Mystery Oil Mist Coming from 5.7

[carrera205]

Recently installed a new mercruiser 5.7 vortec long block in in my boat. Everything seems to be fine it's running high oil pressure 60-80psi water temp at WOT is roughly 160 and everything seems to be fine but there is evidence that there is a mist of oil happening inside the engine compartment in one area of the engine. I can't figure out where it's coming from and it seems like someone is just misting one side of the engine from the top.

 

[wingless]

Isn't there a PCV valve plumbed to the intake vacuum on one rocker cover and a dangling vent hose plumbed to end near the flame arrestor on the other rocker cover?

That setup establishes an airflow within the engine to suck blowby and oil mist into the combustion chamber.

It sounds like a system that should exist is not working properly.

 

[alldodge]

Marine motors don't use pcv valves, they just have hoses coming from valve covers leading up to the flame arrestor and any blow by gets sucked in a burned

 

[wingless]

My 2000 Mercury Horizon 454 Magnum MPI engine was configured by the manufacturer with a PCV valve and a vent hose, as previously described.

A system should exist to suck away and burn the expected blowby, to maintain the block at a negative atmospheric pressure.

 

[Scott Danforth]

either a PVC valve and open elbow or two open elbows will be running to the spark arrestor

make sure you have both hoses

you could have excessive blow-by on the new motor until the rings seat

 

[alldodge]

My 2000 Mercury Horizon 454 Magnum MPI engine was configured by the manufacturer with a PCV valve and a vent hose, as previously described.

A system should exist to suck away and burn the expected blowby, to maintain the block at a negative atmospheric pressure.

I sit corrected, good to learn something, now if I can just remember it for next time

 

[jimmbo]

Just to add to your reference list. A lot of VPs have the PCV Valve too

 

[carrera205]

I do have the lines from the valve covers running to the flame arrester. Seems almost like it’s mainly from one side of the engine it’s not both.

 

[Scott Danforth]

from the oil droplets, that is more of a spray than a mist

you should be able to see it.

 

[AShipShow]

Seems like an odd spot to have oil unless its the hoses going to the spark arrestor...Then again, 70psi oil could probably go quite a distance... Is the oil sender back by the distributor busted or leaking?

 

[carrera205]

That’s sorta the mystery running it on the driveway i top the rpms out about 2500 and I couldn’t see anything but when we run in the lake and I hammer down around 3500 - 4000 rpm I see this after opening the lid.

 

[carrera205]

SOLVED!! In my search for an answer i came across this page http://www.rowand.net/Shop/Tech/MysteriousSmallBlockChevyOilLeak.htm that laid out that there is a bolt hole on the front of a SBC near the mechanical fuel pump that is drilled through to the fuel pump rod cavity and if not plugged will spray a fine oil mist when driven hard. When i investigated this bolt hole on my block i figured out it was spraying out of this hole and partly going strait but also catching the underside of one of the cooling hoses and directing some of the spray vertical and misting the top of the engine. A $1.29 later for a 3/8-16 bolt and it's all resolved.

 

[Bt Doctur]

Recently installed a new mercruiser 5.7 vortec long block in in my boat.

The new blocks dont have that feature anymore let alone a fuel pump there. Sopunds like a reman motor

 

[Lou C]

And from the old days, you removed the short bolt from that hole and temporarily threaded in a longer bolt to keep the fuel pump pushrod from dropping down while changing a mechanical fuel pump, then removed the long bolt and re installed the short one. The 4.3 V6 does not have this feature and that makes changing the fuel pump a pain!