KAD36 Posted December 1, 2012 Posted December 1, 2012 (edited) If your engine is worn and you are interested in eliminating some of the oily blow by from the crankcase breather from getting all over your engine compartment, a PCV (Positive Crankcase Ventilation) system can be built and added for about 20 bucks. I thought it was worth a try, built a prototype to test out, and am pretty happy with the results. Trying a few different valves, I found one that pulled enough vacuum to stop the blowby gasses from coming out the breather at idle and at moderate load. See what you think, and if you have ideas to further improve or comment on the design, please contribute. A PCV system is comprised of 4 basic components: 1) a breather, to let fresh air into the system, 2) a PCV valve that meters engine vacuum to pull the fresh air through the engine and evacuate the blowby and other crankcase gasses, 3) hosing/grommets to plumb the system from breather, to crankcase, PCV valve, and vacuum source, and 4) a vacuum source, usually at the intake manifold or a non-metered vacuum source at the base of the carb. The breather is connected to one end of the valley cover or one of the valve covers in a V engine, the opposite end of the valley cover or the opposite valve cover is connected to the valve side of the PCV valve (usually the larger diameter side of the valve), and the other end of the PCV valve is connected to an engine vacuum source. At idle, when engine vacuum is high, the vacuum pulls a piston inside the PCV valve against a spring and seats the piston such that a very small amount of metered vacuum is pulled through the valve. For a properly sized valve, this vacuum should be enough to evacuate the crankcase of blowby vapors, which are typically low at idle, and low enough as to not adversly upset the idle circuit and performance. Since the vacuum loss at idle through the valve leans out the mixture, it must be compensated for by richening the idle mixture screws anywhere from ¼ to 1/3 turn CCW. Under load, blowby gasses increase, and as vacuum drops with engine load, the spring inside the PCV valve unseats the piston, opening the valve further, allowing more vacuum through the valve, and thus enabling greater evacuation of crankcase vapors. Under conditions of extreme load or worn engine components, the PCV system may not be able to keep up with the generation of crankcase vapors, and in this case the vapors will escape out of the breather. Under load and high rpm conditions, the vacuum flow pulled through the valve is negligible compared to that passing though the carb, and you should notice no difference in engine performance. A PCV system can be either open or closed. An open system, which first came out in the early 60s, used an open air breather feeding a PCV valve plumbed into the intake manifold or carb base to mix and burn the crankcase vapors with the incoming fuel charge. If the PCV system could not keep up with crankcase vapors, the vapors would spill out the breather into the atmosphere. In a closed system, the breather is moved into the air cleaner, or some other location such that any escaping gas would be reintroduced to the engine for combustion either through the air cleaner or intake manifold. Some of us may remember GM cars of the 70s-80s that had the little foam breather in the air cleaner. There ya go. My prototype system is an open type, the parts list is below and ran about 22 bucks at my local parts store. Oil Filler/Breather cap – Stant #10070 (this is a sealed cap with a fitting on it for a PCV hose) PCV rubber elbow – Dorman Help #47028 PCV Valve - PV679 Purolator 11/32 pcv hose - Thermold Various brass plumbing - 1/8” pipe T, 5/16” x 1/8” hose barb, 1/8” adapter When at idle crankcase vapors kind of drift out from both the filler cap and the road draft tube (at least on my car); there is little to no positive ventilation. At speed, the venturi effect of the road draft tube creates vacuum which pulls clean air in through the filler cap and pulls out crankcase vapors from the road draft tube. In my PCV system, the flow is reversed. Air enters the road draft tube, passes through the valley area, out the filler tube and cap, through a fitting in the cap to the pcv valve, and then into the intake manifold at the vacuum source for the wipers. I chose this for 3 reasons – first it was quick, low cost and effective, and second, it eliminated any crankcase vapors from coming out of the oil filler and blowing back on the engine, and third, I could disconnect the whole thing in a minute, plug the vacuum source and put the OEM filler cap back on. The PCV valve chosen is for a 350 V8 engine – I tried one with a smaller port and it did not draw enough vacuum to properly evacuate the engine. Perhaps a tight engine with less blow by could tolerate a lower vacuum valve. Pictures below: So hows it work? Well, so far, so good! Both at idle and with the engine at