AKruizer

I was just getting ready to pull the trigger on a new performer intake (#2701... not using a Qjet) and thought I'd go look at the old Offenhauser and do a mental walk through of the whole project.

One thing I think I didn't consider is crank case ventilation. The motor has 7 fin aluminum corvette valve covers which are non vented so the only venting I have, that I know of, is from the oil fill tube on the front of the manifold that has a breather on it. I don't know if this is typical or not but there is a rubber line with a PCV valve 3/4 of the way up the fill tube tube that runs to a vacuum port on the carb. Being new to this I did some searching to get a better feel for what all is involved. One question came up almost immediately... is my motor being properly vented by having both the breather and PCV vacuum line both operating off the oil fill tube? Seems like typical breather setup is to have vents on both valve covers or for PCV to have a vent on passenger side valve cover and PCV off of the drivers.

I want to understand how the motor should be venting properly before I move forward. By saying that I do not want to open this up to a breather vs. PCV debate... we already have a very long thread with thousands of views on that subject... so for my purposes lets limit it to 'if you go breather do this' or 'if you go PCV do that'. Otherwise we'll end up with
If you're curious or slightly sadistic, enter PCV discussion hell here: Link

Looks like an option to maintain my current setup would be to go with the #2703 Performer intake which has the fill tube and breather. But looking at the fill tube that comes with it there are no provisions for the PCV line it currently has. I'm wondering if the motor is being properly vented with it's current setup so simply recreating what I already have may not be the best solution. Also hoping to keep those valve covers, easiest option would probably be to get some vented ones... what fun would that be if everything was that easy though

So I'm a bit confused and in need of some edukation

Thanks guys!

AKruizer

Thought I'd throw in a picture as a reference:

OMF

You can buy a grommet to fit into a 3/4" hole so a pvc valve can be fitted to the valve cover. You would have to drill and enlarge the hole in the valve cover yourself. The problem your going to have is adding oil to the engine. Once you change intakes you won't have provisions for this. You can remove the valve cover to add oil, but it would be easier to replace the covers for ones with both provisions.

cardo0

How much case ventilation and where is up to u. U can get very creative and very complicated here. Or u can just leave a simple vent on a fill tube or even drill to install one into the valve covers/intake. Most ideas were covered in the link u posted.

But without ventilation your engine will push oil out all the seals and more than likely run poorly too.

Good luck with venting,
cardo0

AKruizer

Thanks for the reply sstocker, it definitely looks like a valve cover change/modification would be the easiest way out. There's a party of me that hates the thought of punching a hole in those classic valve covers though... think I'd rather just get new ones if it comes to that. Anyone else out there with finned corvette covers that modified them for PCV?

I can't seem to find the link anywhere, but I read a post somewhere of one of Lars' engine builds where he put valve cover spacers and tapped the spacers for breathers/pcv.. but he had to do some creative baffling in the grommet to manage slight oil seepage. I know there are plenty of good ideas out there, thought I'd check and see what come up.

Still curious if the ventilation as it is now is adequate....


Keep the feedback coming.. thanks again!!

AKruizer

Thanks Cardo, being the dumb guy here I guess my problem is that I don't know how much ventilation is enough... although it doesn't seem like anybody has really freaked out at how things are currently setup so it doesn't appear that there are any major bubbafication issues.

Easy to drown in the detail going over that PCV thread, guess the important factor is to ensure that you have some form of ventilation in place.. be it breathers or PCV.

And here's the STUPIDEST question of the day in the tech forum. In the absence of any alternative... could you fill the oil via the dipstick

Be easy guys

- The Dumb Guy

oldsarge

That is possible, but very slow and need a small funnel,and alot of time to spare.

lars

For a PCV system to be functional, you need to have an air "inlet" source on one side of the engine (typically the common "breather" or a hose up to the air cleaner from the valve cover) and a PCV pulling air through the engine on the other side of the engine. Under light throttle, the PCV will pull air in through the breather, through the engine, out the PCV, and into the inatke manifold. Under high load conditions when there is no manifold vacuum and high crankcase blowby, the flow reverses through the breather, and the breather allows crankcase pressure to vent out of the crankcase without needing to pass through the restrictive PCV.

I installed early "no-hole" "Corvette Script" valve covers on my '64 with a 496-horse 407 and I wanted a functioning breather system with PCV without cutting holes in the original covers. Since I had to use spacers to clear my somewhat non-stock valvetrain, I installed the breather and PCV into the spacers. Both penetrations have baffles installed on the inside. Results on the dyno show the system working perfectly, with no oil getting sucked or blown out the breather or PCV - crankcase pressures and ventilation are right where they should be. Photos below show details and overview:

Lars

PCV is the screw-in style unit that came on most '64 small blocks - NAPA shows this as '64 Nova:


Breather in the opposite side is K&N, attached to a 90-degree stainless elbow with some heater hose. This also provides oil filler location:


Everything is tucked towards the back of the engine to get it out of sight:


Fuel pressure regulator and PCV system makes things a little crowded in the back, but there's still room for timing adjustment and reasonable access to components:


Rear-mounted "hidden" system gives clean look to engine and the '64 valve covers: Look! No oil filler, breathers or hoses! How does he do it...?

