The numbers quoted by Pace and also by Summit are based on an engine dyno test run by MORE Performance, at least 3 years ago, and printed in one of the Chevy rags. MORE made 429flywheelHP. What they didn't tell people was that in addition to the LT4 kit, they had LT's, a larger TB, and used a $3,000 aftermarket computer to tune it. I suspect there were a few more things they neglected to document.

 

Yea. That sounds more reasonable. It's amazing how they just "leave out" those details and get away with it.

 

You'll be surprised how many people buy that kit. Not everyone with a modded LT1 F-body comes this this website for advice. I've met 2 different people at the track with this set-up and both were running 13s

425hp with this kit is more than possible. The ZZ430 crate motor sold by GM uses the Hotcam and Fastburn heads which don't flow as well as LT4s and its rated for 430hp. However they recommend what carb/intake and headers to use inorder to get 430hp.

The same applies to the LT4 kit. You'll need longtube headers, TB, CAI, reprogammed PCM etc to get 425hp. I remember seeing a post on here once where someone got about 375rwhp with this kit.

 

There are a couple of members on this board who did the LT4 conversion kit and after tuning they dyno'd at or above 350rwhp. That's somewhere near 400 flywheel hp depending on your drivetrain. They also had intake and full exhaust, so the magazine was decently close.

 

Depends if it's an auto or a manual. I believe that Manuals have around 15% loss and autos are ~20%.

 

Broken record....

My Dad's Comp TA with the LT4 "kit" dynoed at 359rwhp. This was with SLP single cat headers and on a HPP+ tune. He has since done many LT1 Edit tunes and more than likely makes more. His heavy pig of a car ran 12.2@113.

My 96 WS6 Formula was basically set up the same except I had stock heads and dual cat SLP headers with cats still intact. I pulled 324rwhp right after him on the dyno. So heads, headers, cats, and my ModernMuscle car programmed computer were the only difference in mods. I ran 12.4@111.

It can and has been done. Its a proven combo that is pretty mild mannered.

 

How much HP is the intake worth??

 

Buy the hotcam kit and have your heads ported... then spend the other $1000 as you wish.... Or better yet! Get a bigger cam and do the heads a little more....

 

You've got those numbers backwards. Manuals are ~15% and autos are ~20%. According to what I've read, it's more like 13%/18%, but close enough.

 

Are porting stock heads a better choice than some LT4 heads??

 

well you know I thought that way until I found a brand new LT4 head for $250...just need to find one more and ill be set....

LT4 heads run $1200 a pair thats why not many people get LT4 heads and port them....LT1 heads can be found for $350ish for a new pair...

 

Just wanted to bring this topic back to life, since i was thinking of doing an lt4 upgrade myself...Good thing i didnt before checking out this site. So it seems the hp/ money ratio is just too little huh? Yeah i think thats a little too much money for maybe 100-125ponys more. Any further imput on what i could do with my lt1 to make it maul the lt4 setup would be appreciated. Im thinking of doing all of this after I do my smog so i dont have to worry about keeping it legal for 2 years. So what could i do to my heads and what cam could i put in there?

 

-port the hell out of your stock heads, approximately 275/190+

-toss in a decent sized cam...all depends on what you want...CC 306, XE 230/236, CC 305, even the HOT cam...

-add long tubes if you haven't already...

 

If theres typically 13-15% drivetrain loss for the M6, and I've read on this webpage many times that most stock M6 LT1s dyno about 260 er so rwhp....

using the 13/15% loss puts it at 242-248 rwhp.

And if thats the case, how in god's name did I manage the number below on the little mods I have?!?!

 

Same here, my '96 TA put out the numbers in my sig (282rwhp/312rwtq) with only a 3" cutout and the WS6 ram-air setup . With the cutout closed I pulled 269rwhp, and that was through the stock crappy non-WS6 factory exhaust. That's 336fwhp...much higher than the factory 285fwhp rating. I expect 305+ when I put my LTs and !CAT mods on there...