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By Eddie Paskey - 13 Years Ago
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Hey Steve,, I know you did a lot of research on what PVC vale to run on your rig. Have a little trouble getting idle right. Believe the PVC valve is not right. Running 4177 Holley, right now running 67 primary jets will go back to 71s seemed to be better, also using secondarys to control idle. 331 stroker, John's heads, Engle Cam #EP-20-Cam lift 321--duration 231-- lobe centers 110. Blue Thrunder. Pvc valve that I'm using is for a 289 Mustang. Maybe too big?? Thanks for all the help thru the years. Still the Best site!!! God Bless Eddie
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By oldcarmark - 13 Years Ago
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Hey Eddie! I started with the same as you and found it passed too much air.Wouldn't idle right.I went to a 78 4 cylinder Fairmont/Zephyr PCV and it was just about right.You can try restricting the one you have now and see how that works.Trial and error.
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By Eddie Paskey - 13 Years Ago
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Thanks Mark, I pickup a 4cyl. valve. Will let you know. Many thanks god Bless Eddie
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By GREENBIRD56 - 13 Years Ago
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I've been away from my computer Eddie and overlooked your note..... I used the PCV for a '64 292 cid truck and it bled way too much air into the intake. The engine acted like it would run on the PCV air alone. Rather than hunt down another, I orficed the line down to a better match. Mark's choice of a smaller valve is probably the right way to go - but the orfice will work too.
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By Riz - 13 Years Ago
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Let me ask you guys I am having idle problems too. I am running a 292 with g heads and a 3x2 offy with holly 94s. everything else stock idle it tends to idle fine in park but when coming to a stop it stumbles a bit. I have been chasing bogeymen like the PV and vapor lock on the fuel line. Do you think it could be the PCV? The pcv does rattle like a machine gun so i know it is working maybe too much. It might be a good quick fix to try a smaller valve I had never thought about that direction.
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By Eddie Paskey - 13 Years Ago
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Steve;; Thank You for returning the email. Think I'll go with Mark's valve, if that is not good will try your restrictor. Many Thanks and Merry Christmas!!! God Bless Eddie
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By charliemccraney - 13 Years Ago
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I used one for a GM 305 in the past and it worked fine. I can't remember the specific application now. A pcv valve is not something you just put on and go. You will need to adjust the carb for it. If you're not able to adjust it because of too much flow, that's a different story but after you've eliminated vacuum leaks. A good way to start is to be sure you can get it running right with only breathers, no pcv.
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By GREENBIRD56 - 13 Years Ago
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Riz - The troubles we were dealing with (downsizing the PCV) are a slightly different circumstance, my engine was acting like it had a big vacuum leak and the idle speed running high. After running out of places to look for a leak - I disconnected the PCV line and plugged it (both ways) and the "runaway" stopped. So I got a piece of tubing and throttled the hose which helped a lot. If your outfit stumbles when shifted into "drive" - it may have too little initial spark advance. Try raising the initial advance to something 10° or higher and see what the results are (at idle transfer). You may need to re-curve your distributor a bit so that you can have more initial advance - and then limit it to less on the top end. Because the two-barrels probably don't have a "ported vacuum" arrangement - you will most likely be needing to run "live" manifold vacuum to the can on the distributor. Because it may have too much travel - "adds" too much to the total when engaged - you may have to limit it as well after raising the initial static.
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By Riz - 13 Years Ago
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Steve
Thanks very much for the advice, this is my first y block. My previous project cars were imports or Sb fords that had a ton of data on them. I feel like I am often going one step forward and two back. Just grasping at staws.I get the idle straight and then tip in is junk. It has a mallory ignition so no vac only vac is for the AT. but great ideas on the timing, I will get back in it.
Well no one said hot rods made good sense. 
Thanks again
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By slumlord444 - 13 Years Ago
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I have a similar idle problem with my other hobby car. 65 Mustang with warmed over 302. Will try 4 cylinder pvc and see what happens.
