LT1 engine swap

In a fit of (some say) madness, I am fitting a state-of-the-art LT1 type engine into an older car, a 1983 Firebird. This is a rather unique project which I am engaging in partly for the mere curiosity of whether it can be done. And I must admit there are sentimental, performance and environmental reasons why I delight in putting a new, ultra-clean 285-horsepower engine technology into an older car. I rather like that car, and I rather don't like air bags. The car's destiny is of a roadster, to be used occasionally. It's not intended as a commuter car. That's what trains are for.

The LT1 is a modern fuel injected V8 engine, a reworking of the classic "Chevy small-block" but with radically new technology which enables it to meet the emissions standards of the 1990's and dispense kick-ass power while being very streetable. It was manufactured from 1993 to 1997.

Normally when you hear "engine swap", you think of a grease monkey working under a shade tree. But in this case, there was no shade tree, and very little grease... in fact the engine/transmission package was swapped "wet" with oil and transmission fluid still in it. An engine change without an oil change.

The "donor car" supplying the engine was a 1997 Firebird Trans Am wrecked by a rear-end collision. The engine is going into a 1983 Firebird. There were advantages to working with a 1983 car: the same chassis was used from 1982 to 1992, which meant that many parts from newer cars could be retrofitted to the 1983 car, such as fuel-injection pumps and wiring harnesses. There was no precedent for installing an LT1 into this chassis, but the physical geometry is the same: engine and transmission mounts bolted right up, even the driveshaft is correct.

The three biggest challenges in the conversion were restoration work to assure the health of the old chassis, adapting the massive wiring harnesses from the fuel-injected engine to the older car, and procuring the dozens of "minor" parts that are essential. All the parts used are original GM parts... the aftermarket simply doesn't make parts for this kind of swap.

The wiring and maintenance of all engine systems and emissions controls is the most critical part of the conversion. The engine is OBD II (Onboard Diagnostics II) compliant, meaning it has far more sensors and diagnostic capabilities than earlier engines. For instance, it can detect a failing catalytic converter, it keeps a log of engine performance, it can even report which cylinder is misfiring. But this also makes the engine more sensitive to alterations. OBD II was a government requirement designed to increase the reliability of emissions systems in cars by making it able to report faults more quickly. This makes the conversion a little trickier, because every system must be fully functional for the car to pass smog - in fact, the computer must "believe" it is still in the 1997 car.

Another example of the electrical challenge is "Pass-Key II", the anti-theft system built into all newer Firebirds. It consists of an under-dash module which reads a key resistance and must send a pulsed signal to the engine computer before it will start. The most practical way to generate that signal was to simply retain the under-dash module, and "fool" the module using a resistor. The under-dash module also supports many luxury and comfort features, such as remote keyless entry and automatic shut-off of accessory features. As time allows, those features could be enabled in the future.

At this point, work is nearly complete; it has passed several operational trials, including the security system. It is only one fuel line away from starting (as said, procurement is a major challenge). Most of the work that remains is physical mounting of electrical components, such as fuse blocks, harnesses, computer, cruise control module, etc. Then a trip to the exhaust shop to have an exhaust built, then a one-time trip to smog referee to have the installation declared smog legal.

Additional Notes

Wow. This page is getting a tremendous number of hits, which surprises me because it was written as an attachment to my work resume... and as such it has only an "executive summary" of the project. And at this writing I got another surprise - someone called me on my cell phone for help with his swap.


Which brings up the question of whether I want to help people with their swaps.

I think I don't. And here's why.

Every job has its prerequisites -- and you can tell whether someone's really serious about doing something by whether they do the prerequisites. For instance, getting dressed. If you're serious about getting dressed, you make it your business to know that underwear goes on first, then pants, and finally shoes. Someone who does it another way either has an incorrect frame-of-mind toward the task, or they just don't have some key basic knowledge that would make their job a lot easier.

LT1 swaps have their prerequisites too... and an LT1 swap is a complex and subtle thing, nothing like a carbureted engine swap. Completely different. Like installing Linux versus installing a garage door opener. That different. I mean, an LT1 probably has a more complicated wiring harness than a B-29 bomber. It certainly has more complex wiring than a PCC streetcar -- an electrical beast if ever there was one. (and I'm not counting the internals of the modules, like the PCM and BCM. Factor that in and it's probably more complicated than the Apollo 11 mission, Houston control included. Fortunately the internals of these modules are of no concern to the swapper. The functions of the control wires are adequately documented.)

So a person's experience with a carbureted engine swap isn't going to help them much with an LT1. New skills are required. (Well, I suppose one could rip all the electrical crap off the LT1 long-block and stick carburetors on it... but that's not what I'm doing and in my opinion it would defeat most of the value of the LT1.)

Here's what I think are the prerequisites are to a good swap.

My observation is the successful LT1 swappers have done all these things. So far, the people who have contacted me looking for help have done very few of these things. I'm not saying they overlooked one thing, I'm saying they've overlooked most of them. It seems fairly clear to me that's why they're stuck.

So my suggestion to swappers is, look at the above list and make sure you're on track on all those things. Those are, in my belief, the prerequisites to success.