305 Vacuum line routing without Emissions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TC70C10 · 06-04-2003, 09:56 AM

I have a 81 K5 with a 305. Replaced the engine in January and put a different q-jet on last night.

I removed A.I.R. pump etc. in Jan. I'd like to remove the canister and it's cluster of hoses this time.

Here's how I'm setup now. Vacuum for high idle top front center port. I've got the vacuum advance run to a strong vacuum on top left of carb(drivers side). PCV to port below fuel filter. EGR is capped off with a plug currently. Intake manifold vacuum source to back middle of carb. Brake vacuum to back bottom of carb.

I still have 2 more vacuum ports unoccupied. 1 small port bottom left of the fuel filter that doesn't appear to pull alot of vacuum and one medium port to the right of PCV port.

I'm eliminating the 4 port EGR TVS plug on the water neck. All I have left is the EFE on the right exhaust manifold and the EGR.

**swervin ervin** · 06-04-2003, 01:20 PM

Since you have done away with the rest of the emissions stuff, why not remove the EGR too? For the EFE, it was routed through the TVS so it would open with engine temps. I would remove the guts from the valve if it were mine, which I did do. If you hook it to straight vacuum, it will open instantly anyway, so it really won't be doing any good, since it's vacuum controlled.

With no emissions, the only things you need hooked up are the distributor, brakes, tranny (where required) and PCV valve. Sounds like you have those already, so just cap the not used ports on the carb.

TC70C10 · 06-04-2003, 01:47 PM

Thanks Mike,

I used your advice on the knock sensor and eliminating ESC unit. I busted the sensor when I pulled my old motor and Autozone wanted 100 bucks. They didn't know what it did and I didn't feel like spending the hundred bucks.

2 ?'s
Should the vacuum advance go to a "strong" vacuum?

Should the primary intake manifold vacuum source go to back of carb (above bowl)?

I started it last night about 9:30 and it sounded pretty good. I could never get the air/fuel mix right on the other carb. I'll clean up the vacuum lines tonight. Thanks for your help

**swervin ervin** · 06-04-2003, 04:09 PM

I always hook the distributor up to manifold vacuum (i.e. vacuum at idle). Any port with full vacuum at idle will do for this.

06-04-2003, 09:56 AM	#1
TC70C10 Registered User Join Date: Nov 2001 Location: Harvest, AL 35749 Posts: 337	305 Vacuum line routing without Emissions I have a 81 K5 with a 305. Replaced the engine in January and put a different q-jet on last night. I removed A.I.R. pump etc. in Jan. I'd like to remove the canister and it's cluster of hoses this time. Here's how I'm setup now. Vacuum for high idle top front center port. I've got the vacuum advance run to a strong vacuum on top left of carb(drivers side). PCV to port below fuel filter. EGR is capped off with a plug currently. Intake manifold vacuum source to back middle of carb. Brake vacuum to back bottom of carb. I still have 2 more vacuum ports unoccupied. 1 small port bottom left of the fuel filter that doesn't appear to pull alot of vacuum and one medium port to the right of PCV port. I'm eliminating the 4 port EGR TVS plug on the water neck. All I have left is the EFE on the right exhaust manifold and the EGR. __________________ 1981 K5 Blazer 305, 4spd, 4x4, 4" Lift, custom bumpers, Warn 9.5 Ti Winch 1995 T10 Blazer 4.3L 4x4 (Son's) 2004 GMC Envoy 4.2L 2WD 2005 GMC Sierra Crew Cab Z71 4x4 5.3L 240 Fun Finder Travel Trailer Harvest, AL 35749

06-04-2003, 01:20 PM	#2
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Since you have done away with the rest of the emissions stuff, why not remove the EGR too? For the EFE, it was routed through the TVS so it would open with engine temps. I would remove the guts from the valve if it were mine, which I did do. If you hook it to straight vacuum, it will open instantly anyway, so it really won't be doing any good, since it's vacuum controlled. With no emissions, the only things you need hooked up are the distributor, brakes, tranny (where required) and PCV valve. Sounds like you have those already, so just cap the not used ports on the carb. __________________ Mike 1985 Chevy C-10

06-04-2003, 01:47 PM	#3
TC70C10 Registered User Join Date: Nov 2001 Location: Harvest, AL 35749 Posts: 337	Thanks Mike, I used your advice on the knock sensor and eliminating ESC unit. I busted the sensor when I pulled my old motor and Autozone wanted 100 bucks. They didn't know what it did and I didn't feel like spending the hundred bucks. 2 ?'s Should the vacuum advance go to a "strong" vacuum? Should the primary intake manifold vacuum source go to back of carb (above bowl)? I started it last night about 9:30 and it sounded pretty good. I could never get the air/fuel mix right on the other carb. I'll clean up the vacuum lines tonight. Thanks for your help __________________ 1981 K5 Blazer 305, 4spd, 4x4, 4" Lift, custom bumpers, Warn 9.5 Ti Winch 1995 T10 Blazer 4.3L 4x4 (Son's) 2004 GMC Envoy 4.2L 2WD 2005 GMC Sierra Crew Cab Z71 4x4 5.3L 240 Fun Finder Travel Trailer Harvest, AL 35749

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06-04-2003, 04:09 PM	#4
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I always hook the distributor up to manifold vacuum (i.e. vacuum at idle). Any port with full vacuum at idle will do for this.



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