MatthewMiller

It's out there somewhere on the webernets. ZF-equipped C4s aren't that rare, since a couple years of L98s and five years of LT cars could be ordered with ZFs.

Yes, you could get a C4 with either the body-colored fiberglass targa top or the acrylic "glass" top, but both are bolt-in targas. Some cars came with both. But there is no fixed roof at all.

So Tom really addressed the torque thing. With a short-runner intake you'll have the same off-idle torque, but a flatter torque curve and a wider rpm range to use, and no hump in torque at 3000rpm like with the TPI intake. Overall it's a better set of characteristics in every way.

I need to recant my last estimate of power on that combo, though. When I typed that post, for some reason I was forgetting that the L98 heads probably don't flow quite as well as stock LT1 heads, and the L98 will have a little lower compression ratio. So let's bump that estimate down maybe 310chp. Sorry for my brain fart there. If others disagree with my estimates, I hope they'll chime in.

Well, a cam is a "bolt-on" in the sense that you don't have to pull the engine and tear it down, but does require the intake to be removed. The idle will still depend on the cam, and I don't have the expertise to advise you on exactly what grind you'd want. But you can get something that will bump the power a bit and still idle pretty much like stock. Hell, even the original LT4 cam was a significant improvement on the power of the L98 grind.

The answer(s) to that is long and debated. But suffice to say that a stock L98 is much less powerful and has a narrower range of useful rpm than the LT1/4. Stock for stock, the LT is a real improvement. And it even got better mileage to boot.

A stroker can get those numbers with a stockish idle, yeah. So can the 400 engine that Tom mentioned earlier (still a small block, but built originally as a 400 with a larger 4.125" bore and a 3.75" stroke). Again, a stroker kit is not a bolt-on. It will be a full engine removal and rebuild, using a different crank, rods, and pistons.

bb62

46,061 Manual 6-speeds from 1989 to 1996
31,434 Manual 4-speeds from 1984 to 1988

286,685 Automatics from 1984-1996

Tom400CFI

Regarding this comment, I'll add to what Matthew said:
*1000+ more usable RPM. The L98 is a fun ride...up to 4000-4500 RPM. That number...that spot on the tach comes up quick in lower gears and it feels limiting. Frustratingly so, IMO. You talked about "L98 sound". IMO, when you shift a stock L98 where you need to for max acceleration, you ear is left wanting -it feels/sounds like you're short shifting. If you don't look at the tach and just wind it out by ear...you end up spending a lot of time in "no man's land" where you're burning gas but not making any power.
*No penalty -you get 50 more hp, the same tq essentially, the aforementioned 1000+ more usable RPM....AND you get better fuel economy. What's not to like?

The looks would be about the only thing that I can think of.

Zak2018

Thanks. It seems my research is not to be trusted. This is why it's better to get info more directly from people with experience with the cars, such as the people here at the forums. In my research I found several people saying the L98 has more bottom torque while the LT1 revs higher. Also several people saying they prefer the L98 sound and even praising it. Then I searched for a few clips on YT and kind of thought the same based on the clips I saw. Of course, exhaust set up play a huge role and "nicer" is a subjective thing. But maybe the comparison is stock vs stock.

But thanks for clarifying the torque issue.

Zak2018

Thanks. So less than a 1/3 of the cars were manuals.

Zak2018

Do you think there could be considerable chassis stiffness gains by making it a fixed roof?


Ok, so between the 98 with better intake, very mild cam, and maybe headers you suggested and the L98 built as a 396 (or is it 383?) and the 400 engine that Tom mentioned earlier , which one would be the easiest to do? Cheapest? And which would be preferable and why? It seems one of these 3 options might be the best way to get what I want, which is a 1990 C4.

Unless I find a very nice 1990 ZR-1 for a great price, full service history etc.

Zak2018

Ok. But I guess with the mods Matthew proposes for the L98 that would change and be a nice engine it seems.

Tom400CFI

People do this constantly and IDK why. We are seeing more of this behavior than ever, in politics right now; the facts are clear, but someone states a falsehood as fact. WTF? IT sucks b/c it does nothing but muddy waters that could and should be clear. Why do people think this about the L98? I think two reasons;
1. When the L98 came out, tq was a dramatic increase over any small block before it -especially at low - mid RPM. No carb'ed SBC before had anywhere near the tq that the L98 had in '85. So it made an impression on people that may have "stuck".
2. Torque is all the L98 has got to offer! So if you own one, that is what you focus on and talk about. 230-245hp @ 4000-4500 isn't what you talk about. So people talk about the "tork monster TPI", instead. Both the LT1 and the L98 made ~340 tq peak, so...