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By pegleg - 13 Years Ago
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Riz, Steve, Just a thought. With the addition of the pcv to the triple carbs, you might want to close down the idle circuits and shut off the end carbs at idle all together. All three plus the PCV working is a lot of air. It would be a lot easier to work with one (center) carb because the velocity of the idle air and fuel will be higher. I didn't see a mention of which distributor you're running, but following Steve's instructions on a later distributor (not a Loadamatic) will help you a bunch. you might need to dig up a Crane adjustable advance can and limit the mechanical advance so you can use 12 degrees or so initial, without the vacuum hooked up. Another issue will be the tendancy for the engine to "hunt" with straight vacuum. As the rpm drops, the advance drops, causing the engine to drop more RPM. then it will pick up etc.
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By GREENBIRD56 - 13 Years Ago
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Riz - Are you running the Mallory distributor (p/n 3738701)? Their info says that the "standard" (01) ignition set-up is 24° at the crank - so your outfit would probably be OK with 12°-14° for an initial setting at idle. That would be 36°-38° total. Mallory has an advance curve kit (p/n 29015) that will let you tune the curve - and quite a booklet about how to do it. You should probably shoot to get it all in by 2500-2700 rpm. The directions for the curve kit are on the Mallory site and worth looking at regardless. Frank is right - there are some specific things to know about the trips - I haven't ever worked through a set before and don't have all of the straight skinny. But....there are several threads on this forum that have dealt with all sorts of issues with the elimination of the end carb idles - use and non-use of power valves, etc. So do a bit of digging around. Where are you taking the vacuum for your PCV - it interests me that it rattles. That would indcate you have fairly low vacuum at idle - which you shouldn't.
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By Riz - 13 Years Ago
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Steve,
Awesome info that is the distributor I am using. I will have to research that part number. Might be quite a journey. Quite honestly I have never really gotten into changing the advance curves a whole lot, but I think you may be right. I did have to add to the timing to work with the new trans. I will wager I have too much initial and idle timing, which could explain the hard starts and poor idle quality under load.
I do have the idle circuits and pvs blocked on the otters on the 3x. I also upped the jets on them 4 sizes to 56 to compensate for the lack of PV.
The PCV is dumped back into the rear of the valley pan. I had to add a new 90 deg port and bend some aluminum pipe to work with the new manifold. The rattling is the valve itself running back and forth. I bugged me for a while, and thought I had something spinster going on. But there are no real vacuum leaks, I also though I could have baleen losing it through the bottom end, but the engine has absolutely zero smoke, and no signs of leaks or leaks out the bottom.
Kinda bugs me that you are worried about it I just chocked it up to new set up differences and dismissed it. What are you thinking?
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By Don Woodruff - 13 Years Ago
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An observation most modern engines have a sealed crankase. The dipstick and oil filler are sealed, air tight. Is it possible excess air is coming in through the oil filler breather and dipstick? I was going to seal these openings on mine.
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By oldcarmark - 13 Years Ago
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I had the same problem initially with my PCV-rattling like crazy at idle.There are a couple of issues when dealing with different PCV valves.The size of the orifice and the spring pressure which works against engine vacuum to open the valve.At idle the valve should be closed or close to it allowing minimal air to enter the carb.Different valves have different spring strength keeping the valve open.The 4 cylinder PCV has smaller orifice and I guess a lighter spring so it is held closed at idle.The 302 valve was opening and closing rapidly at idle causing inconsistent mixture and the rattling noise.Changed to the 4 cylinder one and problem solved.
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By Riz - 13 Years Ago
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I am thinking I have partial issues of all the above. In addition to a small exhaust leak. I am going to have some quality time in the garage this week while we are getting all of this unseasonably warm weather. Figure I will start with the timing and idle and see if that helps the vac. Then on to checking vac at idle and maybe digging more into the PCV.
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By DANIEL TINDER - 13 Years Ago
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Don Woodruff (12/23/2011)
An observation most modern engines have a sealed crankase. The dipstick and oil filler are sealed, air tight. Is it possible excess air is coming in through the oil filler breather and dipstick? I was going to seal these openings on mine.
I had the same idea, since that air is unfiltered/dirty. But, crankcase pressure at high revs always pushes the dipstick out of the tube a bit, and too much restriction on the breather/filler usually causes oil pumping.
