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sbc burning oil

31K views 30 replies 9 participants last post by  red65mustang 
#1 ·
Freshly built 383 all new. I have to add 1/2 qt oil every weekend (about 50 mi. cruising). Blue smoke starting and on decelleration but not while idling, cruising, or on hard accel. Had to put in 3 air filter breathers in valve covers and a PCV to carb to keep valve cover gaskets sealed. Any ideas?
 
#8 ·
alittle1 said:
You did say you checked the modulator valve on the side of the trans for any trans fluid in the vacuum line.
There would be a complaint of loss of transmission fluid if the modulator valve was leaking oil into the vacuum line. He is apparently using engine oil, about 1 qt every 100 miles. I don't see why you directed him to the transmission modulator valve if in fact his transmission even uses one?
 
#9 ·
many aftermkt valve covers do have the holes directly aligned with a rocker so that at 50psi oil pressure it can/will spray the breather and pcv at rpms...

the oil sucked up by the pcv lays in the rough surface intake till ya hit the gas and flush the oil into the cylinders to make smoke....

the fact that 3 breathers have clogged due to oil splash does indicate it's a baffles/breather location problem.....

to get the cylinders clean enough to check the plugs to (hopefully!!!) eliminate any rotating assembly problem as the smoke source....
make a simple "oil accumulator" to stop any oil from getting into the cylinders thru the PCV!!!!
8oz screw top (peanut butter?) glass jar...
couple of (whatever) 3/8" fittings, one around 2" long, the other around 1" long ...
some (scrap) 3/8" hose...
drill 2 holes in the lid and connect the longer fitting going into the jar to the pcv with a hose...
connect the other shorter fitting thru the lid to the carb pcv hose...

now any oil the pcv does pick up will stay in the jar....

a "belt and suspenders" fix for the breather side is improve the baffle and mount the breather higher on a piece of heater hose or tubing etc...
( a plus reason for doing that is the breather will pull cooler air into the block, a pcv does move a fair amount of air thru the block while cruisin')

just for the idea of the oil accummulator set up, here's a pic of one I made from a $13? (wasted!***) compressor water collector I modified,,,,(instant coffee jar works just as well)

***(fun to laugh at yourself), I bought it because it has a spring loaded drain at the bottem,,,,to empty it into a jar....
it "has" threads on the jar, just as easy to unscrew the jar and dump it!!!

definitely correctly retorque your intake manifold!!!!
 

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#11 ·
glen,
should you dump it back in the motor is tough to answer...
depends,
how many miles on the oil, are the additives used up?
how many cold starts on the oil which contaminates it with water and acid?

in this case, with a brand new build that's bleeding 16oz in just 50 miles,,,,I'd probably save the oil to use in my older than dirt lawnmower that does puff abit of smoke...
(more "new" oil additives added to his motor can only help)

if there is say only 2oz in the jar after 50 miles (pcv isn't the main problem),,why not,,2oz diluted into 160oz in the pan (5 quarts) won't hurt....
 
#12 ·
Ok when I say 3 valve cover breathers I mean thats how many are in now, 2 on the left and 1 on the right + a pcv on the right. None have ever clogged. It seemed there was too much crankcase pressure so I added more breathers. I actually had oil squirt out of the right side valve cover (cleared the header and hit the inner fender). My pcv is ran to 3/8 port on the back of my BG Demon. I have shorty headers in a s-10 so no room for an exhaust type pcv set up.
Could it be my rings since it only does it starting and on decelleration, I never see when I'm pushn the pedal (partial or full throttle). Seems like I can make it stop smoking by giving it a little gas.
 
#13 ·
"could it be my rings"
it could be many different things and often is a combination of problem sources especially when you are going thru 1/2 a quart (!!!) in just fifty miles....

deceleration, the pcv is held wide open by the extremely high/strong Hg vacuum level, add oil psi is max plus lots of rpms and the carb blades are closed="perfect" conditions for the pcv to suck up oil....

unless your motor will start with no pedal tap at all=no carb squirter pump fuel added,,,then that's alot of extra "liquid" gas into the intake to flush the oil into the chambers so it smokes at start up ....

when you give it a little gas the pcv is probably not full open because there is less Hg vacuum and less oil pressure at the rockers and the mix is lean with a load on the motor so no smoke ....

