After Market Horsepower for the Beginner

[johnny80]

Guidance on Aftermarket added Horsepower.

Any guidance on getting a few extra horses on an 88 4+3. I am thinking of course of an flowmaster exhuast first but what about these chips i see in the Mid America Vette Catalog? The "Street Runner sounds good? Any advice on that? Also, what about the airfoil intake. Says its a 5 min job. Any truth to that? Just wanting to add 30-40 horses and a great sound too.

SSG Johnny Drummond
Baghdad, Iraq
United States Army Military Police

 

[c4cruiser]

Most of the "Quicky" add-ons like the airfoil are a total waste of money. Some chips do nothing more that start the cooling fans at a lower temp and trick the ECM into thinking that throttle position is at WOT when it's really at a lower position. A heavy right foot will do the same thing!!

A good free-flowing exhaust is a good start. I run muffler eliminators on my 87. Just a quick stop at a muffler shop to have them cut the mufflers out and install a piece of pipe and add some nice looking tips. Depending on your states emission laws, you may want to gut the pre-cats for added flow.

A good air filter like a K&N is a help to get air into the system. Some folks report removal of the MAF screen will help get more air into the intake.

A different set of gears is probably the bigest STOP difference you can feel. Installing a ratio of 3.54 or above will provide a substantial increase in acceleration. The best thing about taller gears with the overdrive is that it won't really hurt fuel economy!

30-40 HP is doable with a good cam, port-matching of the intake runners and smoothing out the intake and exhaust ports. The design of the factory intake is the biggest limiting factor in bouilding HP. A mini-ram set-up will provide much better airflow into the enginge but at a big price. IMHO, there is no way to get to that HP increase you want with just the little 5-minute add-ons.



George
US Army 67-70
Viet Nam 68-69

 

[vader86]

Dont buy anything offered in those catalogs that advertises HP gains, because most of it doesnt.

Buy whatever catback exhaust system you like, theyll all give the same ~10hp to the car. Only real difference is sound.

NO GEARS for the L98, you dont need them. Thats for LT1 guys only. By the time you would ever need them, you wouldnt call it an L98 anymore.

A set of longtube headers from TPiS or Hooker (2149) will add about 15hp.

Further would be intake mods, you would need porting of the plenum/runners/base to get the extra 20. You can just port the plenum and buy a new set of larger runners from AS&M and a larger base manifold from LPE or TPiS. That would also do it.

Anything further depends on what HP goals you have, and the characteristics of the engine that you want. A cam change will benefit (thats when you change the chip, not before) but if you pick one now and want more power later, its alot more labor that you may not want to do or pay for.

 

[livinez]

So lets see if I track this right

Because the L98 only kicks about 230HP stock the gearing change isnt worth doing? Seems it would help 0-60 and maybe et.s I am after real world usage so a grand for gears is a big step.
As I am about to pull my motor for freezeplugs R&R, I'm considering rings, bearings, lapping the valves and replacing all seals. Boiling the block and fresh cam bearings, new cam and lifters isnt out of the picture.
Just don't know jack about L98's and what works for them. If I went with a more midrange torque cam(and I got no idea what that is...,yet) I'd probably gut the cat and see what mufflers flow. Headers too. Why change cams if you cant get it out eh?
Could match the ports but is the aftermarket intake stuff worth it?
I figure if the cost of adding 30+ HP is too out of line I wont bother.
I'm a 1st time vette owner too so this is most enlightening.
Later :cool TC

 

[stumpy]

No gears because the L98 is a torque monster is probably why.

 

[vader86]

You dont need gearing because you already have more low-end torque than is needed. What the engine lacks is top end power.

You put gears in it, you might roast the tires yes, but youll also lose to WRXs and Lancer Evo's once you get past that magical 60mph point.

 

[Rogue]

According to magazine tests, the 88 L98 with the 4+3 tranny gets to 60 in about 5.5 seconds. That's plenty fast. As most guys here point out, the advantage of the L98 is torque. It has plenty and is produced early in the powerband, thus allowing your Vette to accelerate very quickly. If I were you, I'd spend my money on making sure my Vette is properly tuned (new plugs, ignition wires, high power distributor, fresh coolant, oil, air/fuel filter, good fuel injectors, fresh brakes, tires, shocks, etc.) and running correctly. Maybe spend a bit on the K&N airfilter and open top lid and an exhaust. This won't give you the 50 hp you're looking for. Maybe 15. Maybe. But it will go a long ways to making your Vette a joy to drive. Unless you're trying to beat the current C5's, Vipers, M3's, and such, youre Vette is already very fast. To get big power out of the L98, you'll need to go internal mods and that means lots of $$.

 

[johnny80]

Thanks guys for the advice. A new exhaust is what i want initially. any guidance on the Borla "stingers" ? Or should i go with the cat back from flowmaster. Can any exhuast / muffler shop do the same without having to get a name brand? I do like the idea of polished tips on the end too. Thanks again.