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By GREENBIRD56 - 13 Years Ago
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There were "sealed up" systems on several vehicles I've owned - where the PCV is taking "suction" air through the valve from the valve cover - and the sump intake "breather" is getting its air from inside the air filter housing. At lower rev's the PCV is sort of "sipping" air out of the crankcase - but if you get on the engine really hard and fast - and blow-by overpowers that volume by some amount then the "overflow" gets taken directly into the carb.
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By Riz - 13 Years Ago
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Ok played a little with the timing and got it set at 12 deg. Helped the idle but it still acts like a vacuum leak someplace. The PCV is still rattling. It starts up but needs some throttle play until warmed up. I am working on rerouting the choke cable so that is pretty normal. But after warm up it still is hard to start. I am running out of places to look for a vacuum leak. I have a new vac modulator on the trans so that should be ok. Very little vacuum pulled from the engine. Just PCV and trans. So I am thinking that if the PCV went bad or as mentioned is opening too light to go there first. The only other thing I can think of is an internal carb leak and quite honestly I am tired of tearing them down.
What do you guys think go for the PCV first at least to eliminate that and then move on, seems like the cheapest fix. I had a little déjà vu when one mentioned that the engine is acting like running on the PCV alone. Granted I have 3 carb openings but it does act like it could run just on the PCV alone.
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By GREENBIRD56 - 13 Years Ago
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Riz - Seems to me you ought to just start plugging things until you find the culprit!  Bagging the two end carbs - plug the PVC line - that sort of thing should begin to sort things out. I had an old four barrel carb I bought one time that pulled lots of air through the (very) loose butterfly shafts.
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By Riz - 13 Years Ago
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Steve,
I think you are right just start with process of elimination. It has got to be something simple and stupid I will be sure to post the ah ha. Everyone's help has been invaluable if for anything else to have some solidarity and keep me from trading it in on a gentle used Prius. 
At least it will give me something to do for the winter since I just insulated the garage.
I am just going to start with the basics and get the carb cleaner out and start chasing the usual suspects KISS.....
Fuel air and spark should be easy right?
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By oldcarmark - 13 Years Ago
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Have you tried hooking up a vacuum gauge and see what kind of reading you are getting at idle.Sometimes helpful in finding problem.
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By Riz - 13 Years Ago
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Just arranged to borrow a gage this week my last one got borrowed and never came home. This weekend will be spent trying to eliminate any possible vac leaks.
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By Riz - 12 Years Ago
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Turns out I found the leak in the hard line tucked under the hold down. It was just a small crack but I am sure it widened when it got hot. Vac problem solved. PCV now stays quiet. So i took her out for a spin. Trans did not bog and idle only dropped about 150 from park to drive so easy idle adjustment to split the difference.
Now the bad news is that I took her out on the highway and there was a little vibration above 3000 rpm. Took it home and put the timing light to it and it looks like the timing set is skipping a little at higher rpm. So looks like the next project is a new timing set (for all I know this one is orig. might as well throw in a hotter cam if I have to get in there.
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By GREENBIRD56 - 12 Years Ago
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Axial travel of a distributor shaft will cause a "jumping" signal as the helical drive gear twists the shaft ever so slightly as it moves up and down. Shim kits are around that will take up the endplay a bit if you find that is what is happening. Requires pulling the distributor out of the block and checking the clearance of the stop ring pinned under the main body. A slipped or slipping outer ring on a damper will move the TDC mark slightly from the initial position - but I haven't seen one that moved around while you were watching. The valve train might have a cylinder with differing lash - have you gone through the drill of setting all of the valve lash?
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By Riz - 12 Years Ago
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Ok I was wondering how it went from decent timing but not optimal to skipping junk. Went to double check and it turns out the lead was sliding too close to the number 2 lead and picking up that signal of course it would be showing incorrect. I held it closer to the plug and wow the timing was no longer slipping. Set back to 12* and decided to get a beer and leave it alone for a few days. Thanks to everyone for the help, I am an idiot.
I am telling you I want to kick myself in the butt and will stand ready to be made fun of.
Still a few tuning tweaks to be done, but apparently I am in no mental shape to do it.
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