PCV and Air Injection check valves

[2Stock]

I have been driving an '84 GW daily since I bought it in '92. It had 72K then it has 174K now. So, I am not new to some of the problems one can have at inspection time. But I am happy to find this forum to clairfy some things I have been told about the emissions control system. First, I was told by an auto mechanic that the design of the PCV valve in this car (GW with 360) was bad and that it caused excess pressure in the crankcase and oil leaks. Of course I changed the valve, but I never found out if that was the cause. Anybody know what I mean?

Now, I have had a "new" '91 GW for two months and have been tweaking and fixing the neglected maintenance so I could pass the August inspection. I changed the PCV to one that was listed for an AMC Gremlin 360. I changed the plugs, new Bosch wires, brass distributor cap, high performance coil. The 2bbl carb is newly rebuilt by a local company, it has a new air pump and a functioning diverter valve. The check valves show a little rust on the stems going to the hoses (is this really an auto part, or does anyone know where they can be bought cheap - like Graingers?) Well, it still didn't pass and it is running as good as the '84 ever did. The problem is CO%: High - 2.48 and Low - 2.59. If anybody can help I will return the favor. I still have the '84 - I have done all the work on it and it runs "pretty good." I trusted it to take me to New Mexico last winter in the middle of an ice storm. I am thinking I will keep it too.

[Julian Sharp]

yes - you can buy the check valves at a local Carquest Store - I believe their part # AV7 but check and make sure. Their very inexpensive. I have replaced both of mine recently. ( I believe your cost on the check valves will be 10-12 dollars each)!

[nograin]

Without knowing the rest of the info. makes its difficult to guess. If you are just barely passing one of the other items...? Like if you advance the timing curve, or lean it out, then you risk increasing NOx.

Here's the basic relationship (before any cat or air injection) The air injection supposed to reduce HC http://users.erols.com/mathewg/afratio.gif

Now before making mods, make sure things are right that would make it run rich or retarded. Since you failed at both idle and rolling (I guess thats what you meant) then it probabaly not just the idle mixture.

One possibility is that you have the wrong PCV valve! If it lets too little air pass then there is your problem. IIRC (cause this is one I always have to think about) the PCV lets a little air pass at under both conditions. Also, on the FSJ 360, it provides vacuum to the charcoal canister.

The only thing that is obviously bad about the PCV design is the metal tube can clog up and is hard to clean AND the location requires a special S shaped hose. If you don't have the S hose, then make a loop so the hose doesn't kink.

[ August 11, 2001: Message edited by: nograin ]

[2Stock]

Julian: Thanks for the information. I will check out the local equivalent of CarQuest for the valves - Jeep/Chrysler wants $35 each.

Nograin: I believe the Gremlin 360 PCV is OK because it has a larger barrel and I got it because it looked like it would move more air.

The HC standard is 220 and, at 2619 rpm the reading was 88 (PASS), at 1009 rpm it was 102 (PASS) The CO% standard is 1.20 and I have given the readings in my original post. This could be a blockage at the base of the carb where the PCV attaches. I shot some Chemtool in the tube and, at first, it came back out.

Can you clarify what "IIRC" is and have you heard anything about the excess pressure in the crankcase as a cause for seals leaking? My Dad tells me that, in the 1940's Wright aricraft engines had a "sniffle" valve which caused a similar problem.