Okay, here's the plan:

I am having a 402ci stroker LS2 built for my car. Forged internals, custom dished pistons, etc. I also plan to add an STS Turbo to my car sometime in 2006.

My first thought was to put on a set of ported LS1 heads that I already have onto this engine. The engine is being built for a 9.5:1 compression ratio, and with these heads (which are heavily milled) I would end up with about 10.8:1 for now, while it is normally aspirated.

However, I got my hands on a little extra cash and am considering getting better heads and putting them on NOW. The heads I am looking at are LQ9 heads (unmilled) and flow fairly well on the intake, and EXTREMELY well on the exhaust side.

My dilemma however, is about the CR until I add on the turbo kit. My first question is, how much are these LQ9 heads going to drop the CR?

My 2nd question is, how is the driveability going to be (this is a daily driver first and foremost) for the next year or so, until I can afford to add on the turbo, with such a low CR? Has anyone else run into this situation? I've had a couple people tell me that I'm going to lose too much low end pull with that low a compression - but at the same time, I know their experiences are with LS1 engines with stock cubes, not strokers. My understanding is that the stroker ADDS a ton of low-end grunt, so will this just balance out for now?

Finally, how much is having a low CR going to affect my ability to pass smog when I move to California later this year. I've been told that higher compression reduces exhaust emissions...... am I going to run into a problem here?

Oh - and before you ask, I am not sure yet what cam I am going to run. Probably something in the mid-230 duration range, but It'll probably be a custom cam in any event.

I'm posting this in a couple different forums, because I realize there is a lot of overlap here (FI issues, smog issues, heads issues, etc.)

 

Ive always known to myself that a higher CR means more emissions. Might want to go ask in the Forced Induction part of the forum. Those guys know whats up.

Jim.

 

Did that, no responses yet. The real issue is BEFORE I go forced induction, anyway.

 

I don't have a lot of concrete answers, but I've got a few guesses.

If you go to the low CR now, I don't think you'll have any really big problems. You will be down on power some (compared to if you were running 11:1) but I don't think it'll be all that important. Basically you're building a truck engine. Factory LQ4's come through with like 9.4:1 compression, and run well on 87 octane. That might be a plus.

I don't know what your choice of cam is, but if you put the "turbo" grind in now, the driveability should be very good. You'll probably give up a fair bit of power (because turbo cams need zero overlap to keep the exhaust from flowing into the intake (not the other way around as most people think) which limits max duration) compared to a really hot NA cam, but you won't have to take the motor apart again (which might be nice). But you will have also built a fairly expensive truck motor (maybe 375 to 400 hp?).

California emissions might be good fun. I don't have any personal experience with them (I live in MD). But it sounds like the "Emissions *****" (my affectionate nickname for them) might have some choice words about your swap. And maybe they won't, since its a later model of the v8 that you used to have. I dunno. But its not something to be taken lightly.

'Dreamin'

 

I used to live in CA and they are very strict on emissions which include a visual inspection also. I do believe they allow a newer engine to be installed into an older car (needs certification), but not reverse. I would post in the Western Forum for exact requirements.

 

Thanks guys.

I've already spent a great deal of time checking into the CA requirements of engine swaps. I've got everything covered on that end, even spoken with a smog referee. In a nutshell, I have to pass 3 checks:
1.) OBD-II
2.) Sniffer (TR224/224 112lsa will pas with a great tune, 114 lsa will easily pass)
3.) Visual (They are looking for cats, cat locations, headers must be CARB approved, etc)

It's looking more and more like I may run the 224 cam 112lsa, which I already have, at least for now.

Anyhow, from the responses I've gotten to this in a couple forums, sounds like I'll be okay with the low compression.

Thanks again,
Adam

 

buy your heads, and hold on to them untill you put the turbo kit on.
problem solved.

or you can run the new heads, youll be down power but youll still be making more power than your average ls1.