YES. How to do it? IDK.




I like the 400 for the bore and cost. Matthew likes the 396 b/c he's in a different situation; he is limited by the "LTx" platform to a 4.0" bore so to get the cubes, he has no choice but to go w/a longer stroke. That works, and works awesome. But if you buy a '90, a 400 is nearly a bolt in. The one hang up is the flywheel which you can have a machine shop fix the flange and balance to run on a 400.

It all boils down to what's more available and cheaper in your area; a 400 block? Or a 3.85" crank?

81c3

And by the time you do all this work, you could have easily bought a ZR-1 with headers on it (400hp) for nthe same money or less...

Heres the deal of the century....

https://www.ebay.com/itm/1993-Chevro...2:pf:0&vxp=mtr

pologreen1

yeah, but I heard it will need to be run out at full song to get its worth. Tow truck L98 for the win. Imagine the torque of a full tpi setup stock in a 400 block with 400 crank? The TOWAK would be insane for 2,000 rpms of power band and idle insanely nice.

1993C4LT1

I'm interested in the 93. Can't remember the name right now, but sounds like it is the ICM version of the LT5? At least I think that is why it's stalling.

ChumpVette

pologreen1

Nice car for sure. He who hesitates....

ChumpVette

MatthewMiller

The 350 with intake, cam, and headers is easier and cheaper by quite a bit, but less powerful. Either the stroker kit or the 400 engine will provide significantly more power for the same idle quality. I honestly don't know enough about the 400 option to advise. I think you have to drill two cooling passages in the heads to make the 400 block work with them, too, due to the siamesed water jackets. Tom can probably confirm that (or not). I do know more cubic inches for the same size/weight engine is pretty much always better. One other thing I don't know about on an earlier L98 car is how much tuning the ECM would need for the bigger engines. I'm not really sure.

As for which option makes more economic sense, only you can answer that one. Of course the cam/intake/headers on a stock L98 is a much cheaper option than a ZR1. As for the big-inch engines, it depends a lot on how much labor you can put in yourself. If you buy a clean L98/6sp C4 for, say, $6k and then spend another $2-3k for a big-inch engine and do the work yourself, your still in it for a lot cheaper than a ZR1. If you have to pay someone else to do it all and then you might quickly get up to the cost of buying a nice ZR1.

81c3

I more than likely would have if Id seen it.... Why, do you consider it a poor deal for a 93 ZR-1 in that particular color combination?

Zak2018

I think your theory here explaining why the L98 has this bottom torque reputation makes a lot of sense.



How about two pieces of metal on each side in between the targa top, connecting the frame? Then fix the top on top of that?




No idea. I would have to check. Chances are I will have to order online no matter what.

Zak2018

Thanks. Something is telling me I would probably just do the 350 with intake, cam, and headers etc and be happy with the 310chp. Or just buy a ZR-1 if I can find one in good condition and for a good price. If it gets too complicated to do and expensive, given everybody is saying the ZR-1 is reliable, despite the gamble if it does break, it would probably still make more sense to go for the ZR-1.Before spending a lot of money and time in modifying the engine too much etc. As long as I can find a cheap enough ZR-1 and in good condition.

Because I think I would be able to do the 350 with intake, cam, and headers myself. But I'm not a mechanic. So the more complex stroker project I might have to get help. With the 400 it seems I definitely would need to pay somebody.

pologreen1

Or you could do a good a 350 with a good set of heads, cam, headers, open exhaust, 1;6 rr's and use the shorter intake platform of the lt1 style and make 425chp and still be streetable. This has been done for decades now and 10's of thousands of GM cars from the 89'-90's and back.

Someone posted a link here the other day of a crate 420chp 350. The factory is now offering a bolt on built motor, so they are decades late to the party, but not as many people wrench anymore either, and nobody is happy saying they have 250hp these days in a "sports / performance car" Of course wiht this combo or any that improves HP you need to consider rear gear and trans combos. More hp equal lower gears to make it happen based on physics. Unless you built an awesome hybrid intake combining the lt1 with the l98 of course.

MatthewMiller

Yeah, but that crate engine or any other 350 that really makes 425chp isn't going to idle anything close to stock.