Old School Ron

Hi Guys/Gals,
Just got my first Vette, 1989 coupe. Love this car. Would like a little more hp and have heard easy and cheapest ways are headers, cool air intake, and possibly a chip. But would like to hear from folks that have C4's and really know. Please let me know if any of these work and the brands you prefer. Thanks Gang.

aklim

Going fast takes cubic dollars. How much do you want to spend?

Headers. Keep the current manifold or get long tube headers. Shorty ones don't seem to have enough gain to justify the cost. Intakes. Miniram, Superram or Holley Stealth Ram if you are willing to cut the hood and put a hood scoop or they have a version that is shorter and fits under the hood. Cold air? Waste of money. Just cut the ***** off at the air box. Chip? Don't bother with the off shelf stuff like Hyperjunk or Superchips, etc. Get it dyno tuned or forget it. Superram and LT headers will make some improvement but dyno tuning will really wake it up.

SoCal_Vette

Of course, depending on where you live and/or where your car "lives," the issue of smog legality will often rear its ugly head. As you can tell by my avatar name, my options for power mods are significantly limited by my residence in Southern California.

Tom400CFI

Before anyone can give you quality advice, you can help us, help you by clarifying your budget and goals.

Headers help on your car. Cold air intakes for C4's typically don't ingest cold air (they draw from the same place as the stock intake) and the stock intake is not a restriction...no gains there = waste of money.

Same goes for canned chips. Most that I've known personally who tried chips and measured the before-after went slower w/an aftermarket canned chip. Save your money there too.

L98 will benefit from:
Cam
Headers
Exhaust
Intake manifold
Heads
Custom tune

aklim

Out of curiosity my TPIS headers with the "Y" go into the main cat and eliminate the pre-cats, right? It has been so long ago and I only looked briefly and might have forgotten. I changed it to a Random Tech high flow cat. So how much more is the cat back exhaust worth over stock?

Dyno tuning is probably going to be a "Must Have" once you do intakes and LT headers to get the full benefit. However, once we do heads and cam, doesn't it get kinda expensive especially if you can't do the labor yourself?

Paul Workman

w/ the above. In short, there really is no "magic" to it: the more air/fuel in and out = more power...period. And, of course that means the programming (i.e., the TUNE) needs to appreciate the increases.

The thing many noobs to automotive tech fall for are the equivalent of the "get rich quick" gimmicks. And, as these guys (above) have said/implied, a power upgrade us usually the result of a comprehensive, well thought out process where all the components are complimentary of one another: no miracle "bolt-ons" are going to do it (not even if they have an "expert" Japanese-looking guy in a white frock coat to add "credibility" to the miracle gizmo...)

Aardwolf

You still have the stock mufflers and rear y? The mufflers are a huge restriction though they are quiet. The stock exhaust mani is tiny so you did well replacing that. Find a muffler you like to complete the upgrade. Here is a pic inside the stock '88 mufflers:



Starting with a full exhaust kit like the ARH kit is a good choice.

Tom400CFI

call the stock, shorty manifolds "headers" if you want, b/c it has round tubes, but to imply that "they're headers" so you shouldn't bother to change them is misguided advice. They have round tubes, but they certainly aren't conducive to making power, and real "headers" are. The stock intake is not a COLD air intake. It's a hot air intake. It draws hot, under hood air, from inside the semi sealed, "under hood" area. Unfortunately, as I posted above, most C4 aftermarket air intakes do exactly the same thing.



I'm going to steal this great quote from "Ovrebo1":
There's this little hobby that started in the 20's called "Hot Roding". It'll probably never catch on.....

For many part of the fun of ownership is tinkering/improving. It improves the relationship w/the vehicle.

Aardwolf

Both of your thoughts differ from mine.

The stock exhaust manifolds were not tubular at all on my year. They were cast iron and square. They were barely over 1" and very restrictive.

