Hey all heres my car:
305 CID
rebuilt TH700 Tranny (at least thats what I was told)
Stock TBI setup with K&N intake.
Stock everything else.
Fakey 2.5 Inch dual exhaust (I call it fakey cause its one pipe till the muffler)

If I decide to pull the TBI setup, and go for carb, and a new cam, what should I see outta this thing as far as HP goes? It has 170 HP stock as far as everyone here says (LO3 engine)

Also what CAM would be good for this setup?

thanks!

 

The single pipe exhaust is basically the same as everybody else's 3rd gen exhaust. The only thing that varied was the pipe diameter. A system that is made for '86-'90 TPI single-cat application, from headers to tail pipe, will fix that up.

Changing to carb in itself will not produce a HP increase. Changing the cam will be of limited effect because of a different problem: TBI engines got what are called "swirl port" heads, which are made for low RPM efficency, not power. They do a good job at what they were intended, but are poor choices for performance.

If you did these things: Exhaust, heads, cam (computer-compatible), larger TB - in that order of priority - you will see a significant HP increase. Changing to carb will be a step backward in technology, fuel econonomy, and emissions, and may not yield any HP increase whatsoever. You'll have to rig up a way for the torque converter clutch to lock up. There are plenty who will say "Switch to carb, ditch that TBI crap." But, there's no free lunch, so consider carefully your path before you find you've spent a lot of money (which you can't recover) and wish you'd stayed where you were.

 

I get sooo many mixed answers on that thouht of carb vs TBI.......any websites I can visit to see some info on this?

thanks!

 

You'll notice there is a TBI forum and a carb forum on this board. The TBI guys are at a disadvantage due to lack of significant aftermarket support. The factory used a TBI variant for their "hot" engine for '82 & '83 F-bodies, as well as in Vettes. So, it isn't a totally worthless system, just under-utilized and under-understood. To boot, the factory just didn't give TBI cars the performance "supporting cast" (heads, exhaust, cam) that are needed to get decent performance out of that system.

The guys that hang around this carb forum tend towards the old-school non-computer carb camp. A few CC advocates (like me) hang here as well. I'm one of the few that preaches caution before switching from FI to carb.

The tech forum tends to be the referee area, where fewer biases live. Note I said "tends", as "opinion" still tends to reign rather than objective facts.

Most of what I was trying to communicate is that TBI engines suffer from non-performance heads (and terrible exhaust), so address those areas (with TPI parts, either factory or aftermarket) before you make the FI/carb decision.

 

interesting.....so the heads/exhaust can make that huge of a difference huh? wow that interests me....I need more info, are there websites that explain this stuff in some detail as to what all of this does? I really need to know as I have ALOT of time to check things out before I make a decision!!!

thanks!

 

The message is, "It's the package." Everything has to work well together to produce the desired results. The desired results have to be understood to limit or perhaps even eliminate other characteristics (performance vs. economy, top speed vs. off-the-line acceleration, etc.).

The "package" as delivered from the factory produces good driveability and fuel economy, along with low exhaust emissions. 1/4 mile performance is so-so at best. If you want better performance, the exhaust has to be the first thing to change. The cam is next, but with the factory TBI heads, the effectiveness of the cam and exhaust will be severely limited. If you improve all of those things, the throttle body and injectors will become a bottle neck. If you have a cam that revs to 6000 RPM, the engine won't have any low-end grunt, so you'll need a torque converter that allows the engine to rev a little higher before it starts to move the car (higher stall speed, they call it). The factory 2.73:1 ratio rear end gears are fine for fuel economy, but will really hold back a high reving performance engine off-the-line. You can also go overboard, such as putting heads intended for a big displacement, high reving engine on a 305. If the primary use of the car will be drag racing, TBI probably isn't the best choice (carb probably would be in that case), but keeping the 305 wouldn't make much sense, either. Etc., etc., etc.

Spend some time on this board, amoung the various forums (including this one). Listen to what guys are doing, the problems and results they have. Figure out what you want and what you're willing to give up (I gave up about 2 mpg with my mods, but gained a bunch of performance and fun).

 

well im looking to get a decent amount of HP out of this engine. Its a V8 and it absolutely kills me that my V8 has less power (HP) then my friends turbo'd 4 cylinder eclipse. I can't stand the fact that this V8 has only 170HP when its a 305. In my mind it should have AT LEAST 250 or so HP. So I just wanna get it up to a reasonable amount.

thanks!!!