LT4 Lt1 to Lt4

[Tom B Hargrove]

I see that Summit has a conversion to make a Lt1 into a Lt4, it states that the complete kit will produce approximatley 425 hp. Has anyone done this? If a stock Lt4 is 330 hp, what makes this kit get 95 hp more. It has the GMPP hotcam, but I can't see that much of a difference in just the cam, even with 1.6 rockers. I would like to hear from anyone has used this. I am going to be converting a 95 Lt1 six speed. Thanks, Tom

 

[BlackNBlue95]

I've done the top end conversion, I have no proof to claim that 435 is legit I would think this is at the flywheel though. I got my LT4 heads, intake, rockers from a 96 LT4. And puchases the Hot Cam new. def. woke the car up. I was lucky I didn't pay $2,500 for it since I exchanged my labor for everything except the cam and gaskets. Def. a good addition to stock LT1.
-=Rick

 

[Tuna]

I used gmpartsdirect.com's LT1 to LT4+ conversion kit. I'm pulling 328 at the rear wheels or about 380 at the crank. I don't think that the Hot Cam and LT4 Heads and intake are enough for 425 at the crank.

The gmpartsdirect.com kit cost $2100 and that included the LT4 heads and intake, 1.6 rockers and Hot Cam plus all the other gaskets and seals to make it work. (Go to www.gmpartsdirect.com and look up part number PK12550630.) I added the HD timing chain, updated OptiSpark and cover while I was doing the upgrade. I've also got a chip from fastchips.com to make it work.

I'm still using my 92 injectors (24#, I think), the 48mm TB, and stock exhaust manifolds. I am using Corsa cat back exhaust (that made 22HP difference there).

Maybe with long tube headers, 52MM TB and biggers injectors will push it to 425 at the crank. I just don't know, yet.

 

[Vettelt193]

I see that Summit has a conversion to make a Lt1 into a Lt4, it states that the complete kit will produce approximatley 425 hp. Has anyone done this? If a stock Lt4 is 330 hp, what makes this kit get 95 hp more. It has the GMPP hotcam, but I can't see that much of a difference in just the cam, even with 1.6 rockers. I would like to hear from anyone has used this. I am going to be converting a 95 Lt1 six speed. Thanks, Tom

Also be aware that the kit does not give you an LT4. LT4's have a vast number of changes over LT1's, including things that wouldn't be worth changing to, because if you bought the parts to upgrade you would probably buy better than stock LT4 parts. For example, the LT4 has different pistons, crankshaft, heads, valves, injectors......

 

[BlackNBlue95]

Right! The crank and pistons and injectors are different. if you just bolt on the LT4 upperend it's close.

Because I never took the time to find this out what is the compression ratio then of the LT1 w/ LT4 top end w/ hot cam?
-=Rick

 

[Tom B Hargrove]

Thanks for the info on this upgrade. I am probably going to go ahead and do it this summer. I love my c3, but the more I drive this c4, the more I like it. I also appreciate the info on where to find the kit at GMpartsdirect. I had looked, but couldn't find it. Thanks again, Tom

 

[Tuna]

If you'd like a side by side comparison between the LT1 and the LT4, check out www.grandsportregistry.com. The LT1 to LT4 conversion kits do not address the differences in compression ratio and lower end differences. They are basically top end kits and cams.

I've got to get the Tuna Sport back to the dyno this year to see where it is now and I want to change out the injectors and throttle body along with long tube headers and see where that takes me. I'll probably have to do something with the wife's 2003 AE first though as her car has the least HP now and she's starting to complain!

 

[kenwa]

Tom, if I ever pull the heads on my LT1, it'll be to pocket port them myself and get a three angle valve job for a fraction of the cost of a new set of heads. It's easy. Ya just gotta be patient and make yourself spend 45-60 minutes on each cylinder.

Then when you put everything back together (1.6 rockers are a good addition) your computer will still be happy.

Think about it.

Ken