Breather Cap: One or Two? - Page 2

Tim Kay · 01-06-09, 10:05 AM

Here's another breather\puke tank.

Chuck · 01-06-09, 10:25 AM

Very nice. Seperate breather tank for each valve cover.

Who do you use to polish you headers? I assume they are polished stainless?

Ant · 01-06-09, 11:22 AM

Please forgive me but this subject is new to me and i need to understand it so i plumb mine in the best/most suitable way.

There apears to be 2 camps, PCV and non-PCV

non-pcv, from the pictures it looks like you pipe from both valve covers to a catch/puke tank. This then vent to atmosphere via a filter above the inlets and has a drain tap for emptying as and when needed. Catch tank is a UK track requirement and maybe elsewhere as well. This setup suits multi-carb configs and single carb setups.
PCV solution, filter installed in one valve cover and PCV valve installed into other valve cover with pipe connecting to intake manifold, thus under load and high vac, atmospheric air drawn in to engine via filter and engine vapours drawn through PCV and onto intake manifold for them to be 'burnt off'. More suited to single carb setups as better vacum source.

Both must work or people wouldn't be split between them. Is it a case of 'horses for courses'? Th catch tank/non-pcv setup sounds like it provides cleaner internal engines as all nasty vapours are drawn off and collected rather than burnt off and as someone said a good excuse for more shiney metal under the hood.

Sorry if i have hijacked the original thread.

ANT

Chuck · 01-06-09, 12:37 PM

Ant:

I am no expert, hence my original post. But from what has been said on this thread I am doing two things:

1. Added a PCV valve to my Cobra's 427 side oiler on one side, vented filler cover on the other. Easy to do with a Holley carb.

2. Adding a recovery tank connected to vents on both valve covers on my 302 with Webers, since there is no easy vacuum source for a PCV. Moroso and Canton make nice spun aluminum ones.

Can't say which is right or which is better, but it would seem that both work, and both are better than just a breather cap without a recovery tank or PCV valve. Guess I will have both options covered, albeit on different cars!

EGLITOM · 01-06-09, 02:04 PM

Chuck
Just an idea which came into my mind now. May be its a little, crazy but why not.
We could use the rollbar support legs as breather tanks. Each of them are close to 0,5l of Volume, weld in a D10 or D12 adapter plus a flange for a breather and a emptiing outlet. Thats it. They are idealy located. Run a D10 or D12 direct to them from the valve covers. Should give a nice and clean installation with not too much bling and hoses.
I will definitely give it a thought on my car

TOM

Chuck · 01-06-09, 02:44 PM

Tom:

That is a clever idea!

Tell you what. You do it on yours and if it works out, I may give it a shot.

Didn't the 917 have it frame pressurized with nitrogen? Guess we can pressurize the gt40 rollbar with blow by gas . . . . .

Chuck

Randy V · 01-06-09, 03:44 PM

I don't think that the addition of the fittings to connect to the hoses would cause much harm or weakness.
I don't think that would be the case with a 1.25" hole cut for a breather tube.. Unless you could somehow make it structurally sound...

Mick · 01-06-09, 11:32 PM

My RF is fitted with this system . Down under the V8 supercar boys use a 2 stage system. They scavenge through a PCV valve from one valve cover into a catch tank vented to atmosphere through a breather. The idea is that up to about 3000rpm breathing is to atmosphere (low pressure). From the other valve cover you run to a sealed catch tank (Air tight) this tank is connected to one exhaust collector with a one valve in the line before the collector. As the revs build up to over 3000rpm the exhaust system will cause a vacuum and evacuate excess pressure from the sump. This works very well with big cams.

I will post pics tonight

Mick

Mick · 01-07-09, 05:14 AM

Pics of dual scavenging system

Pete McCluskey. · 01-08-09, 01:07 AM

I run a breather each side, both go to puke tanks. See pics.

Chuck · 01-18-09, 06:57 PM

Need an opinion.

Installing a puke tank as per the attached picture. Plan to run a line from the valve cover on the opposite side as well. The tank has a separate fitting on the opposite side. It would be easier to tap the driver side valve cover at the back end, as on the passenger side.

So the question is whether there is any issue about running the vent line from the aft end on both valve covers. Can't see that it would really matter.

The set up in the pic is TEMPORARY, just to get an idea about spacing, etc. The location of the tank, however, is final. We will clean it up the connections . . . .

J. Salmon · 01-18-09, 07:28 PM

While I have the attention of some PCV guys, the valley cover for the LS7 includes the PCV valve, and there is also a tube on the passenger valve cover. I am running a stack EFI.
I had planned to plumb the PCV line to a breather can that also breathes the dry sump tank. I was planning to cap off the valve cover line.

Will this work? I understand the concept, but not the specifics.

Greg · 01-21-09, 03:16 AM

My 302 was using a lot of oil. Did a compression, then leak down test. All okay. Found out oil was getting past the baffel plate inside the valve cover under the PCV valve. It was sucking oil like a vacuum cleaner right into the base of the four barrel carb. Switched to one breather on each valve cover, just like the old 1950's V8's. Problem solved.

Chuck · 01-21-09, 04:46 PM

Greg: Interesing point. Which raises another question.

My valve covers have NO baffles. Pop the oil filler cap and can see those nice new rocker arms just sittin' there waiting to go. Obviously it drips a fair amount of oil through the filler cap and thus that issue needs to be solved.

My intent in adding a recovery / puke tank was to stop the oil from dripping out of the filler cap (which it should obviously do) but unless the line connecting the valve cover to the puke tank goes up hill, oil may well accumulate in the puke tank. So here is the question: Do I need to add baffles even with the puke tank? Or just check it regularly and see how much is 'lost' with real life driving before going to all that trouble?

Sill wondering if I need to run lines from both valve covers to the puke tank or if just one side is sufficient.

(I can almost hear a faint voice from afar saying "both" and "baffles", or is that my imagination???

)

Jac Mac · 01-21-09, 05:27 PM

Its not your 'PH*****G' imagination.

Now do as your told & leave me alone, got some urgent work to attend to!

If you can see the rockers thru the filler/breathers due to lack of baffles your in trouble anyway-- where do you think the oil coming up thru the pushrod & rocker is gonna squirt--yep that right, straight at the pcv valve or filler cap or rocker cover- apart from asking for trouble I have never seen a rocker cover wear out from lack of lubrication, seen plenty of valve springs , rockers etc crap out from the oil not getting to all their little bits & pieces!

Chuck · 01-21-09, 10:04 PM

Thanks Jac. I was right. I was hearing a voice from afar . . . .

I will get right on it.

Howard Jones · 01-22-09, 01:30 PM

If you already have holes in the top of your valve covers. Have a look at the valve covers I am going to put on my SLC engine in "SLC24 Howard Jones" build page. Otherwise read the comments by Jac there. Good solution's both. My "cobra" valve covers on my GTD are done the same way and I haven't gotten enough oil in the puke tank after a whole day at the track (200 miles) to even drain any out the pet-cock on the bottom. I do also run both valve covers to the puke tank.