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Hey all, I am learning how to swap in a Gen II LT1 from a '92 and the 6-speed, ZF6 into my 1975 Corvette. My 75 had an L48 4-speed. I am wanting to hit all 48 states with my car. I decided to log the journey. If anyone is interested or has helpful hints on what they did with a LT1 swap, I'd be happy to hear. Anyway, here is the beginning of the journey if you are looking to do something similar and haven't tackled this before.
I started with the same car, 75 L48 4-spd. Mine was in less challenging condition when I started lol. Like you I also swapped in a new small block and updated trans. Also swapped bumpers and wheels. And seats. And a billion other things.
One difference is you waited 10 years. I started my project a few days after I bought the car. I had the original engine/trans out and sold that weekend.
In your first video at about 3:45 you talk about sending the ecm to an outfit in Tempe. So they can flash it and delete “that”. What is this “that” you refer to? The immobilizer?
I started with the same car, 75 L48 4-spd. Mine was in less challenging condition when I started lol. Like you I also swapped in a new small block and updated trans. Also swapped bumpers and wheels. And seats. And a billion other things.
One difference is you waited 10 years. I started my project a few days after I bought the car. I had the original engine/trans out and sold that weekend.
In your first video at about 3:45 you talk about sending the ecm to an outfit in Tempe. So they can flash it and delete “that”. What is this “that” you refer to? The immobilizer?
I'm from Idaho, so I talk with a heavy accent. I was saying VATS. they deleted VATS, the security.
I would try to convert to the newer vented Opti-spark. That requires a newer timing chain cover and a longer pin in the cam, besides the Opti that is.
Delete VATS. You can do it, as well as any other tuning you want, with free PC software and a USB to serial converter that costs about $3. If you're deleting the charcoal canister purge or EVAP you need to change a few other things in a specific way. Do it wrong and you get stuck in BLM cells 16-18 and the fuel trims don't work right.
You may be the first person I’ve heard of reinstalling the 75 rear bumper. For me it was one of the first things to throw away haha.
oh man, I really considered that. Is that from custom image? Do you have a side shot of that? I might still try to pull this off. I had a bit of a concern with alignment but yours looks fantastic! if you have rear and side shot pics, please post them, I'd love to see it.
I would try to convert to the newer vented Opti-spark. That requires a newer timing chain cover and a longer pin in the cam, besides the Opti that is.
Delete VATS. You can do it, as well as any other tuning you want, with free PC software and a USB to serial converter that costs about $3. If you're deleting the charcoal canister purge or EVAP you need to change a few other things in a specific way. Do it wrong and you get stuck in BLM cells 16-18 and the fuel trims don't work right.
Tempe Speed and Performance deleted VATS for me. I am going to try to learn how to tune it myself. Apparently the LT1 offers free tuning software that I can learn on.
I am going to switch to the vented Opti. I am still a little confused on which brand would be okay and whether I need to swap the entire shaft or just the head. From what you are saying would I need a different cam? or do I drill out something? do you have experience doing this? Thanks for the input! I'm probably going to keep bothering you about it.
The alignment pin on the cam is longer and sticks out past the gear. The back of the vented Opti locates over it. You have to duplicate that. You could probably pull out the original short pin and change it, or just cam swap it and you'll get the longer pin.
Last edited by lionelhutz; Nov 9, 2021 at 04:37 PM.
op here are some shots. It’s a fiberglass cap that just replaces everything back there. A 74-77 C3 immediately looks like a 73 haha. You throw everything away including all factory safety equipment. You can get a pretend chrome bumper for it which I just left off.
There are some legendary/controversial threads on this subject with regards to safety and also the supplier since he isn’t a sponsor. I will pm you his contact.
My car is a 10-footer. The cap fits very nice right out of the box but a perfectionist would need to massage it b4 final fit or painting. You have to mod the oe tail lights to fit.
The ZF6 will present some interesting challenges as it was designed for the C-beam style mount used in a C4. A T56 from an early 4G camaro would bolt up and be easier to modify to fit, for what it’s worth, not to mention it’s easier to source flywheels/clutches and rebuild components.
A 2G LT1 is also not a very compelling swap these days. The aftermarket for the gen 1 smallblock is better, parts are easier to find and they are generally more reliable - particularly if you pick up a one-piece rear main seal block, use center bolt valve covers and EFI.
TunerPro is free to use, like you mentioned. The ‘92 LT1 has some ECM challenges, so I’d recommend going with a later ECM. Moates has info on the challenges you face - you end up having to buy more stuff and certain configurations of tuning are unavailable.
The ZF6 will present some interesting challenges as it was designed for the C-beam style mount used in a C4. A T56 from an early 4G camaro would bolt up and be easier to modify to fit, for what it’s worth, not to mention it’s easier to source flywheels/clutches and rebuild components.
A 2G LT1 is also not a very compelling swap these days. The aftermarket for the gen 1 smallblock is better, parts are easier to find and they are generally more reliable - particularly if you pick up a one-piece rear main seal block, use center bolt valve covers and EFI.