about 2000 rpm in Drive held against the brakes, wheels blocked, there were no traces of any crankcase vapors coming out of either the road draft tube or the breather. Prior there was a visible amount (I used to keep an old sock over the filler cap to filter off some of the oil vapor). Backing out the mixture screws ¼ to 1/3 turn smoothed the idle right back out at 475 rpms in Drive. No issues seen under load when driving. For a basic system, it works well and I'm pleased with the results. Plus the engine can go back to a stock look easily. No fumes out the back or under the hood or in the passenger compartment. Moisture and other corrosive gasses are pulled out of the engine effectively at idle and at speed, and reburned. Makes for less emissions. Let me in fairness point out that there are only about 100 miles of testing on it so far - I don't plan to rejet the carb or anything and am not sure how necessary that is - maybe someone with more knowledge can chime in. If anything goes amiss, I'll give an update. To improve upon the design, the vacuum source should be in the center of the manifold so that all cylinders are equally “diluted” from the introduction of crankcase vapors. Using the current vac port on a 55 intake manifold that goes to the fuel pump for the wipers favors leaning out the front bank of cylinders. My thought was to drill and tap the underside of the manifold in the center, thus better hiding the port. A typical modification also is to retain the open breather at the filler neck, and remove the road draft tube. A freeze plug can be fit or epoxied onto the opening for the road draft tube, drilled and fit with a PCV valve grommet, and the valve placed in the valley pan vs the filler cap. I may go that way after running this setup for awhile. If you wanted a truly closed system, a sealed filler cap could be used and the breather and hose could be placed in the air cleaner, although one would have to be careful if using the oil bath cleaner and not have an issue drilling a hole in the side of the air cleaner (something I couldn’t do!). Another approach is to drill and insert the grommet and valve back of one of the valve covers, and drill the other for a breather (unless the valve cover already has one). Still another variation could replace the current 55 valley pan filler neck with one from 63-67 corvette, which had a pcv fitting plumbed directly onto the filler neck instead of the cap. You can find these on eBay for about 20 bucks. Also, while air is going "backwards" through the road draft tube, I don't think there is any fear of blowing gunk back in the engine - there is not enough pressure to do so. If you are concerned pull your valley pan and check it out. I had mine out about 2 summers ago and soaked it to get as much junk out as possible - although if you follow one of Old-Tanks threads, he outlines an innovative way to disassemble and clean the innards of the road draft tube mesh filter. Basically, you just need a source of intake air and a design that provides cross ventilation through the crankcase back to a centralized point on the intake. So, go out, pop that hood and have a peek... :cool: Edited March 31, 2017 by KAD36 (see edit history) 3
bhambulldog Posted December 1, 2012 Posted December 1, 2012 Most interesting!! Sitting at a stop light today as I watched the vapor from my crankcase waft around the car next to me, I thought; I need a PCV system.Mine is a late '55 with breather/oil filler caps in each valve cover. For mine; I thought to plug the bottom of the road draft tube. Tap the elbow of the road draft tube for the PCV valve and use the wiper connection as you have. I haven't gone as far as you have. Not so far as to even buy any parts, yet. So, I need to thank you for showing a practical way to get it done:cool:
Guest Pletch Posted December 2, 2012 Posted December 2, 2012 great write up and idea. I may look into this next spring.
KAD36 Posted December 2, 2012 Author Posted December 2, 2012 (edited) Jim - that would work too - double check that area on the road draft tube you're eyeballing has enough meat and is contoured to to hold a grommet or a few threads before you lay into it.Thanks for the feedback guys. Edited December 2, 2012 by KAD36 (see edit history)
bhambulldog Posted December 2, 2012 Posted December 2, 2012 Jim - that would work too - double check that area on the road draft tube you're eyeballing has enough meat and is contoured to to hold a grommet or a few threads before you lay into it.Thanks for the feedback guys.Perhaps, It would be easier to remove the draft tube, and insert a grommet into that opening...........
page2171 Posted December 3, 2012 Posted December 3, 2012 Perhaps, It would be easier to remove the draft tube, and insert a grommet into that opening...........Like this PCV Valves & Grommets |. This is the one Russel Martin sells for Nailheads up to '62. Thinking about it eventually for my '62.
