Crank Case Breather SBC

[scuff]

I am going to fit a crank case breather to the engine. I guess the usual spot to place is the fuel pump blanking plate. The questions are...

Where on the plate do you position the tapped hole and the connector? Top middle or bottom or it really does not matter
I would like to use Aeroquip hoses (look pretty and match the rest of the hoses in the engine bay) Which do you use?
What connector and what size? Was thinking of a 10 (1/2" or 13mm)straight
Connecting to a 90 degree elbow connected to the hose.
compression fitting (if that is the right term, screw fit)to the hose at one end and a slip on, push fit connector at the other
Do you use a 90 degree elbow on the hose and then run the braided hose virtically, how far?
Do you use a compression fitting at the connetor at the blanking plate and then a push fit with "hose clip" style fitting at the filter end?
What Filter do you use?
Do you then support the braided hose with fittings on the bulk head or by fittings on the engine?
Does anyone have a picture or two?

Help.

Thanks in advance.

Scuffers.

[steve_d]

I would recommend you connect your breather via a PCV valve to the base of the carb or some other manifold vacuum fitting. SBCs are heavy breathers in standard trim and are much worse when producing the power levels we are using. If you do not have enough natural ventilation then you will get significant oil leaks.

Connecting to manifold vacuum like this worked well on my engine and stopped all the (many)leaks.
Drag racers actually fit vacuum pumps and claim to increase the power of the engine.

Steve

[boosted ls1]

Rig up a pcv circuit, it's easy. Haven't you wondered why ultima's and other sbc kit cars have oil leaks and probably have smelly cockpits? Without a pcv circuit the sump isn't in vacuam.

Boosted.

[p15ton]

Don't use the fuel pump mounting. That cavity fills with oil as it normally carries the fuel pump pushrod & arm. It will puke oil everywhere. It CAN be used as a return from a catch tank, if you've nothing better to use.

[CanAm Dave]

Just like the the rest are saying rig up a pcv circuit. You can get breathers with pcv valves built in and then as Steve says connect it to the base of you carb or manifold. The pic below is one such breather. Only £15 from summit. Earls do a similar one with a -6 fitting.



Regards Dave

[gtr-gaz]

Had this fitted to mine, same engine builder as Tuxmans.

As mentioned, a pcv would suck oil out of it, so only fit the pcv to the heads.

[steve_d]

If anyone has the existing Factory system and wants to use PCV then copy what I did.

A pipe comes from each rocker cover to the catch tank then 2 pipes vent to atmosphere. Remove one of the vent pipes and blank that vent on the tank. Fit the PCV valve in a short stub of hose from the other tank vent and run a new hose from the PCV valve to the carb or manifold. My carb already had a vacuum fitting in the base of the carb which would have been used for servo brakes.

Steve

[boosted ls1]

The pcv valve inlet is usually quite small and should have a restrictor in it. This is what keeps the engine in vacuum. I'm sometimes amazed at the size of some restrictors, on a rv8 it's little bigger then a pin hole.

Boosted.

[scuff]

As Steve D said "SBC's are heavey breathers"

I have the factroy PCV valves on the Rocker covers venting to a catch tank then atmosphere. The reason for the desire to fit a crank case valve is that I mistakenly drove the car for on a 10mile run without a PCV valve in the rocker cover. During the pre flight checks, after topping up with oil, I forgot to put the PCV back in the rocker cover, dohh. As a result there is some splatter, oil pressure was good on the run, however the difference in oil consumption was noticable. I guess that either the PCV's in the rocker covers are not working properly and or there is still too much pressure in the engine in the non pressurised areas, i.e. the crank case and thr rocker covers.


gtr-Gaz, do you have a picture of the vent where it joins the engine? Is it on the fuel pump blanking plate? do you have any issues with oil in the crank case at this point (assuming that the vent is connected there) as was suggested by p15ton?

Any thoughts?

Scuff

[steve_d]

A PCV has to connect to vacuum so whatever you have there at present is not working as a PCV system.

Steve

[scuff]

I guess then that (as they look identicle to the picture that Can Am Dave has shown) that they are either PCV's that are not connected or they are just breathers to atmosphere. I guess that if I take it off and try to suck / blow through it that I will find out?


I have been out and sucked and blew. They are PCV's (you can blow, but on sucking the vavle shuts) however they are not connected to the inlet manifold on the Carb, just to a catch tank. On blowing there is no restiction so they appear not blocked. I would then assume that there is still too much pressure in the crank case that is not venting. My earlier supposition about less oil consumption can not be true, I just thought it was.
Scuff.

Edited by scuff on Saturday 17th February 19:27

Edited by scuff on Saturday 17th February 19:29

[tuxman]

Hi Scuff , fit -10 elbow in the center of the plate then run up 300mm min ,would suggest a bit more ,the fit k/n breather on the end clip it all in place with a large p-clip.you need to get a -10 elbow bulkhead fitting if possible or s atraight -10 bulkhead the a 90 elbow . simon

[scuff]

Thanks Tuxman.

S

[tuxman]

no problem only issue i can see is getting the blanking plate drilled and tapped rest should be pretty straight forward ,get any problems give me a call . simon

[gtr-gaz]

Scuff, I think I might have a dril and tap for said fitting. Can't remember what size it was though?

Simon, glad you're still with us

[tuxman]

Hi Gaz good to still be hear ....been a bit mad though !!!!

[hodgy587]

How about a crankcase evacuation system? Kind of a halfway house between a a straight breather and a vacuum pump

check out jegs for more info
www.jegs.com/webapp/wcs/stores/servlet/product2_10001_10002_751825_-1


www.587racing.com

[scuff]

Gtr-gaz,

Off topic I know....I will mail you the details of the people for the Marham day this week. Just wating for one to get back to me. Will be there Sunday so can I have a gander at your breather?

As for the drilling and tapping, thanks for the offer however, I will have this done in the engineering shop at work.

Thanks for all the help from all who have posted on this thread.

Scuff.

[fastco]

Hello..your best PVC system is to use billet alum valve as in some photos and plumb 3/8 ID braided hose to carb base from PCV valve, and on other rocker cover use 1.25 OD K&N useable filter... job done!

Do not use Moroso crankcase scalvage system on street driven engines..why only works on HIGH RPM race engines.

Sample pics of PCV system on SBC engines
[URL=http://home-and-garden.webshots.com/p][/URL]
[URL=http://home-and-garden.webshots.com/p][/URL]
[URL=http://good-times.webshots.com/photo/][/URL]

[DHGTR]

wow thats some kind of great looking engine in that 3rd picture.!!!