MatthewMiller

Considerably lower weight - like 200lbs, and all of it over the nose.

I'm assuming you meant C6 ZR1, not C7. And yes, they most certainly did overheat on tracks. Inefficient positive-displacement superchargers have a bad habit of doing that.

ORLY? Show me the pleathora of them that exist out there. I have a ~420rwhp 396 LT4 and it doesn't idle like stock at all.

dizwiz24

ChumpVette

Problem is Diz, there is a lot of misinformation being passed around by people who don't know ZR-1's. The ZR-1 group is worried that one more bit of bad information about the car will send prices even further down. At that point you will see a lot of guys jumping off the cliffs about how badly the C4 ZR-1 is disrespected and that GM was foolish to get rid of the LT5 from Lotus, and if it had been allowed to progress we would now see a 4.4 liter LT5 producing 850hp naturally aspirated.

81c3

And then people wonder why ZR-1 guys are "sensitive" with dumb comments like this huh Chump?....

81c3

Dude.... I told you already once.... ask people who really know the car... not ******* who have no clue and only repeat the tripe they've heard over the years but have no actual experience with a ZR-1.... Go over to the ZR-1 section at a minimum... or go over to the ZR1.netRegistry.com site and ask questions for good, honest, intelligent answers to your questions....

ZWILDZR1

Funny thing is now Callaway uses superchargers and not turbos. They didn't have a supercharger that would sit low enough back in the day now they do and he uses them. The LS engine series is such a good and robust lightweight package due to it's single center mounted cam. Which means you can place the engine very low in the car as opposed to over head cam designs. Yes the LT5 is heavier and that has to do with the four cams and the weight being up high in the car. But you can do things to change the weight balance. Like relocating the battery from behind the left front tire to the right passenger side compartment which give you about the same weight balance as an LT1 car.
http://zr1specialist.com/HAT%20Web/p...ry%20reloc.htm

ChumpVette

ChumpVette

ElisTwoCents

81c3

Follow that question with how many failures are there....

dizwiz24

About the LS and roots supercharger ..

a buddy i have is obsessed with cars. He had an 800hp misubishi evo - but he hated how it was a dog off boost (which is how its driven 99% of the time).

next he put an ls3 into a 99 bmw m3 . I thought he’d be satisfied but nope.

next was an 07 c6 z06, but something was wrong with it so he sold it and bought an 09 c6 z06 - which he let me drive.

still not satisfied, he finallly bought a cts-v with ls9 supercharged and he is finally happy (though he gripes about it being an auto). He is convinced i will give up my c4 procharged 6spd and get something roots-blown once i go for a ride.

That said i went in a ride in my other buddies tesla. And wow.

there is no replacement for bottom end torque
Which is where roots superchargers shine

81c3

No, a Buick Le Sabre is "just a car".... Being an advocate the ZR-1 doesn't mean it defines me... this is a Corvette forum after all and 99% of the time were talking Vettes right? I cant stomach the misinformation that spews out almost daily..... Dont confuse being passionate with sensitivity...

Zak2018

I must say I haven't found the ZR-1 owners replying in this thread to be over sensitive.

I think their replies seem to be fair grounded thus far.

Zak2018

So what is considered to be the upper limit for the LT1 and L98 for a streetable motor which idles as stock? In NA form that is. Thanks!

pologreen1

400chp and 420rwhp are 2 different animals. One is a mild / highly modified SBC, the other is highly modified SBC end of the spectrum.

An L98, or LT1 , or about any 350 CI can make 425+chp as a standard rule with a good cam, heads, intake, exhaust, injectors, and a tune. In other words let the air pump breathe and it will make more power.

Very common for people to do top end kits on older cars and yes they idle cool and idle fine if tuned properly.

Matt's car is pushing 500chp with many different factors involved, I don't know his build, but it seems he is in to racing which is a different set up from street.

NRE has been putting out nice idling 2,000hp twin turbo engines for many many years.

N/A is a little different, streetable is up to the person. I have a 3,800+ stall in my car, and 248/252 @.050 about .650 lift. Stick is more forgiving of cams.

MatthewMiller

If we're just talking about 400chp, and we use the 15% rule (which may not be a good rule, btw), then we're just talking about an engine that gives 340rwhp on a chassis dyno. That's probably a 65-70rwhp bump over a stock LT1, or 40-45rwhp bump over a stock LT4. Even at that, I don't know how easy it is to get those numbers with stock displacement and a stock idle. You might be able to do with it AFRs and a hot cam, with long-tube headers. Maybe. But even then, you won't have a stock idle quality. Here are two example of what a hot cam idle sounds like: and Not bad, but not stock.

If you go with a 383 or 396, then yes I think such power levels are attainable with a stock-quality idle. That's not simple bolt-ons, though. And let's be clear, 340rwhp is not a giant power gain. It's going to be a little faster, but not what most people are probably hoping for.

Right, but as soon as you include a cam in any build, you're almost certainly going to lose the stock smooth idle quality. That's not necessarily a bad thing, but it's not what FAUEE's reply was claiming. And btw, Paul Workman is absolutely correct that a big advantage of a good 4-valve head design like the LT5 is that it can attain 340rwhp or more with 350cid with a smooth, stock idle. That was the context of the discussion.

My car is a 396 with the best-flowing ported LT4 I've ever seen documented (similar to AFR 195 Comps), and teeny aftermarket cam with very aggressive ramps. It's a very mild build, is completely streetable, and gets 26mpg on the highway at 70mph. I do autocross it, and it's built to take road-course abuse, but I drive it on the street all the time. But nobody would ever mistake it for a stocker at idle, even though I have it idling at close to 1000rpm.

And yes, if you some form of supercharging on it, you can build tons of power with a stock idle quality. That's a very different topic, though.

