what is blow by?

[79granada]

so i am venting oil out of the breather on the valve cover and im trying to figure out why ive tried everything i can think of just wondering if i can test to see if this issue is blow by or what a good definition of blow by would help

 

[bubba22349]

Blow by is compression getting into the crankcase can be caused by worn rings, a blown head gasket, cracked head, or valves. You can test for it by doing a compression check warmed up and dry than add a few squirts of oil and retest. A bad PVC valve can cause oil issue your describing also.

 

[79granada]

yeah ive replaced the pcv valve have good vac hooked to it ill have to get a compresion test what do i look for on a test low compression on all or one cyl?

 

[bubba22349]

For an engine to run good and smoothly all the cylinders need to be close to the same compression readings of 10 to 15 % or say 10 to 20 PSI of each other and close to stock cranking specs. Worn rings show up as all lower compression than when you add oil they go up considerably, with a broken piston ring land and or ring it will read low and oil won't help raise it much in that one. If two cylinders next to each other are low is a sign of blown head gasket, a single or more but not next to each other indicates burnt valve.

 

[79granada]

ok well i reckon ill have to get a compression test and see whats going on

 

[bubba22349]

Good luck

 

[79granada]

i also get a drop in oil pressure when it starts smoking it goes down to about 10 -20 psi

 

[79granada]

well i rinsed the engine out i put about a pint of kerosene in it i pulled the pcv valve out and noticed that the baffle was pretty sludged up and let it run for about 20 minutes and it has seemed to stop ill take it for a long drive when i get the oil changed.