Hey Guys, um i just got a new 14' diameter edelbrock air filter and case and it has the attachment for the hose to hook into from the oil-breather cap what does this do? can I safely drive with the hose not hooked up to it cause I needed a carb lifter to put the air filter on because it sat too low and the carb components got in the way but the breather cap is higher than the hose attachment on the air filter so the hose is HARD to put on and stay on and also restricts the air filter from being put on without force it is really frustrating, also i saw a breather cap that has a filter on it would this work and make it so I don't need the hose?? Thanks for all your help!!

 

Just get a piece of heater hose (5/8?) and clamps and attach it to the breather and air filter case. FWIW: Edelbrock and others (check Summit) offer air cleaner cases with raised heights so you can avoid having to use those cheap no good plastic risers that let air and dirt by the filter.

I put a 10" Edelbrock on my 2 bbl 2150 and used an aftermarket 3"x10" filter from Advance Auto. I moved it over to my new 4BBL Holley Street Avenger with no problems.

imo, Hook up to the carb is better because it probably creates better pull when the PVC opens.

 

The hose from the oil breather to the air filter is part of the pcv system. It should be hooked to the air cleaner so filtered air goe through it. It does not get hooked up to carb vacuum. The pcv valve goes to carb (or better, manifold) vacuum. Then when the engine is running it draws air from the air filter through the oil breather, across the crankcase, through the passenger side valve cover, through the pcv valve and into the intake. You could replace the oil breather with a filter element style breather and still have the pcv system operational. Instead of getting filtered air from the air filter housing, the oil breather would filter the air instead.

 

Get rid of that Edelbrock filter if you are using the truck for a daily driver and put the stock system back on. Those aftermarket filters don't work as well as the stock system if the stock system is functioning properly. The aftermarket filters suck in hot under hood air that hurts performance. The stock system pulls air in from outside. There are a number of improvements you can make to the stock system also. There are a number of threads here on that subject.

 

So here's the deal: Failed emissions test on 77 F100 302 Hedman hedders.

Hydrocarbons were 732 versus 500 limit.

I'm replacing plugs and PCV. Wires are supple and clean. Distributor is relatively new.

There is an aftermarket chrome air filter cover directly on top of the Holley carb, no hose from valve cover to work with PCV. Would this non-stock configuration (i.e., lack of inlet to air stream from crankcase) interfere with efficient burning of fuel and show up as excess hydrocarbons?

Also, would it help to let the tank run dry and get re-retested while running an ethanol fuel rather than mid-grade regular?

My brother suggests dropping in a pint of grain alcohol while gas is low. I worry that this might be harmful and also might be detected by the testing station.

 

It's running too rich. You may have to lean out the carb a bit. You may also have to back the timing off a little. High hydrocarbons means there is too much unburned fuel in the exhaust.

 

Thanks. Leaning out the carb and getting the idle a bit higher and smoother simultaneously is next on my task list.

Will the lack of breather input to the airstream have anything to do with efficiency of the burn and leftover hydrocarbons?

Seems like this setup would be the same as running with the breather tube disconnected. What impact does that have on running, fuel efficiency, and - most importantly for the moment - excessive leftover HC?

Thanks for you earlier reply.

~

 

Typically, there is a port on the back of the carb for the PCV > Intake flow. The amount of flow is regulated by the spring-loaded PCV valve, which varies with engine vacuum. Not having this connected would also typically upset the Air/Fuel ratio and could be a source of running rich. So, yes, a non-funtioning PCV will send you rich or lean, depending on how the port is left unregulated.

 

Thanks, but the PCV itself is connected, along with the hose to the port on the back of the carburetor.

What's missing from I would normally see and expect is the crankshaft ventilation hose that would lead from valve cover to air cleaner.

If the crankshaft ventilation hose to the air cleaner is missing, how does that effect fuel burning efficiency - and most importantly at the moment - leftover hydrocarbons?

 

Did your truck originally have a catalytic converter on it? Does it have one (or two) now? Do they just do an idle test? After I went through the 302 on my 78, the usual: cam, intake, headers and Holley, it bombed the test big time!
I put high flow cats on it (about $60 ea.) and it blew 0 on CO and 17 PPM on HC! This was on a fresh engine. Make sure to get the cats good and hot before you have it tested.

 

Or, to be more clear if I can:

Is that one hose from the PCV to the port on the back of the carburetor the same as the big oily hose that would go into the air cleaner? I don't see how since the air cleaner intake hose had a filter to ****** the oil from those crankcase gasses.

Is something missing here?

 

The filter in the air cleaner was actually to filter the air being sucked into the engine by the PCV valve on the other side of the engine. Cross flow effect. The filters will usually get oily over time due to worn rings causing some blow-by and the oil vapors that rise after the engine is shut off.

The PCV uses intake vacuum from under the carb to suck the gasses out of the crankcase thru one valvecover. The other valvecover has the breather hose that connects to the air cleaner so that the PCV can suck in filtered air and not dirty air which will contaminate the oil faster.

 

It has a single cat, and not all that old I'm told.

They tested at idle and at 2500.

The truck had been sitting up for about two weeks and the testing station was only three miles or so. However, I sat at a relatively high idle for 15-20 minutes until it was my turn in the stall.

 

you beat me to it. i was going to say the same thing. you can also add factory cold air intake with the stock system the aftermarket air cleaners offer no improvement at all.

 

The other valve cover doesn't have a breather hose. Doesn't have the stock air cleaner, just a round chrome cover over the air filter.