Assuming you leave it as a 350 and you really mean a stock idle (i.e. smooth at 700rpm for an LT4, may be 600rpm for LT1?), I think 320rwhp would be a very good achievement. But I honestly don't know how likely even that is. I believe it would require head work (or aftermarket heads), and very careful cam selection. The LT4 was a pretty well-tuned engine from the factory - it was the equal of the LS1 in terms of streetable power, and it was essentially GM's hot-rodded LT1 that could still meet emissions and durability regs. The best of them hit about 300rwhp from the factory. Getting much more than that will take some compromises in idle and streetability, or more displacement.

Zak2018

Thanks guys. Very helpful replies.

Yes, the idle in the video you posted is too rough for me Matthew. By the way, did you mean to post two different videos? And thanks for posting.

I really need to think the way I want to go. It seems no matter what I will have some work to do to get the C4 I truly want. I will have to customize it one way or another.

I like the classic C4 shape, which means either LT5 or L98.

LT5 is shaping up to be a little more complicated and expensive than I want. This is to be a car which I will enjoy and put miles on. Take road trips and even cross country trips etc. So I'm not sure a LT5 is the right engine for that. The power is not a problem. I would be quite happy with the 405 it gives. So it's not a matter of hot roding it. I wouldn't need to. It's a matter of it being a complex engine, which seems difficult to work on and difficult to find people who can work on it. Rare and difficult and expensive to find parts. Even if it's a reliable engine, at some point something will need repairing if I am to use it as much as I want.

L98 is just a little power starved. I would love to be around 400hp. Would not mind 500 of course. But for example am not even thinking of crazy high numbers like 600 and over. Don't need that. I don't think more is actually more here. 400 would be a great size. More than enough on the road and fun enough on the eventual track days. But it seems getting that in NA form with a L98 will take a lot of mods and wont be as streetable or idle stock or any close to it.

LT1 doesn't seem that much easier than a L98 in NA form and will get me away from the body style I want.

So it seems I have 4 options and none of them seems easy or 100% checks all the boxes:

1. Live with the L98. Like I said it's a bit under powered for this day and age in a sports car. For the street I guess it''s good enough. Especially if I could make the car lose some weight. But 400 is such an attainable number these days it seems, that it almost doesn't make sense to set for 250 for a sports car in 2018. Not a deal breaker though. Just not perfect.

2. Risk buying a 1990 ZR-1. Another problem besides the complexity and expense of the engine is that although not interested in moding the engine I will definitely want to mod the car to try and shave some weight. Since it's a rare car this is another strike against this option. But the main strike is having a LT5 in a car I want to put the miles on.


3. Buy a late C4 with a LT1 and retro-fit the classic C4 body to it. Or just keep the late C4 body, which also looks so nice. This is an option I considered but which now doesn't make a lot of sense based on what I'm learning about the LT1 and its possibilities for power output in NA form.

4. Buy a 1990 L98 and do a swap. But it seems the only swap which would make sense is a LS. A LT4 upgrade doesn't seem to get me much for the work and expense involved. A LS swap would totally turn the car into a hot-rod of sorts. Meaning it's a somewhat special car. No longer a standard car to have it worked on etc. Engine swaps are something I really like to avoid. You no longer have a stock car and it now needs special attention. A smaller disadvantage, and something which may not matter to many, but since this is to be a sports car and not a race car, so the aesthetic side is a huge part of the fun, is that I hate how ugly a LS1 looks. With the clamshell hood it's so nice to open it up and expose the whole drive train. But a LS1 is a mess optically, at least IMO. And the newer the LS the less appealing with all the plastic covers etc. The days when engines looked like a work of art are gone I guess. Of course the LT5 is a beauty to look at but the L98 also look better IMO than a LS1 and so does the LT1.

Not a deal breaker though. But definitely a move in the wrong direction for a clamshell hood IMO. Again if this was to be a race car then all it matters is the power and what the engine can do. But this is a sports car. It's as much about the aesthetic and the fun and it is about performance. So alone it's not a deal breaker. But together with the extra complexity of swapping the engine, expense, work involved and then having a hot-rod Frankenstein-ish car, it adds up to the negatives.

All together what really turns me off about this option though is not having the car stock-ish plus the headache of the swap. If I would end up going this way I would most likely go all the way and do a full custom. Like replacing a lot more things and upgrading a lot more things etc. Probably would try getting a hold of a Callaway AeroBody or something. Once you open that gate I fear it will become one of those never ending projects. But I don't need that. I'm perfectly fine with a mostly stock 1990 C4. If I could easily get 400bhp from a L98 with a stock idle I would just do that and be done with it. Maybe upgrade brakes if needed because of the extra power. But not much else I guess. Know what I mean?

I would probably be happy with any of the options above. But none would be perfect. So I have some thinking to do to decide what would be the best way to go. I guess you could say I have reached an impasse in my C4 ambitions which I need to figure. But these forums are sure helping.

JBPC4

pologreen1

It is real nice to see you putting so much thought in to this decision. It has been about a year since a guy really had such detailed thoughts on doing a build. Keep up the great work.

There is always the option of modifications to optimize cars. Like a TPI is considered a torque monster, and LT1 is high revving, and LT5 is a beast and legend

It was always my understanding that an LT5 swap to a base is very complicated and not worth it, but someone here recently told me that is not the case. Maybe look in to that option.

Zak2018

Thanks.

Do you mean putting a LT5 into a base Corvette? Interesting. What do you have in mind as advantages?

By the way, another thing to factor in which may throw another wrench into my process. I want a manual transmission. Does that limit me in anyway as far as options? I know the ZR-1 and LT4 for example were only manuals. But is it easy to find a base L98 1990 with a manual for example? What about LT1s?