The Stovebolt Site Forums The Shop Area Engine Shop Road draft tube Update

I am thinking of putting a 261 style road tube on my 235 so as to have a pcv setup. Got the tube for the engine coming but was wondering what the rest of the setup looks like. Is there a pic in the 56-59 shop manual that shows it? Does anyone know the pn for the pcv valve it self?

Update. I found the draft tube and am using a PCV valve from a 65 vette. It screws into the tube. Then ran hose over to the manifold. Connected it. Engine starts quick and idles around 800, vac at the PCV is 17 psi. I covered the valvecover inlet and put the vac at dip stick and got 0. With my hand on the vc hole I can feel come vac and if I tape it there is a depression in the tape. Does this sound about right? gona run awhile and then look at #3&4 plug.

I have a series of pictures that begin with a '54 2-ton I parted that had the system installed, there are also pictures that show the removed road tube, air cleaner and valve cover from the '54. You will see several of an NOS set-up I owned a few years ago. The air cleaner I know carried forward some years, I cannot vouch for the rest.
https://www.flickr.com/photos/advance-design_parts_co/8129417263/in/album-72157631868452754/
A couple slides from a '49 set-up.
https://www.flickr.com/photos/advance-design_parts_co/8665388167/in/album-72157633290718528/
https://www.flickr.com/photos/advance-design_parts_co/8666488508/in/album-72157633290718528/

Thanks. That realy shows the whole project. What I found in the manuals was a pic of the valve and a little on the plumbing. Wonder if that valve is avail at the parts store. I think 68 chevys had a screw in valve. wonder if that would work. Good pictures.

I found the correct tube. Is there a pn for the PCV valve or does anyone know of one that will fit? The tube is threaded and would like one that would screw in. Thanks.

Could use the information in this link to help in choosing a PCV Valve. It might take some trial and error to get tit right.

http://devestechnet.com/Home/PCVInstall

Got everything to gather , used a 65 vette PCV and eng runs smooth at 800. Would like to find a pn for the orig PCV as it has threads on both ends to make a cleaner install. checked the vac at the PCV and its 17 . I tried to read at the dipstick tube but got 0 ,Put some tape over the valvecover opening and it detents a little and with my hand it feels like vac there.Could probably make a plug for it to test vac but don't know what a good reading would be. Any ideas?

[quote=59 Any ideas? [/quote]

1-3 inches of Mercury is the desired vacuum on the crank case according to the DEVE web site ........link provided in early post.

If you have any vacuum leak around any of the gaskets, or front or rear crank seal, you will not see much vacuum in the crank case.
The real test is if it works.

^^^^^^^^^^^^^^ in that case the engine is likely leaking oil as fast as you can add it q

If the crank case is not under a vacuum the PVC upgrade is an epic fail and the it might be better to keep the road draft tube.
Too much crank case vacuum you will be sucking oil out of the nine which is also an epic fail. DEVE's testing explains this concept well.

The crank case will never have vacuum in it, except for during the testing process.
I suspect it will work great!

^^^^^^^^^ true..........and without the passing the "vacuum test" it will not have adequate air flow during normal operation to be an effective crank case vent.

Thanks Will review vacuum test and see what results I get . Was thinking of making the same test on my v6 just to see what areas have for vac. Not much $ in this project and all the removed parts are still good. So I can always go back.

I am planning on doing the same..........aquired all the parts an extra draft tube that can be modified. The GMC 228 the draft tube is also the oil filler neck.

Showkey, You may want to look at the 65 vette oil fill tube. It goes in the intake but has the same dia. as the road tube that is the oil fill with a tight cap but is tapped for the pcv. ebay has some if you want to look.

An engine does not need to pass the vacuum test to be working properly.
Lets say for example that during the vacuum test that the vacuum is being drawn in through a gasket leak or past a seal.
Once the fresh air intake is unplugged after the test, the engine will most likely draw fresh air from that unrestricted intake easier than past a gasket or seal.

It does not matter where the make air is entering the crankcase during the test. The test results will be skewed if there all sorts of leaks. The test is to confirm the correct PCV valve is used. As the DEVE testing details there are many sizes of PCV valves and too much or too little air flow is what is being confirmed or determined.
Too much air flow through the PCV will cause two main problems: fuel mixture leaning and crank case oil being sucked into the intake. A secondary concern would be power brake could be adversely affected and vacuum wipers might "suck" more than normal.
Position of the PCV in the system can help avoid oil being sucked.

Guess if you have guess at the size of the PCV go small to not create more problems than it solves. It should be hard to beat the draft tube.
The BIG advantage of the PCV is removing moisure contamination from the oil and real benefit for the collector or daily driver.

In reality DEVE has done all the testing that's needed and using his recommendation for the valve would likely be a good choice. The standard part v237 or the fram PV261 ( same part as per the book) After install just check there is air flow through the system and call it done.