2-5mpg how can i get better??
 

i have a 1967 283 with 327 camel back heads and a 350 cam, i have put the TBI unit on to this engine and put the engine in to my 1989 silverado C1500 4x4 automatic tranny with overdrive, and im still getting 2-5 mpg i have tried alot of things to get better, today i changed the fuel filter havnt really drove it since i did so i dont know if that was what was wrong but is it possable to go from 15-20mpg to 2-5 because of a fuel fillter being dirty??? or should i put a smaller cam in to this engine i was thinking a 305 cam instead of the 350 cam... any advise i thank you now for it.. when i had my 305 in my truck i was getting 15-20 i stuck this engine in and i get 2-5..

Theres something wrong with the TBI. It shouldn't be able to burn that much fuel under normal conditions without running seriously rich and dumping gas unburned.

Holy crap

well, i looked at the post title, was tempted to say something smart, then read the problem, and left this thread in fear of it being contagious...

then i came back as i have a question to ask

exactly how much compression do you have left in cylinders?

otherwise, i can direct you to the site where there is a ton of ideas for carburated engines.

my engine has about 2500miles on it and its got around 150 compresion... when i had the carb on this engine i was getting about 5-10 mpg and then i stuck the !!!! 350 !!!!! tbi on to my !!!! 283!!!!! of course im drumping to much gas i smell it all the time i know its burning rich it blows black smoke out when it loads up... i either need a smaller cam or a smaller TBI unit.......

Ok is it throwing codes? Are you sure timing is correct? YOu unplugged bypass when you changed it? You might need to let the computer adjust it just went through a huge change!!!

incomplete combustion, aye? timing???? camshaft??? rockers?? valves?? distributor?? which i am leaning towards timing badly.

of course, running that rich, your plugs are constantly drenched in gas, so spark ain't worth a dime. but i'd definitely look into timing 1st. if timing is right, and valves are timed correctly, and you have good spark - so what that you run rich? be just a bigger BANG!!

is air supply adequate? as if you have much C(carbon as in gas) and not enough O, as in oxygen, not much combustion will be there....

just an idea.. you want to try to feed propane into the air stream and see what happens? mind you, i did not say get one of them green bottles, he-he.

i unpluged the bypass wire timed it to 3 degrees cause its a 1967 motor whitch my computer takes and adds to my 3 degrees whitchs makes it run at about 25-30 degrees.... i changed my TBI to a smaller one and it works fine now nothing wrong at all so it was because i was getting TO MUCH GAS.....

The computer in an 89 needs to be set at 0 degrees no matter what set up it is the computer expects it to be at 0 degrees! Now While the truck is off unplug the bypass it is underneith the glovebox you have to do this!!!! Now start your truck timing should be at 0 degrees when it is tighten it double check timing to make sure that when you tightened it you didnt move it. Now shut your truck off and unplug your battery and touch the positive cable to the negative to get rid of all electrical currents existing. Plug the Tan bypass wire back in and plug your battery back in. Is there any codes at all?

Oh sorry you must have been posting at the same time I was Glad you fixed it man!!