3rdgengal

I'm looking into buying a 82 Z28 that of course is carbed, my friend (who knows a lot about 3rd gens) says not to get a carb. So my first question is what's the difference? Second how hard is switching a carb to TPI and third how much is it going to run me? Thanks, I'm new at all this and though some think ignorance is bliss... I think I sound just plain stupid

ULTM8Z

Not to worry... there's a wealth of knowlege on this sight. Besides, we'd rather see people in Camaros instead of Hondas!

Your friend is absolutely right about the TPI being better than a carburetor. Here's why:

TPI sytems (or any port fuel injection set-ups) use high pressure fuel injectors that are located right above the cylinder heads and are pointed right at the back of the intake valves. When the valve opens, it fires a highly atomized fuel burst right into the cylinder. This has a nice advantage- the fuel does not have to travel down the intake runner with the air. They call this a dry-manifold system.

On carbureted systems, the fuel has to travel down the runner where it can sometimes form droplets and fall out of the air stream, or stick to the runner walls. When that happens, you basically lose the horsepower that fuel could have delivered to you. This is why carb manifolds are referred to as wet-manifold systems. TBI (Throttle Body Injection) setups are similar to carburetors in that they are wet manifold systems, but they are computer controlled and have high pressure injectors too, which makes them a little better, but not a whole lot.

Since port fuel injection manifolds are dry, it gives the engineers greater flexibility in manifold design. Take a look at a TPI manifold. There's no way whatsoever that you could run a carb with a manifold like that. The fuel would never make it down the runners to get to the cylinders. Also, the plenum is way too big to provide enough of a vacuum signal to a carb to even meter the fuel in the first place! But since TPI manifolds depend on the injectors to deliver the fuel, the GM engineers took full advantage of the torque-building capability of long runners. And therein lies port fuel injection's single biggest advantage- the ability to create wild manifolds like that, which can create engines with tree stump-pulling torque like the TPI's.

Lastly, with electronic fuel injection, the tuning is infinitely more precise. When you really start getting good at working on TPI's, you can start going into the vehicle computer and playing around with the calibration. For instance, when you want to retune a carb for a particualr point in the RPM band, you'd probably change the jets to a different size. Well, now you've changed the calibration all over the place. With fuel injection, it's like having self adjusting jets. You can change the fuel delivery at any particular RPM and load without affecting the engine anywhere else. The same goes for ignition timing.

The drawback is, of course, the cost and effort of installing it. It took me about $1000 to install a stock system and the effort was enormous- several 12 hour-a-day weeknds. You have the advantage of starting with a vehicle that was designed for TPI, so all of the components are a direct swap. Since I started with a 1971 Camaro (where TPI was never offered, or heard of!), the majority of the installation was custom fit.

87350IROC

iTrader: (2)

Also, if that engine is stock its only 145hp and 240lb ft torque. Whereas a stock TPI is at least 190 hp, i think, and thats of course with different stock heads and cam.

ULTM8Z

Unless you're talking rear-wheel horsepower, I believe the numbers were more like 245 hp and 340 ft-lbs of torque on the 350 TPI's. 305 TPI's had slightly less. The 305 TBI's had about 190hp. Maybe that's what you were thinking about..?

I'm not sure what the numbers are on the 82, but it's pretty anemic to say the least. Could definitely use a heart transplant... get a nice well-built small block in there and look out!

formularpm

That would be nice, but TPI is a batch fire as opposed to a sequential style system like the LT1. Instead of firing when the valve opens like it should, it fires one entire bank at a time, so the mixture just sits there til the valve opens. Pretty stupid, really, but still better than a wet manifold system like a carb or TBI.

87350IROC

iTrader: (2)

Here are the facts:
The most powerful TBI: 170hp 255lb ft in 92'

We were talking about swapping in a TPI setup on that 82', therefor we are talking about a 305, so foget the 350 facts, which btw range from 225hp and 330 lb ft in 87' to 245hp and 345lb ft in 92'.

The least powerful 305 TPI was in 86', producing 190hp and 285 lb ft. The most powerful in 92' producing 230hp and 285 lb ft. These facts are straight from the book and can also be found on this site in tech data.

The TPI setup for 305s and 350s are the same. Hp numbers rose of the years due to the change from MAF to SD and new cams, and heads. So for a solid performer I would go with a TPI setup with maybe a ZZ4 cam and ported stock heads, if you're on a budget. Also porting the stock intake manifold will help a lot. But i'm no cam/head expert so maybe the experts will chime in.

Also look into a holly stealth ram, Accell superram, or miniram, which i believe are also made by Accell.

JP

Guest

How much would it cost? Probably more than its worth. Go check out the carb board for other side of the fence responses.