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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: phil85 on December 07, 2006, 04:39:00 am

Title: help
Post by: phil85 on December 07, 2006, 04:39:00 am: hey everyone i just bought a 85 silverado long bed from a guy at work for $700 and it has a good body with no rust interior sucks but it is a haulin truck right now so who cares i'll get to it eventually, but right now the problem is the gas mileage, he had replaced the motor with a 305 out of an 85 van and in the process he diconected the emisions equipment (no big deal around here) but i was doing some work on it the other day and realized some of the vacuum lines are not hooked up and i have loose vacuum hoses and open ports every where, but it starts idles and drives fine, but the vacuum advance is not hooked up to vacuum and i was wondering where the best place to hook it up is. also does any body know if there is a good vacuum diagram for these trucks on the net some where?
sorry if these seem like stupid questions i am a fuel injection guy myself limited experience with carbed engines so some of this is new to me
Title: Re: help
Post by: Blazin on December 07, 2006, 06:19:00 am: The vacuum advance should be hooked to one of the ports on the front of the carb. It will not have vacuum at an idle but will when the RPMs are brought up it will.
Title: Re: help
Post by: Lt.Del on December 07, 2006, 11:39:00 am: I don't know if my 79 pickup is set up the same as your 85, but my vacuum advance goes to a check valve. Two lines come from that check valve, one to a TVS on the thermostadt housing, the other to a port on the front of the carb.

These pics were taken a couple of years ago when i was removing my 350 and replacing it with my 383. You see in my hand below the tvs plug that connects to the tvs on the thermostadt housing. The other line goes to the carb port.

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 12/7/06 11:55 am
Title: Re: help - vacuum switches
Post by: shpark2 on April 13, 2007, 09:17:29 am: Sgt Del, seeing as you already went to the work to get these pictures I figured I would dig up this old post. My 1980 C15 has similar vacuum spaghetti, thankfully the emmisions hose routing decal is in near-mint condition. The EFE vacuum switch I got figured, it's a 2port in the intake - my decal refers to spark TVS which I'm guessing is in the water neck. It is connected to either side of a check valve, which sits in between the distributor vac advance and the carb. I'm tryin to imagine why the distributor advance cares what the coolant temperature is, I can't get my head around it. What is the spark TVS for? Also, can a guy test these switches like t-stat's in a pot of hot water?
Title: Re: help
Post by: Lt.Del on April 13, 2007, 11:32:53 am: I wish i had answeres to your questions about checking the TVS in hot water, or why the spark TVS is there. I simply do not know. I did not reuse my existing TVS when putting in my 383 stroker. I bought a new one--mainly because one of the plastic stems for a line connection broke off years ago. I believe it was like $30, pretty pricey.

Check out My other site (http://www.delbridge.net/vacuum.html)

There are more pics there. Why the distr. advance is hooked up the the t stadt housing TVS, i don't know. Two lines go into the check valve, and two lines go out, one to the carb and one to the TVS. The one line loops back to the TVS, so I guess that perhpas that vacuum source changes as the temp of engine increases.
Title: Re: help
Post by: joesgarage71 on April 13, 2007, 12:23:04 pm: I guess the TVS is for pollution control it gives the motor advance after it warms up.
Title: Re: help
Post by: VileZambonie on April 14, 2007, 09:26:09 am: The Thermostatic Vacuum Switch used for dist advance and EFE makes timing more stable and easier start ups when the engine is cold. It really isn't necessary and if yours isn't functioning just bypass it. AS far as it's original functional design purposes ....

Early Fuel Evaporation Distributor Thermal Vacuum Switch (EFE-DTVS) Refer to the number stamped on the base of the switch or valve for calibrated switching or activation temperatures

The EFE-DTVS is an engine coolant sensitive vacuum switch which controls vacuum to both the distributor and EFE valve. When engine coolant temperatures are below the calibration point of the switch, manifold vacuum is directed to the EFE system and the distributor vacuum advance is vented to atmosphere. When engine coolant temperatures are above the calibration point of the switch, the EFE actuator is vented to atmosphere while the distributor receives ported vacuum for proper spark advance.

Early Fuel Evaporation Thermal Vacuum Switch (EFE-TVS)

When engine coolant temperature is below the calibration point of the switch, manifold vacuum flows through ports 2 and 3 of this switch to the EFE actuator, closing the EFE actuator. Above the switching point, port 3 of this switch is blocked and the EFE vacuum actuator is vented to atmosphere through port 1.

Also the EFE check valve Located in the vacuum line from the carburetor to the EFE thermal vacuum switch--the EFE-CV holds the highest vacuum reached, enabling the EFE heat valve to remain closed until the TVS switches modes.

It also prevents the heat valve from rattling during severe low vacuum conditions (heavy acceleration).
Title: Re: help
Post by: Lt.Del on April 14, 2007, 04:25:01 pm: Easy for you to say. ???
Title: Re: help
Post by: shpark2 on April 14, 2007, 05:03:01 pm: You guys amaze me, thank you. I guess buy headers without AIR holes, a new intake and a chrome water neck and then I have no choice but to strip it all off!
Title: Re: help
Post by: VileZambonie on April 15, 2007, 09:50:51 am: Put a three way cat on it and you won't need A.I.R. The Rhodium is the 1st part of the cat which is the reduction catalyst. It reduces Oxides of Nitrogen and a byproduct of this is Oxygen. The second part of the cat is Oxidizing and uses the oxygen to lower HC and CO emissions. If you eliminated all of your Emissions controls and your engine is properly tuned with a Three Way Cat (TWC) you'll pass emissions and won't have to worry about any of that crap.
Title: Re: help
Post by: shpark2 on April 16, 2007, 10:57:27 am: So in the US, do all states require vehicles of a certain age to pass emissions, or is it just some states? Or is it all vehicles?

I been told if I take it to the exhaust shop most people recommend in Sherwood Park, it certainly won't have any cats in it when it's done. We (Canada) had some emissions testing in the past, but as far as I know there is nothing currently for any personal vehicles. I was looking at an inspection form for insurance, it's quite basic. I know if exhaust is too loud, that can become a problem - tickets, etc.

(http://i169.photobucket.com/albums/u210/shpark2/Inspection.jpg)
Title: Re: help
Post by: Lt.Del on April 16, 2007, 12:08:55 pm: No, emissions are not required in MOST places. I don't even think it is a state thing, it is a locality thing. Here in Virginia, I don't need an emission test in Richmond area, however, up in Northern VA, around Wash. D.C., emissions are required. In a nutshell, if you live in a high populated metropolis, most likley emissions tests are required.
Title: Re: help
Post by: chevyfan on April 16, 2007, 05:13:35 pm: well i live just east of sherwood park and i have never heard that emissions are required. I know lots of people without cats or anything emissions related left on their vehicals
Title: Re: help
Post by: mrbetelman on October 21, 2020, 01:48:39 pm: Found this trying to do exactly what is discussed 14 years after it was posted. Thank you everyone for not removing this! Pictures posted by LtDel are VERY helpful.

85 GMC K2500
350
Muncie 4 speed
Posi rear
quad shocks up front
all factory installed