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LT-1 Conversion



I would like to know if anyone has installed an LT-1 in a mid seventies model and where I might find some tips and tricks about making the conversion.

I am specifically concerned about clearances around the shock towers and mechanical vs. electric fans.

Any help or links would be GREATLY appreciated, especially around the fourth or fifth time I'm trying to set the motor in the mounts! <Grin>

Craig Sharp

Hey, the LT-1 (I assume you mean the 1992-1996 fuel injected version) is a great motor.

I have NEVER installed one in a C3. However, I have installed several of them in other types of vehicles.

Here is what I can tell you.

It bolts up much like a standard small block. You will need to make sure that the flywheel is from the LT-1 to avoid vibration issues. The only place you will run into problems is on the front pulley system.

Street and Performance, March Performance, and a handful of other companies make accessory brackets for the LT1. I am pretty sure you can use the stock 92-96 Vette brackets. The problem with the F-body (camaro/firebird) is they put the a/c down low causing clearance problems with the cross member.

Remember, you will need a high pressure electric fuel pump and supporting wire harness/computer to run the engine.

There are two types of LT1 engines. The 92-93 use a very basic computer and can be "chipped" to run in your C3. The 94-96 engines use a more sophisticated computer (OBD II) that has to be reprogrammed. They also use sequential fire injection instead of batch fire.

This is where it gets expensive. The newer LT1 is superior to the older, but the harness ranges from $500 to $750 and requires either a lap top computer and software, or a minimum of $250 to send the computer out to be reprogrammed. You can do the older version for about $350 on the harness and about $200 for the chip.

Here is the downside. The computer will be tricked into thinking it is still in the donor car. It will not be getting inputs from wheel sensors, antilock brakes, quad 02 sensors etc. You will be running at the most basic level of ability. Most systems also require running as a speed density (no mass air flow sensor). The lack of the mass air flow sensor and running as speed density causes you to loose some hsp and create a few driveability issues. You won't get the factory adverstised fuel economy as a C4 with the same engine as the computer will be running it on the rich side most of the time.

For the most part, it is better than just running a carb. However, by the time you buy the engine, brackets, replace the ignition, special fuel lines, etc. etc. you could have installed a sweet big block that will kick the tail out of the LT1. Plus, the LT1 does not have the visual appeal of the old L98 Tuned Port engine. However, when geared right, the LT1 will run circles around the L98.

Electric fans are no problem. You will not run into any clearance issues with the radiator. You will however have to get pretty creative to route the air intake. Most guys just put the small front mount street rod air cleaner. The problem is, it is so small that it chokes the engine. You will need to get some custom 3.5" mandrel bent tube to run from the throttle body intake to a remote area with a larger air filter.

If you do decide to do this, get back with me and I will do what I can to point you in the right direction.

Unless you get a motor for free, be prepared to drop about $5,000 to $6,500 total less any labor if you pay others to do this for you. Like I said, you can get a nice head start on a big block or ready to go crate motor for that kind of $$$$$$$.
BTW-sorry for the book, but we are just scratching the surface on this swap. The last one I did was in a 1936 Ford. Total cost including the transmission, cut down drive shaft, Street and Performance pulleys, hoses, wires, computer, harness, electric fans, etc. etc. just uner $10k including paying me a few bucks for dropping it in.

The one before that I put into a 1989 1500 pick up. Total cost for the engine, trans, computer, etc. etc. etc. was right at $8,000 (with giving me a few bucks).

The one before that was a 1990 1500 pick up. This one we used a 1993 LT1 and got out the cheapest of all. Total cost on this one was $4,500. However, that was my buddies truck and there were no labor charges and we got the motor and trans together for $1,100.

These prices include headers, dress up valve covers, fuel lines, etc.
heart transplant

I too am thinking of putting in an updated enginein my C3, only I'm going to go with the L98 engine. I have a friend who put in a 89 vette engine into a 74, he got lucky and found a donor car to do the swap. Me I'm still looking.I have found an 88 vette engine with harness and computer for 2500.00 thinking about it though. You can get the 700R4 for 866.00 out right at 700r4.com they have a good conversion kit for the C3s. wiring if you need that try painlesswiring.com. like I said I want to do this swap to my 80, I'll most likely do all of the work myself so I hope to keep the cost down. I plan on going to my friends house in the summer and checking out what he did and taking alot of notes.

