Yep. But I wanted to run progressive linkage on the carbs due to gas prices. So my options were either buy a 4 barrel intake and get a 2x2 adapter, or use what I already had (the 3x2 intake) and buy a $90 Y adapter. I'm cheap and lazy. This solution was the best given those parameters. I get asked about this all the time. I spend most of my time trying to make people believe I went through all the options first.
No I sure don't. There was a tune up cabinet full of old PCVs when I bought my shop. Unfortunately there was no catalog. I can't even give you an application. This particular one had a hose connection on both ends. Sorry
I just read through this post. thanks for the info! I am running a 302 Ford in my Model A. I have the PCV on the drivers side valve cover in the rear position drawing vacuum from the carb riser base. I've got the breather on the opposite valve cover in the front. Around town the system seems to work fine, but if I drive the car at highway speeds for any length of time I get oil out of the breather that coats the firewall, header, hood sides and frame rail. Any suggestions?
This is a great tech thread TOMMY .Thanks for posting . Having acquired a 27 roadster running 4x97s on an Un modified Weiland intake , I'm learning the down side to no PCV and one breather/filler . So running through some options as far as modifying valve cover breathers etc , I still need to get the vapour air back into the intake , and was woundering if this would work , as posted by CHRX ? I initially ran the hose from the PCV valve onto a fitting at the base of the carb, but switched it to come in at the top of the carb a few days ago. The Rochester 2GC has provisions for both built-in. My uneducated guess behind doing this is that the vacuum will still draw vapors from the crankcase, yet not affect the air/fuel ratio entering the intake manifold. From reading the earlier posts here, I am led to believe that running the hose in below the carb is the established way to go. Can I really gunk-up the venturis and metering system by drawing the crankcase vapors in upwind of the venturis? Anyone ever try it this way? Also, I am still using non-detergent oil, so I don't know how that might weigh-in on this issue. Open for suggestions, Chrx Any thoughts on this ? Cheers Shrappy
...........................Sadly, we lost Tommy a couple of years ago, thus the Member Emeritus status. Luckily most of his posts endure on here and they were many, always helpful and informative. He is missed.
Ah Gutted . Yeah , um , I've been very dormant on here for way to long , and finally get back into the scene proper . Sorry to read of tommys passing , his way of putting pen to paper , particularly with the PCV system and how it works , really made things very clear . Shrappy
.............................Thanks, Tommy was a local hot-rodding icon and always willing to help anyone with great advice.
Folks tend to over think a PCV. all you need is a metered vacuum leak hooked to the crankcase. here is a picture of the PCV I retrofitted on my 55 GMC 287 Po ntiac mill. The carb and horizontal P CV valve came from a 66 chev 283. Hose to grommitt in valve cover. Simple and works fine.
I'm not sure what you're referring to with "switched it to come in at the top of the carb...The Rochester 2GC has provisions for both built-in". The vacuum source for the pcv should be from the base of the carb, or from the manifold. However, with a closed pcv system, instead of a pcv valve plus a breather that is open to atmosphere, a closed system doesn't use the breather, instead it connects the point where the breather would normally be to the air cleaner. So under low or no vacuum conditions, where the crankcase pressure exceeds the manifold vacuum, then the "breather" side will exhaust into the air cleaner, and the fumes will still be contained in the intake stream. So the answer is yes, it is standard operating conditions for closed pcv systems since the mid 60's to draw fumes into the top of the carburetor. No, it will not gunk up the venturies and metering system. But again, this should be the breather side, the pcv side of the system should still be plumbed to the base of the carb, or the intake manifold.
The explanation seems correct but I believe the drawing of the closed system has one mistake. The hose from the air cleaner to the sealed cap on the valve cover should draw air from the inside of the element, allowing the air to be filtered before it enters the engine. The drawing shows the hose entering the air cleaner out side of the element.
If you vent the breather to the outside of the air filter. All that does is put a film of oily residue on the air filter clogging it faster. The crankcase fumes excaping thru the vent don't require filtering. Those vapors are not a bit dirtier than those which are vacuumed thru the PCV system.
But the air flow goes the in opposite direction, look at the arrows on the diagram. I have seen more than one air filter canister that has a port on the clean side of the filter. Another issue is that if the PCV valve is located in the valve cover it should have a baffle below it to avoid sucking oil from the normal splash that lubes the valve train. At least this is how I see a system that works correctly.
The two paragraphs in my post that goes on about running the PCV line into the top of the Carb , were copy and pasted from chrx's post on page one. I don't particularly want to modify my manifold (pic at bottom of my first post) and after reading this thread , was curious as to if returning the PCV line direct into the base of the air cleaner/top of a Carb would or has worked for others? Unfortunately chrx hasn't been active for a long time so am figuring I can't ask him direct as to how he got on. Am happy to modify the valve cover breathers (blocked off by a previous owner) to make the system work , just really hoping to NOT have to modify my 4x2 (Weiand with 4 X 97s on it) manifold to make it work. It has only one vacum port which currently has dist and Trans hooked into it . Cheers Shrappy
Yes it would be best to have a baffle oil separator at the end of the hose. But mine on my GMC doesn't suck any oil (theres not the volume of oil in the valve train on the early Pontiac engines as there is in the Small block chevys and newer Pontiac engines.
And now for something challenging out of the shed of Shrappy's Originals , after hours of course , can't pay the bills doing homers ! So , I've been having a weeee issue with Oil Spray over the RH side wind screen , firewall , body etc at open road (100kph) speed on the 27 Roadster. Due to No PCV Valve system I suspect . This Old Weiand manifold only has one small vacuum port , which is used for the distributor, and No vacuum port for a PCV Valve system. Im guessing the old Draft Tube was what was used back then , which results in an oily undercarriage. From what I read up on , and what I learnt ( mostly from Tommys post here ) , was that we definitely need a PCV system , but what I also knew , was that I didn't want to make any visible changes to the old Weiand manifold. Lots of options were on offer , but none to my liking. After a weee while of giving the Grey Matter some late night work outs , , , this is my solution. Basically a PCV Valve system , attached on the manifold plenum underside ( in the block valley ) out of sight. Lots of pros , mostly the unseen on this manifold one , but the one Con ? If the PCV Valve starts playing up , it's manifold off to replace. From here , the pics can do the talking , Bit hard to tell in this pic , but the RH side wind screen , firewall and body is well coated in a mist of engine oil. The only vacuum port on this manifold. Used for distributor. Screw in PCV Valve. I made up a tube shield , to try and stop any direct splashes of oil getting into the PCV Valve. Underside of the manifold plenum. Shield faceing the back of the block PCV Valve screwed in place. When I was drilling , taping and fitting the 1/4 bsp fitting to the underside of the manifold , I found the casting to be very Gummy and I lost faith in everything staying put for any length of time , so I decided to add a support bracket. I also added a saddle over the Tee fitting. I used a Tee fitting for just in case the PCV Valve isn't big enough ( this was the biggest screw in type I could find and usually found on the side of a Nissan motor ) and I need to add another. The fixings used are 3/16 Button head set screws ( they were fun to get in through the intake runner ! ) . I also added a screen just to be sure splash Oil won't land in/on the PCV Valve. Result ? About An hour and a Halfs driving at our open road speed limit ( 100kph/60mph) and no oil mist over any part of the car . MINT Shrappy
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