if you havent bought the LT1 yet you might want to consider just getting an LT4. i believe its availible as a crate engine or you might be able to find one out of a salvaged vette. i would do that versus finding an LT1 and then adding the LT4 components. as mentioned the LT4 conversion is expensive, but if you ever plan on going any further than what you have in mind right now i would do the LT4 conversion. it is better than an LT1, but it does cost a lot up front. and yes youll pass emissions with that cam. i would look into a good flowing cat system. random tech builds a good product that works. ill be using their dual cat ypipe on my formula. Trey

 

Go for it! LT4 heads can be ported to flow better then ported LT1 heads! I my self will be doing this, money is not easy to come buy for me but soon ill be paying off my car and will be able to save a little extra cash. Like said before it will be a little more money up front but I rather pay a little more and do things right the first time then squrew it up and wish I had done something different.

 

you will never see 425 hp on a lt4 conversion. you wont see that at the fly wheel.

 

If he has healthy O2s, installs LTs, a good cat-back, CAI, and gets a good PCM tune....oh yes he will see 425. I've seen it with my own eyes on the dyno. In fact, I've seen 450 (384rwhp, M6). Jpaugh, a guy in the Central Florida F-Body club (CFFB) and a member here, has proven it and I've been there to witness it. He even posted the dyno chart because everybody called him a liar: http://www.imaliar.net

 

I don't doubt you could acheive 425 fwhp with that conversion, without the right supporting mods. For an M6 car with 15% drivetrain loss that would equal 362rwhp. I'm pretty sure some people have reached that with this kit and all the usual boltons. I don't like how Summit and Jim Pace advertise it as a "proven 425hp" package and don't mention anything else needed such as a good CAI, headers and better exhaust system. I agree no one is ever going to see those kind of #'s just bolting that whole kit on their car with stock manifolds & exhuast, that's pretty misleading.

 

I assume you meant 'without the right supporting mods' in the first sentence. I do agree with that, doing an LT4 conversion on a stock LT1 setup will not yield the 425hp rating - no way. Add CAI, full exhaust, and PCM mods and it really shines.

 

Yes, that's what I meant to say, made the correction

 

sorry i still dont believe it. thats 139 rwhp over stock using longtubes and conversion, and tuning. sorry

not trying to start a debate i just dont sorry

 

The car in question (Jpaugh's 96Z, M6) was 284rwhp before the conversion (I believe he had CAI and cat-back at that time)....after the conversion and with Hooker LTs, !CATS, high flow y-pipe & cat-back, LT4 hot cam, 1.6rr, and PCM tuning the gain was roughly 100rwhp. I didn't believe at first either, but when I saw the results with my own eyes I changed my stance. In fact, I'm doing the conversion over this coming winter. I'll post numbers afterwards and maybe we can debate it then.

 

What is 139 rwhp over stock? Are you assuming stock is 223rwhp? (362-139=223) That seems a little low for a stock LT1 M6 to me, I thought they were usually closer to 250rwhp stock. There are guys here that have dynoed over 300rwhp with all the boltons only, no head/cam/rr's. I don't find it that hard to beleive they couldn't pick up 60rwhp with LT4 heads/intake/hotcam kit and proper tuning.

 

Sorry when I said lifters I meant rockers. Anyway I do believe that that much power can be made with this setup. But only with a good exhaust and computer tuning. Which as far as I am concerned is a given. You cant put all that intake on without any exhaust.

 

Just to pitch this in...my 96TA M6 dyno'd 269rwhp 309rwtq when it had 18k on the ODO and the only mod was a K&N filter. That is 316fwhp. The difference for me is 109fwhp when compared to the LT4 conversion. Add in full intake, a set of Long Tubes, cat-back, LT4 Hot-Cam, 1.6rr, freer flowing heads, and PCM tuning and that 425 will be very possible if not surpassed. When I put my Jet-Hot LTs and y-pipe on in the next few weeks I'm very positive that I'll pull 300+rwhp on the stock heads & stock cam.

 

there are alot of guys running bigger cams than that. and yeah they get near that, and some alittle more, but most stock lt1 m6S put down 245, and to get to 384 as stated above, thats 139 difference. im still a little scepticle. but hey to each his own.

my whole point to this is that there are people putting alot less money into there cars and getting better numbers (not that his arent good). i just think all the money (2000 dollars) can be spent in alot better fashion than that kit. like having the heads done by loyde, and a bigger cam, and headers and tunning. every body knows that the heads are the biggest problem with these cars and the lt4s are not a fix unless ported. and for less than the cost of the lt4s you can get the lt1s ported and do better than unported lt4s by along shot.

agian im not saying its not a good kit, i just think the money can be better spent.

 

At my elevation (1000ft) and with temperatures around 60-70 degrees, I have yet to see an M6 LT1 in good running condition dyno anything under 255rwhp. Again, in the conditions that I've witnessed. Taking all of the conditional factors (weather, engine condition, etc) involved into account it IS possible to hover around that 425fwhp mark with the LT4 conversion and misc bolt-ons. However, A4s dyno'd in the summer will yield lower values due to less air density and M6s dyno'd in the early spring/late fall/winter will dyno slightly higher than usual. So based on what I've seen, "rwhp / .85 + 100" is a very rough estimate of where you MAY be with an LT4 conversion setup similar to that I mentioned in a previous post. For me, that would be 428fwhp or 363rwhp - definitely possible.

97Z-M6, I do agree that the money that would be spent on the LT4 conversion could be better spent for more gain. No doubt about that. Some people just like the bragging rights of "I have an LT4 conversion in my car". To each his own!

Sorry to lag on about this, I just like debating this topic because I'm about to do the conversion myself. $$$ to burn I guess...

 

it is good to see that some people have good results with the conversion, and good luck to yours.