The Stovebolt Site Forums The Shop Area Engine Shop 1962 Chevy 261 Excess Crankcase Pressure!! help!

hey stovebolters, been doin a lot of drivin and bolt turnin' on the chevy lately, and have come to notice that im experiencing too much pressure in my crankcase.im getting oil spray out the top of the dip stick, and at the bottom of the distributor.Once i put some rtv and a spring to hold down the dipstick to seal the spray, i then got a leak from the crankcase breather where it meets the block.I then installed a pcv on the crankcase breather and ran the hose off of it to the side port on the intake.i thought that this would draw some more air out of the crankcase to relieve pressure, yet i am still getting heavy flow of oil from the bottom of the distributor.It has 2 new gaskets on, and all surfaces are clean.Also, my valve cover does have a breather styled cap just for the record. my next plan on diagnosing this problem is to check my compression on all cylinders.maybe im getting too much blow by? Stuck ring(s)?
If any ya'll have any ideas or tips in sealing up a tough dist. leak or have had a similar problem, i'd be happy to hear! No more oil spray on the back of my cab....i can see the day...

I would also suggest doing a cylinder leak down test. When you put air in the cylinder you will hear where the blow by is.
Did you remove the draft tube? Just curious how you connected the PCV?

The pressure is very likely caused by bad rings. The crankcase cannot and should not be sealed.

Get a vented oil filler cap, make sure the road draft tube is open. If the blow by of the rings is bad enough, a PCV valve may not keep up.

Do a compression test like you talked about and find out what your readings are. Or as already suggested, do a leak down test.

You might be surprised how much compression is getting by those tired rings.

What is the draft tube? and i have not gotten to the truck yet but ill let you guys know what my readings are. Thanks for the replies!

-Dan

Looking at this picture on the left,the orange color pipe is a road draft tube. road draft tube


Tim

hey again, i got some pictures to show you guys my set-up as it may help with some answers.These show my pcv set-up and where it goes into the intake.and also my breather cap.i will do the compression testing today and let you guys know where im at.
Thanks again!

-Dan

[IMG]http://i612.photobucket.com/albums/tt202/dantheman176/IMG_1076.jpg[/IMG]

[IMG]http://i612.photobucket.com/albums/tt202/dantheman176/IMG_1078.jpg[/IMG]

[IMG]http://i612.photobucket.com/albums/tt202/dantheman176/IMG_1075.jpg[/IMG]

Is it possible that the PCV valve is installed backwards?

My 54 car 235 started peeing oil out of all of the same places that you have described. Some of it might have been caused by excessive blow by in my engine, but 90% of it was caused by years of dirt and funk that built up deep inside the body of the road draft tube. I soaked the tube for a few days in a bucket of diesel and tons of funk ran out of the tube. The car never squirted oil out due to excessive block pressure again. However, chances are you have bad rings.

hey fellow bolters, ive been off the radar for a bit due to getting sick, but i have returned with some compression check #'s for you guys.cylinder 1: 115 lbs, cly2: 120lbs, cyl3: 110 lbs, cyl4: 105 lbs, cyl5: 121 lbs, and cyl6: 121 lbs.
They all held their pressure for 5 minutes.

How do i perform a leak down test? thats next..

and Jason Barnett, hopefully im having the same problem and all i need to do is clean that road draft tube out!

and as for the pcv being backwards, it is not, i intsalled the pcv after i started having the leaking problems. im going to go attack that road draft tube now.ill let you guys know what i find!

Thanks for the help!!

Oh wait...Jason, you were right, my pcv was backwards.oops! that might do something! but anyways, i took apart my road draft tube and it was pretty clean.i was able blow air through the baffle system with my mouth and there was little resistance, if any.so that means that my excess crankcase pressure problem still resides within the engine...once i figure out how to do the leak down test, ill go from there.any other suggestions/comments are great!

thanks again!

Dan,
The original road draft tubes had an elbow that ran down towards the road. Something like a 1" diameter or thereabouts. Your picture doesn't show that part of the tube...or I missed it if it does. Seems like maybe your crankcase is bottled up too tight without it. Jim

I think the EGR valve comes off the crank case, which those engines did not have. To much heat and pressure from the road vent tube at running speed. Your PCV valve should come of the valve cover. All that stuff is for smog control and was not on those engines. How ever, if you want that,I would look at how it is set up on a 250 or 292 engine from the mid 80's. Those engines are a lot like the 235's. It's been a long time since I've had a 235, but 120lb. sounds about write Also, that test should be done on a warm motor to get the best resalts. If you run a PCV valve, an EGR valve should be used. Hope this is usefull to you, good luck.

A PCV valve does not need a EGR valve to function.

I'm curious how things work with the pcv valve pointing the right way.

cm

The PCV backwards would have had its large orifice open constantly, and act like a vacuum leak - idle too high, doesn't respond to adjustments.
If it's working there should be less vapor from the dipstick tube, breather cap etc., perhaps none at idle and low speed light throttle. If the rings are bad, pressure will still escape from these places but should be somewhat less.

Don you are write I did not mean it that way. But in most cases, they vent the lower and top part of the engine to the intake for a more even pressure, so it burns those gasses from the crank case off in the cylinders. My question is, why does he need it on that motor? I've never seen one on a motor that early. In my opinion, he does'nt need any of them.

You need the correct PCV valve. The correct valve is CV695C or equivalent for that setup. It flows the correct direction as well as meters correct volumes . I see one on E-Pay, but it is way overpriced and ugly.

I assume you have not over-filled the crankcase.

I had a problem with pressure when the muffler got blocked by large piece of rust from the inside of the muffler. Oil was being forced out all over. I unplugged the exhaust and all was good.