Blow by

[Anonymous]

I think my piston rings are getting worn. My crankcase vent tube it puffing smoke rather heavier than usual. I figure I'll have my spare motor rebuilt in a month. But, in the meantime I'll add an additive to help seal the cylinder. Here's my question. Can I direct this blow by to the carb by directing a hose from my tube to the carb? I remember someone had made mentioned this set up sometime ago, but I can't find it....ZZ

 

[addo]

That is the easiest way. Plumb it into the manifold log, not the carb. Use fuel - compatible hose or it will rot quickly. You may need to reset your mixture screw due to the effect of the gases.

Adam.

 

[Anonymous]

When I first got my 63 the previous owner had plumed the crankcase vent into the carb spacer. He also added a PCV in line to the system. I later replaced it with an original draft tube. Sounds like your doing the reverse. Should run fine.

 

[BIGREDRASA]

I had a '57 T'Bird with rotten floorboards and a road draft tube. Picked up a PCV style carb base/spacer, and stuck a PCV valve into the road draft tube hole. Connected said valve to carb base with rubber hose (oil resistant). Worked like a charm.

 

[Anonymous]

Okay..let me get this straight. If I direct it to the carb spacer I should use a PC valve. Now if I go to my intake manifold log, I'll have to put a Tee to also accomondate my vacuum line to my trans. Do I also use a PC valve in this case?

 

[BIGREDRASA]

The PCV valve is needed to regulate the vacuum to the breather.

 

[Anonymous]

Well, I tubed from the downdraft tube to my carb spacer. At an idle everything appeared OK. But, with a higher RPM my vlv. cover breather was spitting up oil. I was over pressurizing my crankcase. How? My theory is : Even though I'm sucking air from my crankcase. It's not enough due to th 1/4 NPT opening in my carb spacer. Let me know why yalls didn't do this...ZZ

 

[Anonymous]

It sounds to me like your PCV system is blocked somehow. Have you pulled the hose and checked for suction? Do you have vacuum to your PCV? Pull the PCV and put your finger over the end of it. You should be able to detect a strong vacuum. If not, you may have your PCV in backwards. It should go to the base of the carb below the throttle plate this is manifold vacuum. If your engine is in good condition, you should be pulling 18 - 22hg at idle.

To me, it sounds as though your PCV system may be clogged or not connected properly. Mine was connected with a brass "Y" along with the Vacuum advance from the Dizzy, not the Trany Vacuum. Try switching it and see if it makes a difference.

By the way how is your oil pressure and compression?

 

[BIGREDRASA]

The PCV valve is a check valve in one direction, and a restricted/regulated orifice in the other. It needs to be there, properly oriented, with flow to the carb base, not vice-versa. 8)

 

[DaGr8Tim]

Speaking of this subject....Is it possible to have too much vent of your crankcase.

I just replaced the PCV valve in my car and put an aftermarket crankcase breather. It it possible to get too much vent and it to cause problems?

 

[rickwrench]

The PCV valve, of course, is just a controlled vacuum leak that sucks air/fumes/blowby out of your crankcase. The more air a paticular PCV valve lets through - the richer you will have to run your carb. If your old PCV was shot (all clogged up) and you tuned your carb to perfection while using that old PCV valve, then you might now be running a little lean with the new, working, PCV valve.
As for having too much crankcase ventilation, many performance guys run vacuum pumps to create a partial vacuum condition in the crankcase (and power their brake boosters to boot). The reasoning is that the rings will seal better if they don't have to push crankcase air out of the way on the down stroke. You'll never even get close to that kind of vacuum with just a PCV valve, but then, most people just want to keep oil from blowing out the breathers.
RickW

 

[BIGREDRASA]

I don't believe the size vent makes much differnce, but the PCV valves have different size springs and poppets. I have no idea how to read them.
I guess when I have nothing better to do, I could check the vacuum properties, then take one apart, measure the spring and weigh the poppet.

 

[Anonymous]

I just did the same thing. My solution was puting a valve cover breather with the pcv in the bottom & a nipple out the side onto where my original breather was. I plumbed that to the nipple on the carb spacer & that took care of it. Looks fine, works fine, smells much finer.
David K
63 Comet

 

[Anonymous]

After everthing was plumbed correctly, I pulled the hose off before the PCV valve and there was plenty of suction. How about this: I run a hose from my downdraft tube to my carb spacer. I'll install the PCV valve into vlv. cover grommet and then run it to a Tee, that I'll put into the hose running from my downdraft tube. Then, I'll be pulling suction from both top and bottom of the engine....What do ya think?...ZZ

 

[Anonymous]

ZZ Top,

One or the other should be fine. If you set it up with a tee as described above you would be splitting your suction between the two. If you want to eliminate the draft tube opening and just run the PCV from the rear grommet like a modern engine, you can get a standard freeze plug and block the draft tube opening. Just measure it and go to the parts store, again.