I've always held the position that the stock air filter is cold air at least while you're moving. It's very easy to test with data logging. There is a gap under and over the filter to let in ambient air.

pologreen1

I'm not far from you, you should be able to do what you want to the car, or have you just not gotten to true duals yet?

aklim

I got a Borla Stinger system because it was on a sale. It is rather loud on the lower RPM range. Some have suggested going with the LT1 to quieten it and not lose too much power

aklim

At the time I transplanted the motor, I wanted an SS system. I didn't think anyone made it in true duals.

mtwoolford

start with a cam swap and new timing chain and work out from there.

aklim

Why is that? With a cam swap, either you go with something close enough to stock where it won't mandate a dyno tune or you go with something more radical that will. If it is the former, it is kinda spendy for a $600+ dyno tune. If it is the latter, it might not work well with the heads, intake and boat anchors they call exhaust manifolds.

Tom400CFI

You guys will have to help me understand where this "ambient air" is coming from.... There are no vents into that area. The area is the same space as the engine (not sealed off or segregated in any way). I'm

I have watched my scan tool and MY intake temps sure don't look like ambient temps to me.

mtwoolford

well I can only relate my own experience; performance in and of itself is not the only goal.

I've never seen a old car, especially one that used the oem link and pin style timing that didn't have a significant amount of slop;

If you do realize a performance increase, by whatever route you choose, and drive it accordingly, you DO NOT want to rely on an oem style timing chain...ask me how I know this to be true? At a minimum a double true roller timing chain is called for,

a thirty year old cam is almost certain to have cam lobe wear, which has, or soon will result in lobe failure;

The art and science of cam design has moved on. there are a number of cam upgrades which do not require dyno time or a retune; for instance I swapped in an LT4 hot cam, a nice performance upgrade, and it sailed through California's strict smog testing...which indicates to me at least, that a reasonable performance increase is possible within the parameters of the oem computer program. And there are probably more modern designs that arguably could have done even better.

so, yes, I am not knowledgeable about cams for L98 engines, but I would invite those who are to share their thoughts and insights.

Bendeco

Keep it stock it will be worth twice as much when you get sick of it. Plus all stock is cool. After the few upgrades and a C7 will still blow you away

aklim

I agree that the cam, depending on amount of use will have wear and the chain will have stretch. At the very least the chain should be changed and the cam checked.

Help me out here. The cam increases the air intake and as long as the volume isn't too large the ECM can compensate. Compensation is contingent on one item NOT being too radically different from what the rest of the system. With the Tri-Y headers and Superram intake, there was a noticeable change in the way it ran. Once we reprogrammed the ECM, it became better. So what is the definition of "a nice performance upgrade"? A few HP, sure. IMHO, it isn't really worth it to put a cam in where you are hamstrung by limiting yourself to being around the window of the stock cam.

aklim

If you are looking at money wise, unless it becomes a collectable, it drops value every few years.

If you are in a competition for originality, sure.

Point? There will always be something faster. Only thing is as you get up the heap, there will be fewer and fewer of those somethings if that is what you are looking for,

mtwoolford

I can't argue with your success, and certainly reprogramming the ECM is justified after any substantial engine modifications.

I see that you are not from California. In California headers, aftermarket intakes, you name it, except for a few parts blessed with a California Air Resources exemption number, are an automatic "fail" on the visual part of the test; so that limits options to mostly internal engine mods...which brings us back to camshafts. The smog man can't fail you on the visual based on something he can't see...and there are CARB exempt cams out there. But non exempt cams, some fairly radical, will pass the tailpipe part of the test. Google "LT4 Hot Cam versus California Smog, the results are in" for the results of my cam swap.

Bang for buck? cam swap, $300 for cam plus incidentals; new heads or rebuilding / porting existing heads? stroker kit? not much else you can do engine wise except cat back exhaust systems.

Which brings up another subject, instead of trying to increase horsepower, take the same money and spend it on suspension and handling upgrades, but that's another discussion for another day.