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Discussion Starter · #1 · (Edited)
After reading many many posts looking for answers to my newbe PCV questions, I couldn't find my answer, so here goes- I'm dealing with TWO issues. Q1-The PO of my recently acquired '69 w/454 had installed a pcv valve (pass.side valve cover, breather on other side) with a 90* fitting with TWO barbed hose fittings(?) Why two? Q2- Can I plumb the pcv valve hose directly to an intake manifold vacuum fitting, instead of the open air cleaner? If so, there's an unused bung plug in the manifold I can replace with an appropriate fitting. I don't have any available fittings under the carb spacer and don't want to drill any. Will utilizing direct manifold vacuum act like a vacuum leak, hurting performance? Presently have major eye-watering stink while cruising!
 

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How about post a picture of what you have now. The pcv doesn't go to the air cleaner, it needs to go to manifold vacuum. How much blow by do you have with the pcv out of the valve cover and the breather off? If you are smelling it inside the car then you may have a problem. So how much blow by do you have? And show us a picture(s) of your current setup.
 

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Discussion Starter · #3 ·
Eugene, attached is a pic of the installed pcv valve that's plumbed to the air cleaner's base plate. I plugged one of the two barbed fittings as the PO had it just vented to atmosphere(?) I'm thinking of maybe going to a "low-vacuum" style replacement valve anyway, as reported in another thread. Can also connect directly to the intake manifold if that's advised.
 

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David. If the pcv valve hose is connected to the base of the air cleaner it is doing absolutely nothing. Connect it up to a source of manifold vacuum either at the back of the carb or direct into the manifold with it's own source. In other words don't Tee into the same source as your power brakes. PCV on one valve cover and a breather cap on the other should do the trick. You can buy a PCV valve that doesn't have the two connections for very little money. You didn't say how much blow by you have. How bad is it?
 

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Discussion Starter · #5 ·
Eugene- Thanks for the followup. Funny you mention the "don't tee off with the power brakes" comment- that's exactly how I found all this connected at the time of purchasing this car! Plus, the second of the pcv's two barbed connectors was open to air(!) Wow. So, after fixing the brake vacuum hose routing (and gaining alot of braking power LOL), my plan after reading yours and some others helpful comments/threads on this great website, is to do exactly what you suggest. The aluminum intake has a bung plug that i'm removing to take to the hardware store to find an appropriate brass 90* fitting and I just bought a napa pcv valve to fix all this. BTW, when the motor's running, I don't see any smoke/vapor emanating from the VC hole. Thanks again!
 

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If you have no blow by then you should be in good shape once you get it hooked up to manifold vacuum. You may have to do a slight adjustment on the carb once you have done all this to adjust the air fuel mixture but see how it runs first. Let us know how it turns out.
 

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Does your carb have a 3/8 manifold port on the front, if yes use it for the PCV.
 
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Discussion Starter · #8 ·
Eric- FWIW, the 3/8" fitting is under the rear of the carb, but there's two smaller (3/16"?) ports in front. As I understand it, the one near the center is full vac., and the left one is ported. So I'm using the rear for pcv, and the middle front for vacuum adv.
 

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Discussion Starter · #10 ·
UPDATE- I've got everything re-plumbed the way everyone suggested. Now I've just taken my first "official" vacuum reading after buying a (Lisle) vac. gauge- it reads a steady vac of 5 1/2 to 6 inches @ 900-1,000rpm. This makes me think I need to get a different pcv valve that more closely matches the lower vac., which i'll do... The other issue I'm dealing with is the HEI dist.- I've put an MSD advance spring kit on, after removing the "baling wire" the PO had on to lock out the centrif. adv. While doing so, I tried moving the vac. adv. plate by applying a suction (by mouth, OK no jokes). It wouldn't move. It moves alittle by hard finger pressure, but with the motor running @ idle, there's no difference in timing, plugged or unplugged, as seen with the timing light. My existing as-found "locked out" static timing as was set by the PO, is reading 38-40* @900rpm, and when I rev it up to 2500-3000rpms, it now kicks in the centrifugal advance adding more advance, as I would expect. Sooo, 2 questions- what's a good static timing setting w/ the centrif. adv. now adding it's own? Any suggestions concerning the "reluctant" dist.'s vac. adv. can? Any comments are Welcome!
 

