I have a offenhauser 3x2 manifold on my SBC & i want to put the Pcv valvevthru the manifold( to keep the valve covers"clean" lookin) where can I drill thru the manifold ?It looks like right in front of the distributor hold down theres a spot.Anyone ever do this? I ran it without a pcv but its spittin out oil onto my windshield when i'm on the highway. JimV
My center carb has a hole drilled and tapped in the base and that's where I put my PCV. It still blew a liitle oil onto the hood at speed but I solved that by extending the breather tube.
I already have a hose in the vacuum side of the manifold, I want to know where I can put the pcv valve instead of thru the valve cover!! JimV
The PCV valve is the part of a closed crankcase SYSTEM that operates at IDLE. The part that works at speed is the vent hose that goes directly from some area open to the crankcase, usually a valve cover because it's easy to do, to the INTAKE of the carburetor, usually in the aircleaner base, inside the air filter area. They usually have their own sponge-like filter commonly called a "bowtie" that collect the liquids. You need both these parts, the PCV valve and hose and the crankcase vent hose, for it to work correctly. Check out where these parts go on a '70s car and try to duplicate the function if not the location.
Here's one solution for those who don't want holes in valve covers. Run the PCV from the oil breather tube to the base of the carb. The vacume differential keeps the oil vapor from blowing out the breather. Just drill the tube, stick in a grommet with your PCV and run the line back to the carb base. No blowby and you can run those vette valvecovers. Oh, and we welded in a little baffle above the PCV inthe breather so the oil will go by it when you fill and not into the PCV line.
I used a Mopar slant 6 cap on an Olds Rocket once. I don't remember if it's the same size as a Chevy or not. It's closed, no vent in the cap except the hose nipple and that's the one you want to go to the carb INTAKE although you may get away with T'ing it to do both.
It's just a normal cheapie chrome breather. It was one of the old chromed goodies gathering dust high up on the wall at my local performance parts place. It's been up there since I was in High School. 1969 or so. Bought the chromed coil that was up there next to it too. Don't remember the brand. Probably Cal-Custom.
DRJ - you got me thinking here... on my 401 I filled the road draft tube hole with a grommet and PCV valve, then ran a hose from the PCV valve to the base of the carb. Both the valve covers sport vented filler caps. Seen this done before and seems sensible enough, but does this sound like a workable 'system' to you?
[ QUOTE ] DRJ - you got me thinking here... on my 401 I filled the road draft tube hole with a grommet and PCV valve, then ran a hose from the PCV valve to the base of the carb. Both the valve covers sport vented filler caps. Seen this done before and seems sensible enough, but does this sound like a workable 'system' to you? [/ QUOTE ] Sorry' but it won't work the way a PCV system should and does work. You get oil coming out of those breathers don't you? Or you put your old Gym socks on them like "booties" to collect the stuff... You are redirecting what sed to go out the draft tube to come out the breathers. Draft tubes were usually cut like a venturi so low pressure of passing air would draw out the fumes, while drawing fresh air in the V-C vents. Now you have it working backwards. It's called a Positive Crankcase Ventilation system because it is just that. all the fumes positively get ventilated THROUGH THE ENGINE and burned! The valve cover breathers defeat the system as it should function. The PCV valve can't keep up with the pressure at any air flow higher than an idle, in fact, they are designed to restrict the flow. The majority of the blowby fumes are supposed to go out the breathers into the hose that then goes to the base of the carburetor, inside the air filter where the carb is drawing them into the engine along with fresh air, to be burned. If you keep the vents open on the valve covers you should keep the draft tube open too. At least then the mess will go on the frame and not the firewall.
Sorry - no mess on the valve covers, intake valley, etc... Everything is nice and clean and the car has run just fine for a coupla years now... I was just hoping to avoid an eventual problem and perhaps make it run better if the current setup was causing minor problems. Would I be better off capping the road draft tube hole, installing the PVC in one valve cover with a sealed cap (with hose running to base of carb), and leaving the other valve cover vented...? Isn't this the basic factory PCV setup?
[ QUOTE ] Sorry - no mess on the valve covers, intake valley, etc... Everything is nice and clean and the car has run just fine for a coupla years now... I was just hoping to avoid an eventual problem and perhaps make it run better if the current setup was causing minor problems. Would I be better off capping the road draft tube hole, installing the PVC in one valve cover with a sealed cap (with hose running to base of carb), and leaving the other valve cover vented...? Isn't this the basic factory PCV setup? [/ QUOTE ] Sounds like you have a fresh engine with all the rings seated as they should be and virtually no blowby, Congratulations! The PCV valve and hose can't handle High RPM crank case pressures in a "seasoned" motor. That's what the open vented side is for. Or what the draft tube was for on an old system. but with a PCV system, that side isn't just a vented cap. It is a sealed cap or hose that directs all the crank case fumes and oil vapor into the carburetor by way of the aircleaner base instead of just out into the ambient under hood air. Old system, air going under the car siphoned off the fumes, remember most draft tubes were cut on some angle so the airflow would suck the fumes out? This actually drew freshair INTO the breather at the top of the engine. If you get rid of the draft tube and don't direct those fumes to the carb intake. They end up coming up out of the vent that was supposed to have fresh air going in. Most of the aftermarket airceaner housings have the pipe for the hose to go on. I just run the hose up one of the air intake scoops on the '55 Olds I usta have. I think you have a tight clean engine, if and when it starts some blowby you will probably want to trade the vented cap for a hose to the airceaner.
all these responces & I still was wondering if I can just drill a hole behind the last carb,infront of the distributor hold down. JimV
Jim, I dont have a pic here, but I drilled and tapped a Intake in front of the dist where you mentioned. It seemed to work just fine. Actually you can buy a pcv that treads in to 1/4 pipe tap hole. I'm pretty sure it's a mopar part. You end up with a real clean OEM looking instalation. Hope this answeres you question.
