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overthinker extraordinar
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650 Posts
Discussion Starter #1
Hey Folks,
I took my 1985 2.8L s10 to firestone to get the A/C compressor charged. They screwed my truck, bad. Behind the compressor on the top of the intake manifold, right next to the thermostat is a 4 port vacuum control switch. The knocked the tubing off and they busted one of the plastic ports. My truck will not pass emissions without this switch. It controls the EGR valve.

So does anyone know where to get a four ported EGR TVS. I checked with the chevy dealers. The part is no longer made. I did find a 5 ported version made for jeeps, but I have no idea which ports do what. I think I am going to pull the switch and heat it with boiling water. Then I can test and see what happens.

Anyone have any ideas? I have checked all the CL ads for parts cars - nada. I will call some salvage yards and see if I can find one. This part would only be on a 1985 or older vehicle. Newer ones used fuel injection.

daaaaammmmmm firestone................
 

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overthinker extraordinar
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650 Posts
Discussion Starter #2

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4 Year Intermediate Tech
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1,829 Posts
I was about to say I've got a brand new one in the box here
 

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overthinker extraordinar
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650 Posts
Discussion Starter #4
Well thanks just the same!!!

I noticed I am only at about 12" vacuum at idle. Time to start looking for a vacuum leak. I found this break when I was looking. I capped it off and it didn't help that problem at all.

I think I if find all of the vacuum ports that have to do with pollution and cap them, then check vacuum, I will be able to see better how my motor is doing.
 

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4 Year Intermediate Tech
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1,829 Posts
12" hg at idle is very low for these. With the stock cam it should run at 17-18" hg at 800 rpms hot idle in park or neutral. Remembering how many lines I had running off the varajet carb you can bet you have some vacuum leaks. You are testing from the brake booster line correct?
 

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4 Year Intermediate Tech
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1,829 Posts
You may need to advance the dizzy a few degrees. Altitude also plays a part in hg. For every 1000 ft above sea level subtract 1" hg.
 

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overthinker extraordinar
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650 Posts
Discussion Starter #7
12" hg at idle is very low for these. With the stock cam it should run at 17-18" hg at 800 rpms hot idle in park or neutral. Remembering how many lines I had running off the varajet carb you can bet you have some vacuum leaks. You are testing from the brake booster line correct?
No I was testing on a different line. I will try the brake line and post back. I have my timing set at about 13-14 btdc. I should be around 15, maybe even 16.

I have replace all of he lines that came off the carburetor. And yeah, they were completely shot and leaking terribly.
 
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