I've read responses from members who did this conversion over the years here and the best i've seen from it is 350rwhp. That's with tuning, full exhaust, and every bolt-on there is.

Lloyd does some damn good port work and the parts in his kits are set up to complement eachother. The cam grinds are matched to the flow properties of the heads. His LE2 package is hitting 380+rwhp with stock bottom ends. Even after you get his package and buy RRs, you're still paying 4-500 less than the LT4 kit and you're getting better parts (springs, valves, seats, etc).

Personally, I'd skip right over the LT4s and go for AFRs if I was looking to abandon the LT1 heads. An AFR 210 head flowing 300cfm peak will kick the crap out of an LT4 head flowing the same (if given an equal amount of effort). There's a lot more than flow numbers at work when it comes to heads and making power.

 

Hmmm... just looked at the GM page and the kit is coming down in price (finally, they're usually 23-$2400). $2100 isn't bad, but you can still do Lloyd's package for a couple hundred less.

 

It was not. it is a packaging of various GM parts. The kit is not a Chevy product.

It will not give most people what is advertised (425 at the flywheel) since most people will have a full exhaust wtih cats which the test engine did not.

What guarantee is that?

 

To add to steve's post, keep in mind that MORE performance in NC made that 425 crank HP test. That was with a very expensive ignition system and aftermarket computer (MoTec). You won't get near the fine line of tuning of a MoTec with a stock LT1 PCM. You're looking at 390-400 crank horsepower on a good day on a good tune with the stock LT1 computer, off the shelf headers and other parts with the LT4 conversion kit. You could replace that hotcam with a solid roller and make 400+rwhp with the stock LT4 heads, but do you really want to rev past 7k rpm?

It's been hashed out here before many times. Do a few searches and see. Even with putting the parts together yourself, one of the more well-known vendors on here can put up an awsome performing package for much less money AND better parts AND a better performing package. Both Phil and Lloyd do fine work and have proven it many times over. In my honest opinion, you're better off to send your money to one of those guys and get a better product than some factory pieced-together pile of parts. You won't be disappointed. Myself, i'm dreaming of Elliot's LE3 heads coupled with an XE 230/236 cam... that would be an absolute beast throughout the whole rpm range. And probably still cost just as much as the LT4 conversion kit. Don't forget you'll need to pay for PCM tuning no matter what route you go. I'm just hoping to help you realize that you can get more for your money in other ways with an LT1. It's your money though, spend it however you wish.

 

LE1 kit: 370-390rwhp $1100, only a grand less.
LE2 kit: 400-420rwhp $1650, only a few hundred less.

Go with a LE heads an cam kit.

-Dustin-