Ray Y

As another alternative to consider since you said you might change valve covers but like the finned Corvette script, check out the vintage look PML valve covers that are already set up with a hole in each cover. They come as cast, painted, or polished. I'm putting a set of the polished ones on a new motor right now. Google PML valve covers. They are a little pricey compared to drilling and taping a hole or two.

Lars-
Your engine looks great!

Ray Y

http://www.yourcovers.com/valve_covers_11042.php

This is the link to the PML covers.

noonie

If you are going to use the intake with the front oil fill tube and breather, you can always drill and tap for a threaded pcv valve at the rear of the intake beside the distributer.
Might not be quite as good as using the valve cover area, but this would closely resemble the venting system used for the old "road draft tube" method.
Have seen it on several old motors over the years, but don't know how effective it was.

427V8

Make sure you baffle that PCV hole or you will be sucking oil into your intake.
oil lowers your octane...

AKruizer

Thanks for the link Ray, have to say I love the looks of those corvette script covers Some great looking motors there too!

Definitely going to take your advice on baffling, but only because you have good taste in paint

Lars, That's the motor I was talking about!! I'm still a little fuzzy on a few details though.. I think I could work it out if you could send that bad boy up here to test in my 75.. I promise to send it back after my 4th set of tires, probably about 2 days

All seriousness aside, thanks for the pic and other info..looking at what you said in the quote above how much of a problem is it that I only have venting through the oil fill tube instead of the balanced system that you described. Would that translate into any specific symptoms?

AKruizer

Opps.. missed ya Noonie, I'm hoping to get by without having to drill a new intake. Looks like my current setup with a fill tube vent is not in line with a properly vented motor as described in other posts here. So it looks like Lars' solution is my best bet if I decide to keep the script covers and not poke holes in them, also like how clean the setup is

lars

If you look at your system, you have a vented cap (it vents through the holes in the bottom of the cap) with a PCV 1" below it. Basically what your PCV is doing is sucking clean air in through the vented cap, pulling it right down to the PCV, and pulling that fresh air into the intake. The engine itself it getting no ventilation at all, although the crankcase pressure does get relieved through your system. Thus, you won't see any symptoms of anything actually being wrong, but you're not getting the benefit of a true crankcase ventilation system that keeps the crankcase purged of bypass contaminants. To achieve this, you really need to space the inlet breather and the PCV as far apart from each other as possible so you get some airflow through the crankcase.

As noonie stated above, a good place to stick a screw-in PCV is down through the intake into the engine's lifter valley right in front of the distributor. Just attach a baffle to the underside of the intake where you drill through to prevent direct oil splash into the PCV hole. With a PCV at this location and a breather-type fill cap on your fill tube you will achieve good crankcase ventilation.

Lars

73, Dark Blue 454

Obviously that intake was designed for use on a 1967 or earlier SB. Is the block also a 67 or earlier? If so, it likely has the draft tube provision in the back.

Back in the day, we used to route a hose from a modified draft tube to a bung on one of the header collectors on some 327's we raced. It helped pull fresh air into the engine from the breather (aka, oil fill cap) on the front of the engine and kept the underside of our cars a bit cleaner.

FWIW

AKruizer

Thanks for the follow up information Lars, glad to know I'll have another gremlin out of the way when this project is all wrapped up

DarkBlue - I looked up the suffix code (CKB) and it looks like the engine is a 72-74 era. Don't have any history on the car so can't say what the strategy was by configuring it the way it is... did have some second had info that a different setup may have been scavenged off of the motor prior to it being put up for sale. I should pull up some ID numbers off of the Offenhauser and see what I can find out. Thanks for info and for giving me something to research

Golden

That's a seriously clean looking engine.

7T1vette

While your PCV valve is actually connected to the carb 'correctly', there is a problem with your setup. The PCV is connected directly to the breather pipe. This means that the crankcase "vent" and the crankcase "exhaust" are connected at the same point. Normally, the "vent" [to draw in fresh air to the crankcase] would be built into the air cleaner and the "exhaust" [to rid the engine of oil/fuel vapors] would be built into a valve cover.

With your setup, I'm not sure that any vapors will actually flow through the PCV valve...I think they will just get expelled out the breather pipe, as it would be the path of least resistance. And, with that (intake) breather in the system, putting the PCV valve in a valve cover won't really help it that much. If you don't get much oil film blow-by into your engine compartment, I would suggest that you just keep it "as-is". If you do get a lot of oil mist around the engine and you have to keep wiping it down every so often, you should consider re-plumbing the system by removing/capping-off that breather pipe, putting the PCV valve in the left valve cover [and hooking the output hose from the fuel vapor cannister to it via a "T" fitting...then running it to that same carb fitting], and running another 1" diameter hose from the right-side valve cover (or from that capped-off breather fitting) to the air cleaner body.

Golden

Although I'd agree that there's no intake of fresh air into the engine, it will probably still attempt to evacuate dirty air from the engine as normally this type of cap has a sprung valve inside that operates a little like a PCV valve.

That said if there is a sprung valve in the cap and you put another valve in the system then the manifold vacuum probably wont be able to overcome both valves.