Fuel Delivery Problem
09-24-2006, 03:05 PM
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Fuel Delivery Problem Just can't figure it out... Got a '79 Firebird with a 350 sbc that runs too rich and chokes out at very low RPMs, but on take-off will jerk your head back. You gotta ease into it, otherwise it will stick, and when the tranny downshifts, it chokes... 
Carb just been rebuilt, but vacuum advance don't have a very strong suction.
Here's my set-up:
'86 Chevy Blazer block 4 bolt main 350, factory bore/stroke
Factory botom end
1 5/8" headers (full tubes)
'76 model Chevy 250 heads milled slightly, 2.00/1.6 valves
stock length pushrods
1.6 ratio full roller rockers
factory springs
Edelbrock preformer RPM intake
Edelbrock 1405 Carb (600 cfm- manual choke- not hooked up, but present)
Stock (new) fuel pump- mechanical
stock distributor
Accel 8mm wires
Standard Resistor Autolite plugs (#26)
Stock HEI coil/brass terminal cap
stock TH350, no stall, open 10 bolt 2.73 rear end
So far, here are my and other peoples' theories:
1) Vacuum advance is not functional- I have no history on that distributor
2) Coil not putting out enough current
3) Rockers could be out of adjustment
4) Pushrods are too long
5) Stock fuel pump is too low-volume
6) Vacuum leak in the main line
7) Can't run pump gas for my higher compression
8) Crane PowerMax cam- sort of mild (212/218 degrees)
9) Choke stays open since it's not functional
This hapened after I put in a cam kit and a set of heads. After that, I let someone adjust the rockers and the carb (after it was rebuilt- I bought it used- never again). It fixed the problem to an extent, but not completely (not even close). When you stand behind the car, you can tell it runs too rich because of the strong smell of gas, but if you set the timing down anymore, it will hardly run. When the car lopes with the lights on, occasionally they dim on the lopes, so the timing is retarded as is. I am frusturated, so if anyone can give me some pointers, that would be great. Thanks in advance.
Carb just been rebuilt, but vacuum advance don't have a very strong suction.Here's my set-up:
'86 Chevy Blazer block 4 bolt main 350, factory bore/stroke
Factory botom end
1 5/8" headers (full tubes)
'76 model Chevy 250 heads milled slightly, 2.00/1.6 valves
stock length pushrods
1.6 ratio full roller rockers
factory springs
Edelbrock preformer RPM intake
Edelbrock 1405 Carb (600 cfm- manual choke- not hooked up, but present)
Stock (new) fuel pump- mechanical
stock distributor
Accel 8mm wires
Standard Resistor Autolite plugs (#26)
Stock HEI coil/brass terminal cap
stock TH350, no stall, open 10 bolt 2.73 rear end
So far, here are my and other peoples' theories:
1) Vacuum advance is not functional- I have no history on that distributor
2) Coil not putting out enough current
3) Rockers could be out of adjustment
4) Pushrods are too long
5) Stock fuel pump is too low-volume
6) Vacuum leak in the main line
7) Can't run pump gas for my higher compression
8) Crane PowerMax cam- sort of mild (212/218 degrees)
9) Choke stays open since it's not functional
This hapened after I put in a cam kit and a set of heads. After that, I let someone adjust the rockers and the carb (after it was rebuilt- I bought it used- never again). It fixed the problem to an extent, but not completely (not even close). When you stand behind the car, you can tell it runs too rich because of the strong smell of gas, but if you set the timing down anymore, it will hardly run. When the car lopes with the lights on, occasionally they dim on the lopes, so the timing is retarded as is. I am frusturated, so if anyone can give me some pointers, that would be great. Thanks in advance.
09-24-2006, 05:16 PM
#2
It's the edelbrock carb. You need to go to their website and look at the manual for it.
I have found they do not like more than 5.5 to 6 psi fuel pressure and some stock pumps put out more than that.
Also you need to have a real good filter on it as close to the carb as possible.
You need to check the calibration of the power enrichment pistons, be sure they are not stuck and the springs are not too strong for the vacuum your combination makes.
You also need to check the float levels, and tune the size of the jets and metering rods.
I have found they do not like more than 5.5 to 6 psi fuel pressure and some stock pumps put out more than that.
Also you need to have a real good filter on it as close to the carb as possible.
You need to check the calibration of the power enrichment pistons, be sure they are not stuck and the springs are not too strong for the vacuum your combination makes.
You also need to check the float levels, and tune the size of the jets and metering rods.
10-16-2006, 08:27 PM
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The carb shoots gas through the barrels when the engine chokes out and you let off, but the car also has a '78 model 305 distributor (HEI) with '76 model spark plugs (Autolite 26). '86 model sbc calls for either Autolite 145 or 24... Does that sound more like an ignition or carburation problem?
