Crankcase ventilation adequate?

Technical advice Q&A
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mtnjag
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Location: Santa Cruz, California
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#1 Crankcase ventilation adequate?

Post by mtnjag » Wed Sep 25, 2019 2:17 am

I have 4 cars of similar 60s vintage with no real smog. The Sprite, Chevy chevelle v8, and olds cutlass v8 all have engine air intake through a valve cover intake, and a crankcase outflow via vacuum going to the air cleaner or carbs.

My 62 E has no engine air inlet, only the front crankcase heather to the air cleaner box. No pulling pressure at the oil filler cap as the other cars have.

Really just realized this as I was working on the Sprite, got it a short time ago, and was going through the systems.

Far be it for me to question the engineering but was thinking of picking up a spare set of cam covers and adding an inlet vent at the rear.

Beneficial? Not needed? Inlet air supplied from somewhere I haven’t realized?

Thanks for your info.
Layne
Car #876005, 62 OTS

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Tom W
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#2 Re: Crankcase ventilation adequate?

Post by Tom W » Wed Sep 25, 2019 5:59 am

Getting enough air out is more of a problem. The crankcase seems to generate enough positive pressure on its own, either from blow by or windage. When Jaguar developed the XK engine for racing, they added extra breathers to the top of the cam covers and blanked the usual breather on the front of the head. My car is on Webers, so no longer has a factory airbox to pull vacuum from. It used to blow oil out all over the place until I enlarged the size of the breather.
Tom
1970 S2 FHC

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mtnjag
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#3 Re: Crankcase ventilation adequate?

Post by mtnjag » Wed Sep 25, 2019 1:43 pm

Thanks, I was thinking that actual venting for inflow air would promote better scavenging of the crankcase air. The other 3 cars scavenge with vacuum to the carb vs. the jag sees little vacuum by venting to the air box. No vacuum inlet other than for the dist in the SUs so that the scavenging at that end is as good as it gets I guess.

If it’s not beneficial then no reason to go through the time and expense.

Anyone done this and is there a benefit?
Layne
Car #876005, 62 OTS

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mtnjag
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#4 Re: Crankcase ventilation adequate?

Post by mtnjag » Sat Sep 28, 2019 1:35 pm

No one try out inflow venting?
Layne
Car #876005, 62 OTS

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Moeregaard
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#5 Re: Crankcase ventilation adequate?

Post by Moeregaard » Sat Sep 28, 2019 2:53 pm

My '65 FHC had the breather with the vertical cylinder and small outlet, and it was totally inadequate. I modified the breather assembly from an earlier car, giving the breather outlet an ID of 1.00" and this worked well. I just let the fumes dump out under the car.
Mark (Moe) Shipley
Former owner '66FHC, #1E32208
Former owner '65FHC, #1E30036

Planning on getting E-Type No. 3 as soon as possible....

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#6 Re: Crankcase ventilation adequate?

Post by mtnjag » Sun Sep 29, 2019 1:43 pm

So you did not provide any addition venting to allow additional air into the crankcase breathing circuit and reverted to a larger ID road tube rather than the air cleaner box connection. Is that right?
Layne
Car #876005, 62 OTS

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