Can someone give me a honest opinion of how much horsepower can be produced with the original plenum, tubes, and manifold. I would like to increase the horsepower by approximately 100 horses. I have varying opinions as to the amount that can be generated using stock components. My intention is to either supercharge or do the heads, cam, roller rockers, headers, ignition type work. I want to keep the engine as original as possible, yes, the supercharger might give it away if I go that route, but with only 40,000 miles I wish not to go off the deep end. It is a 1990 six speed.

Thanking you in advance for the information

 

With stock cam, probably only another 50chp can be done, all from exhaust. The heads are not a choke point on a '88-91, they could support your extra 100chp, but the intake cant flow it.

With a new cam, you might get about 75chp with the exhaust work done, even that might be a stretch.

Its hard to say definitively what number, since most people do the intake before ever considering cam changes.

 

I'm in exactly the same position as you with the same make/model...also a 1990 6 speed...high flow cat and cat back exhaust...the other usual bolt on stuff...my stock intake is off the car being ported at a machine shop...told this guy is good...using a flow bench and match porting cylinder heads to the intake...not sure what cam is gonna be used yet...gonna find out tonight what is being suggested...told something a lil' more aggressive then a hotcam (which I thought was a lot of cam)...the car is being kept a dd, so very curious what this mechanic is thinking...wondering what everyone's thought's are??...oh, and to the original poster, listen to vader..he really knows his stuff...I'm being told by my mechanic that all this work is being done for me at a really great $$ and that his friend is incredible with these motors, so trying not to push too hard...but, wondering what the potential of a ported tpi is??...I know a super ram would be a superior setup, but not sure I want to invest in one at the moment....I am optimistic as far as the tpi is concerned due to the fact that Carmen and Dennis at thevettedoctors (always took care of my car...not doing this work though)...seem to get 350hp out of similar mods done to a ported tpi...and 350 with stock headers and cats...I'm being told, when all is said and done, that the car will produce in the neighborhood of 25-35% more power...seems like a realistic goal to me??....also, I have a feeling that people will question why I am not having the work done by the aforementioned shop since they are extremely proficient at doing this job...simply because $5,000 is way, way out of my budget for this...

 

100 hp is fairly easy to get with the stock tpi manifold, tubes ect. as long as they are ported, get the heads ported and a mild cam custom tune and you will be on your way to 350+hp in no time

 

I dynoed my 89 before I touched the Top end and it made 263 hp and 360 Tq. Car Just had LT headers and a catback and all cheap mods.

So Vader is right on. 50hp for the exhaust and another 13hp for K&N, airfoil,frisbee delete,smaller pulley and TB bypass.

 

If you REALLY pay attention to the details....

>400 CHP is attainable from the TPI setup. I'm there...and it still idles like a stocker...with just a little lump to the idle.

Check out the link to my web page...go to "Recipe for a 400 HP L98"

 

wowthatisreallyhardtoreadandpickoutallyo urquestionsmaybetryandusesomeperiodsandp oaragraphs?

 

50 HP for exhaust mods? I would imagine thats also a cam or some head port work,not just exhaust alone.Never heard of the L98 engine freeing up 50 more HP with a stock cam and etc by doing exhaust mods.
Not being a Dick,just letting you know never seen it or heard of it.

The 89 Vette made 240 HP and 340 or so ft. lbs of torque...If the above said 263 hp,I would imagine rear wheel numbers,which makes sense for LT mods and some other free HP ponies...I do not imagine its flywheel,and know you never said so either,but it sounds inflated.

What the above poster needs to know,you cant create any more HP without forced induction,but you can FREE up some thats restricted,but it takes alot more than exhaust mods to do that.

 

I apologize diel...new to this...didn't realize my previous post was difficult to read....thought I was being clear and concise...

 

50hp at the crank. Typically we net about 25-30 at the wheels at best.

 

found out the info I needed...I'm wondering what everyone's thoughts were...

my tpi intake is being ported and cylinder heads are being match ported to the intake...the cam being suggested is a comp cam 210/220 with approx. .500/.510 lift...I'm not sure of the exact cam...these are the only numbers I was told thus far...less agressive then the hotcam (my mistake)...without taking off the heads and doing them and burning a new chip this is about as strong a cam as I can use....

promagnum rr are gonna be used since they work well with the valve covers...

so, the block isn't being touched really...being told that all the work (the cam, intake porting, rockers, springs, pushrod, lifters, etc) is gonna cost approx $1,200-$1,500...is it all worth it??

 

I am making about 360 RWHP and close to 500 RWTQ with the stock, unported TPI components, stock cam, stock heads, Hooker longtubes, and a 100 HP shot of nitrous.

Spray it man, put a bottle on it and forget it. You'll make more HP than all the TPI mods in the world, and it'll still have all the stock manners and mileage when you tool around town.

Check out this write up I did sometime when you are bored. Most people won't even consider nitrous because of all the rumors and BS associated with it, this kinda explains how N20 works.

http://temp.corvetteforum.net/c4/vader86/nitrous.html

 

I do have the dyno graph to prove it. All stock internals 263 rwhp and 360 rwtq.

not inflated numbers I have receipts time slips and dyno#s

 

My stock heads/cam L98 made 272rwhp/386rwtq. It does have nearly every bolt on you can think of including runners, intake, 1.6 RRs, 24 lb injectors, custom tune, full exhaust (no cats), pulleys, etc. etc, etc. The heads are untouched and the car is NA.

These number were however before I added Hooker long tubes, so I'd expect it makes a bit more now.

 

Here's an idea...
Sell your C4 and use the money for a down payment
on a brand new C6 Corvette, you will boost your HP to 400+

 

I would never sell my C4 to get a C6 unless I had enough money leftover to mod the C6 to out perform my C4.

Raced a C6 this weekend and a LS2 GTO at a Muscle car shootout at our local track. Both cars were new and I don't believe they were modded at all. C6 wasn't even close but the GTO was with me all the way.

Hippy never showed up so I didn't get a chance to race him.