100% newb to the carb scene

[Shawn5800]

Hey guys,

New to the site and new to the carb type vehicles. I have always heard nightmares about them but im hoping i can "set it and forget it."

The truck i just purchased had a 400 SB swapped into it by a shop with an Edelbrock 1406 carb set up and its supposedly cammed, that im not sure of. It ran great driving it home about 25 miles, and ran great the first day i drove it. I stopped at the gas station before a car show and put 87 octane into it (thats what the PO said he has used since he had the truck).

I dont know its related but since that time the truck has been "surging?" forward at stop lights and stalling or sounds like its starving for fuel but sometimes will stall and sometimes teeter on the edge but never die. If i keep light throttle it will stay running. Funny thing is it seems fine at WOT and never runs rough under normal speeds. It does NOT do it when its cold started but within about a mile of warm up it will start. Did i get a bad batch of gas or did i make a mistake using 87 octane?

Also, the PO told me that in order to start this truck you must hold the pedal to the floor for a second to engage choke, is that flooding it to much? Sorry for the newb questions but im really trying to figure this out without taking it to the shop. Any who feels like enlightening me on this carb setup and what 4 barrel means would be awesome!

Also, does anyone know where the hell the oil dipstick should be located on this engine? I literally cannot find one.

Thanks all!

[bigmac73]

okay if it started after you put gas in the truck, I would start there, maybe got some water or trashy gas, I know it might sound basic, but process of elimination

[Shawn5800]

Hi Bigmac,

Thanks for the response. I should have mentioned that this issue came about at the same time as I am having issues with my transmission not shifting into 3rd. It will go into drive, shift into second fast then the rpm a keep shooting up because it never gets into third. I have to pull over, put in reverse and park then it will work again.

From what I was just reading, the vacuum modulator or governor could have a bad diaphragm that's leaking tranny fluid into the carb and maybe causing bad shifts?

Sound reasonable?

[morethanstock66]

Carbs control the Air/Fuel ratio and also control engine speed. Don't worry about transmission fluid leaking into the carb, if the carb is connected to the trans it will be via a vacuum line, not a fluid line. If you are having difficulty shifting or surging, it will be to do with your transmission. It sounds like a valve body issue to me as the valve body is the "brain" and controls when and if you shift gears... Just my $0.02

[BigDan3131]

Did you check the fluid level of the trans hot? The dipstick should be on the driver side down low unless the original owner changed the oil and didn't put it back in.

[Shawn5800]

I checked the fluid hot and it is right where it should be, it also looks fairly fresh and doesn't smell burnt. I also just traced the vacuum line off the tranny modulator and the line seems to be crack free, although there are a few places where they transitioned from hard pipe to rubber tubing with no hose clamps.

I read that if that diaphragm is leaking by it could pull ligt fluid into the beginning of the line via vacuum tune connected to carb. True?

The truck does surge forward like it's trying to move but it could just be it's so close to dying of fuel then gaining fuel again which is why it feels like it's hopping.

Any more ideas?

Thanks again guys.

[Dead Parrot]

If not bad gas, could be some additive in the new gas reacted poorly with residue left by the old gas. Was it ethanol gas or real gas?

Might pull the vacuum line from the metal line to the transmission that goes to the manifold vacuum port and inspect for fluid. If it is dry there, probably not sucking fluid.

One thing I have found useful to do on my 1405 Edelbrock is to occasionally clean the power pistons in the carb. With the engine cold, pull the air cleaner. On top of the carb are two small hex head screws holding down two small metal plates. One on each side. Loosen but don't remove the screws. The plates should lift up. Pivot them out of the way. Under each is a small piston and needle. Lift each out and spray both piston and cylinder with carb cleaner. DON'T lose the small springs. Use lots of cleaner. Spray, let set and spray some more. Wipe off the piston. Reassemble.

While you are at it, check ALL of your vacuum lines.

[cadillac_al]

A vacuum leak will make an engine die down when putting it in drive. With good vacuum the engine won't die down when you put it in drive. It sure sounds like a vacuum leak to me; either at the trans or anywhere else.