Hi there. This winter I've decided to finally sit down and learn a bit more about my engine and truck and how everything works. Well, more like it was decided for me when my carburator finally started going out on me. Anyway, I've recently purchased and installed a Weber 34/34 DGEC (a rebuild was not possible with this one), and after a little adjustment of my distributor timing, new spark plugs, wires, and a cap and rotor, it's running pretty good. As soon as possible I'm going to go in and adjust my valves and give it a new head gasket. It's not perfect yet, but it'll get there.

So, with this carb, I unplugged the eight or so vaccuum hoses from the old stock one and only plugged one back in, capping the others (and piping a few differently) There are no emissions laws where I live, and so I'm wondering what I unplugged that is important? Is all of that stuff unneeded for the proper (although unclean) running of my engine? Is any of it?

The EGR system: I heard before that your engine will not run properly if you don't have this hooked up. Is this only in the case of a carburetor that has an EGR port? Can I plug up the pipes going to and from the EGR and the EGR Modulator and forget it's attached to the engine?

The Air Switching Valve (ASV) and resonator: The resonator used to connect to the inner part of the air cleaner. Currently I have it hooked the same on the weber with the engine's breather hose leaking down and out. (Weber's instructions said to put the breater in the air cleaner and didn't mention the resonator's hose.) Should I do this? Or should I put the breather back in the air cleaner and plug up the resonator. Can I remove it all together and remove vaccuum from the ASV?

Vacuum Control Valve (VCV): A little hub of hoses that doesn't appear to have much function anymore. Can I remove it altogether? (This means plugging the ASV)

Charcoal Canisters: I have two. Any use to me anymore? Is it safe to plug the vacuums off. Should these continue running?

What about the vacuum coming out of the distributor that is not the advance line going to the carb?

What about the little switches I didn't mention? The VSV, BVSV, and VTV?

ahhh... where to start... where to start...


EGR: Engine will run fine without it. Might need to back off the timing a bit since the EGR will reduce cyl temps due to the "inert" exhaust it dumps in. Best thing to do is get the kit from www.LCEngineering.com to block off the whole system.

The vac lines on the carb are for the vac advance on the distributor. The one above the throttle plate is for the outer (I think) and the one below the throttle place is for the inner.

Charcoal canisters vent excess pressure from the gas tank. You can vent them to atmosphere but watch your gas mileage when doing so. Run one take plugged and one not. I saw a few points different once.

All the other valves just do Air Suction and EGR stuff for the most part. None are "needed" other than to help the enviroment.

LMK if you need any clarification.

<img src="/forums/images/graemlins/cheers.gif" alt="" /> Cheers! <img src="/forums/images/graemlins/cheers.gif" alt="" />

Interesting, I think I'll have to pickup an EGR block plate. If I put on a block plate, will I still need to mess with the timing? I already did back it off a little after installing my carb because I was preigniting when I turned the truck off. So, the cylinders will run hotter without EGR? Is this bad?

On the charcoal canisters, do you know why there is vacuum running to them? I'm not sure if it's hooked to a vacuum source anymore, I'd have to look. Sounds like I'll keep them up and running.

So, no thoughts on the air switching valve? It's about the size and shape of the EGR, but in the front near the fuel pump. If I remember right it's hooked into the engine block and the intake manifold. It also feeds to the resonator (this is just an empty container for noise pollution, right?) which feeds back to the air cleaner. I can't remember if it's recycling air back to the carb or drawing air to the ASV...

I unhooked the ASV that you are speaking of...truck seems to run pretty good without it.

iam getting a little dieseling at shutoff also. i have blocked off my egr and my timing is advanced to 8btdc because it seemed like a rich condition. im goimg to back the timing off to 5deg and try that, it only does it after running it on th eroad for untill it warms up completly. i never thought the egr would cause this but after thinking about it, it makes sense. im not trying to jack this thread but i have a similar problem.

btw its an 85-up block with everything from an 84 truck , enginbldr head , 261c cam and a weber 38.

So, does an active EGR increase gas mileage? How does a Weber factor into that and the cyl temps? Would I be better off keeping it in place? If so, can anyone recommend the best way to keep vacuum to it with a Weber installed?

If you have a Hayes manual check out some of the Canadian emissions systems from the early to mid eighties. I don't have the manual near but I did this on a 86 2wd 22r with a 32/36 and it passed emmissions in AZ (roller test) with flying colors. You pretty much figure out which vac lines are above the thottle plate and which are below. Then hook them up accordingly.

On my 86 22r with a 38mm I blocked the entire system without any major ill effects. I've had to do alot of engine work with it but with all the perfomance stuff on it and how hard it's run it's difficult to pin problems on minor things like the EGR.