NTX5467 Posted December 8, 2012 Posted December 8, 2012 The first PCV systems which Chevy used in the 1967 model year utilized a "cap" which went into the road draft tube "hole" in the engine. One longer 1/4-20 (?) bolt held the cap in, through the top. The cap had a nipple to which a tube was attached for an "inline" pcv valve, which then was attached to a dedicated rear vacuum port on the carb's rear base housing. If the road draft tube on the Buicks is of the same size and such, a similar situation might be done on most any earlier road draft tube-equipped vehicle. The pcv might have screwed into the carb's base housing, possibly, but it was all "back there" and very out of sight. In that model year, the oil filler tube was still in the front of the intake manifold, topped by a filtered breather cap. To me, the key part would be the "cap" which would replace the road draft tube and supply the hose nipple, from which the tubing and valve could be "freeformed for the application" and pretty much out of sight. That cap and bolt should be available through the Corvette restoration vendors, or a few other '60s Chevy parts vendors, I suspect.Just some thoughts,NTX5467
bhambulldog Posted December 8, 2012 Posted December 8, 2012 Like this PCV Valves & Grommets |. This is the one Russel Martin sells for Nailheads up to '62. Thinking about it eventually for my '62.[ATTACH=CONFIG]165876[/ATTACH]That ought to do the trick!!
60FlatTop Posted December 9, 2012 Posted December 9, 2012 On many road draft tube systems there is a steel wool mesh that should be checked every 50 years or so.Also the tube has a bologna sliced end with the long side facing forward. That creates a partial vacuum while driving and draws fumes out at higher rpm. If your car does not have a cloud coming from the tube a guaranteed method of creating one is to do just a valve job. Tightening the valve sealing will blow more combustion gases past worn rings.Just a couple of thoughts.Bernie
old-tank Posted December 9, 2012 Posted December 9, 2012 I thought for sure some California guys would chime in. Back in the '70s I saw a few 55s from CA that had a PVC system installed and it was my impression that it was a required retrofit. Before installing change the oil and then go for a 200 mile drive to cook out all the volatiles dissolved in the oil and loosen up the rings. Also be sure the draft tube vent system is clean and working properly (see tech tips on my website).Willie
NTX5467 Posted December 11, 2012 Posted December 11, 2012 (edited) As mentioned, CA had pcv-retrofits for vehicles going back to 1955 model year . . . required. Some looked more "cobbled" than others, from the pictures I saw in the later 1960s.Head over to www.wildaboutcarsonline.com and go into the magazine section, you're looking for CAR LIFE magazine, August, 1965 issue. In there, you'll find an article on the then-new A.I.R systems and a history of the pcv systems and CA "desires" back then. Quite interesting! "More Smog Control = More Expense" is the title of the article.Just some thoughts,NTX5467 Edited December 11, 2012 by NTX5467 (see edit history)
usnavystgc Posted November 29, 2021 Posted November 29, 2021 (edited) OK @KAD36, I too have blow by coming out the vented filler caps. My engine has 2 vented filler caps (1 per side on the valve covers). If I get a Stant 10071, a pcv valve, some vacuum hose and a T fitting for the vacuum on the intake manifold, can I set it up like this? Install the T fitting on the intake manifold and run one line to the PCV valve, attach the PCV to the Stant 10071 filler cap and be done? Is there anything else I would need to do with the road draft tube pipe? Would it be better to install a sealed filler cap on the other valve cover and just let the air be drawn in thru the road draft tube? Note: The vacuum on the center of my intake does not go to the wipers but, to the power brake unit. The wipers have a dedicated line from the fuel/vacuum pump going straight to the wiper motor. I also do not want to drill a hole in my air cleaner/silencer. Edited November 29, 2021 by usnavystgc (see edit history)
JohnD1956 Posted November 29, 2021 Posted November 29, 2021 Our engines have the vent tube at the back of the valley cover and that works by driving the car. As you move the pointed end of the tube creates a separate vacuum and the fumes are pulled out of the engine while fresh air is pulled in via those breathers/oil fill caps. If you are moving this is not a problem. When you stop then you may see fumes exiting the engine via those breathers. And thus the phrase: Buicks were meant to be driven. Lol..but really, a closed pvc system is probably just looking for trouble as those fumes will be routed through the aircleaner to the carb and then just add back to what is already being generated in the engine block. Consider how much the car is used vs how much investment is needed for a fix that will give minimum payback. At least that is my opinion. 4 2