TunerPro is free to use, like you mentioned. The ‘92 LT1 has some ECM challenges, so I’d recommend going with a later ECM. Moates has info on the challenges you face - you end up having to buy more stuff and certain configurations of tuning are unavailable.
The ZF6 will present some interesting challenges as it was designed for the C-beam style mount used in a C4. A T56 from an early 4G camaro would bolt up and be easier to modify to fit, for what it’s worth, not to mention it’s easier to source flywheels/clutches and rebuild components.
A 2G LT1 is also not a very compelling swap these days. The aftermarket for the gen 1 smallblock is better, parts are easier to find and they are generally more reliable - particularly if you pick up a one-piece rear main seal block, use center bolt valve covers and EFI.
TunerPro is free to use, like you mentioned. The ‘92 LT1 has some ECM challenges, so I’d recommend going with a later ECM. Moates has info on the challenges you face - you end up having to buy more stuff and certain configurations of tuning are unavailable.
Yeah, its going to be a pretty interesting hookup underneath. I bought a 94 Camaro ECM and sent it off to get programmed to avoid the '92 problems. I think a T56 would be significantly smarter, all of this just came together in a cheap unit that it was just hard to pass up. I like the ZF6, I had one in a C4 15 years ago and it seemed fine. I also would rather do a LSX or a later LT1 or a 454 or 427 build. But, one step at a time. I found this and have the majority of parts for it. So, I just thought gotta start somewhere. plus, I think the gII LT1 is a clean looking engine when taken care of.
Great input though. I am a bit worried now about hooking the ZF6 up. I'll have to pay more attention to it.
Yeah, there isn't much aftermarket support or interest in them. Probably why I got it so cheap. Its not the final engine for the car. But, it definitely is going to be the first swap into it!
You could probably find a taker for the ZF6 in the C4 forum, though I honestly have just about zero knowledge of what the market is like for those. You’d be way ahead starting with a T56. At this point, I can’t even remember if I’ve driven a stick-shift C4.
A local friend of mine has a 92 that’s getting a new opti and front seal… and a cam and AFR heads along with that. I will likely drive that one in a few months when we’re done assembling it. This is where I picked up the knowledge on the 92 oddities.
You could probably find a taker for the ZF6 in the C4 forum, though I honestly have just about zero knowledge of what the market is like for those. You’d be way ahead starting with a T56. At this point, I can’t even remember if I’ve driven a stick-shift C4.
A local friend of mine has a 92 that’s getting a new opti and front seal… and a cam and AFR heads along with that. I will likely drive that one in a few months when we’re done assembling it. This is where I picked up the knowledge on the 92 oddities.
Do you know which Opti he chose to put in it? The ZF6 isn't anything that really terrifies me. I think that pulling the body off and installing it will likely be necessary, which sucks, but if that happens I can at least clean my frame up and protect it...if I were to consider my glass being half full.
Except for the front end - timing chain cover and water pump - the LT1 is pretty similar to any other later small block. The opti is a weak spot, but the stock EFI is good for the age of it.
You might want to consider a 24X conversion for it. EFIConnection and Torqhead both make conversion kits. This would put you closer to ready for a LS swap in the future, or at least get rid of the opti and also get even better GM fuel injection. With PCMHammer it's possible to DIY tune it without buying a ODBII tuning suite.
Red Dragon 79
I actually did some troubleshooting on a friend's LT1. For a few years I had 730 ECM and was burning my own chips using an AutoProm and Tunerpro RT. My buddy called and asked me if I could eyeball the LT1 in his Woodie wagon. I found a file and went over. He actually got a chip from one of the chip companies and I was able to read it and all his engine parameters. I found a bad temp sensor which was affecting his system. It really was quite easy to figure it out (but I was more proficient with the Autoprom back then Tunerpro). I swapped my RamJet 350 over to EZ-EFI 2.0 so I haven't used the stuff for a while .....but it is pretty cool to see all those engine parameters on a computer screen and to be able to adjust just about anything.
I mention that because you say you want to learn how to tune it yourself.
Originally Posted by Red Dragon 79
Tempe Speed and Performance deleted VATS for me. I am going to try to learn how to tune it myself. Apparently the LT1 offers free tuning software that I can learn on.
I am going to switch to the vented Opti. I am still a little confused on which brand would be okay and whether I need to swap the entire shaft or just the head. From what you are saying would I need a different cam? or do I drill out something? do you have experience doing this? Thanks for the input! I'm probably going to keep bothering you about it.
Last edited by carriljc; Nov 11, 2021 at 12:24 PM.
You might want to consider a 24X conversion for it. EFIConnection and Torqhead both make conversion kits. This would put you closer to ready for a LS swap in the future, or at least get rid of the opti and also get even better GM fuel injection. With PCMHammer it's possible to DIY tune it without buying a ODBII tuning suite.
I agree. If an LS motor is the end game, it'd be nice not to have to re-wire twice.
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Swapping in LT1
