Hey everyone I'm new here and have got some money to start modding my z28. I have had my eye on the Gm Performance LT4 conversion kit which claims it will give my stock z28 a proven 425 horsepower. Is this true? I see on the LT4 intake it says that it supports 425+ horsepower is that just a coincidence? I am a little skepticle that heads, intake and cam will increase the power by 150 big ones. I would think more around 380 tops and around 340 rear wheel horsepower. Any help will be appreciated

thanks.

 

The test in Chevy High Performance that made 427 fwhp also had headers, a 52mm throttle body, and a serious tune.

For just a little more, my bet is with AFR heads and a Comp Extreme cam. You should be able to make as much horsepower at the rear wheels as the LT4 kit did at the flywheel.

 

...and for a lot less you can port your LT1 heads, add an XE cam along with supporting valvetrain, and even go with a full exhaust (3" header-back) and make more power than the 320-330 rwhp of the LT4 conversion kit...

 

So by doing the LT4 kit and exhaust and say air intake, maf, I would be at around 330 rear wheel horsepower ?

 

That's probably not far from the truth. I'm sure it's not a bad daily driver setup, but you'll probably end up wanting more when it's all said and done.

 

This is true. Haven't seen many people out there that are simply happy with their full exhaust with nothing else done...like, say, heads and cam or raising the cubes...

 

Or both!

 

No I would get all that with the LT4 conversion kit! Would it still be like 330 rwhp ?

 

You can sink the same amount of money into your stock heads, add cam of your choice and come out with more power than just adding the LT4 kit. From what I've seen, the LT4 heads won't add much power unless you've got the EXTRA funds on top of the purchase price to have them ported.

 

Yes. You'd need to have the extra funds to port the LT4 heads and because of the raised runners, they wouldn't work AS well with a stock bottom end as they would with increased displacement.

 

anyone on this site do this type of thing before ?

 

 

This is kind of a good question. I've been wondering the same thing myself.


Let's leave costs out of it, pretend we have unlimited funds.

With all the heads available for the LT-X, is an LT-4 head worth it?

Obviously, I could port my stock heads. I could also buy the new Trick Flow heads, AFR's... Canfields I think... They have an LT head, right?


So basically, is the extra height on the intake ports WORTH buying an LT-4 head and matching manifold, or is it better to just go right to an aftermarket type of head regardless of price?

 

those TFS heads look real nice

 

i have a 383 stroker in my 95 ta, with AFR 2.02/1.60 heads, lt4 hotcam, lt4 manifold, 52mm bbk throttle body, full-length headers, borla cat-back, 6-speed with a moser 4:10. allll the bolt ons and suspension parts possible. I am about to get a tune, because it has never been tuned...anyone know what I could dyno at?