454 TBI intake manifold... Even flow

[journeyman]

[journeyman]

After talking to a few people and having another conversation with Klein's engines in AZ, I have determined that the machining on the intake manifold is probably going to give minimal/marginal improvements at best.

It seems the wisest/ most straight forward course of action is what was said here (getting the injectors cleaned and matched) as well as adjusting the fuel table and the ign. advance curve on the chip.

[SMOKEmUP]

I'm sure it's possible. However "your mileage may vary" quote comes to mind here.

[Big Dave]

I'd be inclined to believe him. I have never met a TBI that worked worth a flip (big block or small block version). In every case I got more power and better mileage with a carb; even while leaving the dismal TBI cam in place (which is equally useless). I have no idea what GM had in mind other than getting a dirty big block Chevy engine to pass Cali emission testing, so they could sell units to the rest of the country.

Big Dave

[journeyman]

Big Dave,
What is it, specifically, that you don't like about TBI?

Granted, having a sequential injection system with an injector at each port would be ideal, but it seems like short of that, the TBI is a reasonable option, especially comparing it to a carburetor. To my untrained eye, it seems like the TBI is just a 'smart' carburetor. With no secondaries

[Big Dave]

TBI is limited to what is in the computer air fuel map. If you encounter something it isn't ready to deal with (like climbing a mountain in Colorado where atmospheric density changes) the MAP sensor sends the wrong info and the oxygen sensor over corrects which causes a lean hot motor that won't get you over the hill. A carb on the same motor flys up the hill no issues.

High humidity causes the electronics to roll over and die (Florida is subtropical) we have what we call a wet heat here eight months out of the year. I have replaced a number of sensors that are not used on a carbureted engine.

Get any kind of vacuum leak (such as occurs with wear or thermal expansion when your truck over heats climbing a hill) and you no longer have a running vehicle. A carb just idles faster and dies off when asked to idle down. No mater what you do to a carb it always in limp home mode. Ask the same of a TBI and it will leave you on the side of the road waiting on a wrecker.

Finally I can get much better performance out of a carb and cam change than I can with raising the TBI height and filing on the venturi of the injector body to improve air flow (change the cam and it won't even crank up) or swapping out the intake manifold for an Edelbrock TBI version with a larger plenum chamber. Just sticking on shorty factory part headers off of a motor home caused my TBI to protest with a drop in mileage of 1.5 miles per gallon.

It is very unforgiving to any changes it encounters. I can say this because I have put 150,000 miles on a 454 TBI, and another 150,000 miles on a 350 TBI both in the same truck driving from the Arctic Circle to the Tropic of Cancer from the Atlantic to the Pacific visiting every state in the union (and all of the Northern "states" of Canada) except Hawaii (I'm still waiting on the US Senate to extend the bridge to no where all the way south to the big islands). I love my LS-3 with EFI port injection but I won't play with a TBI (if I was forced to accept EFI due to annual inspections I would install an aftermarket port injected FAST system in place of it).

[10sec.et]

[rleprechaun]

You need to look at cfm thechologies website at marine-performance-parts.com ... When you get through with there suggestions go to a Holley 670 cfm throttle body and an Edelbrock 3764 intake

[af2]

This isn't St Patty's day is it?

[journeyman]

[rleprechaun]

Ok, after doing cfm technologies suggestions, to to the Edelbrock intake. Grind the name off. Then paint with metallic gray paint. If you use the right paint a magnet will stick to it. Nobody will ever know.