But you still gotta have the larger vent hose that normally goes from the air cleaner to the valve cover. If you have a manifold with a fill tube at the front you could tap into it, I assume you do, otherwise how would you fill oil. Maybe go off fill tube to one of air cleaners with the vent hose & fab a cap for oil filler tube that does not breathe?
JimV, I did just what you're proposing with a single 4bbl on a Edelbrock performer. 1. Drill a hole in the front of the intake for a press-fit oil filler tube. 2. Drill and tap a hole between the carb & distributer for the pcv valve. 3. Weld a baffle under the pcv hole to prevent oil from getting sucked out. 4. Connect the pcv to the base of the carb (I got fancy with a polished ss hard line).
Don't mean to hijack the post, and I dunno if anyone remembers awhile back when i was having problems with this stuff, well the problem never got ficed i just drove the thing to the shop blowing out a little oil. I'm not a mechanic so I didn't know what the hell that hose hanging down from the back of the intake was until my teacher at school told me it was the breather hose. He told me it was probaly stopped up and i just needed to take it off and soak it in some gas and clean it out. Is this most likely going to fix the oil coming out of the dipstick problem? Is the hose supposed to be connected anywhere besides where it mounts to the intake or does it just hang down? looks like it had one of them filter things like mentioned above maybe it's just stopped up. Thats the only problem with the old 389 so I'll feel alot better about it if i get it taken care of. All the damn bodywork ain't no good if I'm spraying and burning oil off my exhaust....
FYI, the 63-ish corvette oil fill tube has a nipple for pcv hose hookup & is available through corvette repop shops. WWS
I'm at the same crossroads right now. So, if I've got a set of Cal Custom V/C's with no holes, all I have to do is drill hole into front of edelbrock intake to accept oil fill tube, then drill hole into tube, add grommet, and put PCV valve into that and run line to base of carb?! is this correct? I'm a simpleton sometimes and if it is, what type of cap should go on oil fill tube, vented or solid? thanks
Grumpy, My pcv takes a suction off the lifter valley area under the intake, as opposed to off the oil fill tube. Either should work. I used a vented cap. Air comes in through the cap, mixes with the fumes, and is vented out through the pcv to the carb base.
I'm also in this same predickament . But my problem is that my carb closest to the distributer (3x2) only has two vacume ports. 1 for my distributer and 1 for my PCV. I need another for my tranny (350 turbo). Can I Tap my intake and hook my tranny to that? Or do I need the tranny to be hooked up to the carb? And if so, will hooking the filler tube to the intake work? I know it seems like I'm asking the same questions that have been answered, but I just can't seem to get it worked out in my head. Could someone draw a diagram with kindergarden level words on it? (I'm stupid!) RICH
You should be able to tap manifold vacuum for the tranny modulator, and for crankcase ventilation you should be able to do what the other posted here... run your carb vacuum port to a PCV tapped into the oil fill tube, This should give you essentially the same arrangement as replacing a road draft tube with a PCV valve connected to the carb base. HOWEVER, with that said, I'm still not sure why DrJ says this is not a workable system (?). My brain says that the carb is 'pulling' the hot crankcase gases out thru the PCV/road draft tube hole in the manifold (or oil fill tube) and re-feeding these gases to the cyclinders. The hot gases are replaced with fresh air flowing in thru the valve cover vents. Right? Am I missing something basic here?
yeah, except, I won't have any V/C vents. my cal custom covers have no holes and won't. I basiclly want to put pcv into base of oil filler tube hooked to base of carb. with a vented cap on tube. nothing else. will this be good? I agree with I'm braindead on this. can't get it to work in my head.!
Buford, you forgot that most of the gasses in the combustion chamber file right out through the exhaust pipes.
OGNC - Umm... no I didn't. I'm talking crankcase gases, not cylinder gases. Since the role of the draft tube (as I understand it) was to pull hot gases out of the crankcase, it made sense to me to replace that vacuum action with a PCV valve connected to the carb base. The road draft tube vented the hot crankcase gases to the air under the car, but this setup pulls these crankcase gases into the cylinders and burns them with the air/fuel charge. The hot gases in the crankcase have to be replaced with fresh air entering thru the vented valve cover caps. Now... where am I wrong? Huh? Where?
I have a pair of old Cal-Custom valve covers for my 283. I didn't want to drill any holes in them either. I am using an Edelbrock RPM manifold. It has a boss in the front to allow for drilling a hole for an oil fill tube that can then be pressed in. It will be topped with an oil breather cap. This will allow fresh air to be drawn into the lifter valley. In the back of the block (near the distributor), I have the old fitting for the road draft tube. It looks like a small cup turned upside-down with a nipple for the hose. I am going to screw an inline PCV into the base of the carb and run a hose from there to this. This will draw the crankcase gasses through the lifter valley to the carb, with fresh air following. The only concern I have, is that on the original setup, there was a canister that sat in the lifter valley to keep excess oil from clogging the tube. It seems to me that it might be a good idea to use one with what I want to do. Problem is , I haven't been able to locate one.
The Jalopy Journal
