How do you hook up a thermal vacuum switch?

[FlintBuick4Life]

Hey guys, this guy dupperskeez on Youtube is having trouble figuring out where and how to hook up a thermal vacuum switch on a Edelbrock Intake, 4b Carb. N/A 3.8. I never put mine back in, maybe you guys might know how and I will inform him.

dupperskeez: did you put the thermal vacuum switched back in the new manifold. how did you hook up all your vacuum lines? I have the switches in but having trouble figuring out what to route where. there are two switched one that sticks out the bottom-pax side-front and the other sticks out the top of the front-right-pax side. the edel carb only comes with the two vacuum sources(timed and manifold vacuum). thanks again.

 

[charlief1]

the E-brock intake won't work if he's trying to keep the factory stuff. That may be his problem. See if you can direct him to the forum so we can get a better idea of what he's trying to do.

 

[FlintBuick4Life]

the E-brock intake won't work if he's trying to keep the factory stuff. That may be his problem. See if you can direct him to the forum so we can get a better idea of what he's trying to do.

I told him to make an account and gave him the link. Thanks

 

[charlief1]

We'll see if he does it then.

 

[231_natural]

i'm dupperskeez...small world. I just put in the intake and carb with the two thermal vac switches out of my old manifold. the only thing not hooked up is the egr. I followed the deci label under the hood and everything else seemed to hook up. My biggest concern is am I hindering anything if everything is hooked up with no leaks but may not necissarily be needed. For example the line from the timed port on the carb goes through two of the switches as it did on the stock manifold to the vac advance. The vacuum is at the advance and increases with RPM, but should I just be running it directly from the carb to the advance? Any insight or explanation on all this would be great. thanks

 

[FlintBuick4Life]

i'm dupperskeez...small world. I just put in the intake and carb with the two thermal vac switches out of my old manifold. the only thing not hooked up is the egr. I followed the deci label under the hood and everything else seemed to hook up. My biggest concern is am I hindering anything if everything is hooked up with no leaks but may not necissarily be needed. For example the line from the timed port on the carb goes through two of the switches as it did on the stock manifold to the vac advance. The vacuum is at the advance and increases with RPM, but should I just be running it directly from the carb to the advance? Any insight or explanation on all this would be great. thanks

Hey, yeah small world lol I have some pics of my EGR and carb set up...

http://img689.imageshack.us/i/1000609q.jpg/

http://img689.imageshack.us/i/1000612.jpg/

http://img694.imageshack.us/i/1000613.jpg/

http://img35.imageshack.us/i/1000614b.jpg/

 

[charlief1]

As far as the E-brock intake you may as well dump the emission parts and just set it up simple. If you want a heat riser off the exhaust get an air cleaner off of a 90's chevy pick up with a V6 in it. That one doesn't use ported vac switches to activate it. It has a bi-metalic strip that opens the heat riser so you'll get the heat you need for the carb and it will open when it's hot enough only but has a huge inlet for a snorkle.

 

[231_natural]

Yea I should ditch all the switches in the intake. All I am really using is the switch for thats connected to the advance, another one connected to a switch on top of the alternator. I'm not sure what that switch is even for, I was thinking maybe a/c which I no longer have installed. And the other one goes to the efe.
If you're talking about the snorkel and airfilter assy off a v6 truck, It won't fit under the hood. I have a 10x2 airfilter on there now and that doesnt leave a whole lot of room.

I'm still runnning stock timing of 15btdc advance and would like to find the best timing with the new intake and carb and the lack of egr. I've heard to use a vac gauge connected to manifold vac and adjust timing for the highest vacuum for best timing. Is that a good starting point? How do you guys recommend finding the best timing?

 

[charlief1]

Total timing is what you're after. Get one of the HEI advance kits and do some playing with it. I used to run some where around 42 degrees total on my old NA car. As far as the idle speed the best way to set it is like you said but when you do this make sure you have a tach hooked up and once you get the best vac see what the highest idle rpm is. Once you do this recheck the vac/timing and if it hasn't changed then move the idle mixture screws out 1/4 to 2/3 turns out to get the best mix on the idle. It should be a little rich at idle. It's refered to as "best lean".

 

[231_natural]

sorry you kinda lost me. so check for the highest vacuum and the corresponding high idle? then reset the idle and check the mixture?

 

[231_natural]

when I set the mixture i tuned the screws in until I got an idle drop and then screwed them out about a 1/2 turn for highest idle. Would that be "best lean"?

How did you arrive at 42 total advance? What was it sitting at for base idle? What kinds of mods had you done?

Thanks

 

[charlief1]

when I set the mixture i tuned the screws in until I got an idle drop and then screwed them out about a 1/2 turn for highest idle. Would that be "best lean"?

How did you arrive at 42 total advance? What was it sitting at for base idle? What kinds of mods had you done?

Thanks

My old engine had a slightly larger than stock cam. Ported heads. 1&5/8" primary KB headers. And a modified 4.1 intake. I had Rhere and Morrison do the block work. I used TRW forged replacements and had the rotating assembly balanced. The block and heads were decked .030 and I was using Felpro 1000 head gaskets. With the TRW pistons and decking the heads and block I had just below 10:1 compression.

I did testing to see how the car did and whether I had knock issues first. This was when leaded gas was still around so I'd mix super with leaded to get some extra octane. With a total advance of 42 degrees and no knock but I don't remember the base timing. Sorry.

To set this up, get the car warm first. At this point set your idle speed and check timing. If you have to change it do it now. Then go to the mixture screws and adjust them to get the highest idle out of the engine. Turn the mixture screws out 1/4 to 1/2 further out and you'll see the RPM drop slightly. That's what you want it to do. This is "lean best"

Once you've done this recheck the timing. Change it as you need to. If you have access to an adjustable timing light check total timing at different RPM's so you know what the curve is. Mine went to max around 1800-2000 RPM. This was best for what I was doing with the car.:biggrin:

 

[231_natural]

Thanks for the reply. i advanced it from 15 to 17 today and it seemed to be an improvement. Would you say that I could keep advancing a degree or so at a time give a test drive and at the first sign of knocking or pinging back the timing off a little and that would be my best timing. Unfortunetly I don't have access to an adjustable timing light at this time.

 

[charlief1]

Make sure to do your knock testing at all conditions. WOT, medium, and light throttle. This will make sure you don't end up with a broken engine.