The L98 is a very economic swap. You can get a painless harness around $250 and a chip for around $100. The L98 can use a variety of the older computers that are available everywhere. The L98 also uses the same type of brackets for the accessories as almost any other small block. The only trouble you run into there is the air cleaner clearance. Get creative, and you will be in business. The L98 was also designed for torque and they were all batch fire systems. However, you will also have to run it in the speed density mode loosing a little driveability.

The other thing about the L98 is it performs great with modest rear gears. It performs even better with a 700R due to the low ratio of first gear.

It makes for a great economical swap. The only draw back is that it is hard to really get the upper end hsp out of it with the stock intake manifold and basic computer.

Both of you are going to have a blast with these conversions.

Let me know if I can help out.

Thanks 69
I'm sure I'll need all of the help I can get, that's why I plan to visit my friend see how did the swap.
Have you seen Noel site?
He put a TPI into an 82 collectors ed. He has a little more $$$ than I do to do this conversion.
Well, I'm going to use a later model LT-1 that has the programmable computer and I will be using a mass air flow sensor. I really don't think that I will have the kind of dollars in this that some of you are estimating, but we shall see.

The engine that I'm getting has the ac compressor low on the right side, so I will have to relocate it. It is out of a 96 buick and has low clearance air intakes on it so I think that I can find a place to mount the MAS, air cleaner, etc. in front of the engine especially if I use a set of electric fans.

I want to bolt the engine up to my existing 400 tranny so I'm not sure about the flywheel issue, yet. The tranny is newly rebuilt so I'm going to stay with it.

I know of an installation of an earlier tuned port into a 73 convertible that went fairly well but it didn't have the MAS so I think this will be a big improvement.

The harness comes well marked and with a good manual so my primary concern is with the mounting of accessories and anyone's experience with that.

Any links, magazine articles, books. etc will be greatly appeciated.

If I go through with this (it looks pretty certain) I will pass on my experiences.
Did you say Buick?

Anyway, wise choice to try and keep the Mass Air Flow. It will run a little stronger that way. Like I said, get real creative on the routing and you will be fine.

Does your motor have cast iron or aluminum heads? The only reason I ask, is there is a smaller cubic inch LT1 look alike out there found in many police cars, caprice classics, etc. The are very plentiful, use the same electronics, but don't put out near the hsp.

There was a local fellow buying those at the police auction and selling them like crazy. He got into a little trouble when his customers found out they were not 5.7 liters.

Good luck. The only way to really do this is to jump in with two feet. Sounds like you are going to make it happen. Please post pictures of your progress.
Yep... I said Buick. I'm pretty sure it's a 350, tho, with cast iron heads. I'm aware of the police cruiser models.

I can always get some HiPo alum heads if I want, but as I understand it the cast iron heads only cost about 15 H.P. over stock alum heads. I'm after better gas mileage and more punch than the stock emission control choked 350 that came in my '75. I'm not going racing.

LT-1's are getting hard to come by. Doing a top end add on is pretty expensive. I don't want to miss this opportunity because I'm getting a good deal on the engine, harness, and computer mods. I'm also not trying to make it a show car so stock valve covers, etc. will be what I'm after. I may get a K&N filter but that's about it. I'm doing the work and I shouldn't have more than $4,000 in it, including the exhaust setup. A 350 crate motor starts at $3,500 and that's without a carb, exhaust, etc. I also expect to get a lot of miles out of this engine, compared to one that's more performance oriented such as the crate motor. Besides, I will have my old 350 to play with as I can afford it <grin>.

Thanks for your help.

crate motor info

I can get a 350/ 330 complete from carb to oil pan for 3K, I believe it's jim pace chevy. paceparts.com just some info
I too am after the gas mlelage and low end torque, Just looking for a cruiser, I have another car if I want speed.
Well, i got the go ahed to get the engine but it's to cold for me to do the work right now.
I live in an appartment and don't have a garage yet. But that too is in the works.
Well, I'm just about ready to try to start working out a "fit". I have to find brackets to put the AC, Powersteering, Alternator, etc. on the sides of the engine that I need them on. I'm also thinking about using the LS-1 catalytic converters since they are small and are on each side of the engine... I just have to see if I can get the ECM to work with the sensors on that setup.

I am thinking about getting my own scan tool to set the ECM up, too... since I want to play with it it will be better than paying someone $100 a pop.

