Help with vac hose connections - 1977 w/250 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

D13 · 04-10-2011, 09:08 AM

1977 C10 250 six manual trans 1bbl integrated head. This thing is soo boogered I have little idea what goes where

, I just know it doesn't go where it was (sticks, screws, loose, etc.) Looking for help! Need a diagram or even words.
I know the PCV goes to the big tube on the Y on the mainfold. (side note - wish they had run a breather and replaced the rotting grommets, I took about a cup of sand out of the valve cover

).
The cannister purge line looks like it goes to that same Y (since it's labelled PCV).
The fuel vapor hose is hooked to the cannister, that's good.
The third cannister hose look like it's hooked to the EGR (in front of carb)?
There is a small hard vac line that runs around the back of the engine to a switch, this is capped at the switch and open in the carb area. Any idea what that is? Where did it hook up?

The distributor advance vac hose was clipped to the fuel line and appears to come from the Y on the carb base. This would be ported vacuum?
So that leaves:
One small open port in the rear of the intake (capped with hose and screw), I suspect this is where the line that goes behind the engine hooked originally.
The EFE valve (behind the carb)(capped with hose and stick) (not even a golf tee like civilized mechanics use!).
One leg of the Y in the carb base.

Help!

1425956 · 04-10-2011, 11:01 AM

Click here. This is a complete vacuum diagram for your truck.

D13 · 04-10-2011, 11:36 AM

Thank your. You da man!
For anyone who sees this thread:
The cannister / PCV connection is a Y vacuum fitting on the manifold between the carb and the valve cover.
The distributor/air cleaner Y is on the front of the carb.

Interestingly, mine has no heated air cleaner door. Explains the hose and screw.
I think the EFE TVS is the one on the right rear of the engine, that would have been the pipe on the back of the valve cover. The EFE valve is the one behind the carb.
The rest I'll have to look at. I'll probably delete EFE and EGR for now, but I need ot figure out the fuel evap system. It appears that the carb bowl vent is NOT part of the vapor recovery, the hose size does not work with any of the cannister ports. Weird.

Thanks Again 1425956!

04-10-2011, 09:08 AM	#1
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Help with vac hose connections - 1977 w/250 1977 C10 250 six manual trans 1bbl integrated head. This thing is soo boogered I have little idea what goes where, I just know it doesn't go where it was (sticks, screws, loose, etc.) Looking for help! Need a diagram or even words. I know the PCV goes to the big tube on the Y on the mainfold. (side note - wish they had run a breather and replaced the rotting grommets, I took about a cup of sand out of the valve cover). The cannister purge line looks like it goes to that same Y (since it's labelled PCV). The fuel vapor hose is hooked to the cannister, that's good. The third cannister hose look like it's hooked to the EGR (in front of carb)? There is a small hard vac line that runs around the back of the engine to a switch, this is capped at the switch and open in the carb area. Any idea what that is? Where did it hook up? The distributor advance vac hose was clipped to the fuel line and appears to come from the Y on the carb base. This would be ported vacuum? So that leaves: One small open port in the rear of the intake (capped with hose and screw), I suspect this is where the line that goes behind the engine hooked originally. The EFE valve (behind the carb)(capped with hose and stick) (not even a golf tee like civilized mechanics use!). One leg of the Y in the carb base. Help! __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors

04-10-2011, 11:01 AM	#2
1425956 Registered User Join Date: Mar 2011 Location: Joplin, MO Posts: 161	Re: Help with vac hose connections - 1977 w/250 Click here. This is a complete vacuum diagram for your truck. __________________ Jeremy I have done so much, for so long, with so little, I can do anything with nothing! 1984 GMC Sierra Classic-1/2 ton-SWB (R.I.P.) 1986 GMC Suburban 3/4 ton 4x4 2014 GMC Sierra LTZ Z-71 Crew SWB Last edited by 1425956; 04-10-2011 at 11:07 AM. Reason: Link

04-10-2011, 11:36 AM	#3
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: Help with vac hose connections - 1977 w/250 Thank your. You da man! For anyone who sees this thread: The cannister / PCV connection is a Y vacuum fitting on the manifold between the carb and the valve cover. The distributor/air cleaner Y is on the front of the carb. Interestingly, mine has no heated air cleaner door. Explains the hose and screw. I think the EFE TVS is the one on the right rear of the engine, that would have been the pipe on the back of the valve cover. The EFE valve is the one behind the carb. The rest I'll have to look at. I'll probably delete EFE and EGR for now, but I need ot figure out the fuel evap system. It appears that the carb bowl vent is NOT part of the vapor recovery, the hose size does not work with any of the cannister ports. Weird. Thanks Again 1425956! __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.