Johnny:cool :cool :cool

 

[kingman]

L98 Torque??????????

Hi Rogue

Are you sure about the 0-60 time for a L98 being approx 5.5 secs.

My Lt1 barely does 5.5 secs and l have 50 more hp (auto 3.07 rear).

Alan

 

[Rogue]

Got the 0-60 mph from a Corvette book quoting a magazine test. Can't remember which magazine. C/D tests recorded a 6 sec 0-60 on an 85 L98 with 230 bhp. So the quote from the book of the later L98 with 250 bhp doing the 0-60 in 5.5 seconds is believable.

If you're using a stop watch it will register MORE time to 60 mph. I'm sure the magazine tests were done as an average of several runs with hard launches.

I don't know if this makes a difference but the L98 has MORE torque than the LT1. I'm only guessing but I would think the L98 would get to 60 about the same time as an LT1. But the LT1 will beat it to the 1/4 mile due to superior top end. No?

 

[livinez]

Thanks Vader86

This new guy always needs enlightening!
Just got the car in buddies shop where I'll do the work.
Car pulled hard even with code 32 and slight vacuum leak. Just got my OBD1 today to pull codes, but knew I had problems.
Still I saw what you mean about grunt!
Injectors will go to witchhunter for his magic.
Will most likely get headers and will definately replace the whole exhaust with no catalytic converter( cant see spending $ for good flowing 1 when I don't have smog checks here) & Hooker Maxflo mufflers.
Don't know if I'll do a cam change yet as I don't want to pop for the porting. Havent priced it yet. I And havent investigated what works well with the L98. But if it will run good without the porting & a converter change I'll do it.
But as the rest of drive train will need attention, new tires as well, I'm spending more than I intended. Thankfully it has a fresh tranny.
So I'll keep asking newbie type questions and reading old posts til I can make educated decisions on mods.

Good luck Johnny, saw a Walker Dynomax Super Turbo system in Summit for 1/2 the cost of other name brands if you are hanging them yourself. Dont know if they flow any better than stock though.

 

[vader86]

L98 is very capable of getting mid 5s to 60.

LT1s dont have quite the low-end, so are only marginally faster to 60. That can be cut down with more rear gearing quite a bit. (like .1-.2)

 

[sothpaw]

Hey Vader!

...Is there any Plenum porting, port matching, intake runner change that I can/should do to my LT1, that you know of?

--Did the heads&cam already, but I am always opened to more!

 

[tntcorvette]

How much money do you want to spend? And how much work can you do yourself?

there is the free stuff you can do:

1. cut air filter lid completely open or buy one that is already cut open
2. bypass the coolant going through the throttle body. Simply get a new hose from the auto store and run it from the heater core inlet on the pass. side straight to the front of the intake manifold.
3. I think on your year there is a "frissbee" that can be removed from the water pump.
4. If you have a air tools and a grinder you can pull the plenum and port it yourself, but you gotta know where to remove material 'n stuff.

I think that it for the free mods.

 

[ratorto]

I put in the Hypertech street runner chip in it and I noticed an improvement in acceleration (only took 15 mins).
Also,the K&N setup, airfoil, Borla's.
The most impressive gain in performance came when I replaced the 2:55 rear end with a 3:75.
Soon to come is an ATI Procharger.
Hope this helps.
Bob

 

[vader86]

Re: Hey Vader!

...Is there any Plenum porting, port matching, intake runner change that I can/should do to my LT1, that you know of?

--Did the heads&cam already, but I am always opened to more!

On the LT1, other than port matching the manifold to the heads, I cant think of anything. That is, if the heads have been ported at all.

 

[ratorto]

How did you get the 50HP?

Hi Rogue

Are you sure about the 0-60 time for a L98 being approx 5.5 secs.

My Lt1 barely does 5.5 secs and l have 50 more hp (auto 3.07 rear).

Alan

Alan, how did you get the extra 50HP?
bobcorvette

 

[drags1998]

Ihave a BORLA catback system Iremoved from my 90 coupe,VERY NICE COND. will sell for half price!!!!! Iam trying to get the car back to original EMAIL me@drags1998@aol

 

[voorthuist]

ratortor the LT1 was a new generation small block when introduced in the 92 model year. It was the stock Corvette engine from 92-96 and its output is 300 hp.

Engine power for 88 models was 240hp except for coupes with the 3.07 axle which had 245hp. NB - The 5 hp increase came from less restrictive muffs which were deemed too loud for verts and for 2.59 coupes.

 

[warren s]

The L98 does NOT have more torque than an LT1, it has the same 340 foot pounds but it gets produced lower in the power band by almost 1000 RPM.

L98s run out of breath way before an LT1.

A killer combo would be an L98 with a 3:73 rear, and worked heads with a good cam to open up some high RPM breathing. The power band may start slightly higher, but with a 3:73 rear it would be some ride.