Of course…excess crankcase pressure… Glad it wasn’t so bad as to be overwhelming a normally operating PCV valve. It was the valve itself…very common. Glad you figured it out.
Blackbird
“Good engines those slant 6s.”
Bullet proof. Back a few years I took my kids to the County Fair to watch the annual demolition derby. Once a car received a knock-out blow to the radiator and spewed steam, it didn’t last long before it was dead.
Some cars are better than others for crashing and surviving. I recall that big old Ford wagons were good demo cars because the radiator sat far back of the grille area, but I was surprised by Chrysler cars that had the slant-six, apparently another popular choice of contestants.
I watched a slant-six go up in a cloud of steam early in a derby. I was sure it was gone. However, it survived several heats and went on to win the derby… with NO engine cooling!
CSA
but I was surprised by Chrysler cars that had the slant-six, apparently another popular choice of contestants.
The slant-6 was one of the most durable engines ever made. Pain in the but sometimes to work on…but damn they were reliable. It was the other things external to the engine that in the Volare’/Aspen’s that made them extremely unreliable vehicles.
I bought a cheap 1976 Volare’ for $300 to drive to work in the early 1990s. It was one owner 60,000 miles with all maintenance/repair receipts. The only repair was a dealer (she only did dealer) carburetor replacement. Ran and drove like a champ. 4 speed M/T with 4th being overdrive. Factory Hurst floor shift! It was actually kind of fun to drive. R&R oil filter was a b**tch. It was horizontal very close against the sub-frame. I ended up buying an oil filter socket which made it much easier. Of course it was a near base model so no “Rich Corinthian” leather for me. When I visited Corinth in 1998 the hewn through solid rock (shortcut) canal was an amazing accomplishment of ancient engineering. The only possible leather bearing animals I saw were a handful of scrawny goats.
I wonder to what extent the PCV system increases measured HC tailpipe emissions?
The truth about “Corinthian leather” is somewhat less exotic.
I can’t imagine a problem PCV valve would affect HC emissions, except as an evaporative emission.
What I’m wondering is if you did two experiments, measure tailpipe HC’s with the PCV system hooked up vs the PCV system disconnected, whether that would affect tailpipe measured HC’s? Since the PCV routes crankcase gases to the engine and crankcase gasses contain unburned HC’s. You might expect with the PCV hooked up you’d get higher HC’s at the tailpipe.
I’d be interesting in hearing the theory behind that. I’ve never really thought about PCV valves as affecting tailpipe emissions.
It is my understanding that blow-by in the crankcase was originally vented straight to the outside air . The pcv system takes this blow-by & returns it to the intake stream for burning in the engine before it exits . Unless it is 100% burned when run through the engine it would have to add something to the exhaust at the tailpipe . I would assume that by the time it is run through the cylinders & burned & then through the catalytic converter that the amount that showed up at the tailpipe would be miniscule .
Pre-PCV valves, the blow-by was emitted through a vented oil filler cap - so it wasn’t tailpipe emissions, but it was adding unburned hydrocarbonss to the air by a more direct route. PCV systems result in less air pollution.
Anyone remember air injection systems - pumping air into the exhaust stream at the exhaust manifold? The official explanation was that introducing air at that point helped hot HCs to burn. Another explanation was that the air simply diluted tailpipe gasses, so the tailpipe emissions fell below the allowed concentration. Kind of like building higher smokestacks - “dilution is the solution to pollution.”
I remember small block chevy engines that had a metal tube that ran down to the bottom of the engine & was open ended down there . I think the vented oil filler caps allowed intake air that exited out the down pipe . As you drove down the road a draft was created by air flowing past the end of the open down pipe .
On all pre-PCV cars, crankcase fumes exited the car via a “road draft tube” usually down the rear or rear side of the engine. The oil filler caps were sometimes vented with a filter inside to let out fumes an hopefully not oil.
What I'm wondering is if you did two experiments, measure tailpipe HC's with the PCV system hooked up vs the PCV system disconnected, whether that would affect tailpipe measured HC's? Since the PCV routes crankcase gases to the engine and crankcase gasses contain unburned HC's. You might expect with the PCV hooked up you'd get higher HC's at the tailpipe.
I’ll bet dollars to donuts you see absolutely no difference at the tailpipe. Couple reasons. First, the system is closed loop. The computer will simply dial back the amount of fuel being injected to compensate for any recycled PCV gases. Secondly, the cat has enormous reserve potential compared to the inlet gas volume. It will easily consume the volume of HCs being produced through blow-by unless there is something seriously wrong.
Sloepoke: Thank you for saving wear and tear of my fingertips by describing the down pipe. I think my first PCV equipped cars were 1963s.
@Sloepoke, how much fun was it changing that pcv valve? I did mine on my 97 Nissan PU 2.4 and I did not enjoy it at all.
Yeah… I still love me a Slant Six… What great engines… Im partial to all inline Sixes come to think about it.
Damn @“oldtimer 11” you remember those vented Oil filler caps too ? I believe Mopar used those pretty often if memory serves… Yup…I remember those.
Blackbird
Remember vented caps??? H3ll, I still have a bunch of cars with vented caps on valve covers, vented caps on gas tanks…everything vented to atmosphere…
I grew up with vented caps. The Clean Air Act wasn’t passed until 1970. Vented oil filler caps were common.
I’m inclined to agree with TT. There should be no difference. Oil is, after all, a hydrocarbon, and whatever gets drawn in through the PCV system is aerated.
I'll bet dollars to donuts you see absolutely no difference at the tailpipe. Couple reasons. First, the system is closed loop. The computer will simply dial back the amount of fuel being injected to compensate for any recycled PCV gases. Secondly, the cat has enormous reserve potential
It would be an interesting experiment to do. You’d have to have a gadget that measures tailpipe HC’s. I wonder if there are any reasonable price versions available. To do this experiment it wouldn’t have to be perfectly accurate, just more or less linear and consistent. You only want to know which has more HC’s, not the exact amount. You’d think there would be inexpensive silicon sensors that could do it.
@keith I watched a u tube video & changed it that way . Remove front passenger side tire , remove rubber splash shield behind tire , remove oil filter & looking through from the fender well it’s right there looking at you . Compared to the ones in the valve covers it’s a pain but wasn’t really that bad . Probably took 30 or 40 minutes in my driveway .