RyanS_Z28

ok so im looking through a new summit racing mag and i come across this LT1 to LT4 conversion kit including heads, HOT cam, intake manifold, roller rockers, gaskets, valves and springs. The next sentence in the description confuses me. "The kit will give you a proven 425+ HP."

At this point, does that mean "this kit will make your dyno sheet at least 425HP" or do they mean "this kit can handle as much as 425HP". If the answer is the first choice, then this would be better than a supercharger. Am i illiterate or will this $2,289.95 kit give me 425HP pulls?

Part number is NAL-GMP3287-1 if you were interested in looking at the description.

got_hp?

if you did a search, this has been discussed.


the 425 is FLYWHEEL horsepower.


most people with this conversion dyno around 360-380 rwhp i believe.

not really worth the money when you can get more power than that with a heads/cam package utilizing your LT1 heads.

mile_high

Thanks for the clairification (GotHP?).

On another note -- should we have to search everytime we have a question? I'm glad Ryan mentioned the LT4 conversion. I would never have searched for it otherwise.

Thanks to you both.

RyanS_Z28

i did search for it and found some crappy discussions. i wanted to specify. anyways, what would you recommend for a better setup then?

Fast Caddie

The 3 or 4 people on this board who did the complete conversion and dyno'd it came out around 350rwhp after tuning (this is with the standard intake/exhaust bolt-ons).

If you're wanting to do the whole thing, get the stuff in pieces. Jason Cromer has the heads assembled for $1,200/pair, the HC kit for $465, and I forget what the LT4 intake was($250?). Anyway it comes out to less than the ~$2,300 you see at Summit and Pace. With all the gaskets and all you should be under $2,000.

Then you can sell your LT1 heads and intake for around $300 to recover some of the cost. Then let Lloyd do a little work on them to set things straight. You should be able to hit 370-380rwhp easily and have a pretty broad powerband.

Just my $.03

RyanS_Z28

Two things. Who is this genius Jason Cromer and the Saint, Lloyd. The three of us need to have a convo about my car and my friend Mr. Horsepower

Fast Caddie

Jason Cromer is the parts man at this dealership in Florida, a wholesale GM parts supplier. The same one that sells the optisparks for $187. You'll need the aforementioned parts plus: head, intake, exhaust, and WP gaskets, timing cover gasket, and maybe a couple more things that I'm forgetting. You'll have to e-mail or call him on the LT4 intake (might as well ask him about all the other parts too). Paceparts has it for $250, so I'm sure he'll match or beat that.

www.samtaylor.com/html/parts.html

Lloyd Elliot is "Nighttrain66" on this board. Search for and PM him for details and prices on his portwork. Great guy to deal with and has VERY reasonable prices. Many people on here will vouch for his work. HTHs

BTW- "Mr. Horsepower" (Chuck Riddeck) is the "real" genius on this board. He knows cars better than you know the back of your hand. I hope to work with him one day.

FacelessZ

<== Was looking into an LT4 conversion...

I ultimately decided on having my LT1 heads and intake ported by Elliott Portworks (Lloyd) for $1,200 for the heads, which included everything for easy bolt-on, and $100 for the intake which opens to 58mm. The heads will flow ~200cc at ~275/190, which is just about the max you can get out of LT1 heads. He provides a bench which will give me ~360-370 rwhp with my A4.

Now I questioned Lloyd about having LT4 heads ported, but he explained to me the large valve increase between the two heads, LT1 and LT4, and said that I'd see more gains with just having LT1 heads ported than the LT4's.

I also decided against the LT4 HOT kit and am going with the Comp Cam Xtreme 239/236 .112 ls. It was between that one and the CC306 but decided the Xtreme was a more 'streetable' cam.

Hope this helps!

Fast Caddie

That brings up another interesting point. Here are some flow #s on some max ported LTx heads:

Maxed LT1
.100 65/51
.200 142/111
.300 202/148
.400 244/178
.500 272/189
.600 278/195

Maxed LT4s
.100 74/51
.200 144/113
.300 206/161
.400 253/193
.500 281/214
.600 301/227

If you look at many flow charts on these heads out there, you'll notice that the LT1s are comparable to the LT4s up until about .400 lift on the intake side, at which point the LT4s take off. But when it comes to exhaust flow, the LT4s crush the LT1s about all the way through. This helps a lot on top end as it cuts your pumping losses at high rpm.

Hmm...maybe Lloyd will chime in with a little more perspective.

TCAL95Z

I hope he does come in here. I have ported LT4's for a new engine and thats the first I have heard that

FacelessZ

Getting stuck in #'s is never good...every car runs differently considering year, miles, mods, etc

LT1 heads offer higher compression than the LT4's do. If you're able to compensate for the larger ports in the LT4 with, say a procharger, than you'll get your "max" out of LT4's. You'd also need a BIG *** cam to help for the compensation as well...

For us who don't have the $8,000 to blow, LT1 ported heads work great!

Fast Caddie

Not that I'm getting stuck in the numbers, just adding some ideas to the pot. Flow #s aren't everything, I know, but they do give about the best non-running indicator as to how they'll perform when they are running. I'm around engineers all the time, and have a pretty good idea as to what goes on in cylinder heads

You can always mill the LT4s to get more compression if you like. Or get higher compression pistons if you go into the engine. And you won't need a big cam to compensate. The better your heads flow, the less cam you need.

There are a million ways to build these cars up. Pick your path...

FacelessZ

I agree Fast...but if you take that "path" you'll be putting up thousands of dollars....

If you have it, then more power to ya....

As for the rest of us, the ported LT1's are an easier bolt-on than the ported LT4's