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With the vacuum advance you could have 2 different things happening.The vacuum advance "Pot" could be bad with a rupture inside or the plate that it attaches to could be ceased. Look where the pot attaches inside the distributor and disconnect it. Try sucking on the hose again and see if the arm moves with nothing connected. If it doesn't move then it is probably shot. If it does move then go to the distributor and see if something is hanging up or if it is ceased. More often it is the pot that ruptured inside. They are available at any parts store. If you had a hand operated vacuum pump you could check it with that as well but sucking on the hose will work too.
 

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http://www.chevelles.com/forums/13-performance/189195-ignition-101-a.html
Read Timing 101, which is a fantastic "sticky" in the Performance section of Team Chevelle. This will really help in understanding any timing issues.

A couple of quick thoughts:

As stated, you need to find out about the condition of your vacuum advance pot. Simply sucking on it is not a definitive test (No comments, pls) and just because you could get it to move does not indicate it is working properly/fully advancing. For a very simple test, if you have a Mighty Vac or similar vacuum testing tool, you can hook it directly to the vac advance pot hose, and check the amount of vacuum required to move the advance as far as it will go, as observed with the distributor cap removed. For a more definitive test, you can do the same test with the engine running, and observe on the timing light how many degrees the pot advances timing AND very importantly, how many inches of vacuum were required to achieve full vac advance.

Your vacuum reading of 5-1/2 to 6 is pretty low, make sure you don't have another leak to close off. You need a pot that will give you full vacuum advance at one or two inches BELOW your vacuum reading. For example, my vacuum advance pot works great, but it requires 16 inches to reach full advance. My setup would be useless on your motor, because not enough vacuum. If your vacuum test shows you need 15 inches to fully activate the advance, your 5-1/2 to 6 inches of manifold vacuum may produce no vacuum advance at all, or not enough.

There are different opinions on running locked out versus initial & vacuum advance set-ups, which I won't get into. You indicated you want to use the vacuum advance, so as a ballpark starting point, if your engine has a performance cam, start with about 14 degrees timing with vac advance disconnected and vacuum line to engine plugged. Find the correct pot to work with the vacuum you have. Many distributors will add approximately 15 degrees of vacuum advance timing. Initial advance setting, amount of vacuum advance, and amount of centrifugal advance can all be tailored in terms of individual amounts, total amount, and at the RPM and vacuum range they are activated.

It all gets a little technical for a shade tree guy like me, but one takeaway I have is do not make the common mistake of retarding initial timing to compensate for too much total timing. Better to limit vacuum and/or centrifugal advance amounts than to retard initial timing and lose the real benefits it offers.

Good luck with it and let us know how it works out. Again, take the time to read the timing article.
 
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Discussion Starter · #13 · (Edited)
UPDATE #2- Upon checking out the dist., I found the vac adv. pot is an adjustable one. When I inserted the allen wrench, I found the screw backed out fully CCW, so I turned it in 5 full turns as recommended elsewhere here for 14-16* @ 5-7". I will verify this tomorrow.
 

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Discussion Starter · #14 ·
Update#3- well, I discovered the vac. adv. pot on the HEI dist. was not responding to any adjustments, so I checked the vac. adv. hose for vacuum, was none, and found it connected to ported vac., (my mistake,) so I switched it over to manifold vac. Still nothing. So now I'm looking at a new pot- the Echlin VC1825, unless someone convinces me there's a better one, based on my 5-6 inches Hg @ 900-1,000rpm idle. I've researched the Lars Grimsrud paper & it's list of advance controls, and it seems to point to the vc1825. Any comments?
 

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Sounds like you are on the right track with the replacement. Pls keep us updated.
Is it correct that you do have good vacuum available, but just have a faulty advance can?
 

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Discussion Starter · #16 ·
Steve- yeah, that's what i'm seeing. I needed the can anyway, and this vc model appears to be well matched. Steady, low vac. @ idle of 6" Hg. I'm recv'ing it tomorrow so we'll see how it does.
 
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