stupid carb question/problem

[Graystroke]

first, you don't need lead additive as jimmy pointed out if you have hardened seats. It's to keep the exhaust valves from burning if you didn't have hardened seats. I'm suprised ferd still had unhardened seats in '78..but it is a truck and that was about the time everything was starting to switch over to unleaded.
the mechanical pump is fine. don't listen to these yahoos and start throwing money at it until you figure out the problem.
you said it happens when you top off the tank. check the vent line for blockage. the pump may be oveworked if there is no vent.
also check the lines for cracks or dry rot. may have a split somewhere which would cause your mechanical pump to suck air. if these don't fix it check the pick-up on the tank.

[Moose]

first, you don't need lead additive as jimmy pointed out if you have hardened seats. It's to keep the exhaust valves from burning if you didn't have hardened seats. I'm suprised ferd still had unhardened seats in '78..but it is a truck and that was about the time everything was starting to switch over to unleaded.
the mechanical pump is fine. don't listen to these yahoos and start throwing money at it until you figure out the problem.
you said it happens when you top off the tank. check the vent line for blockage. the pump may be oveworked if there is no vent.
also check the lines for cracks or dry rot. may have a split somewhere which would cause your mechanical pump to suck air. if these don't fix it check the pick-up on the tank.

this sounds more logical. vent lines? you mean the emissions hoses? i took 90% of those off when the EGR was blocked off when the intake was swapped long before i owned it. the only vent lines i can think of would be on the drivetrain. is there one on the tank? i'll check on the pickup. thanks.

[jerryg79]

this sounds more logical. vent lines? you mean the emissions hoses? i took 90% of those off when the EGR was blocked off when the intake was swapped long before i owned it. the only vent lines i can think of would be on the drivetrain. is there one on the tank? i'll check on the pickup. thanks.

there's a vent line on the gas tank, it lets the air out as you fill up the tank, else gas would shoot out as you displaced the air in the empty tank.

But dont listen to us yahoos, I mean fuel pump quite the off the wall suggestion, cause they dont suck at all on those motors

[Moose]

drove it last night to see if maybe it'd go away like it's done before (didn't have much time after work). nope. it did backfire a little on take-offs. and now, i can smell gas... like the choke is sticking?

[agjohn02]

i had venting problems with my tank before i put the pump in it. it never affected the way the engine ran, but it would push fuel out when the tank got warm from sitting in the sun. oh yeah, and jerry's right, it'll shoot fuel at you when you fill up.

the choke idea sounds pretty good to me.

[73bronco]

I dont even have a vent on my tank and no problems and if its carb there should be no return lines.

[Violentv8toy]

sorry to hi-jack, but what happens if you do have a return line for a carb?

i've always had a little bit of fuel problems, and i run a return line. Should i block it off?

[Graystroke]

I meant don't listen to the crap about putting on a electric pump. Also, does you carb have an accelerator pump that can be blown out like Holley's? It only takes one backfire through the carb to blow the diaphram.
I had a sticking choke on a Holley I had on my old '63 Chevy. The choke would hang if it backfired and you had to beat it loose w/ a hammer! It was a manual choke...if this is the case it shouldn't run at all.
it's easy to check the pump...disconnect the line at the carb, add some hose and aim it where you can see it squirt and crank the engine w/ the coil wire removed. it should squirt across the driveway.

[Moose]

alright. i'll check that stuff. it sticks shut. shut means lack of air, too much fuel; therefore the smell of gasoline, right?

[Moose]

don't laugh. summit sells the parts i have, so i emailed them basically the same thing i wrote at the top. this is what brad had to say:

Discussion Thread
---------------------------------------------------------------
Response (Brad) - 05/05/2005 12:45 PM
Two quick things here.
1) You don't need the lead additive since you have hardened seats now.
2) Don't use higher octane than what the engine requires.

That said, I think you answered your own question;

"5) vapor lock; loosen fuel cap (this could be an option since every
time i top the tank off, this happens, and it usually goes away after i
drive it a couple miles. and it's the original gas cap"

Now, let me explain vapor lock. Vapor lock usually happens after a
short stop, or long idle period, and shows up as a sag on acceleration,
which usually stalls the engine. Cold weather doesn't do it. Look for the
following;

*No black smoke from tail pipe.
*No fuel pressure.
*Dry carburetor air horn.
*No accelerator pump discharge.

Now, there is also fuel foaming. This happens after a fillup of fresh
fuel, when cold fuel hits a hot carburetor. It will show as a sag, or a
series of short jerks on acceleration, also stalling the engine.

Look for the following;

*Black smoke out tail pipe
*Normal fuel pressure
*Normal accelerator pump discharge
*Engine starts after a long, wide open throttle crank.

Want more?

Alcohol mixtures and octane boosters effect the volatility of the fuel,
with hard starting, and driveability issues.

How to fix it?
*An electric fuel pump near the tank pressurizes the fuel lines, and
prevents vapor lock. A mechanical pump has a vacuum, which causes the
fuel to more easily turn to vapor.

*Insulate the carb, and fuel lines from heat sources.

*Eliminate any sharp bends or kinks in the fuel supply lines.

*Use a vapor separator filter, and a return back to the tank. (rarely
done)

*PICK YOUR GAS STATION BASED ON EXPERIENCE WITH THEIR PRODUCTS!

*Avoid alcohol, and octane boosters.

Hope that helps.

Brad

Auto-Response - 05/03/2005 12:55 PM
Technical Support

i already replied with some of the same things discussed here. it's starting to basically sound like i just need to shoot some carb cleaner in there.

it was interesting to see what he had to say about the electric fuel pump.

[uglyota]

wow...and I thought the Summit employees were all Wal-mart castoffs

[Moose]

it's the electric choke. after a medium or more throttle, the flap thingy wants to stay open too much. so, i can either swap it or use it for a cool paper weight that smells like gas or adjust the choke or adjust the float. neither of which i know how to do. looks like i have to go to school again dammit!

[73bronco]

choke isnt hard to adjust. While your engine if off and cool just losen the 3 screws that hold it down and turn it until the flap is almost closed. You're all set just make a few minor adjustments later for how you like it.

[Moose]

choke on the edelbrock carb was a b!tch to adjust. they want you to unbolt the cap, measure how much the wing thing falls... no more than a 1/4 inch...? the pictures were terrible. their drawings looked nothing like the carb.

so i swapped it for a holley. NIGHT AND DAY! runs like she did before i left well enough alone, except w/out the blown head gasket. it's easy to adjust too. the response time after adjustments are none. if i turned one of the screws on the edelbrock, nothing would happen, so i'd turn another screw, then nothing would happen. then something would happen, and i didn't know which adjustment changed something... nightmare. it was so out of whack by that time... had to start everything back over again.

i'm an idiot mechanic and even i can adjust this thing. edelbrock should have just stayed in the air transportation department and left fuel delivery alone. now i know what everyone is talking about when they're discussing float bowls, sight levels, and jets, etc.

only thing is: now i know why carbs (at least holley) are so bad for off-highway vehicles. those float bowls are kinda sensitive. if you stop too hard at a stoplight/sign, she'll tend to drop in rpm, then pick back up after stabilization. the edelbrock didn't have that problem. that's why it was such a b!tch to adjust the floats on that one. but i already know how to fix the holley. but holley already sells a jet kit for off-road.