Crankcase Breather

[wmelki]

Hello All,

I'm fairly new on this forum, I'm not sure if anybody discussed this issue before so I would appreciate some help.

I have a 79 Fiat spider with U.S. Specs, came with the horrible 28/32 ADHA, which I had to replace with 34 ADF (the chinese copy that is).
I must say the Chinese carb works fine so far, I felt a tremendous power increase even though I haven't changed the Intake manifold yet.

One problem though : The ADF 34 has only 1 Vacuum line, which I connected to the distributor. I was left with the Crankcase hose breather plugged to the air filter case, but without any vacuum. Car started acting strange on Idle, felt like the air going through the carb was not pure enough.

So I unplugged it completely, and turned it down, I noticed a lot of accumulated greyish sludge dropping to the ground. Car drove better afterwards and acted better on Idle, but I am fairly certain I'm doing something wrong here.

What's the solution for the crankcase breather on a 34 ADF ? Any experience out there ?

Thanks !

[131]

The 34 ADFA is standard on the 2 litre 131 in Oz, the crankcase breather goes in to the base of the aircleaner. If it's adversely affecting your idle, you've probably got excessive blowby, and from your description that sounds like the case.

[wmelki]

The 34 ADFA is standard on the 2 litre 131 in Oz, the crankcase breather goes in to the base of the aircleaner. If it's adversely affecting your idle, you've probably got excessive blowby, and from your description that sounds like the case.

it was ok with the old carb, it's just that the ADF34 doesn't have the vacuum port for the breather. I can still connect it to the air filter, but the secondary line that goes to the vacuum has to be plugged.

[seabeelt]

Grayish sludge might indicate water vapor Of check your oil for that same milky sludge. If ok it's probably just moisture condensing on the tube. If you find milky oils on the dipstick and or oil fill cap I would suspect a head gasket problem.
Most crankcase vent tubes attach to the air cleaner housing outside of the air filter. There is a small vacuum hose that attaches in the same area, however if you have a lot of blowby it will get sucked through the air filter into the main carb body

[85redpini]

Hi
are you using the stock air cleaner? the vapors are sucked into the air cleaner, so nothing to do with vacuum lines with carbs. the comments that it is your engine just make me laugh.
Jay

[131]

Hi
are you using the stock air cleaner? the vapors are sucked into the air cleaner, so nothing to do with vacuum lines with carbs. the comments that it is your engine just make me laugh.
Jay

So you've never seen a car with excessive crankcase fumes affect idle. I suppose ignorance can be humorous.

[wmelki]

Hi
are you using the stock air cleaner? the vapors are sucked into the air cleaner, so nothing to do with vacuum lines with carbs. the comments that it is your engine just make me laugh.
Jay

Yes, stock air cleaner. Pretty sure there was a side port connected to the vacuum in the old ADHA carb. I will post a picture later on of this detail.

I monitored the fumes coming out of the crankcase breather, seems quite normal to me. I don't think I have excessive blow-by. I'm trying to adjust the mixture on the new carb to see if it changes anything.

Thanks for the help.

[Fiatlanta]

Ever get this sorted out?

[maxdog]

Hi
"Kermit " [ Well he's green] my 1979 2000 had been comprehensively desmogged in a previos life . Thr's no cat converter , air pump , or vacuum connections to solenoids , etc .
There is a hefty pipe from the crank case to a grey lump mounted above the fuel pump . I assume this is a crankcase ventilation gizmo . The large [ 3/4 , 1 inch ??]out board connection from this simply vents to the side of the engine, doing nothing good for the environment . I suppose it should be connected to the inlet tract some where,to recycle the fumes, but where ?
There is a small bore connection on the manifold down stream from the carb , which I suppose was a vacuum port for the smog gear . This now plugged .
The lunch box air cleaner has a 1/2 inch hole in it's base plate , between the air filter element and the carb . This would be a logical point for the crank case ventilation to be connected to.
Is this correct , ?
Why is the crank ventilation hose so big ,can I reduce it to fit the air cleaner hole ?
Do I need a.flame trap in this line??
Can I junk the whole system and fit a standard N/American PCV valve in a smaller hose ?
This works on a 7 litre Chrysler V8 with no problems .
Maxdog











how shold i red

[brackie1]

This is certainly an interesting thread. On my '77 when I replaced the carb and de-smoged it I just wrapped a small piece of cheese cloth around the end and let it vent to the atmosphere, which is the way those of use here do it.right or wrong it runs great.

[So Cal Mark]

there is a calibrated vacuum port on the carb that was connected to the vent nipple on the air cleaner, that vacuum helps with positive ventilation. If you just leave the hose dangling you lose that positive ventilation. Without that positive ventilation you're making the pistons force the vapors out during the downstroke. If you have pressure in the crankcase, consider it as resistance to the piston moving down in the cylinder resulting in a slight power loss and a contributor to oil leaks.
Reducing the crankcase hose down isn't the best thing to do

[AJFiat]

Mark,

Where would you recommend one gets the vacuum for the smaller fitting on the bottom of the stock air cleaner from. I have a 1979 with a single plane manifold and the Chinese 34 ADF carb. On the side of the carb is a fitting that is connected to the distributor. On the front is one connected to the charcoal canister for the fuel tank. So it looks like my options would be to tee it into the charcoal canister line or take it directly to one of the ports in the intake manifold.

[ORFORD2004]

Mark last connection...
Last active:Sat Jun 24, 2017 3:03 pm

[AJFiat]

Thanks. I decided to hook the small vacuum line from the crankcase vent tube on the air cleaner to the vacuum on the carb. Then I'll get a fitting for the intake manifold to add the small vent from the top of the charcoal canister. From what I could find online this seamed to be the most logical way to do it.

[SteinOnkel]

there is a calibrated vacuum port on the carb that was connected to the vent nipple on the air cleaner, that vacuum helps with positive ventilation. If you just leave the hose dangling you lose that positive ventilation. Without that positive ventilation you're making the pistons force the vapors out during the downstroke. If you have pressure in the crankcase, consider it as resistance to the piston moving down in the cylinder resulting in a slight power loss and a contributor to oil leaks.
Reducing the crankcase hose down isn't the best thing to do

Wow, I haven't read this much nonsense on a car forum in a long time. I know he hasn't logged on in a while, but I cannot let this go uncorrected for all eternity.

Every single ICE engine has positive pressure in the crankcase. The reason is that it is impossible to perfectly seal the piston rings in their bore. Therefore, combustion gases, exhaust gases and all manner of pressurized air is always being forced passed these rings on the compression and exhaust stock. This sneaking passed the rings is called blow-by. Every engine has it. Likewise, oil also gets passed the rings and thus being burned off during combustion. This is why every single engine burns oil.

It's all a question of how much. In the OP's case I suspect there was something inherently wrong with the engine. That much blow-by is excessive, usually due to worn out cylinder bores, worn out or cracked rings or holes in pistons.

Also, please don't vent to atmosphere. Apart from making polar bears homeless, some people (like me) get raging headaches from unburnt hydrocarbons.