The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 04-20-2017, 09:22 PM   #1
46stude
Registered User
 
Join Date: Dec 2014
Location: Rockport, Texas
Posts: 187
PCV problem? Oil leak

I've got a '93 350 in my Cheyenne, pretty well stock innards w/ a real mild cam. It's got a Q Jet on an aftermarket intake, 1" spacer under the carb.

A week or so back I noticed the PCV hose had rubbed a raw spot & was sucking air, so I poppped on a fresh hose. This truck is a POS & it's sat way more than it's been driven, so I don't know how long the bad spot had been in the old hose. Not more than 1000 miles, I can say, though. Doubt I have 1500 miles on the truck since I put the stupid thing together.

I now have oil leaking off the back somewhere, enuff to coat the underside of the truck during a 70 mile trip today. It'd never leaked oil before. I've been all under the truck & on top of it, but nothing is glaringly obvious as to the source.

I keep coming back to the PCV hose, though. I've attached a pic of my set up. Does this need a breather on the drivers side valve cover? I just feel like the oil is something I caused when I put on the new hose.
Attached Images
 
46stude is offline   Reply With Quote
Old 04-21-2017, 12:19 AM   #2
rocknss
Senior Member
 
rocknss's Avatar
 
Join Date: Oct 2004
Location: Milwaukee, WI
Posts: 400
Re: PCV problem? Oil leak

This is how I have mine setup. I have the PVC on the passenger side going to the Carb and a Breather on the driver side circled in red.
Attached Images
 
__________________
Steven
69 Chevy C10 Suburban 350 700R4 w/Disc brakes on all four corners
2017 50th Anniversary Camaro SS
2004 Chevy Impala LS
2016 Chevy Malibu LT
rocknss is offline   Reply With Quote
Old 04-21-2017, 11:03 AM   #3
46stude
Registered User
 
Join Date: Dec 2014
Location: Rockport, Texas
Posts: 187
Re: PCV problem? Oil leak

Thanks for the comments, guys.

Yeah, that's what I'm about to do. My mistake came in NOT having a breather on the drivers side, methinks. With the bad hose, the PCV wasn't working correctly. With the new hose, I think I pressurized the engine & blew out part of the rear intake seal because the PCV was working & had no source to draw in air.

Sucks because I was gonna take it on a road trip this weekend to a car show in Texas City. Don't have time to pull the intake & fix the oil leak, though, so the truck'll just sit at home instead.

Moral of the story- a properly plumbed PCV system needs a breather, or you're gonna have problems. Just one of those things I overlooked.
46stude is offline   Reply With Quote
Old 04-21-2017, 11:32 AM   #4
demian5
Registered User
 
demian5's Avatar
 
Join Date: Aug 2016
Location: Lake Forest, CA
Posts: 863
Re: PCV problem? Oil leak

Quote:
Originally Posted by 46stude View Post
I think I pressurized the engine & blew out part of the rear intake seal because the PCV was working & had no source to draw in air.
If PCV hose is connected to manifold vacuum on the intake manifold or base of carb (as it should), that creates a vacuum (negative pressure).

This would cause the opposite of oil leaks, it could possibly smoke from sucking oil from the crankcase through the PCV and into the intake.

So, you could have "sucked " the seal into the lifter valley. That would make sense.
__________________
"Work hard, use your vacation days."
1970 C15 GMC Long Bed
1986 C20 Scottsdale (grandpa truck)
1964 Impala SS
1959 Austin Healey 100-6 BN6
demian5 is offline   Reply With Quote
Old 04-21-2017, 11:48 AM   #5
46stude
Registered User
 
Join Date: Dec 2014
Location: Rockport, Texas
Posts: 187
Re: PCV problem? Oil leak

I believe that's what I'm dealing with. "Blowing" out the intake seal was the wrong description. I think.
46stude is offline   Reply With Quote
Old 04-29-2017, 12:12 PM   #6
46stude
Registered User
 
Join Date: Dec 2014
Location: Rockport, Texas
Posts: 187
Re: PCV problem? Oil leak

Update: I did cause the problem.

When I first put the truck together, every so often while running down the hiway, the PCV would pop out of the valve cover. I knew when it happened because the oil smell would come into the truck. So I'd pull over & pop it back in. I believe this was the direct result of not properly plumbing the engine for the PCV. I had no breather on the opposite valve cover for the PCV to circulate air into the 350.

Apparently, at some point the hose must have layed on the exhaust manifold long enuff to partially melt it. So the hose was sucking air, which is also probably when the PCV magically stopped popping out.

So, when I noticed the hose was bad & I replaced it, the PCV had, over time, locked itself into the grommet. Instead of being able to pop itself out of the valve cover, the PCV instead popped the intake seal at the back of the engine, resulting in the oil leak. And it apparently only leaked while under load & actually running down the road. You'd think the oil leak's location would be obvious, but it wasn't.

So, I yanked the intake a couple days ago & replaced the gaskets & RTV on the china walls. There was an "extra" grommet I'd plugged, so I bought a grommet & breather at O'Reillys & put them into the drivers side valve cover.

I put 40+ miles on the truck yesterday, & no oil leak. Problem solved..... I think.
46stude is offline   Reply With Quote
Old 04-29-2017, 12:15 PM   #7
46stude
Registered User
 
Join Date: Dec 2014
Location: Rockport, Texas
Posts: 187
Re: PCV problem? Oil leak

Pics for anybody running factory TBI style center bolt valve covers like mine:
Attached Images
  
46stude is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 08:19 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com