whats so bad about the tpi?

[jag7819]

I have heard so much about the tpi on my car just being worthless. Its an 87 formula 350. What can i do to make it not worthless and what is the problem with them anyways?

[kman87iroc]

IM no expert here but from what i hear they dont breath well at high RPM. if you have ever raced it at all it hits a brick wall around 4700 RPM. you can port out the runners and base i believe,

[Fred Jones]

I have heard it called the best truck motor GM ever built. The "problem" with them is they are all low end grunt. It's a seat of the pants power rather than top end. Great for the street & auto crossing. Sucks for track and 1/4 mile stuff. The "problem" is how you look at it.

[JBPNumber3]

To make your TPI motor I did a few mods and have a 13.8 second car. I've got an adjustable fuel pressure regulator(55.00), a K& N Filter(30.00), Chopped my airbox(Free), Catback Dynomax exhaust(150.00), New 22lb/hr fuel injectors(160.00), Custom burned chip(200.00), MSD Blaster coil(40.00), 3.73 Axle Gears(140.00 and best mod I made), and a B$M Street/Strip Shift Kit(40.00) and thats it. Stock Cam, stock heads, stock intake. So I don't really see a problem with the TPI motors.-Jimmy

[Jaysz28]

TPI uses a long runner design that develops torque down low in the rpm range. The down side is that it stops making power around 5k or so. It just doesn't allow enough air in.

I think you are talking about TBI, which does suck and you can't do much with. GM used it in just about everything because its great for gas mileage.

[jag7819]

so putting 58mm runners and throttle body on it would solve the airflow problem or would it still not get enough?

[Fred Jones]

Getting air in & out is the key. If one end is blocked openning up the other end won't do squat.

A valve body would be my last purchase. I would do exhaust, runners, cam chip & injectors then valve body.

[Corey]

By that time you would need a new lower intake too.

Check out www.tpis.com

:cool:

[jag7819]

thanks for the help...i have a chip ive done exhuast and i was going to get a throttle body runners and probably a new base plate....i have a cam on the way so thats also out of the way so what else whould be a good idea?

[Jaysz28]

58mm Throttle Body is overkill on a relatively stock 350. Go with a 52mm. It will match your combo better. As you will find on TPIS.com, the 58mm TB causes too much air tuberulence and actually killing your low end power, and not gaining enough up higher in the rpm range. The 58mm was designed for 383's or larger displacement motors.

Bigger injectors, fuel rail, etc won't make much of a difference if you dont' have the mods to support it. i.e. cam, heads, headers. etc

[jag7819]

i will eventually build up a 383 i just planned on gettin my tpi set up right first...(also lest costly)...so will it actually suffer that bad with the 58mm runners & throttle body...it would be about 4 months before i build to a 383...so what would yall do?

[Corey]

I would probably just stick with the 52mm. It should still be ok on the 383 and I would imagine be a little better on street manners, but I would ask someone who has used them both. You should also port the plenum, you can do it yourself or TPIS will do it for like 80 bucks if you send them yours.

[jag7819]

what size are the original runners and tb...ive heard 48mm but is it?

[Revis_Racing]

Keyphrase is resonant pressure wave. That is what the long runner produces. I forces in the air charge at lower rpm, but on the higher rpm range it hasn't the flow to keep up.
I had my car on the dyno with 52mm TB(good mod you can tell difference), SLP runners, edlebrock base, flowmaster, 3.73, k&n's and TES Headers. I ran the car up on the machine and at 5400rpm the car could not rev any higher. I mean I held the throttle wide open at 5400rpm for 8 seconds! It still would not rev over 5400rpm, the TPI just killed it.
With just bolt ons i'm making 225.7rwhp/325.4lbft at 87 degrees.

PS- Anyone have a copy of dyno sheets for a tpi vs superram on the same engine?

[XLR8TORZ28]

TPI is a hard motor to build. You have to get a cam made to work with the TPI because of its long runner length. Never get in a rush to put parts on that you are not ready for yet, you will get discouraged. Take your time and get everything together then build your motor. Do all of your free mods. The dual filter setup has shitty air boxes, take them out and cut the bottoms out of them around the slotted area. Bypass your throttle-body coolant lines. advance your timing 2 degrees. Make sure your O2 sensor isnt too worn out (makes a big difference). And the 58mm TB your talking about is 1000 cfm. Unless you are planning on making over 600 hp, dont use it, the 52mm TB is rated around 790cfm. If you are going to use the stock plenum, you need to take it off and grind (port the opening to match the gasket, take out the middle portion, and grind down the humps that sit behind the openings, porting (or gasket matching) the plenum to runner opening is not a bad idea either. Never forget your routine maintenance like spark plugs, cap & rotor, regular oil changes ( preferably synthetic ), tire air pressure ( yes it matters ) it is harder for your car to push low tires, air filter ( preferably K&N or equivalent), proper cooling, everything matters. I have run my car to 6000 RPM and havent had any problems. You might want to start upgrading things that you can utilize without having to have motor mods yet, like upgrading your ignition system ( add an MSD Blaster coil), better spark plug wires. Hope I helped .......

[JBPNumber3]

ADJUSTABLE FUEL PRESSURE REGULATOR!!!

[XLR8TORZ28]

true true true ..... very important