Ford Muscle Cars Tech Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter #1
Can anyone think of a possible reason why plugs 4 and 8 (the cylinders closest to the firewall) are dark on my '87 mustang motor with mass air? I'm hoping there's a logical air/fuel mixture reason and it's not just burning oil in those two cylinders. It will smoke out the exhaust after idling for a while and smoke quite a bit when I gas it after it has been idling for a while. The plugs also get darker after letting it idle for a while.
Thanks in advance,
-Eric
 

·
Registered
Joined
·
809 Posts
If the oil drains in the back of the heads are clogged, you will have a oil problem on the rear cylinders. Could also be due to bad valve stem seals or leaking intake gaskets. If the screen under the PCV valve is missing it will suck oil, but I would think it would affect all cylinders.
 

·
Registered
Joined
·
27 Posts
Discussion Starter #5
What are the oil drains in the back of the heads? Is there an actual plug? Can I get to them from the outside of the engine?
Thanks.
 

·
Registered
Joined
·
809 Posts
The drain back holes I am refering to are at each end of the heads under the valve covers. Often times the rear ones clog and causes excess oil to stand around the valve springs. It is then sucked in the valve guides into the cylinders.

Pull a valve cover and if there is oil standing(and running down the side of the block now that the cover is off) the drains are clogged. Clean them with a stiff wire or rifle cleaning brush. Plus clean any crud around the springs etc.
 

·
Registered
Joined
·
27 Posts
Discussion Starter #7
Hmmm... I recently replaced a valve cover gasket and didn't notice too much standing oil. Although the car had been sitting for several hours when the valve cover was removed. Do you think the oil would have drained in that amount of time? Is the clogging a common problem or is it mostly in real high mileage engines?
 

·
Registered
Joined
·
280 Posts
Sounds like a PCV sucking oil.
remove carb and look into runners of 4 and 8 and compare them to centre and front runners.
PCV is usually plumbed at rear of throttle body. You really notice the oil on a propane motor as there is no fuel to wash the inlet.
If the inlet is oily put a home made oil separator in the line between the PCV and the TB.
Easy to make from little 150-250ml jar with two holes in screwtop lid. Put some flywire in it to catch oil vapour and "liquify it".
If it fills with oil quickly you may need new PCV or oil/air separator.
 

·
Registered
Joined
·
27 Posts
Discussion Starter #9
Well, the engine is a fuel injected motor, so I can't take a look at the runners unless I take off the upper intake. Plus the throttle body comes before both intakes, so I'm thinking the pcv would affect all cylinders. Any thoughts???
 

·
Registered
Joined
·
809 Posts
Yes the clogged drains are usually a high milage/poor mantiance deal. Sounds like yours are probably OK.
 

·
Registered
Joined
·
27 Posts
Discussion Starter #11
If it is the oil drain holes, do you think I'd get more smoke while I'm on an upslope as opposed to a down slope? Today I noticed a puff of smoke when I started the car up cold - it had been parked on an upslope. I don't usually notice the puff of smoke on a cold startup and I usually park on a downslope (my driveway).
 

·
Registered
Joined
·
809 Posts
Parking it with the front down(downslope) should make it smoke less if the front drains are not clogged. Maybe a good idea to check out those drain holes.
 

·
Registered
Joined
·
27 Posts
Discussion Starter #13
Well, after it is good and warmed up, it does smoke while idleing on the downslope, and the front plugs are not dark afterward, only the rears. So maybe that's not the problem, unless the drain plugs have just caused the valve seals to go bad in the back. I'll go ahead and pull another valve cover when I get some time to check it out a little closer.
 
1 - 14 of 14 Posts
Top