I have a 91 D150 with 166k miles on a completely stock 318. I'd like to go with a performance rebuild on the 318 and my target is 300hp or so. Assuming this would be out of the question with the stock TBI and intake manifold(?), would anyone recommend converting to a carbureted setup? If so, how involved is it and how would it affect my emissions system?
Thanks for any input.
mills9

 

It won't be emissions legal. You could get it to pass the sniffer test, but visual inspection would flag it as a modified emissions system. You can convert it to a newer engine, but back-dating isn't allowed.

Having said that, it's way easier to tune if you go with a carb setup. My buddy's truck we just dyno tuned and it put down 185hp and 250 lb-ft at the tires. Not bad for a little .030 over 318 - stock 2bbl heads with a edelbrock performer intake manifold, 600 cfm carb (or was it 650?) 14x3" filter, and a comp 220 cam iirc. Stock compression too. If you stroke it or bump the CR up you could get more. The cam he used is also targeted more at low end grunt instead of high horsepower. heads would make a huge difference.

 

Thanks for the feedback, Horatio!
Visual inspection isn't a concern here, and if it'll pass the sniffer test, I'll be a world ahead of where I am now! I installed a new 02 sensor, EGR valve, rebuilt the throttle body, removed, blasted/cleaned the intake manifold and replaced with all new gaskets. New distributor, coil, spark plugs and wires, fuel filter, air filter, etc. Didn't check the MAP sensor, though. Could that be the problem? It starts great, but runs rough and just won't pass emissions. So, rather than push it off a cliff, I figured I should rebuild the engine and chalk it up to a learning experience!

 

Cat concerter? It could be old and clogged up.

 

I would not suggest cobverting to a carb, you are gonna loose economy big time.

 

Not totally true - you can tune for economy, power, passing emissions, etc. The major drawback is cold weather starting - gotta let it warm up especially if you've got an auto.

 

Fuel injecton is more efficent than TBI, which is more efficient than carbs. They atomize the fuel better.

 

Oh yeah, I forgot about the brand new cat and new timing chain, gears, and cam thrust plate.
As far as fuel injection vs. carburetion efficiency, I'm not nearly as concerned with it as I am in getting more power and utility from the vehicle. Right now I estimate I'm getting somewhere between 6 and 8mpg and it drags like I'm pulling a house behind it - it's terrible to drive!
What would be involved in converting to EFI? New ECM, intake, fuel pump?

 

To remain legal you could yank the engine, emissions control crap, electronics, and whatever else needed from a newer pickup and stuff it in there. If you're doing that, you might as well go for a 360 while you're at it

 

Yeah you are basicly gonna have to do it as a package deal.