R-Steffen 99ls1

I need to know which 6.0 I need to buy with my 4l60e to swap in my 99 trans am. I've heard certain ones won't match up. What else do I need to do the swap? The more info the better I need all the help I can get. I plan on putting a 112 cam in with a fast 90 intake and 243 heads.

Paul Bell

iTrader: (9)

Is this the transmission that came in the '99 car?

LS engines all have the same bellhousing bolt pattern.

R-Steffen 99ls1

Yes it is

Paul Bell

iTrader: (9)

Here's shots of the LS1 & LQ4/9 engine bellhousings:

Paul Bell

iTrader: (9)

You'll need to be careful about one thing: As I recall, the truck cranks had a wider rear snout and needed a different flex plate to accommodate it.

Some can jump in here to detail this?

gagliano7

The early LQ4's had a longer crank(I think the ones with iron heads 1999-2000) those are the 6.0's that will be a problem.

R-Steffen 99ls1

So I need one out of the 03-06 escalade or what?

gagliano7

Cadillacs have the lq9 if that is what you want.

https://ls1tech.com/forums/conversio...-question.html

https://ls1tech.com/forums/generatio...ck-please.html

https://ls1tech.com/forums/generatio...4-ls1-t56.html

Justus67

iTrader: (3)

There is a website that will tell you what engine you have, I'll try to post it this afternoon. Keep in mind the LQ4 has dished pistons .011 and will throw your compression calculations off if your counting them as flat tops. LQ9 has flat tops. You will also need a different flexplate.

R-Steffen 99ls1

Yeah I plan on bumping the compression up with 243 heads either way, lq4 or lq9.

Paul Bell

iTrader: (9)

It sounds like to accommodate the 4L60E flexplate that came with your F-body LS1 engine, you'll need an engine with the short crankshaft.

R-Steffen 99ls1

Anyone know which year range lq4 or lq9 that would be and what vehicle it's in