I have a 94 5.7 TBI that I am thinking about changing over to a 355 TPI? Is this a smart decison or not? LMK what you guys suggest. Thanks in advance..

 

TPI will give you a boost in mid-range torque over TBI.
It will also limit you to about 4500 RPM, regardless of cam choice.

There's a lot of factors involved, such as supporting mods, do you have the ability to datalog/burn chips, etc etc.

 

OK... Well if you wanna know the truth, the motor I am building is going into a truck. I am going to be using the truck to pull with, I would like around 350-400+ HP. This is juts the only site that I found that talked about these motors.. So any advice for torque would help... Thanks... Dont hate us truck boys!!!

 

Davis
Stay with TBI. TPI is great for mid range power. The key for truck engines is a low end torque (overall torque as well). You do not need as much high RPM HP as you may think to get the job done. After all HP = (rpm x Trq)/5252

Cam selection - hydraulic roller camshaft, high speed intake flow port cylinder heads, and free flowing exhaust are the key to making torque and power. Standard truck engines came with punny cams - less than 0.400” lift and 172/180 at 0.050"!

TPI has eight injectors which require 45 PSI fuel pressure. You'll need new fuel pump. ECM will require a custom tune to reach your goal (in both cases BTW).

//RF

 

You're in the wrong forum for this question. Ask anyone who has done the swap and they have not regretted it. A truck engine would LOVE to have TPI's torque for acceleration and pulling power. A truck engine doesnt care if it goes over 4500 rpms or not, and TPI isnt limited to that anyway.

 

Agreed. If I would have known it was for a truck application, I would have said go for it.

On a side note, I should have said that the STOCK TPI is limited to about 4500 rpm.

 

TPI or TBI question has been (and will be) kicked around for a long time. In the end it all comes down to $$$.

Now I need to find a ride that I can stick a TPI system onto - 73 vette perhaps???

//RF

 

Actually you are wrong there, I have dyno'd before and after on 2 seperate engines, TBI to TPI. The TPI setup has LOST low-end torque in BOTH instances. TPI pulls more solidly through the mid-range and wheezes out up top. When you increase the diameter of the runners or decrease the length, you lose some of the "tuned" effect that boosts the mid-range torque and trade it for more top-end HP.

 

And you know I have dynoed an engine from TBI to TPI too, and it gained 70 peak TQ at the rear wheels, and it was up on torque across the power band from idle to 4500 (stock TBI camshaft and heads).

I have also added larger runners to a TPI engine, and it gained tq and hp across the board. Mostly torque, with a maximum of 10 at peak and 4 peak horsepower.

Much like "global warming" everyone has a study that proves their point and discredits the others.