Bloo Posted November 29, 2021 Posted November 29, 2021 (edited) On any crankcase vent system, PCV or not, there needs to be a filtered way in and a way out for the air. Sucking air from under the car through the draft tube is in my opinion a horrible idea, even if there is a mesh (filter) in it. Yes, technically it would work, but if I were doing it I would get rid of the draft tube. A bigger problem is the vacuum source. Some of those California conversions are terrible. Often they just hooked the PCV to some random vacuum line. It screws the fuel distribution all up and makes the car run bad. Ironically, the emissions also go sky high. Look at any factory PCV system (well. almost any) and you will see that the vacuum is plumbed in such a way that it mixes evenly with the air/fuel coming out the bottom of the carburetor. Usually there are 2 ports right below the idle jets. The holes through the vacuum hookup need to be pretty large or they will just plug right away with carbon. The easiest way is to use a carb with a PCV port built in, although Ford used an adapter plate for years. The jetting/calibration of the stock carb also may or may not be close enough. Don't forget you are letting more air in Use a PCV valve for an engine of the same approximate size and RPM range (Chrysler 318 for the 322 maybe?). There is a physical limit to how much air you can pull without making the engine run horrible, and no PCV system keeps up 100% of the time, even on a new engine. When it doesn't keep up the vapors blow backwards, and you still get a mess around the breather cap. It just gets much worse as the engine ages and wears. In the 1970s they plumbed the breather cap up to the air cleaner in an attempt to control the mess, and to burn the vapors even when the PCV couldn't keep up. All that did was make a mess on the air filter element instead of around the breather cap. Edited November 29, 2021 by Bloo (see edit history) 3 1
usnavystgc Posted November 29, 2021 Posted November 29, 2021 Unfortunately, I don't have a carb with a PCV port or any spare vacuum port for that matter. Based on what John said, I'm not sure if I'm gonna do this but, I am interested in the right way of doing it (if there is one). Since I don't have a carb with a dedicated PCV port, would the vacuum in the center front of the intake manifold be a good alternative? If not what are the disadvantages of using that vacuum port? I don't see any way to use a spacer on the carb to add a PCV port since the air cleaner already dents the hood insulation. It would have to be a thin spacer. In reality, it just sounds like this isn't really doable if you want it done the right way with the fewest mods. I don't want to do any major mods to my car. I would like to improve whatever I can and at first glance this seemed like an easy, cheap improvement that could be made to easily go back to stock. One question to help me understand why you say drawing vacuum up the draft tube is a horrible idea. Doesn't the current road draft system draw vacuum up the road draft tube already? As far as taking the road draft tube out completely, I don't want to do that because it modifies the stock look of my car and it would be a pain to put back if I were to ever go to a show. If I do any mods at all, I want them to be simple, cheap, beneficial and easy to return to stock. That's just me. From what I'm gathering, this is none of the above if you want to do it right. 1
ted sweet Posted November 29, 2021 Posted November 29, 2021 isnt the draft club the exit not the intake of air 1 1
Bloo Posted November 29, 2021 Posted November 29, 2021 (edited) 2 hours ago, usnavystgc said: Since I don't have a carb with a dedicated PCV port, would the vacuum in the center front of the intake manifold be a good alternative? If not what are the disadvantages of using that vacuum port? Nothing is a good alternative to dumping it into the airstream right below the carburetor, preferably right under the idle jets but at least under the primary barrels. A manifold port is an easier way for the engine to draw air than sucking it through the idle system and/or the carburetor venturi. PCV has been done with other vacuum ports, it just leans out the cylinders that have the vacuum port between the carb and the intake valve. You will have to richen the idle way up, causing the other cylinders to run way rich. It may be enough to fix part throttle cruise, but maybe not. If the port is out near the end of a runner, it will kill that cylinder entirely. The short version is it wont tune up and the exhaust will stink. 2 hours ago, usnavystgc said: Doesn't the current road draft system draw vacuum up the road draft tube already? No, the draft tube creates suction when the car is moving. The clean air goes in the breather cap and the vapor fouled air goes out the draft tube. Until you stop moving, or until the volume of crankcase vapor overpowers the system. Then the vapor comes out both ends. 2 hours ago, usnavystgc said: One question to help me understand why you say drawing vacuum up the draft tube is a horrible idea. There's a lot of dirt, water, and other contaminants blowing around under the car. I don't recall if the nailhead has a filter in the draft tube. I think an earlier post says it does, but if it doesn't (Chevrolets don't for instance, they just have an oil separator), you would be sucking all that right into your engine. Still, the air up just under the hood is much cleaner and drier. Pulled in through the oily mesh of a breather cap, it probably isn't too bad. 5 hours ago, usnavystgc said: I too have blow by coming out the vented filler caps. My engine has 2 vented filler caps (1 per side on the valve covers). 2 hours ago, usnavystgc said: As far as taking the road draft tube out completely, I don't want to do that because it modifies the stock look of my car You could just plug it somehow. Since you have 2 caps you could run a PCV valve on one of them and an open breather cap on the other. Air goes in through the oily mesh on one valve cover, through the engine, and air and vapors go out the other valve cover. This was the standard method on a whole bunch of American cars for years. 2 hours ago, usnavystgc said: I don't see any way to use a spacer on the carb to add a PCV port since the air cleaner already dents the hood insulation. I don't have a solution for that part. Edited November 29, 2021 by Bloo (see edit history) 1 1
