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Henrik_K Samba Member
Joined: November 17, 2013 Posts: 181 Location: Denmark
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Posted: Wed Jun 03, 2020 12:22 pm Post subject: Type4 - Crankcase breather |
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Due to oil fumes in engine room, I've decided to run a hose from the stock breather to my inlet manifold - below the carb.
The idea was that the vacuum would "suck" the fumes into the manifold - and as a side effect making a small vacuum in the engine, to keep oil leaks to a minimum.
Unfortunately, my engine backfires a lot with this solution.
What did I miss? will the oil fumes prevent a proper fuel/air mixture going through the manifold?
I previously tried to let the hose go to the airfilter - but theres not enough vacuum.
Any other solution?
Thanks |
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telford dorr Samba Member
Joined: March 11, 2009 Posts: 3555 Location: San Diego (Encinitas)
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Posted: Wed Jun 03, 2020 12:34 pm Post subject: Re: Type4 - Crankcase breather |
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What you missed is that you added a large vacuum leak, causing the engine to run lean - hence the backfiring. At a minimum, you need a metering valve or orifice to control the air flow, and you need to compensate the mixture so it isn't lean. This is not a trivial modification.
Might be better to fix the engine (pistons and cylinders) to stop the blow-by, eliminating the need for the extra venting... _________________ '71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST) |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Wed Jun 03, 2020 1:21 pm Post subject: Re: Type4 - Crankcase breather |
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vent to the air cleaner and be sure to install a flame arrestor so you don't blow the engine up if you have a backfire with a flame front. You can add a catch can instead but you will need to drain it every so often of foam and oil or it will puke all over the engine bay. If you have a bus later than 1968 or 1969, you may run afoul of the law for venting crankcase gases to the atmosphere if you end up in any kind of vehicle inspection. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50352
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Posted: Thu Jun 04, 2020 2:28 pm Post subject: Re: Type4 - Crankcase breather |
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What fuel system do you have?
What kind of breather do you have VW used multiple designs depending on the fuel system.
Pictures of your engine would be nice. |
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Henrik_K Samba Member
Joined: November 17, 2013 Posts: 181 Location: Denmark
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Posted: Sat Jun 06, 2020 12:11 am Post subject: Re: Type4 - Crankcase breather |
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My breather looks like this. I run carbs...
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XXX/Rx/RnR Samba Member
Joined: March 01, 2008 Posts: 405 Location: valley of the sun
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Posted: Sat Jun 06, 2020 5:41 am Post subject: Re: Type4 - Crankcase breather |
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Swap to a breather from a 72-74 stock carb t-4. Breather hose is "T" into fuel vapor return to air filter. That way fuel vapor and oil gases are sucked into engine. _________________ 78' westy, 2.4 195hp ecotec, audi turbo a/t, a\c, 2 1/2" lift spindles, index rear, 930 cv's & axles, 225x65x17 BFGs ## 77' hardtop 2.0 T-4 duel 44 weber's, 225x50x17s ## 74' baha bug |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51152 Location: Surrey B.C. Canada, but thinking of Ukraine
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Henrik_K Samba Member
Joined: November 17, 2013 Posts: 181 Location: Denmark
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Posted: Mon Jun 08, 2020 12:12 pm Post subject: Re: Type4 - Crankcase breather |
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Thanks for the advice.
Whats the difference between the different boxes?
Rgds, Henrik |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50352
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Posted: Mon Jun 08, 2020 1:11 pm Post subject: Re: Type4 - Crankcase breather |
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Henrik_K wrote: |
Thanks for the advice.
Whats the difference between the different boxes?
Rgds, Henrik |
The two boxes on the right have PCV valves that are designed to be plumbed into the intake manifold.
The second box from the left is for FI and has a valve to control crankcase pressure. I lot of people who swap from FI to carbs do run this box.
The other two valves were for use with carbs, they have a baffle in them but no other restriction.
The cap that is on two of the valves is the oil filler used in some application. |
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