How Much Blow-by is Too Much?

[JedIEG]

I am having a hard time getting my 318 to run right and pulled the pcv valve off the carb to eliminate as many vacuum leaks as possible. When running without the valve, I am seeing a decent amount of blow-by puffing out of the breather tube. I don't see any signs of oil consumption on the plugs (just a lot of dry carbon from the rich carb). Rings are original with 84k miles.
Should I worry about this? How much blow-by should I be seeing?
I'll try to take a video of what I'm seeing tomorrow.

 

[TopBanana72]

Pulling the PCV valve off the carburetor would cause a vacuum leak.

You may want to do a cylinder compression test. My 120,000 mile 318 checks in at 135 psi or so. The FSM lists minimum is 100 psi.

 

[JedIEG]

Do you test with the engine warm?
I would prefer to do it cold with the carb off the manifold so I'm not pulling fuel

 

[BB BELLA]

yes warm, first question is do you have clean uncontaminated oil?dirty/moisture filled oil will create what looks like blowby but could be steam or other contaminents vapourizing when heated.
perform dry and wet compression tests!remove all the plugs first!dry test will give you comparison and base line comparing cylinder to cylinder,wet should give you a good indication of ring/blowby problem if readings improve 10%!2 pumps from an oil can aimed at high side of piston if space permits! just block the throttle wide open and leave it there through the entire procedure or remove the carb if you insist,but with the plugs out the vacuum on the intake and fuel pull is reduced to almost nil other than the one being tested!
there are other possibilities but start with compression test!

 

[JedIEG]

I ran the dry test tonight and got 140psi on all cylinders except one at 135psi and one at 145psi, so I would say that is better than I expected from a 8.5 CR engine.

 

[eldubb440]

if it puffs more than the pcv can suck, it's too much

 

[JedIEG]

This was with the pcv disconnected so it was puffing out the open breather.

 

[eldubb440]

with pvc connected, you should have vacuum at the breather..... I pull the breather off and put a dollar bill on the hole and it sucks

 

[JedIEG]

Yep I'm not really worried about the pcv system. It's all new parts and working fine. I just don't want to be introducing excessive blow-by to my intake and create another variable for getting the engine tuned right.

 

[dvw]

It's a 84K 318. It runs fine? Doesn't use a ton of oil? Run it.
Doug

 

[Rusty 72]

^^^ What DVW said.
My slant in my 66 burns oil like nobody's business. So much blow by I had to route the valve cover breather underneath the car so I wouldn't get poisoned. But performance wise it still runs like a champ. I don't run it too often though. I'm planning a rebuild whenever the current project is outta my single car garage.