Exhaust puffing from Valve Cover?

Tiny
DANAROTHROCK
  • MEMBER
  • GMC
I own a 78 Delta-88 with 403. She runs and runs and runs. 200k-400k miles (speedo doesn't work).

Why does exhaust blow out the valve cover?

I replaced the gaskets, but the passenger side cover still puffs quite a bit of exhaust. Could be bent cover. I will try a second gasket.

But why exhaust?

I replaced the PCV valve and tubing is not restricted.

The head doesn't look cracked. There is a patch on the valve cover where the paint burnt off directly over the exhaust leak. What does this indicate?

Thanks
Do you
have the same problem?
Yes
No
Tuesday, February 28th, 2006 AT 7:48 PM

9 Replies

Tiny
MECHANIC116
  • MEMBER
LMFAO! Sounds to me like your father's oldsmobile is wore SLAP out. That "exhaust" as you put it, that's coming from the valve cover is what's called "blow-by" Combustion gasses that leak past the piston rings of a running engine. Means she's wore out. Scraps way up. That car would prolly bring close to $150 at the crusher. Good luck!
Was this
answer
helpful?
Yes
No
Tuesday, February 28th, 2006 AT 7:56 PM
Tiny
DANAROTHROCK
  • MEMBER
Can I get a second opinion? :Cry:

If it is "blow-by", judging from the burnt paint, it is coming from the 2nd set of valves from the front.

No problem anywhere else.

There is a solitary lifter rattle on that side, but I haven't identified which lifter.

Could a lifter need adjusting?

I thought "blow-by" was into the crankcase. She doesn't smoke.

You must understand I paid $600 for this car 10 years ago. My daughter and two sons drove this car to high school. I have been driving it all over the country for the past 4 years. It is good for teaching driving lessons to Texas drivers. I once won a chicken contest with a concrete truck. I never have a problem entering freeways. Parts are cheap.
Was this
answer
helpful?
Yes
No
Tuesday, February 28th, 2006 AT 8:58 PM
Tiny
MECHANIC116
  • MEMBER
Lol. Ah. Now I am thinking that perhaps you have an exhaust leak where the manifold bolts up to the head on that side, and it is blowing upwards, on the valve cover. As old as that car is, that might be a challenge. In order to fix it, you'd have to remove the exhaust manifold on that side. The likely hood of those bolts coming out without breaking off is almost non-existant. Also, what you think is a lifter tapping is probably the sound the exhaust leak is making. I dunno if I'd mess with that or not, taking into account what you paid for the car and how much use you have ALREADY gotten out of it.I think I'd just let'r ride.
Was this
answer
helpful?
Yes
No
Tuesday, February 28th, 2006 AT 9:10 PM
Tiny
DANAROTHROCK
  • MEMBER
You don't know how hard it is to find a decent car in Houston.

No, just had exhaust manifold gaskets replaced (by a mechanic!) A year ago.

The exhaust puffing is on the top, inside - toward the carburator.

When I took the valve cover off, it was covered inside with crusty, burnt oil. Had to scratch it off with a wire brush and gasoline.

Can I run the engine with the valve cover off, to see what is going on?

Coming home thru Missouri last week a state trouper pulled me over for doing 90. (Speedo doesn't work.) Trucks were supposed to do 55, so I figured if I passed them at about 10mph, I would be safe. The trucks must have been doing 80. The trooper tried to shake me down for $220 cash. I showed him my credit card, he let me go - no ticket!
Was this
answer
helpful?
Yes
No
Tuesday, February 28th, 2006 AT 9:48 PM
Tiny
MECHANIC116
  • MEMBER
AH HA, now I know what you're talking about. Your exhaust crossover on your INTAKE manifold is leaking exhaust where the gasket it. I HAVE seen this occur as a result of the intake actually rusting out there, hopefully that's not it. Prolly just a simple intake gasket change will fix this.
Was this
answer
helpful?
Yes
No
Wednesday, March 1st, 2006 AT 6:13 PM
Tiny
DANAROTHROCK
  • MEMBER
This could answer why the intake manifold was so hot. I couldn't figure that one out.

Now, how do I get to the intake gasket?

My Chiltons doesn't show that much detail.
Was this
answer
helpful?
Yes
No
Friday, March 3rd, 2006 AT 2:36 AM
Tiny
MVANNESSJR
  • MEMBER
A Chiltons will not give a lot of detail. The service manual is what you are looking for. They usually are rather costly for a service manual. Basically you will need to remove the bolts from the intake manifold and assuming they aren't rusted shut you should find the gasket right there. We replaced the gaskets on my vehicle with copper instead of cork but it will require you scrape off the old gasket and possibly do some sanding to give it a level surface, replace the gasket with one of your choosing and use a torque wrench to connect the bolts back in giving equal pressure along the gasket.
Was this
answer
helpful?
Yes
No
Friday, March 3rd, 2006 AT 2:43 AM
Tiny
DANAROTHROCK
  • MEMBER
Also, I put a second valve cover gasket on, but the exhaust puffing continues.

I don't understand this. The gasket had valve cover indentation all around it. No gaps, but the exhaust billows out. Confounded puzzle.
Was this
answer
helpful?
Yes
No
Friday, March 3rd, 2006 AT 2:44 AM
Tiny
MECHANIC116
  • MEMBER
YOu will need to remove your intake mainfold in order to replace the gasket. This is a fairly easy job. Just make sure you drain your cooling system before you take it off, so you won't spill coolant into your crankcase when you remove the intake. Make EXTRA sure that you get the gasket sealing surfaces both on the HEADS and on the INTAKE, as clean and smooth as possible. Also, DO NOT use any silicone on the intake gasket. Silicone shoud only be used at the corners of the intake, on the front and the rear, where it seals to the block/head. Good luck.
Was this
answer
helpful?
Yes
No
Friday, March 3rd, 2006 AT 4:19 PM

Please login or register to post a reply.

Recommended Guides