I have a situation of excessive crankcase pressure. Like...massively excessive. popping out the dipstick, and/or blowing off the valve cover vent line (that feeds fresh air INTO the engine) with a sound like a semi-truck venting brake line air, type pressure. The PCV has been replaced, but I noticed that the hose going from the valve to the intake is collapsing under vacuum. My first step will be to get a stiffer hose and see if that solves the problem, but I'm not holding out much hope.

A compression test is forthcoming to see if it's pistons/rings/head gasket related (I hope it's nothing along those lines) but I was wondering if there might be other issues I cold look for?? I did a search, but didn't find anything that seemed to relate (other that pistons/rings/ HG).

It's early, and I'm stressed (broke down 250 miles from home) so my mind is muddled and having a hard time thinking straight. If anyone has any ideas please share.

Thanks

 

I would check the pcv valve to make sure its operating correctly, replace the hose as you mentioned with a stiffer one, the vent hose just behind the oil fill doesn't feed fresh air into the engine, it vents crankcase pressure out and equalizes the pressure, normally sucks the fumes back into the carb if connected to the air filter, if just a filter on there, it just vents.
Make sure it is not plugged, like possibly the oil baffle inside the valve cover is full of sludge and not letting it vent. If those fixes don't help then possibly some internal problems like excessive blowby from broken ring(s) piston, or such allowing to much pressure to build inside the crankcase.
Good luck.

 

I had that happen on my 04 mustang... do you have a lack of power?

I thought the engine was worn (182k mi.) So i replaced it and it still was messed up. Turned out 1 of the 4 catalytic converters was plugged.

 

Well...problem solved...after a fashion.

After a brief commiseration with a couple of local gear heads, the consensus was a buggered engine.

So I bought another truck off Craigslist. $700 for an 84 Xtra cab 2wd. The 77 will get towed home and the engine gone through over winter. The 84 has fewer things wrong with it, so eventually the two will swap engines and the 77 will go up for sale next spring/summer.

 

i think you should just looking through the vacuum lines for sure. Just look over it on the side. and then maybe the cat like Burnz said.

i'm sure its a minor issue

 

It's a 77.

No cat.

Swapped the carb to a Weber 32/36. The only vacuum lines are for the PCV (freshly installed), the brake booster, and the vac advance on the dizzy.

Even with the PCV hooked up, if I unscrew the oil cap and just rest it on the opening it gets blown off to the side by the crankcase pressure.

Engine is buggered.

 

did you try running it with the pcv completly taken off? make sure the port out of the valve cover isnt plugged up with oil residue?

 

You said a couple local gear heads concluded the engine is buggered, what did they do to determine that, leakdown, compression test? just curious. If the engine ran OK, didn't use a lot of oil or smoke excessively, and has fair compression numbers, it still might be something plugged.
The oil cap does get some pressure under it from the oil, want proof, fire it up with the oil cap off, you'll get a oil bath real fast. Theres only 2 places to release the crankcase pressure, the pcv and the valve cover vent, if somethings plugged it will pop the dip stick and eventually take out the rear main seal. The oil baffle inside the valve cover on the early engines were bolted in, If it were me I would pull the cover, pull the baffle and make sure its not caked full of crud to the point that the vent and pcv are unable to do their job. But if the engine is in bad shape compression and oil useage wise then forget what I said and proceed with your current plans.

 

this....
even a dead hole with the rings wasted doesnt go crazy on the crankcase pressure....i would search the engine first before i scrapped it.

 

Never said I was going to scrap it. The 77's engine will get pulled and gone through at leisure over the winter, installed in my 81 4x4, whose engine will be put in the 77 and then sold.

OR...I may play musical engines, turn the 81 engine into another hybrid after the swap, drop it into the 84 and put THAT engine into the 77.

So I'd wind up with an 81 4x4 w/22r/20r hybrid, and an 84 2wd w/22r/20r hybrid, and a 77 w/bone stock 22r.

I've got the 20r head and intake already, but it looks like I'll be searching out another Weber for the second hybrid.