barfoot164

1988 L98 Engine performance modifications

John A. Marker

Somewhat in order....remember it all costs $$ for HP. And before you start you need to line up a tuner.

Cam
Heads
Intake
Exhaust

Or go for gears.

Cjunkie

To do what?

vader86

Need information on goals and budgets.

aklim

I disagree. He needs to line up his wallet first.

billschroeder5842

Aklim speaks the truth; money is the first decision.

aklim

Spending money on mods for a car is like foreplay with a woman in general. However much you plan for, double it.

Space387

Never have I seen more true words.

Joe C

since the original question was "best performance mods" without stating a budget, i have to agree with john marker - it's all about air-in, air-out" but i'm with Cjunkie on this one - "to do what?" if the OP is not tracking his car, and using his 88 as a Saturday night cruiser, or just a daily driver, i say leave well enough alone. as boring as it sounds, on the street, a stock L98 corvette will break any posted speed limit. anything above that is overkill.

on to performance mods - for a driver, personally, the best thing to do is let it breathe a bit better - eliminate the pre-cats, and install a hi-flow main cat, and maybe a premium cat back exhaust (as for the cat-back - probably not much performance gain, but at least it will sound faster - ). for a street driven car, i'm all for gaining performance through (routine) maintenance, but not so much for spending money just to go from red light to red light a bit quicker. just my 2-cents....

aklim

A prius can brake a speed limit. Assuming the driver hasn't died of boredom in the mean time. So, by how much does he want to accelerate?

My money is on intake and headers first. Tuning next. Cam and heads next and more tuning.

Space387

I usually suggest all internal parts at once. If the op is going for a 383 eventually leave the cam and heads alone. If you change them now he will just be replacing them on the 383 build. When I did my LT1 build I ported the heads swapped cam and rebuild the engine in one shot. Stock intake and exhaust but they can be swapped later without cracking open the engine.

Joe C

can't argue the prius vs speed limit thing, but "acceleration" is more about torque than horsepower. heads, cams, headers, etc. all build horsepower, so unless you're tracking the car, more so at a drag strip, building excessive horsepower for a street driven corvette, IMO, is not the way to go. for the street, i'd rather build torque than horsepower, and personally, if it's purely just red light to red light acceleration, I'd look into rear end gearing first. personally, I'd rather invest in brakes (first) and suspension than top end HP. for the most part, folks drive in the 1500-3000 RPM range, and that's where a stock L98 shines brightest. so again, how fast can anyone accelerate on the street, IN TRAFFIC to boot? on the street, it's all I can do to co-mingle with soccer moms in mini-vans and idiots on texting cell phones. it still comes back to what does the OP wants to do?

BTW, i'm sure it's just a typo, and no flames my friend, but it's "break" -

GREGGPENN

Because of the hp vs torque formula, torque will always be greater below 5252 rpms and visa-versa. Because hp is directly related (derived) from torque, you can't consider torque more important to acceleration than horsepower. That's misleading.

The RATE you accelerate can be a function of traction, increasing power (versus the prior slice of time), gearing, etc.... Having SAID all that, there are elements of torque and horsepower worth considering.

In general, UNLESS MAJOR CHANGES ARE CONSIDERED, you might want to look at the type of transmission first. When you press the "go" pedal, where do rpms drop...and where does it shift to the next gear? If you don't change THAT, then it becomes the window for building power...don't you think?

L98s are hard to change because they ARE built around lower rpm performance. Intakes alone can be expensive AND necessary to get significan high rpm (horsepower) improvments. Compared to later engines, the intake represents ADDITIONAL cost compared to say...an LTx engine.

For post #1 in this forum (as the OP represents), I typically assume smaller budgets. In THAT regard, the exhaust manifold seems the place to start. It's the biggest bottleneck for the factory design. Simple removal and porting of the manifolds can be "free" power. You COULD say porting of the intake is too...though is much harder through curved tubes. As such, I like bigger runners.

If even a modest budget is available, 1 5/8" headers and large tubes might be the best option. Gearing would be good consideration too...depending on the factory ratio. If you're paying for the gear install, you're already up to the $2000-$2500 range.

It's hard to justify a cam w/o heads and visa-versa. And, it's hard to justify a cam/head PACKAGE w/o doing the stock intake/exhaust first.

