I've been on here a lot reading through as much as possible and it seems that the L98's main weak point is the induction system. I have been pricing options out on upgrading the TPI system and one thing seems to stick out, its pricey. I'm really tempted to through an Air-Gap and a good carburetor on top of this motor and call it a day. The only thing stopping me is the reliability and fuel economy that the TPI system offers over carb setup.

The plan now is to get a FIRST or Mini-ram intake and put bigger injectors on then Patriot Heads and find a matching cam. Which is looking like 2800$ish to make maybe 380FWHP.

/sigh maybe I need a cheaper hobby.

 

Hello Nicelysedated!!

What do you plan on doing with car??? Racing or Daily Driver???

 

Mostly a daily driver. I just want to embarrass every house wife with a Mustang. I am new to doing EFI builds and am just not in my comfort zone of good ole carbs.

So far I have rebuilt the front end and put on Hedmen shorties with true duals all the way out back. Generally the next step is to get more air in the motor which is where I am at now. I am really torn on what way to go with the induction system. The FIRST intake seems like a solid choice, but at 1K$ is pricy and it looks like I would have to spend more for parts to drop it on.

 

Hello Nicelysedated!!

IIRC, I do believe that "stock" TPI will support up to about 330HP, and 3500 - 4000 rpm, before it starves for air!!

Don't quote me on these "exact" numbers, but that's in the ballpark, memory is great until you lose it!!

That should be plenty enough to beat "most" housewives in their Mustangs!!

Key here is a stock looking daily driver, or as the old school guys say, "sleeper"!!



Anything north of the numbers above, you'll want to go a different route!!

 

I just want to avoid buying an intake twice if I decide to go a little more wild with it, which I inevitably will.

 

Hello Nicelysedated!!

IIRC, you can by a "bigger" TPI intake manifold, and still use the old TPI parts, of course you'll only gain the benefits of the bigger TPI manifold once you upgrade the other parts!!

This is of course if you want to maintain the TPI look!!

the internet for more info on the parts!!

Is NOS out of the question?

How about a rear gear change?

 

Yes, spraying is out of the question. Illegal on a street car and not the kind of stuff you want to carry around on the daily.

I will be upgrading the heads and cam. The Manifold I go with will go a long way in determining the heads and cam I go with.

I am wondering what the dome volume is on the stock pistons. CR seems low for a 64cc head. I wonder if the TPI would take 11.5:1 CR you would get for going to a flat top piston.

 

HELL YES ITS WORTH KEEPING! lol there very easy to mod, easy to work on, parts are by the dozens if you need them, bolt ons require little to no computer tuning (depending)

there all around great systems to keep, but if you do switch to something else, dont sell your TPI setup unless you have to, who knows, you might what to go back to it sometime

 

The beauty of TPI is not in the sheer horsepower output, but in the ridiculous torque numbers. Your car's rated at 345ftlb bone stock...that's more than the LT1 OR LS1 was rated from the factory, with the same displacement and OLDER head technology. And initial acceleration (read as: embarrassing Mustangs from stoplight to stoplight) is all about torque. In a street car you don't spend much time at 5000+rpm anyway.

So. My personal opinion is that you should definitely keep the TPI. Tweak it. Tune it. Play with the suspension a little. A cam upgrade can get you a decent boost in power without breaking the bank. And if you're dead set on an intake swap, look into the StealthRam.

 

I have decided to keep it. I just bought a set of Phase II Bowtie heads (not the best, but I picked them up for really cheap) that will flow better then stock.

Exhaust is done, heads are set, now just need an Intake,cam, pushrods, and rockers to finish it up.

 

Stock TPI is great from stop light to stop light, but from a roll on the highway it's useless....

 

Port the stock plenum and get larger runners. The stock throttle body flows roughly 660-cfm, and with an airfoil it jumps to over 700-cfm. See where your BLM's are, and if you need more air to get where you want to go, then get a larger throttle body....

 

You can defiantly tell when it stops breathing. I am hoping with heads,cam, exhaust, and a new intake it does better on the highwa

 

Oh absolutely, after 4000-RPM it definitely falls alseep. Take a look at what I did to mine to wake things up a bit....;

https://www.thirdgen.org/forums/powe...ond-305-a.html

 

Lol. You have a deeper wallet then me my friend. I have the go fast fever again. I stopped buying sports cars when the family came along. This here 91 z28 came along and I couldn't pass it up.

 

Are you kidding??? That nine second T76 305 project is on the cheap, and I'm doing all of the work myself. Porting, installing, welding, wiring, tuning, everything....

 

Well looks like I need to do some more reading! Inexpensive is good if you can get quality. Walking around on I-64 is dangerous....

 

Actually, we now have a number of TPI cars with between 350-420 RWHP, all with different versions of modified intakes. We do a lot of experimentation, and have seen good results from a well-ported baseplate and siamesing aftermarket runners with a stock plenum. There are a number of different designs and variations, but the key is really the baseplate, the OEM baseplate is horrible and the aftermarket units (apart from FAST) are not much of an improvement, and in some cases are worse. The FAST system is not perfect, but seems to have more potential than anything else both out of the box and after modifications, the HSR is also decent, but needs a lot of porting to get it to run up top, and it seems to trade off torque.

Before you make any decisions, read this thread "Quest for a better flowing TPI" (2nd from the bottom in the stickies area):

Good luck
TA

 

I work up in Hampton and I'm putting a HSR on my '90 IROC w/L98 this weekend. I have a new TPIS Big Mouth intake, polished SLP runners and a completly ported and polished plenum that I was going install on mine but I decided to do with the HSR instead. If you are interested or if you have any questions PM. I would keep the factory TPI parts if you want to go back to stock and what ever you decide put some 3.73s in the rear.

 

If you can do your own porting, Buy a used Base and runners. Port the hell out of the base all the way through. Do a major port job on the heads, port or Extruded Hone the runners as far as it can go(1.70sq in), any cam with a 224-228 duration LSA113-114.
This combo will get you into the 380's-400whp and 390's-415wtq. Keep the stock gears for FWY crusing. The TPI will make plenty of torque to move the car.