Inliners International Forums General Discussion Engines 261 crankcase breather question

On my 261, the crankcase breather(down draft tube) is routed over the engine into the intake manifold. Can someone please explain the story behind this? Just curius as to if was a common thing or if anyone else has seen this? Am I going to need to keep this configuration after the rebuild?
Thanks

block casting number is 3769925

[This message has been edited by nolan0 (edited 06-16-2003).]

A picture is worth a thousand words...

That is one of the factory's early attempts at a PCV system. If you want to do your part to keep our air as clean as possible, hook it back up. There should be a spring-loaded valve inside the straight piece that screws onto the 90deg. fitting. Clean it out with some carburetor spray, and soak it for a while if needed. If you can, soak the pipes also, as they tend to get coated internally with a thick layer of gummy stuff, which restricts the air flow.

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David
newbie #4153

I would be happy to trade you for the stock road draft tube setup if you don't want a PCV system, I have been looking for one.

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1950 Chevy pickup with '62 261, 4 speed.

Dear Noaln;

Both of these gentlemen are correct.

I would go with the early system it's out of the way and won't pollute as long as the engine is okay.

Take 4onthefloor(s) offer, is my acvice.

Good luck, John M., #3370

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I just finished TIG welding up three road draft tubes for a local enthusiast who's converting all his 235/261 rolling stock to a setup just like in your photo. So not everybody wants to give up the "waste oil delivery" system. I hear it keeps the garage floor a little cleaner. "Just a Six" is right, though, the inside of these is really loaded with GOO, welding gets pretty smokey. Try to soak it for a week in something really mean.

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Ron 1801

4onthefloor, If NolanO wants to keep his I might have an extra in the garage. I have two 261's and they both had that set up. I didn't use it on my first one and don't know if I will use it on the second one. If you want one send me a message at chevyman1937@aol.com

Wheelspin is right, the PCV valve in the old motor is a real plus. The negative pressure inside the crankcase so far has reduced oil leaks to a minimum. The downside though seems to be differential pressure between the motor and the gear box causing a trans leak, mainly on the "high banking".

Hi again guys,

I don't want to sound like a preacher, but I want to explain a little about my own personal stance on PCV systems.

If you read up in most any modern repair manual, they describe a procedure called a "cylinder leakdown test". Most of them call for an acceptable range of 4% minimum to 8% maximum leakage. What the test measures (assuming the valves are OK) is how much air/fuel mixture bypasses the rings on each and every compression stroke, along with some other gasses and partially burned fuel from the power stroke. That means that every compression cycle looses that much air and fuel to the crankcase. It also means that enough air/fuel mixture leaks past to equal 4 to 8 combustion chamber volumes out of every 100 compression cycles.

A PCV system returns that unburned fuel to the intake, whereas a road draft tube spits it out into the air. That is no different than a complete cylinder misfire every 4 to 8 times out of a hundred. Personally, I think that's a lot of unnecessary pollution. Out here in the desert, it reacts miserably with the heat to form smog and ozone.

Take your pick, and I'll get off the soapbox. And thanks for letting me spout off.

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David
newbie #4153

Fantastic and thanks so much for the replys. I can't believe how much information you folks have. Thanks for sharing it with the rest of us.
Would hot tanking ruin it? What color would this have been?

The only part of the system that I would recommend you NOT hot tank is the valve itself. The acids in the soup will literally eat up the spring inside, and you may have a lot of trouble finding a replacement.

An alternative is to have the parts cooked in an oven. All the paint and the sludge inside the pipes will turn to powder, which can then be removed by pouring some BB's inside and shaking around for a while. But again, DON'T cook the valve itself because the heat will damage the spring.

You can go to your local parts house a buy a can of carburetor parts dip for about $15. Berryman Cleaner is about the best I've used, and I'm sure there are other brands that work just as well. Soak the valve in that stuff for several days to a week, and agitate the fluid for several minutes about 2 or 3 times a day if possible. It'll turn out nice and clean inside.

Paint it whatever color flips your switch I like to do stuff the original color that it came with when it was new, regardless. But I have seen multicolored paint schemes that look as though a bodyman spent weeks on it. Just have fun with your toy!

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David
newbie #4153

Great topic. If you were going to use a modern PCV valve on an 235/261 what kind would you use?

Any brand PCV valve for a 350 v8 will work on a 6banger. I've tried the ones designed for late model 6's on the older engines, and they don't seem to have enough airflow. Sometimes they work and sometimes not. It depends on how recent the engine was rebuilt and how good a job was done on the rings.

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David
newbie #4153