It's been said before (in this forum), modifications to get power on an L98 aren't really a simple "bolt-on" weekend project.

That said, the earliest L98's dominated the SCCA circuit which can be read about in this thread. Also... Lingenfelter's modifications (superram, cam, head porting, headers, and exhaust) would be another roadmap to building an L98. When you read about his upgrades, you'll see they included the intake, a cam, head porting (when equipped with alum "D" port heads), headers, and a large exhaust.

Anything in between is a matter of preference/opinion. IMO, a lot depends on transmission (manual vs stick) and gears. Even more depends on whether Mr First Poster ever finds his/her way back to this thread again!




P.S. Because Joe, I'm sure you can't tell (by my post above), I agree with you on the value of torque for a street car. It's what I (heavily) built. When you get to highway/passing speeds -- which are ALSO part of "street driving", horsepower IS of equal/greater consideration. And, especially to the point of what type of transmission you have, it's pretty hard to make a fast HIGHWAY car if you only focus on torque. When you "kick down" an automatic, I personally consider it's "looking" for horsepower....especially when you add in what the torque-converter does. (Which, btw, can basically be replicated by how you rev/control the clutch).

Joe C

Gregg - I totally understand what you're saying, and I do understand the torque vs horsepower relationship, but what I was trying to get at is, for a typical street driven car, IMO, torque is more a consideration than HP. I know "street driving" includes highway and passing, but what percent of daily driving does that entail? on the highway, we're still legally limited to 70-75 mph, and as for highway passing, granted maybe a bit more HP maybe beneficial, but is it worth cost per HP? I see too many guys with 400, 500, 600, even 700 horsepower, with their 4.56 gearing, chugging up and down the road at 50 mph, basically going nowhere fast. unless it's just about bragging rights, personally, I don't get it. bottom line, we still have to abide to traffic laws, so just how fast can you accelerate in traffic? headers, intakes, exhaust, air-in, air-out stuff is really only beneficial above 3000 rpm, and on the track. for example, at lower RPM's, my junkie, old iron head, 624 castings, and stock exhaust manifolds, damn near flow as good as any high dollar aluminum heads and headers, so why would I invest a several grand in something that would only benefit me 1% of the time, if that? my 230 horse 85 L98, in stock form is more than adequate in passing at highway speeds anyway, so why do I need an extra 30-50 HP? I still stand by (rear end) gearing for strictly red light to red light acceleration, but personally, I'd put my money on brakes and suspension, more so than trying to build horsepower (and torque) for any street driven, daily driver C4 corvette. I guess this is just my old man thought process about spending money on performance. gawd, i'm starting to sound like dad -

it still comes back to what the OP wants to do - street, track, or a combination of both? Saturday night cruiser, IMO, keep it stock - occasional track car - OK, but you'll spend a lot of $$$ to go a little faster. i'd like better braking on my car, but I can't even justify that - . i'm really getting cheap in my old age -

TorchTarga94

It appears everyone in here as built you a pretty stout L98. Have fun.

DMITTZ

As everyone has said we need to know what the OP's goals and budet are...

However, If I had to pick just a couple engine mods I would say Camshaft (best mod), headers ( second best mod). Lots more can be done but if you just want to do a couple things those are where I would start.

John A. Marker

Well......two days without a reply from OP. And only a single post.....TROLL?????

In my reply I did say that HP costs $$$$...so your correct....bring out your wallet. After that it is goals/end use. Or just sell it and pony up for a C6.

I also have to agree, do all internals at once it will end up costing less.

856SPEED

Is it just me or are we seeing more trolls out there? I wonder if the video game allure is pulling back and this is more entertaining for the wills of light minded youth????

one thing for sure, I enjoy aklim's responses! Priceless!

Phoenix'97

What is YOUR idea of "performance"? High RPM power or Low RPM power? Is the vehicle in question intended for use as a daily driver only, an occasional visitor to the drag strip, or is this vehicle going to be pure track only?

Why do you want to modify your vehicle with "performance modifications"? The answer you have will be the start of your journey into what you seek and the research necessary to make it happen.

856SPEED

Do you own a Vette or an F-body?

Where is aklim?? This guy again.......