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Old 03-26-2006, 10:46 PM
airraptor airraptor is offline
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backfire thru carb

i have a new 383 built by T&L engines in NC.

it has dart heads 180cc runners, air gap, roller cam, roler rockers, small cam pertronic's flame thrower with ignitor II, blaster coil, headers of 1 1/2 or 1 5/8, two cats and mufflers all in 2.5" tubing. the truck is an 84 chevy k-10 with 33" tires new rebuilt 700r4 and stock gearing for now i think 340's. the carb is a road demon of 725 size with electric choke.

i have a holley electric fuel pump regulator set at 6.75lbs at carbs, and two filters one before pump and one after.

the pump line to carb goes regulator. then one side of regulator goes to carb and one goes back to tank thru original fuel lines (small one)

its rich at idle ( i can smell it ) gets about 7 mpg. doing a slow increase of engine rpm (100 rpm a sec) the engine will pick up 300 rpm very quickly at 1600 rpm. it does this in park or while driving. most of the backfire thru carb occur prior to it reacing 1600 rpm. i did have backfire thru carb at wot after this rpm point of 1600 but the holley fuel pump fixed that problem.

now now while driving before i hit the 1600 rpm point it acts lean when give a small quick throttle movement, kinda like its not getting a big enough shot.
if i stab it it pops and drops to about 200rpm then comes back to idle of 800 if i let off the throttle once it pops.

the bowls are showing right in the middle, no fuel out of the boosters that i can see or feel.

this engine was dyno broke in and tuned with this carb or so they say. i do know the engine was ran because of the soot on the exhaust ports and the residual oil in oil pan.

it came with auto light 3922's and i have when hotter with the 24's. they seemed to help a bit but not much.

the most vaccume i can get is around 12 indicated. i have the line in the back of the carb going to brakes and and the untimed one going to the a/c / heater controls.

my question is why the rpm change from 1600 to 1900 very quickly?

what to do about the backfire thru carb?

i have been talking to loyd at T&L and he is sending me some larger squirters but i really dont think thats the proble but could be.

also one other problem is that that with the choke on it just pours out black smoke. i now have it fixed in the full open position till i get the other problems fixed.

thanks for all the help in advance
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