I am installing a DUI HEI distributor and have blocked off the EGR since mine was not working. I have removed the majority of emissions components. DUI recommends running the HEI vacuum advance off manifold vacuum, so I have a line running to the distributor from the manifold port that supplies the brake booster. I have all of the ports on the carb capped off (not sure that's right) .
Do I run the PCV to the same manifold fitting that supplies the brake booster? There are no manifold vacuum ports on the carb that I have. This would mean that all 3 (HEI vacuum advance, PCV, and brake booster) would tie into the same fitting?
If all of the above is correct (I'm not sure it is) I don't know which lines I still need to run to the CTO switch. I don't have a source of ported vacuum to connect. Should that be run off of the fitting on the front of the carb (circled in the pic below with the blue cap)? I'm not sure what this fitting is.
Thanks in advance for your help. I appreciate it greatly.
You really shouldn't run anything that needs manifold vacuum from the same spot as the PCV source. That carb doesn't have a single manifold vacuum source? Did it originally have a spacer with a PCV port?
The carb came from the "ebay guy." The only ports on the carb are the one picture I posted and one under the rim for the breather to connect to. It came with an adapter plate, but not the plate that has the vacuum port.
The port that is circled in the pic is ported vacuum. It doesn't sound like you need it, so leave it capped. Without the EGR or the vapor canister, there is no reason to hook up the CTO.
You can share the same manifold vac fitting for the brake booster and the distributor vac advance. It should be the fitting just above the EGR valve.
For the PCV, either install an adapter plate that has a PCV port, or drill/tap your existing adapter plate to accept a PCV port, or install a vacuum fitting in the plugged intake runner on cylinder #6 (see pic).
If it were mine, I'd be looking for a spacer with the PCV port. The plug Matt mentioned may work as a manifold vacuum source but I'd put a gauge on it first to see how jerky it is, being so close to a cylinder.
Shawn makes a good point, the PCV is basically a metered vacuum leak, so the strength and steadiness of the signal is important. So check it before using the #6 intake runner port.
Shawn makes a good point, the PCV is basically a metered vacuum leak, so the strength and steadiness of the signal is important. So check it before using the #6 intake runner port.
I was talking about a source for the distributor. Don't use that port for any sort of bleed vacuum or that cylinder will run lean as hell and self destruct.
Would it be OK if I ran the fitting circled in yellow for the PCV and then spliced a tee in the area of the green circle for the dist. in the line for the brake booster? Or would that still be considered a single source?
I still have the canister connected to vent the fuel tank. So I should probably hook to the CTO and the ported vacuum port on the carb for that, correct?
The yellow circled port should go to the distributor. I would NOT splice into the brake booster line for the PCV.
Again, the PCV is metered vacuum leak. Meaning the engine is dependent on a specific amount of air from the PCV to keep the air/fuel mixture correct. Splicing into the brake booster line may not provide the proper amount of air.
OP, disregard my suggestion to use the #6 intake runner for the PCV. It's a bad idea. The PCV air should distribute to all cylinders, so it really should connect to the carb base, or spacer.
I find it interesting that he added that port. I bought this carb from him, and the instructions he sent with it say to hook the PCV to the fitting above the EGR and to not hook up the vacuum advance to the distributor.
"If you have a NON-Smog kit with no PCV port on the rear of the carb, you can use the fitting at the throat of the intake manifold where the brake booster feeds from for your PCV port… NOTE: Some carbs will have a large PCV port in the rear. Some carbs (My Non-Smog Kits) will utilize a port at the throat of the intake either where the powered brake assist is plugged in or right next to it.
You can also "T" off of the power brake hose (Only if you have the Smog-free kit). It all goes to the same place in the same manner. It doesn't matter where or how it gets there.
If you have purchased a Non-Smog kit, and do NOT have a ported vacuum port (most won't) you will not utilize the vacuum advance to the distributor. Don't worry, your distributor will still advance itself two other ways. The vacuum advance is more of an emissions control than a performance booster. Simply advance your timing 2-6 degrees and you will be very happy."
I think I'd forget that guy's website and email address.
See if you can hunt down a spacer with the PCV port so you can use the brass fitting for distributor vacuum and your brake booster. It looks like the port he added is simple enough to drill and tap, assuming you have the tools and don't manage to crack the base while tapping it.
Yeah, I've read Gronk's install instructions, too, and I wasn't impressed. He seems to have a clear misunderstanding of the purpose of the vac advance, and how manifold/ported vacuum actually works.
I have a friend with a similar problem. No PCV port on her 2100. She got the adapter plate from Gronk, and was told to remove the spacer that had the port on it. Can she use regular gaskets for the spacer, or does she need those thick ones that come with the adapter?
The thick gasket is a heat insulator. It is designed to prevent the carb from heating up and boiling the gas in the bowl. It's definitely advised to use, but that doesn't mean you can't use the ported spacer.
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