Truck died last night

[chrismoore701]

Originally Posted by jjzepplin

If you have a turbo 350 it does not have vacuum at the carb. It is supposed to be manifold vacuum at the rear of the carb there is a fitting that screws into the manifold and goes to the vacuum modulator on a th350. The modulator is sometimes adjustable to fine tune your shifting. You may have the trans connected to ported vacuum and this would be not so good.

I have a port on my intake on the back side of the carb. Right now I have the brake booster and my heater vent vacuum connected there with a tee. I can easily pull my heater vacuum off and connect my trans there and see what difference that makes. will let you know.

Thanks
Chris

[jjzepplin]

That is right. Your heater vac should go to constant vacuum. Should be a small port somewhere on the base of your carb. Only good way to tell what is what is to hook up a vacuum gauge to each port or read instructions. Heater vacuum usually goes to a canister of some kind to store the volume of air as a reserve. Not a real fan of vacuum advance elimination on street vehicles. Streetability suffers a bit in my opinion.

[chrismoore701]

Ok so I added some Trans fluid. Took the Trans vacuum line off the carb and added it to the spitter on the back of the intake. Opened the fuel filter and cleaned it. Ran worse than before. Hobbled back home and bypassed the fuel filter. No better. Not sure if it is starting to miss or if it is loosing fuel. Pressure before the carb shows about 10 psi. I have the pcv valve going to the back base of the carb. The brake booster coming off the intake. With a tee and the Trans now connected there. I have a couple caps on the front vacuum ports. Have not checked the brakes. Will try that tomorrow.

[Gregski]

Originally Posted by chrismoore701

Ok so I added some Trans fluid. Took the Trans vacuum line off the carb and added it to the spitter on the back of the intake. Opened the fuel filter and cleaned it. Ran worse than before. Hobbled back home and bypassed the fuel filter. No better. Not sure if it is starting to miss or if it is loosing fuel. Pressure before the carb shows about 10 psi. I have the pcv valve going to the back base of the carb. The brake booster coming off the intake. With a tee and the Trans now connected there. I have a couple caps on the front vacuum ports. Have not checked the brakes. Will try that tomorrow.

Dang it, that sucks, only advice I can share is please try to only change one thing at a time, I know it takes more time, but trust me it pays off in the end.

[nonstop]

After checking brakes, check the float level of the carb and confirm the fuel pressure. 10 psi sounds pretty high, and could be causing the needle to be overpowered, causing it to flood out. But as said above, do one thing at a time to make the elimination easier.

[RodsGreen10]

10 psi is to high. Holley spec fuel presuure 6-8 psi.
With 10 psi you will probably blow the needle of the seat.

[chrismoore701]

you can see from my pic on the previous page I have a cheap inline pressure gauge. And that thing wags all over the place, my best guess is it was 10 but it bounces from between 8 and 12 or so. I will check the floats tonight. I have a typical on engine fuel pump, think it is a holley. Do I need to get a pressure regulator and install inline?

[chrismoore701]

Originally Posted by RodsGreen10

10 psi is to high. Holley spec fuel presuure 6-8 psi.
With 10 psi you will probably blow the needle of the seat.

Blow it, like tear it up? or just blow by it?

[jjzepplin]

Shouldn't destroy it. But would cause the fuel to flow past it creating a constant flooding issue.

[hatzie]

10PSI will intermittently force the needle valve open regardless of float position. Not a flood with gasoline fountaining out the bowl vent but the float setting will not be reliable along with the associated intermittently over-rich fuel mixture issues from the intermittently overfilled float bowl. Just like a bad needle and seat but without the bad parts.

Holley and most other carbs don't like much more than 6-7PSI...

[RodsGreen10]

Originally Posted by chrismoore701

Blow it, like tear it up? or just blow by it?

I was being sarcastic. But the fuel pressure you are guessing you are running is overkill.
You seem to have more than 1 problem start with one thing and move on. A ton of good and bad info on Holley carb tuning.

[chrismoore701]

What about the venting of my gas tanks? Anybody running the charcoal canisters? I think I have vented gas caps and I am not running the canisters. Could this cause a problem?

[hatzie]

Originally Posted by chrismoore701

What about the venting of my gas tanks? Anybody running the charcoal canisters? I think I have vented gas caps and I am not running the canisters. Could this cause a problem?

The only issue that makes is the missus may not like the smell of raw gasoline in the garage.

Not much to a basic charcoal vapor can, zero performance hit, and the garage doesn't stink.
Ported vacuum to the purge valve vacuum actuator port.
Canister vapor purge "OUT" teed into the PCV line or run to manifold vacuum.
Raw vapor line "In" from tank vent(s) to the canister vent line connection.

The later model vapor cans resemble a Rube Goldberg device from hell. Probably to make the EPA Oberführers happy. There's absolutely no reason to have more than three hoses on each can. GM didn't make a larger can for dual tank trucks so you may need two cans.

[Gregski]

I deleted my charcoal canister on my '74 and went to a single line sending unit and truck runs fine, great really, and no gasoline smell in garage at all

[chrismoore701]

I am going to pull the carb off and clean it

[Gregski]

Originally Posted by chrismoore701

I am going to pull the carb off and clean it

Good call, clean the float needle areas real good and check for cracked floats

[chrismoore701]

OK so I pulled the carb off last night, looked clean, but cleaned all the ports, open the needle and cleaned that, threw it back on and it ran but would fall on its face off the line. Talked to a buddy of mine and he told me to drop it in first and light it up a couple times. Running pretty good now. I guess it just got a little dirty and loaded up with carbon. Still not perfect, but I will take it to my engine guy and let him have a look at it. At least I can drive it now.

[Pontiac1976]

I prefer Fram G3 fuel filter install it right @ the out tube of the fuel pump near frame, it's cooler and works better there and you can see it, and check it change regular.