I'm looking at a nice C4 race car but it has an L98. The motor has ~300+ RWHP, it's been balanced and blueprinted, has a racing exhaust (headers, short pipes, no cats) and a fairly aggressive cam (~0.530 lift). Heads and intake are stock but I'm not sure if they've been worked over. I sent owner that question.

Class rules will allow me to up the power a bit and still be legal. For an L98 how do I get about 40 more HP from it? Can some head porting and intake matching get me there or is this going to cost big bucks?

And what's the redline of an L98?

That sounds pretty similar to my setup less the blueprinting. I would guess that the heads AND intake have had some work if it's making over 300rwhp. At a minimum the heads are reworked to handle .530" of lift.

You should be able to get around 320-335 rwhp max w/ a TPI setup. The downside is that your power is done by ~5200 rpm. You can always add a MINiRam but I think that would bump you out of TCC or vintage??

What year is it and what's it weigh?? The MAF cars have an advantage If you are trying to keep it in PT instead of ST since you can get away w/ most engine mods without burning a new chip. (saving 5 points)

If you want the car down around 2700 lbs then plan on lexan,aftermarket hood, and a melrose top.

Sounds cool. Keep me posted.

Oh yeah,

1) aluminum underdrive pulleys
2) Time w/ a grinder on the intake
3) Remove all of the parasidic crap (A/C, Air pump,....)
4) 10:1 CR is free (points wise)
5) CNC ported 113's w/ larger valves flowing ~260
6) 24 lb. svos that are probably on the car already (adjust as needed w/ FPR)

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Dude...you have no idea what we've gotten ourselves into. I'll call you shortly to tell you about it. You're going to laugh....

But, it's all good news (potentially)...

I assume you want to keep the TPI. AS+M runners sound like the best for the TPI, ported, with a ported stock or accel or other good aftermarket base. Extrude honed plenum, or talk to forum member cuisinartvette, I've heard he has become excellent at porting TPI stuff. Depending on what, if anything, has been done to the TPI I think that is the best place to start, followed by headers and exhaust, depending on what your rules are.

400hp L98...complete instructions

Look on left side links for "Recipe for 400hp L98"

Joe90's home page

Thanks, Dano.

If I can help out wake that L98 up, shoot me a pm.

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It is looking more and more like a done deal, once I get exact specs on what has already been done to the heads I'll be in touch.

So what does it take if I go beyond the limits of TPI? Full new injection system? I will never go carb'd.

The existing fuel injection (ecm) will work with any of the available replacement intakes. A tune would of course be needed.

That FIRST Tpi system looks like a real winner to me, it appears to flow an absolute ton of air and will still appear to be a "TPI".

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Not sure what you mean by 'first' TPI system.

So what exactly is the limiting factor with tuned port injection? Is it the fuel delivery or electronics?

Air is the limiting factor. You could put a converted LT1 intake on, a stealth ram with custom plenum, superram, etc. The electronics will run it fine. You can change injector size, throw in a 255lph fuel pump, tune the computer, and the computer/electronics are good to go. The electronics can give it all the fuel and management it needs, just need to get more air in there to make more power. Depending on the power level reached (how much air you get in there, so to speak) a tune may be all you need. The stock TPI restriction is that the runner length from the plenum to the valve is so long that after about 4500 rpms it can't get enough air to make any power. It is a torque monster due to the air velocity at low rpms, but sucks up top. I've heard people say for autocross or road course type racing a modified TPI with the right heads/cam is the way to go because of the low end torque that accelerates you up out of the corner. I don't do that tho so I have no experience there. For drag racing it is best to scrap the TPI. I am currently putting a holley stealth ram on my L98 along with a CC503 cam and reworked heads. I can't wait to see how it runs.