carb to EFI.
http://gmecm.mine.nu/ is a great forum for EFI stuff.
I'll dig up and send you some save pages I have on converting from carb to EFI.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
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From: Chattanooga TN
I don't think you can put an LT1 intake on early heads, can you? I thought LT1 had a unique angle on the heads? You can put Tuned-Port or TBI on early heads. You can buy carbed intakes for LT1 heads, but I do not think you can put an LT1 intake on anything but LT1 heads?
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Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
Originally Posted by markdtn
I don't think you can put an LT1 intake on early heads, can you? I thought LT1 had a unique angle on the heads? You can put Tuned-Port or TBI on early heads. You can buy carbed intakes for LT1 heads, but I do not think you can put an LT1 intake on anything but LT1 heads?
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by I'm Batman
I'd use the TPI harness that you have and a 7727 weather-sealed computer (might have to modifiy the harness a bit for the WeatherPak plugs. I can get an adapter to make chip changes easy on the P4-style memcal (I've already assembled two).
http://gmecm.mine.nu/ is a great forum for EFI stuff.
I'll dig up and send you some save pages I have on converting from carb to EFI.
http://gmecm.mine.nu/ is a great forum for EFI stuff.
I'll dig up and send you some save pages I have on converting from carb to EFI.
Unfortunately I sold the TPI harness and all the TPI stuff a month or so ago...I no longer have it. Can I use the LT1 harness and the 7727 computer?
Advanced
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From: Gilbert AZ
Thread Starter
Team Owner
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From: Columbia Missouri
Originally Posted by Corv3tt3
I read that. The closest they got to my application was carbed TBI cars.
Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
Originally Posted by Durango_boy
Unfortunately I sold the TPI harness and all the TPI stuff a month or so ago...I no longer have it. Can I use the LT1 harness and the 7727 computer?
I'll dig around on the desktop comp for those carb-to-EFI files. Did you get the LT1 head modification article? Some of the steps in it aren't necessary if you're using an LT1 manifold.
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by I'm Batman
Did you get the LT1 head modification article? Some of the steps in it aren't necessary if you're using an LT1 manifold.
Yeah, but I spoke with Jeff at the machine shop today in detail about this project. He said I would have more problems by switching to the LT1 heads than if I just modded the intake to fit the heads I have. He said they CCed about the same, but these heads are already designed to fit this block and have the steam holes and are ready to go. He suggested just the intake. Sound about right?
I can still go either way since I am buying the whole motor.
Everyone, please help me find a 7727. Ironically I just sent one to an Ebay buyer with a custom harness made just for my Vette, that would have worked well for this intake. Bummer. I did just email him about that harness to see if he was in fact going to use it.
Team Owner
Joined: Oct 2004
Posts: 23,831
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From: Springfield MO
St. Jude Donor '07
Originally Posted by Durango_boy
Yeah, but I spoke with Jeff at the machine shop today in detail about this project. He said I would have more problems by switching to the LT1 heads than if I just modded the intake to fit the heads I have. He said they CCed about the same, but these heads are already designed to fit this block and have the steam holes and are ready to go. He suggested just the intake. Sound about right?
I can still go either way since I am buying the whole motor.
Everyone, please help me find a 7727. Ironically I just sent one to an Ebay buyer with a custom harness made just for my Vette, that would have worked well for this intake. Bummer. I did just email him about that harness to see if he was in fact going to use it.
I can still go either way since I am buying the whole motor.
Everyone, please help me find a 7727. Ironically I just sent one to an Ebay buyer with a custom harness made just for my Vette, that would have worked well for this intake. Bummer. I did just email him about that harness to see if he was in fact going to use it.
Racer
Joined: Mar 2004
Posts: 292
Likes: 2
From: Plumas Lake CA
I think you can use the LT1 computer and harness. The computer can be tuned to ignore the 4L60E Impala tranny and VATS. Talk to Bryan Herter at PCMSFORLESS. If you are going with the overdrive auto, maybe run a built 4L60E? That would let you tweak the engine and tranny through the LT1 computer. Oh, the LT1 computer mounts behind the driver's side headlight in the Impala so you could mount it under the hood somewhere.
BTW, I run an LT4 head, comp 503 cammed 383 in my 94 Impala, backed by a T56. Bryan did the tune for my car.
BTW, I run an LT4 head, comp 503 cammed 383 in my 94 Impala, backed by a T56. Bryan did the tune for my car.
Last edited by 1mpalss; Nov 8, 2006 at 04:21 AM.
Safety Car
Joined: Dec 2004
Posts: 4,071
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From: San Diego CA
One thing I can successfully add to help. Remember LT1s came equipped with manual transmissions, too. So you can either have it reprogrammed to ignore the transmission or get a computer from like a six speed car. You'll probably just want to go ahead and have the computer you have reprogrammed anyways, though. You'll want to get it to ignore most of the pollution control stuff and only pay attention to the critical sensors like the TPS, MAF, and O2.
Oh and something to add to your list of things that need to be done! Weld a bung for the O2 sensor on to one of your headers.
Oh and something to add to your list of things that need to be done! Weld a bung for the O2 sensor on to one of your headers.
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by I'm Batman
What did he seem to think was the problem with the LT1 heads? You only have to weld plugs in two holes per head, then surface them and drill steam holes.
He didn't say there were problems with the LT1 heads, just that I wouldn't see any gains from swapping. I already had the machine work done to the heads I have, and removing them and adding the LT1 heads would require more work. He also mentioned but was not sure but I would run into compression problems adding the LT1 heads to the 400. He just thought the gains would nit be there to justify the swap away from the heads I have.
Melting Slicks
Joined: Aug 2004
Posts: 2,906
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From: Oakbank Manitoba
Originally Posted by 1mpalss
I think you can use the LT1 computer and harness. The computer can be tuned to ignore the 4L60E Impala tranny and VATS. Talk to Bryan Herter at PCMSFORLESS. If you are going with the overdrive auto, maybe run a built 4L60E? That would let you tweak the engine and tranny through the LT1 computer. Oh, the LT1 computer mounts behind the driver's side headlight in the Impala so you could mount it under the hood somewhere.
BTW, I run an LT4 head, comp 503 cammed 383 in my 94 Impala, backed by a T56. Bryan did the tune for my car.
BTW, I run an LT4 head, comp 503 cammed 383 in my 94 Impala, backed by a T56. Bryan did the tune for my car.
You can get the "7727" weather proof computers in the wrecking yards for next to nothing. They were installed in Grand Prix, Regal,Cutlass Supreme and Lumina in the early nineties (89/92). You cannot however use the memcal(chip) from the computer as it is designed for a six cylinder engine.
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Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by KENS80V
I don't think you can use the LT1 computer and harness on the earlier small block due to the different styles of distributor. The optispark setup on the LT1 is completely different than the HEI setup on your car. Also, there are other problems like the crank sensor on the LT1 used for sequential firing of the injectors that is not compatible/installed on the earlier small block.
You can get the "7727" weather proof computers in the wrecking yards for next to nothing. They were installed in Grand Prix, Regal,Cutlass Supreme and Lumina in the early nineties (89/92). You cannot however use the memcal(chip) from the computer as it is designed for a six cylinder engine.
You can get the "7727" weather proof computers in the wrecking yards for next to nothing. They were installed in Grand Prix, Regal,Cutlass Supreme and Lumina in the early nineties (89/92). You cannot however use the memcal(chip) from the computer as it is designed for a six cylinder engine.
Do you think things like that crank sensor can be ignored by the computer? If you can tell it to ignore the transmission and smog stuff, why not the crank speed? Also, what is VATS?