usnavystgc Posted November 30, 2021 Posted November 30, 2021 @Bloo, I really appreciate you taking the time to explain all these things to me. It looks like this is a no go for me. On a positive, I now have a greater understanding of PCV systems and what it takes to do them right. 4
KAD36 Posted November 30, 2021 Author Posted November 30, 2021 (edited) Little late to the party…..great discussion. So for context and explaining the background of this “bright idea” at the time….the engine didn’t have any “pressure” pushing air out of the breather so nothing was broken - but at idle, at stop, hot engine, 20W-50 oil, in drive or under low speed load it was just an oily mess wafting up out of the breather, getting blown back by the fan all over everything and faintly seeping into the cabin even with all the firewall grommets sealed up. At speed the venturi effect at the road draft tube worked ok - just the way it was supposed to. So what I was looking for was a way to make a worn engine have less noticeable blowby without irreversibly modifying something (like drilling a hole in the air cleaner or manifold) and only spend a little bit of money. Sucking the vent air backwards up the road draft tube was admittedly not the perfect answer, but consider the engine was already worn, there is an oily mesh in the valley cover where the draft tube connected and the car is pretty much driven on clean roads, so I figured that was not much worse than driving on a dusty road with the fan blast sending dirty dusty air to be filtered by an equivalent mesh in the oil filler cap breather and be drawn into the crankcase in normal operation. This set up did reduce the noticeable stink and mess and had no adverse effects on the engine for the couple seasons I ran it A centrally positioned vac source on the manifold would be more desired, but hood interference as discussed is a valid concern, I just used the existing vac ports, and the spark plug nearest that port might have looked a little different when the time came to clean it but all in all it worked ok, nothing broke worse. Certainly room for improvement. I had seen some older period photos of west coast cars that show a tube coming out of the air cleaner, so perhaps that’s where the road draft tube was re-routed, maybe prior to PCV valves? A better way if you're really interested is to consider removal of the road draft tube, get a grommet to the fit opening in the valley cover then insert a PCV into the grommet and into the valley cover and run the PCV off manifold vacuum - I believe that’s how the Centerville kit works. I bought one for the new engine but never installed it because the new engine didn’t need it. On a 56, air would come in through both valve cover breathers, filtered by whatever mesh is in there (admittedly not as good as if the air was sourced from a port from the clean area in the air cleaner like the 70s-80s cars) through the crankcase, out the valley pan through the PCV and into the intake manifold. At least I think that’s how it works but correct me if I got it wrong. Now if you preserving the look of the car is important, then I’d vote +1 on Bloos idea of running the PCV valve on 1 breather cap. The best way to solve the problem was to just rebuild the engine. Now there is no mess coming out of the breather. I do keep an old sock over the breather to catch any oily film that might blow back on the firewall because the paint and decals are all fresh and I’m too #&$@*$# about keeping it clean and I ain’t stripping that firewall and painting it again…..couple thousand miles and it’s still a clean machine. Hope the background is helpful and you decide on a course of action that works for you! Edited December 1, 2021 by KAD36 Editorial clarifications (see edit history) 5
2carb40 Posted December 7, 2021 Posted December 7, 2021 Interesting discussion and it brought to mind that I still have the air injection pump that was factory for 1972 on the 350 V8 in my Buick Skylark. Didnt bother to research function of system. Like alot of things it seemed like a good idea at the time, I suppose. Made some engineers look good at the company for awhile till knee jerk inventions for pollution control gave way to computerized control reducing emissions with more accurate control being able to be achieved. I do wonder how they regulated pressure from the air pump. First guess is increase/decrease per rpm the engine spun pump? Thoughts? Seems as though it would increase crank case pressure... Now seems similar to story of The Pied Piper...chase the rats then chase the cats.... 50% could go electric. Last publicized study said the planet has 50% of lithium needed as soon as we go all elec battery powered! Hmmm. We are the ultimate concerned keepers of the planet when we don't allow rebuildable resources to be melted down to make someone's latest fallacy.
