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Does the oil fill cap on a 59 corvette provide enough crankcase ventilation?
I am using a later block that does not have the provision for the rear draft tube.
Thanks,
George geopar@gvtc.com
210 748 4693
Last edited by Corvettes by George; Oct 28, 2016 at 02:19 PM.
You need a means to scavenge combustible, corrosive vapors out of the crankcase. Either a road draft tube or PCV system. So, in short, no - the cap alone is not sufficient.
From: Las Vegas - Just stop perpetuating myths please.
What may help is a simple drawing of the ventilation system - for the crankcase. It reads like to many owners overlook the big picture and it's fairly simple system. It just needs a clean air source - usually down stream of air filter. The a less than atmospheric pressure exit to pull the piston blow-by gases out of the crankcase. Technically it's the higher atmospheric air that pushes the spent blow-by from the crankcase into the lower pressure of the intake manifold but use whatever makes sense for you.
Now later cars use a PCV valve to control/regulate this air flow such that you/we don't have a major vacuum leak. The early, early cars used a road draft tube instead of engine intake vacuum to draw out the crankcase gasses but it was not as effective and dropped plenty of oil on the ground. Circle track race motors just allow the crankcase to breath and vent through large filters on the valve covers - as you can see on the GMPP catalogs circle track crate motors.
Hope this helps and whatever you come up with remember you need a clean air source and a low pressure exit. Good luck.
Last edited by cardo0; Oct 28, 2016 at 04:29 PM.
Reason: Stupid autocorrect!
So, either I vent to atmosphere through valve cover(s) breather(s),
No. You need to draw fresh air through the crancase to evacuate, moisture, acid and gases. What I quoted above out of your statement will only vent pressure from the crankcase. It won't circulate fresh air.
Yep. What Mike and Bill said. Even the old road draft tubes circulated air through the crankcase....the air was drawn in through the breather, and exited the tip of the road draft tube via venturi effect. Problem was, it only really worked well at speed. PCV systems are much more effective and cleaner inside and outside of the engine. Very simple to plumb one in. My '61 had no breather of any kind when I bought it. Leaked oil like crazy. I installed the correct breather, plumbed in a PCV, and no more oil leaks. I can even put oil in the engine how without pulling a valve cover!
I didn't want to use breathers on the valve covers (for cosmetic reasons)
My solution was to drill the intake manifold, and pull air from the lifter valley (using a make-shift mini-oil separator [drilled copper tube]), through a PCV valve, and into the vac port on the rear of the carb.
You need a breather (non-closed) oil fill cap for this setup.
Edit: I didn't notice you are FI.. Not sure if this will fit with FI.
From: Las Vegas - Just stop perpetuating myths please.
Originally Posted by 1960fi
So, either I vent to atmosphere through valve cover(s) breather(s), or run a pvc valve off of a valve cover through the intake plenum?
You need to choose this for yourself as I/we don't know what you truly want to do. But to keep you from major mistakes and get a functional system you need to have the right picture. Did you draw up your system or any options? Rememberfor a PCV system you need a clean air source and a low pressure exit controlled by a PCV valve to prevent a major vacuum leak. For a vented only system you still need air filters to keep contaminants out of the crankcase.
Okay,
Draw me up a system that will work with what I have:
350 block without draft tube "escape" provision.
'59 FI unit with open oil fill/breather tube in the intake adapter.
Nice steady 17 inches of vacuum which I do not want to drop below 15 inches.
Not shown, but to be used, a reproduction air cleaner assembly that I prefer not to plum/modify for clean air intake.
Thanks,
G.
Last edited by Corvettes by George; Oct 29, 2016 at 04:21 PM.
Okay,
Draw me up a system that will work with what I have:
350 block without draft tube "escape" provision.
'59 FI unit with open oil fill/breather tube in the intake adapter.
Nice steady 17 inches of vacuum which I do not want to drop below 15 inches.
Not shown, but to be used, a reproduction air cleaner assembly that I prefer not to plum/modify for clean air intake.
Thanks,
G.
look at my previously posted picture, I reckon you can figure it out from there...
From: Las Vegas - Just stop perpetuating myths please.
Originally Posted by 1960fi
Okay,
Draw me up a system that will work with what I have:
350 block without draft tube "escape" provision.
'59 FI unit with open oil fill/breather tube in the intake adapter.
Nice steady 17 inches of vacuum which I do not want to drop below 15 inches.
Not shown, but to be used, a reproduction air cleaner assembly that I prefer not to plum/modify for clean air intake.
Thanks,
G.
Well I don't need to draw mine because I know how it works and it works well as is. If you need to learn how your crankcase ventilation system is going to work you need to be able explain it to yourself. I can explain how to install a system step by step over the internet but that doesn't mean you will install it correctly hundreds or thousands of miles away out of my sight. With all those vintage horses in your stable understanding and utilizing a functional crankcase ventilation system on each car should make you an expert in short time or at least you should be and expert. Otherwise your problems just got multiplied by the number of cars you own and maintain.
There are plenty of drawings and images on the internet through google and that is something thats just as easy for you to do as me. If you truly wanted to do this correctly you would search and verify any ideas for yourself with what you can find online.
If you cant imagine and draw a simple high pressure to low pressure system yourself I don't think there is much I could help you with when the problems become more difficult as when the PVC valve does not match your requirements or the valve covers do not have adequate oil separators.
Well I don't need to draw mine because I know how it works and it works well as is. If you need to learn how your crankcase ventilation system is going to work you need to be able explain it to yourself. I can explain how to install a system step by step over the internet but that doesn't mean you will install it correctly hundreds or thousands of miles away out of my sight. With all those vintage horses in your stable understanding and utilizing a functional crankcase ventilation system on each car should make you an expert in short time or at least you should be and expert. Otherwise your problems just got multiplied by the number of cars you own and maintain.
There are plenty of drawings and images on the internet through google and that is something thats just as easy for you to do as me. If you truly wanted to do this correctly you would search and verify any ideas for yourself with what you can find online.
If you cant imagine and draw a simple high pressure to low pressure system yourself I don't think there is much I could help you with when the problems become more difficult as when the PVC valve does not match your requirements or the valve covers do not have adequate oil separators.
Geeze, and I thought there were not stupid questions, only stupid answers?
Okay, I will google search and figure out the best solution for this application.
Thanks anyway
From: Las Vegas - Just stop perpetuating myths please.
It's too bad you feel that way but what your doing here is a bit of re-engineering. Since you are the one that has to implement/install it a miscommunication will be even more irritating. Proper PCV operation is a major factor to good engine behavior and a clean engine. The good thing is it uses very few parts - less than 6 if you include the flex hoses. Just have to organize them correctly. Once you understand the system you will know the function of each part and what to do with it. It really won't take long to master this at all and it should be an essential skill for all your vintage horses.
Make it the way you want it and have fun doing it.
Set it up the way Bill did in post #7. That way you'll have the proper baffles in the intake side of your system in the valve cover and you can install an OEM PCV valve on the left rear side of your plenum and you are in business.
Just takes, '68/later valve covers to convert. You can leave the intake air in the wire mesh oil fill cap instead of the valve cover like he has.
PVC question