I did find some excellent books to help out... but not specifically for putting the LT-1 in a '75.

New motor in 68-82's

Just to get in the fray here I have toyed with this idea for a long time for my 72; and now that the original motor needs a rebuild I thought about the late model implant; and although those computer motors are good, how about a brand new ZZ-4, 340 horses out of the crate, aluminium heads and no major electronics to mess with. The motor is brand new with a warranty for something like $3,500 give or take a little and you use most of your accessories out of the orignal car.... If anybody has got experience with this I would love to here it....

Thanks in advance...

what is the problem with using the factory harness in a swap like this would just need a custom chip or factory manuel trans chip ? or am i way out inleft field:confused :beer
Re: conversion

bradfordsvettes said:
what is the problem with using the factory harness in a swap like this would just need a custom chip or factory manuel trans chip ? or am i way out inleft field:confused :beer

It can be done. I have done it both ways and have found that buying an aftermarket harness is much faster and less headache than parsing off wire after wire that the conversion won't use, not to mention tracing back through the entire system to pick up all the other correct leads.

I have a factory 95/96 LT1 trans am harness now. It would take three hours just to find the ignition power lead. In comparison, the aftermarket harness is labeled and comes with fairly clear instructions and suggestions.

Oh yes, you almost always have to get it chipped or reprogramed to over come the VATS system, and or at least to get the speedo calibrated (if it is a 94-96).

I would not waste my time on the conversion unless I had the "real deal" F body or Corvette engine to do the swap. It costs the same to get any of them including a Buick donor, police car, or Impala SS to run, so why cheat yourself. The hsp difference and Wow factor of the aluminum heads makes all the difference.
Unless you change the transmission, too, plus put everything in using new technology you won't need all of the sensors and controls that come with a C5 or C6. Plus, when they ripped my LT-1 out of the car at the, er... recycling center, they cut the harness in numerous places.

I haven't even looked at what I will have to do for things like an ignition switch. I would have thought someone had done this already, but I haven't found much help. I'm pretty much on my own so I'm taking my time.

One of the prime motivators for me is more horses with better mileage still remaining stock with the LT-1. You can get more exotic but I'm not after that. A custom harness will let me tune the programming to get the best that I can out of the ECM and the engine even though I don't have all of the same inputs.

Cast Iron

The cast iron headed LT1 style motors are getting much easier to come by, and more people are getting tricked into thinking they have a 350 on their hands. A good friend and coworker of mine just bought a complete LT1 with transmission, wire harness, and computer for $450 with a reported 60,000 miles of use.

He was told it was a Corvette motor. I hated to burst his bubble, but it turns out it is the small cubic inch 4.3 liter version with the cast iron heads. These things are popping up everywhere. All you have to do is get the plastic injector rail covers from a corvette, pop them into place, and most people get fooled.

He intends to put his in an Elcamino. This is the third friend of mine that bought one, brought it home and only found out later it was not what they were after, nor have any of my friends been prepared to deal with the true cost of getting one of these things to live under the hood of another car.

Do your homework on these things. Like I said before. It cost just as much to make a 4.3 run and install accessories as it does a 350. The 4.3 can't compete with the 350 version on any level other than looks.

One of these fellows I know got his to put into a 260 Datsun Z car. He bought his from a salvage yard with a 90 day warranty. Well, it took him about six months to gather the extra parts and pieces needed to get it going, and when he went to install in the car he found out the motor was actually seized up. The bone yard won't warranty because he is out of the time limit. He would give his away if he could, and it is a small cube version.
I hear what you are saying Keith. My dad worked for Chevrolet when the IROC came out. We had the very first IROC in the state of Florida, and my dad delivered it to the Florida Times Union auto columnist to write a story on it.

The difference between the tiny LT1 engine and the 305 HO are night and day. No interchangeable parts, except for maybe the oil :L .

Most 305's are sluggs, but once in a while you will run across one with some real get up and go. Sounds like you had a sweet ride. You do know that the 85-91 TPI runners were originally designed for the 305. A TPI 305 will rev higher and has a longer power curve apples to apples than a 350. However, the 350 still makes more hp and torque.

Here we are getting off subject.
any updates on the conversions? Let us know? Im thinking of doing this myself. Has anyone tried a LS1? Is it easier than using a Lt1? That I would like to know! Thanks

GIT R DONE_______________________________ BORDERBUM

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