EmTee Posted December 8, 2021 Posted December 8, 2021 The A.I.R. (secondary air injection) system pumped air into the exhaust manifold to oxidize unburned fuel in the exhaust. It had nothing to do with the positive crankcase ventilation (PCV) system. 2
2carb40 Posted December 8, 2021 Posted December 8, 2021 3 minutes ago, EmTee said: The A.I.R. (secondary air injection) system pumped air into the exhaust manifold to oxidize unburned fuel in the exhaust. It had nothing to do with the positive crankcase ventilation (PCV) system. Correct 1
KAD36 Posted December 8, 2021 Author Posted December 8, 2021 (edited) Is that why the pressure regulation may not have been important because of where the air was introduced - and it was proportional to engine speed and exhaust flow? Edited December 8, 2021 by KAD36 (see edit history)
60FlatTop Posted December 8, 2021 Posted December 8, 2021 On 11/30/2021 at 2:47 PM, KAD36 said: The best way to solve the problem was to just rebuild the engine. Maybe the rebuilder told you the valves were in great condition and needed very little. I have seen times when a worn engine has been diagnosed as needing a valve job. It is fairly easy to pull the heads and grind the valves. Those stories lie in the dust under round wood stoves in country stores across the country. Most engines wear out equally. No one part or system has a longer life. Looking at the combustion sealing of an engine you have the valves sealing the top end and the rings sealing the bottom end. When an owner does a valve job the top end gets tightened up. But the rings remain the same and blowby will increase due to the increased sealing. When you sit at the gate of a car show you can see the "puffers" come in with their blue gray pulses showing under the rear of the engine. That is leakby from each cylinder pressurizing the crankcase and relieving through the draft tube. It will build up and push oil out of seals and fittings as well. This is for a worn engine. A low mileage engine can also have low end blow by from long term storage. A used, but not worn out engine will come to rest with its cylinders in various locations in the taper of a worn cylinder. The rings will be expanded near the highest wear at the top and compressed at the bottom of the bores. Setting like that for many years will usually cause the compressed rings to stick in the ringlands. The upper ones may follow the taper and maintain compression if the cylinder haven't rusted badly. These cars will start hard when cold but about 200-300 miles of use a compression test will show things back to normal. But they may also show signs of crankcase pressure by the puffing ar vapors wafting from the oil fill pipe. It is pretty much an all or nothing deal. You really shouldn't do just a valve job on an old engine now that we are out of the 1920's. 2
EmTee Posted December 9, 2021 Posted December 9, 2021 One of the first things I did to my '56 Bel Air was a valve job. This was when I was 16... Prior to having the car given to my by my grandparents, it sat in their garage for years (at least 6 or 7). The car had about 60K-ish miles on it at the time. After the valve job it smoked like a fiend out of the road draft tube (as well as exhaust) when sitting at a light. I wound-up replacing it with a good running 283 with an aluminum Powerglide that my father sourced. So, I concur 100% with Bernie's comments above. On the other hand, I have 'bought time' on a car with worn valve guides by simply replacing the valve stem seals. Just be aware that such decisions have consequences ("pay me now AND pay me later"). 2
JohnD1956 Posted December 9, 2021 Posted December 9, 2021 In the decades of the 80's the head gasket on the '56 started to leak. Thats when one burnt and two cracked valves were discovered. The heads were sent for a valve job under the advisement that this could lead to low end problems. But I was fortunate and to this day the lower end has never had to be reworked. Sometimes I do see some fumes escape from the valve cover breathers while at idle and warming up. However, it is usually started and then driven through the warm up period so I can't say for certain that it doesn't produce these fumes while I am moving. I can say that I don't see evidence in the rear-view mirror of the fumes or oil burning while driving, and no one on a tour has ever told me that it is burning oil. 1
MZ3033 Posted June 23, 2022 Posted June 23, 2022 (edited) I'm a little late to the thread but as I'm leaning more about my Buick as it gets taken apart and restored I realized I probably have the California retrofit. My 1955 Model 63 was build in CA and stayed there. It did not have a draft tube when I got it and instead had this carburetor base plate that allowed for a hose connected to a valve that fit into the valley cover. You can see the base plate from the back side and the rubber hose attached to a valve as well as how it sat in the engine bay before I pulled it. I can't seem to find that base plate anywhere, but the air cleaner fit...although it doesn't have the insulation currently. Figured I'd share. Probably the system old-tank referenced? Edited June 23, 2022 by MZ3033 (see edit history) 2 1
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