I have a question for the Chevy gurus: I would like to run so-cal style ribbed valve covers (unvented) on my 305 HO when I rebuild it. I am asl going to run a performer manifold with the oil fill in the manifold. My question it will the engine breath enough with the oil fill cover as my only source of crankcase breathing? I could put a set of bolt on breathers like Offy and Edelbrock makes. Todd
i need the same info also can you run an older intake on a newer sbc i have a 71 block sorry on the hijack tom
the oil filler tube up front will give you enuff breathing , but with out a PCV valve you will get oil blow-by out of it. i'd try installing one in the rear of the manifold , or in a valve cover. make sure you use a baffle my `28 tudor with a 350 sbc has no oil fill in the mainfold....just a vented cap in one valve cover , and a PCV in the other...it's been fine for over 10 years
PCVs replaced breathers for emissions, not performance. Breathers work fine. Regarding the old/new intake deal, if the heads are pre-Vortec (Vortech heads have vertical intake bolts, pre-Vortec heads are angled) they will fit just fine. It's not about the block, it's about the heads. ~Scotch~
So do I need a PCV or just a breather? Will I get blow-by if I the motor just breathes through the oil fill? Todd
I remember (some old rod mag) seeing a contraption in the lifter valley, machined into the rear of the block. It was a length of pipe that was tapped into the block, from the inside, with a few tiny holes drilled in it, with a breather hidden at the back of the engine, you could even run a 3/8 tube as a road draft, and its totally hidden. That would take a little pressure off the fill tube and allow lots of venting with little - no mess.
you'll get blow out when you hammer it - you can put a sock in it I hook the vacuum to the pcv valve then hook that to the oil fill tube - that way the shit that would normaly blow out the oil fill tube - mostly gets sucked into the vacuum PCV tube I no longer have oil on my motor/firewall from the oil fill tube. look at the mid 60's corvette oil fill tubes - they have provisions for pcv valves
Yes. There's nothing wrong with PCV valves, they work great, and they can be hidden in some clever places so as no to spoil the look of the engine. They suck off crankcase gasses and return them through the engine and also eliminate blow-by from your breather when you put your foot in it. Heh heh! I said "suck off". Do a search for some posts. Here's one: http://www.jalopyjournal.com/forum/showthread.php?t=64338
Unless you already have your manifold, there is a Performer model with a hole for a PCV valve behind the carb. That was the setup I ran on my 327 with solid valve covers and the fill tube. Bill
i tapped a 1/4 NPT hole in the back of my intake underneath where the coil sits. from there i used a 90° street elbow for a '65 corvette screw-in pcv valve. the hose tee's into the line running to the power booster. if i didn't just tell you about it, you'd never know it was there. ed
The pvc is a performance item, NOT emissions. The pvc was in use about 10 years before they got concerned about emissions. It helps ring seal. You do want it.
1965 (I might be a year off??) was when the government mandated that all cars come with a closed crankcase. This is the first "emissions equipment". You do want to keep a neutral or slightly negative pressure on the crankcase mainly to control leakage. It takes a much larger vacuum to really start effecting the ring seal. Instead of sucking the oil/vapors into the carb like a PCV does, you might want to consider and exhaust scavanger, which does effectively the same thing but vents the crankcase to your exhaust instead of through the engine. On industrial engines the CARB (on the left coast) is starting to look at non-fuel based emissions, meaning oil, and different types of breathers are required to meet the standards. Another problem in lean-burn natural gas engines out here (pre-chamber stratofied charge) is that the burning of non-fuels causes a build-up of carbon deposits in the combustion chamber which shrouds the valves and hurts emissions. In some instances top-end rebuilds are needed before a leak check requires it because of poor emissions.
Maybe a couple points of interest on this subject.... One- if you bore the intake in the area behind carb it will give you access to the lifter galley where the PCV will eveacuate the pressure,BUT it will need a shield over it or it will siphon oil splatter into the intake charge if not..... I have tapped a hole in one or both valve covers on the sides next to the intake at the center so it fits the PCV in between the valve springs there. I then made a metal shield like a tube with baffling to prevent oil entering the PCV..... it works and didnt look that bad.
Hotrodders have been running without the PVC since the 50's. The oil fill tube up front will work. You may get "some" mist out of it when you get on it. I have seen people put terry clothe wrist sweat straps around the tube under the breather cover or a sock over it. But it WILL work! And has for decades. (To answer your question)
I remember someone here telling me they have two motors, one with just the oil fill breather, and one with a pcv and breather on the oil filler. The one with just the breather works, but it leaves a fine mist of oil on the motor and firewall. The other don't. To keep the valve covers intact, do what 36-3Window said, and drill the pcv into the manifold over the lifter galley. You can also bury a pcv in a bolt on breather, someone here did that as well. Search under PCV. Good luck.
I have a wrist band right under my oil filler cap but I also have offy breathers off my valve covers. Seems to work fine. Before I had the offy breathers on, I seemed to get more blow by out of the oil tube(but the wrist band solved that). Probably don't need the wristband on anymore but I leave it there just in case my foot gets excited! I just check the sponge things in the valve cover breathers once a month or so to dry the oil, and put them back in. But haven't had any oil on my firewall or motor since. my .02...
We're also going to run a later model style sbc with closed v/covers. I will install an intake with oil fill tube with a hose bung and closed oil cap with hose to air cleaner or either a regular tube and vented cap. Then we'll drill into the lifter valley of the intake for pcv access and attach the pcv to carb. I'm not sure what is the best way to baffle the oil from the lifter valley to prevent it from entering the pcv. The older sbc's had a ventlilator can that was located under the intake in the lifter valley that was attatched to the hole in the rear of the block for this purpose. Does anyone think that using an aftermarket llifter valley oil baffle would work? They are cheap and easy to install.
Yes you'll get blowby the PVC replaced the road draft tube. Your block is to new to put a pvc into the intake but you can put a PVC into the side of the rocker cover they make 'em just for that application. You will still need to baffel it.
Man, this is the weekly question. What is Racefab doing on this years raffle engine? This simple question could sure benefit from a tech tutorial... The fill tubes with a spot for a PCV have been mentioned a few times - usually in association with Corvette resto suppliers. You can find them in just about every GM resto catalog out there.
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