I was thinking of picking up a LT1 for 500, the entire Police car, THen I would remove the LT1, rebuild it and put it into my 87 Formula, but using the existing ECM.

I would think that it is possible, all I would have to do is remove the optispark and then use a regular distributor...

Anyone ever do this. THE ENTIRE BLOCK not just the intake.

John

 

You can not run a TPI ecm because of the opti-spark distributor. The signal from the optical pickup in opti-spark is completely different then the HEI distributor output.

 

I think he already has that covered... ^^^^^

 

Yeppers.

Just do it like u said and away u go.

Just you will actually be doing an LT1 swap, not an Lt1 intake swap lol

Have to get into some tuning to make everything kosher obvioulsy, but shouldnt have any real issues being that the engine will be stock or close to it/


later
Jeremy

 

Soooo --- $500 is not a bad deal??? Should I do it and sell my L98 car?


John

 

I did the same swap to my 91 RS Camaro except I had a 93 Z/28 LT1 and matching 4L60 trans.

The LTI requires the correct ECM to work. I used a Painless harness and tied it into the rest of the stock TBI harness.

The hardest part of the swap is connecting the fuel lines to the LTI fuel rail.

Pretty easy swap mechanically.

 

If I use all my stock sensors, why would it not work?

John

 

Depending on the year of the LT1 it could be sequential port fuel injection and not batch fire like the TPI cars.

It also uses a completely different ignition system with all the parts mounted on the front of the engine. The coil is mountd to the front of the drivers cylinder head and the ignition is mounted on the timing cover.

It also uses two oxygen sensors, one on each side.

I have never heard of anyone retrofitting a stock LT1 with an older TPI computer. If it was easy many people would have done it to eliminate the OBD II system. Instead they go back to an OBD I LT1 computer.

The LT1 computer is much faster than any TPI computer and the 94-up systems can be reprogrammed through the ALDL port. This alone would be worth ditching your stock computer and going with an OBD I LT1 computer system.

Mine have all been 93's and still used a PROM chip. This year is speed density which made it easier to plumb the air intake. The newer ones were all MAF systems.

I have put LT1's into four different cars. The first was a 66 El Camino, then a Jaguar XJ-6, a 91 RS Camaro and then a 67 Chevelle. It is a great engine and well worth the effort and expense.

 

If you modify the intake to use a standard distributor, you should be fine. Its up to you to figure out the hole left in the timing chain cover though. either leave the opti igntion in place, but not hooked up, or remove it and put some sort of RTV'ed plate over the cam snout area.

other than that.....some minor details like:

-marking the balancer for a 0 degree mark for setting base timing.
-some throttle lever/TV cable details, depending on the year of car/engine/cable.
-if running A/C, the whole AC harness/compressor/frame interference
-pass. motor mount due to possible A/C.
-some tuning
-fuel line compatibility

i think thats about it. the rest should be the same as any other TPI/SBC stuff. I beleive all the important sensors have the same connections as the earlier stuff, except maybe/definitely the IAC.

 

I see no reason why it wouldn't work...the injectors don't care how they are fired, and you'd be doing away with the worst thing about the LT1 in the process (the Optispark). If your car is an auto, run a 93 style TB (93s had the 4L60=700R4, so they have a provision for a TV cable) and TV bracket. Everything else is well documented.
OBD 1 swaps became popular for a few reasons; one, it only requires you to swap the computer and knock sensor, and you no longer need 4 oxygen sensors and the acts to go with them. The other is that a distributor won't easily fit in an LT1 4th gen. A third gen doesn't have the same issue.
The TPI computer may be slower, but if that really bothered you it could be easily replaced with an aftermarket unit at a later date.
I mentioned doing just this a few years ago, just decided on another engine beforeI could get started. I say go for it, the price is right!

 

You can not even use the speed of the processor of these ECM's as a comparison for which one is better, it's a totally irrelevant and bogus argument. The LT1 has a faster processor because it has to run a ton more code to control a transmission, sequential, and other stuff. If you think you car will somehow run faster since the processor in the LT1 ECM is faster then the 7730 TPI computer this is completely incorrect.

The 7730 TPI ECM runs a very small amount of code compared to newer ECM's and PCM's and in turn run's very fast. The two ECM's have the same ALDL data rate so you are not going to log data any faster. You can run an emulator on the TPI computer and the 93 LT1 ECM but not the 94-95 LT1 PCM.

Since you are running a LT1 engine might as well run a LT1 computer with the opti. If you don't like the opti you can get a delteq unit and run DIS for $350. Your other option is to run the TPI ECM but you will have to drill the intake for a distributor as mentioned above, you will also have to eliminate EGR which may or may not be a problem depending on if you have to pass emissions.

 

$500 for a running LT1 car? If your not buying it let me now, cause I will, your not that far from me :-)

It wouldnt be a real hassle to do the swap with the full LT1 swap or to do a "retro" swao and run it using the TPI ECM.

Take a little work either way.

U know, poke around on the prom board and on the net, some guys have put the opti into the distrib and made it work :-)

U could do a full LT1 swap that way and make the Opti next to a non issue like that if u wanted.

later
Jeremy

 

I guess now for the tough question....

By using my TPI ECM, would there be any performance loss??? I know that I would need to tune it, no big deal really, I have all stuff to program any chip I want.

AND what are the LT1 injectors rated at??? Are they 22# or 30#, I know my 305's are 19#, and my L98 are 21# or 22#
The reason I ask is that might change how I do the swap...


John

 

I've had them flowed and cleaned at about 25#. that seems to be the closest nominal value, though they are probably officially rated at 24#. That was 2 sets already, also.

you should make pretty much the same power, the ecm is more than capable of running the engine. You might experience a couple of minor things; it might be slightly, and i mean slightly less smooth due to the regular distributor, and batch fire.

otherwise, it'll run fine.

 

Should I consider a LT4 intake, cam and heads too

John

 

I would run the 93 opti computer. The spark and fuel tables are already calibrated for a short runner intake and the LT1's heads and cam. The LT1 ECM also has extended fuel and spark tables (which can be done on the 7730 with patches).

Horsepower wise they will both give you the same numbers if both are accurately tuned for the engine. The 7730 will just take more initial tuning because all the values in the calibration are setup for a LTR setup. It's not that big of a deal though, just use whatever's easiest for you.

 

Ive never seen the block of an LT1, but does it have a hole in the lifter valley for a distributor even? How is the oil pump driven when normally its driven off the distributor?

 

There is a small piece at the back of the lifter valley that bolts on where the distributor would fit down thru normally. It keeps everything in place so the camshaft can drive the oil pump.

 

The block is drilled just like a GEN-I SBC just has a small oil pump drive bolted in as seen below.

 

a-hah! I thought it would be something like that. Thanks for info guys!

 

You will need to use your throttle body, and your knock sensor, and have the intake drilled for a dizzy, but there is nothing that wakes up a stock LT1 like a little more initial timing that the distributor allows. Do it your way, don't look back.

 

92 LT1 (in vettes) and all 93's had 22lbs. 94 and up had 24lbs.