For a while i have been trying to decide what to do with my LT1(cam, heads, conversions, etc...) and been posting my many questions and have gotten some great answers..thanks! Now for my latest question....

I recently came across another opp. At first I thought about just doing the LT4 conversion. Now, I have been shown an LT4 engine out of a vette for less than the conversion kit. He said it had about 65,000 miles on it but about 5,000 of those was after a rebuild. I would probably take that and put a new cam in it, and would be very happy for what i am looking for. Now for the questions...

1. The engine does not come with a computer. Could I use my LT1 computer with the LT4 engine?
2. Would it mount easily although it came out of a vette?
3. How can I tell it is a TRUE LT4 engine??

 

You can use an F-Body LT1 PCM to run the LT4. You will need to ignore one of the two knock sensors on the Corvette engine. And of course you will need the LT4 program loaded into the LT1 PCM, or custom programming.

The front accessory mounts (alternator, PS, A/C, etc) and fuel connections to the rails are two differences that come to mind immediately.... nothing you couldn't swap over from the LT1 you already have. The LT4 will not have an EGR system.

Check the various part numbers against this:

LT1 vs. LT4

 

1. Yes, you can use the stock LT1 ECM with the LT4 engine. This is what SLP did with all their LT4 f-bodies. Just make sure you get it tuned (I'd recommend madz28.com)
2. You will have to use the LT1 accessory mounting positions instead of the Vette positions, but otherwise it will mount just fine.
3. Red intake manifold. LT4s in Vettes had the black valve covers. TB plate should have "Grand Sport" on it. If you can find out what car it came out of, all 6 speed manual 96 Vettes had the LT4.

If you go the route of the LT4 engine, I'd recommend at the very least an LT4 hotcam. If they replaced the stock valvesprings during the rebuild then you won't even need new ones as the stockers will run the hotcam just fine (I wouldn't reuse 65K mile valvesprings though).

 

He said that with the rebuild, "minor" valvetrain parts were replaced(springs, pushrods, etc...) So as far as accessories, I would have to take the brakets off of my LT1 and put them on the LT4? Why would the vette's LT4's not work?(just for my knowledge) As far as the LT4 not having an EGR system that would probably be a problem as far as emissions goes. Could you put the LT1 EGR system on the LT4, or am I thinking WAY to far out there?

 

Ok, if the springs were replaced, then I'd just stick a hotcam in it. You won't need to change anything else except the programming, and you'll be doing that anyway.

Yes, just use the brackets off your LT1. The Vette accessory positions won't work because they are placed differently and won't clear in an f-body engine bay.

As to the EGR, the LT4 didn't need it to pass emissions.

 

You'll also have to use the throttle body from your LT1 if you decide to purchase the LT4.

 

????? Why? The throttle body is exactly the same, the only difference is that it has the "Grand Sport" on the TB plate.

 

The B-body LT1's used 2 knock sensors, might use their engine wiring harness you u really want & pcm.

 

I was told that you will loose cruise control if you use the Vettes.

 

As far as the egr, the lt4 didn't come with it but it still had the provision in the back of the intake. Gm blocked it off with a block off plate, so you can adapt the egr from the lt1 to the lt4. If in doubt, you can always look. On the vette it's easy to see back there.

 

As far as the egr, the lt4 didn't come with it but it still had the provision in the back of the intake. Gm blocked it off with a block off plate, so you can adapt the egr from the lt1 to the lt4. If in doubt, you can always look. On the vette it's easy to see back there.

 

well here's my deal with the EGR...
the vette it came out of was of course an OBDII, and mine is OBDI. In GA, you have to pass the smog test with an OBDI. Now I just wonder....what if you have an OBDII in a car with the VIN that would say it's an OBDI. Would they just scan it like an OBDII, or would they still have to do the sniffer test...hmmmmm......

 

\


Emissions tests will always be done in regards to the year of your vehicle. So, yes they would put it on the rollers.

 

Well then emissions stuff will have to go on...i hate this emissions crap. Should get a z28 with an OBDII so I can just go all out on it, and not have to worry about the sniffer..lousy piece of crap clean air act

 

No, it WONT. That engine doesnt NEED an EGR system. The camshaft has enough overlap that the EGR system is pointless. You don't need the AIR pump to pass emissions at all. Just a single CAT.