Dirty Oil!

[Adam H P15 D30]

PCV needs a manifold vacuum source to function correctly.  If you want a "closed" system you could plumb the breather to the air filter assy, but not the valve itself.

 

Adam

[LeRoy]

Thank you Adam

 

I wasn't necessarily thinking of a closed system. My thinking was thinking the vacuum above the carb would be enough to suck the fumes out of the crankcase (PCV) and let the fresh air come from the atmosphere via the filler cap. 

 

After reading your response and looking at the factory document it looks like the filtered air from the carb is the supply going into the filler tube and the PCV / manifold vacuum is the discharge. Makes sense now.

 

Thank you, I appreciate the advice. 

 

Andy

[Harvie]

Just following up on this issue - dirty oil and plug carbon was caused by foolishly listening to local car guys and using premium gasoline.

I now use regular and there is not problem.

[keithb7]

Is there an explanation offered for this phenomenon? Premium gas causing dirty oil and carbon on plugs?

[Hickory]

Im curious of the reasoning of this too.

[desoto1939]

21 hours ago, keithb7 said:

Is there an explanation offered for this phenomenon? Premium gas causing dirty oil and carbon on plugs?

 I also question this statement.  I would think that the carbon on the plugs would have come from a timing issue or worn out dizzy cap, points condenser or rotor needing to be replaced.

 

I run regular ethanol gas and found my plugs were dirty so I did a tune up and found that the gap was off and change out the roto and cleaned the points and no more carbon on the plugs.

 

Rich Hartung

Desoto1939@aol.com

[Sniper]

Only thing I can think of is that premium is more resistant to knock (uncontrolled ignition of the fuel) so it may not light off as easy as regular when you want it to.  The stock ignition spark is kind of weak.

[Los_Control]

I skipped through the last several replies .... I have been using Castrol oil in all my cars ... The known characteristic is dirty dark oil.

I'm just saying I have changed brands of oil because of such dark & dirty oil from Castrol ....

 

While this is a known issue of castrol oil, it is possible if you change the brand of oil & get good clean readings.  .... You did not say what oil you are using?

[Sam Buchanan]

1 hour ago, Los_Control said:

I skipped through the last several replies .... I have been using Castrol oil in all my cars ... The known characteristic is dirty dark oil.

I'm just saying I have changed brands of oil because of such dark & dirty oil from Castrol ....

 

While this is a known issue of castrol oil, it is possible if you change the brand of oil & get good clean readings.  .... You did not say what oil you are using?

 

So does this mean the Castrol is working superbly by keeping more contaminants in suspension?

[Los_Control]

Just now, Sam Buchanan said:

 

So does this mean the Castrol is working superbly by keeping more contaminants in suspension?

I can not answer that ... it seems it a a different base of oil then most.

This may explain the dirty oil the op is asking about.

 

Nobody has convinced  me the Castrol is better then the rest .... I'm just tired of dirty oil & switching. .... Would be my luck the dirty oil meant it was working better then the rest.

 

[Harvie]

Well gentlemen - all I can say is that the plugs are clean, engine runs smoother and no more black oil now that I am using regular gas instead of premium. Just putting that out there in case anyone was having the same trouble. Thanks for your comments I appreciate it.

[Tom Skinner]

These old buses ran on 74 octane back in the day. Use Non- Ethanol gas if avialable. 87 Octane good.

Crap Gas (Ethanol) will screw things up. Clean Plugs and set them. Use a Vacumm Gauge after you set your timing (about 4-6 degrees in advance) and set your Carb lastly with a Vacumm Gauge. To its Highest setting. Good Luck!

Tom

[Adam H P15 D30]

On 10/21/2022 at 2:08 PM, Tom Skinner said:

These old buses ran on 74 octane back in the day. Use Non- Ethanol gas if avialable. 87 Octane good.

Crap Gas (Ethanol) will screw things up. Clean Plugs and set them. Use a Vacumm Gauge after you set your timing (about 4-6 degrees in advance) and set your Carb lastly with a Vacumm Gauge. To its Highest setting. Good Luck!

Tom

Probably less than that.  Refineries didn't start cracking fuel until after WW2 which gave us high octane and led engine development into the muscle car era.

[Sniper]

2 hours ago, Adam H P15 D30 said:

Probably less than that.  Refineries didn't start cracking fuel until after WW2 which gave us high octane and led engine development into the muscle car era.

 

They had high octane aviation gas during WWII, one of the advantages we had over the Axis.

[Adam H P15 D30]

6 minutes ago, Sniper said:

 

They had high octane aviation gas during WWII, one of the advantages we had over the Axis.

Yes, the process was developed for WW2, not available to the public until after the war.

[Sniper]

3 minutes ago, Adam H P15 D30 said:

Yes, the process was developed for WW2, not available to the public until after the war.

 

It was done by dumping increasing amounts of tetra-ethyl lead into the gasoline.

 

TEL started being used in gasoline in 1921

[Adam H P15 D30]

17 minutes ago, Sniper said:

 

It was done by dumping increasing amounts of tetra-ethyl lead into the gasoline.

 

TEL started being used in gasoline in 1921

No, not exactly.  Though some increase can be achieved with a lead additive, it couldn't get where it needed to be and lead fouling was an issue.  Here is a snip I wrote about fuels a while back:

When your manual was written, the fuel available was what is called "straight run gasoline."  Straight run gas is basically what boiled off the top of a distillation tower and condensed into the fuel your manual was written around (think moonshining).  Very volatile and very low octane compared to what is available now and that's where the refining ended due to the technology of the time.  During WW2, there was a need to fly higher and faster which required much higher cylinder pressures to and in turn required high octane fuel.  It was found that high octane fuels could be found in the heavy oils at the bottom of the distillation towers (where the fuel oil and asphalt lives) but the molecules will have to be cracked using a catalyst.  The other option was super heating but a catalyst can do the same at a much lower temperature.  Cat-cracking was born out of this need and the cracked fuel is now blended with straight run fuel to get desired octane and volatility which are all much different that what was available pre WW2 when your manual was written.  There is much, much more to this but I am not in class and it will get off topic, but you get the basics.