30 minutes (?) to rig together a oil accumulator, drive it 50 miles and see if still it takes a full 16oz to hit the full mark on the dipstick....

do also retorque the intake, decelerating at 25Hg vacuum can make the heads suck up alot of oil if there is just a tiny tiny intake gasket leak!!!

side note:
vacuum Hg example illustration/analogy,,,, your 2HP wet/dry shop vac with the hose end necked down to about 3/8" diameter "might" be able to pull 12-15Hg max worth of vacuum force on a guage....
at only 12Hg it will pick up ALOT water on the floor fast as hell .....
decelerating/engine braking a motor that seals decent does pull 25Hg+ so think of a pcv as a "super sucker",,,every time you back off the gas the Hg does go to 25Hg for atleast a moment!!!!!

external oil leaks can be a sneaky contributor to oil loss....
wash the motor to remove any oil on the surfaces....
use baby powder/talc powder/whatever fine powder that you can put in your hand and blow all over the motor so any oil will show up
...........................................................
"it seemed (???) there was to much crankcase pressure"

how many miles on the motor?
on a brand new motor, until the rings and particular cylinder hone grit finish (correct for the rings type!) are worn in to make a good seal it's common to have some blowby....

for a diy'er, lack of absolute "white gloves test" cleaning before assembly is probably the most common cause,,,machining grit scored the walls so now there is blow by...

if it is indeed "excess" crankcase pressure, it can be due to many things....
I picked this link off google almost a random to cover the most (?) common causes:

http://www.nulon.com.au/facts/Factsheet 110.PDF

do one test, one step at a time till you can truly "diagnos" the problem source....
LOL, might as well do it in easy to PITA test order.....

if there is next to no oil in the jar after 100 miles, (remove all the plugs and keep them in order for the machine shop) and do a compression and/or leak down test to determine if the rotating assembly is sealing correct and equal on all 8 cylinders....
all cylinders test equal and good psi, then valve stem seals and guides are abit "more" suspect for the oil loss....

adding a breather to the cover with the pcv valve totally defeats the purpose of the pcv.....
the pcv is pulling next to no air "thru" the whole block from the other head cover breathers....
it's just sucking air from the breather on the pcv cover
block off that breather...
 
#15 ·
How accurate is your oil dip stick? You could be over filling the crankcase causing excessive crankcase pressure that will cause blow-by and excessive oil consumption. Put in 4 quarts and see if its at the add mark and then put in the 5th quart and see if it's at the full mark.

Do your valve covers have baffles under the openings for the PCV valve and breather. If not, the PCV valve will suck out any oil splashed on it and oil will mist out the breather.
 
#16 ·
No baffles in the valve covers but I do have baffled grommets under the filters. And I guess I was wrong earlier when I said I currently have 3 breather + a pcv. I have 2 breathers in the left and only a pcv in the right but no baffle or anything to stop oil from being sucked up the pcv. My oil pan is a 7qt for sure. I put 6 in and it is at or just below the bottom of the "safe zone". I'm definetly going to look into the pcv system before I go any further.
 
#17 ·
more opinion than tested fact:

I don't like or use those roughly 80 durameter rubber baffles because soaked with oil and hot they "can possibly" collapse and restrict the breath....
(the small opening "lip" is limper than a "you know what" if you poured 200* oil on it!)
if that does happen the pcv will suck unfiltered air and dirt in thru the dipstick tube or where ever....

"if" a $.02 cost rubber baffle could work,,,the oems wouldn't spend $2 on (pretty sophisticated design) metal baffles....
 
#18 ·
Ok so I went out and bought an air compressor air/water seperator, took out the 40 micro filter and put it in line between my pcv and carb. I then drove about 10 mi. lots of stop and go. At first it still smoked quite a bit but then after just a few miles I didn't see any more smoke. The last time I started it just before going to put it up I didn't even notice any smoke on start up. It was kind of windy so hard to be 100% sure. Just before I got to the garage I was cruisn about 30mph, maybe 1/4 throttle, I then "goosed" it (from 1/4 to about 1/2 and then completely off throttle), rpms went from about 2g to 4g and then right to 1500 (still in gear) and then I finally seen some smoke again. Maybe some still inside the intake runners? I would say 6 of the 10 mi. I didn't see any smoke at all. Oh yea, that seperator had almost a shot glass of oil in it, I think that is about 2oz. I'm going to drive some more before making any more changes.
 
#19 · (Edited)
"follow the instructions" (please!)

with the filter removed,,,there's nothing to stop the oil from "wicking" big time across from the inlet to outlet openings on the compressor dryer and going into the intake at high Hg and velocity....
(the jar is acting as a "vacuum accumulator" not a oil accumulator)

that's why I said to use a "longer and shorter" fitting into a peanut butter jar....

(grrrr.....after 30 minutes plus to find the one I made...grrrrr....then 20 minutes sorting out a software conflict to download this pic....grrrrr)
here's a pic showing that I cut off about half of the filter so any incoming oil from the pcv is directed at and trapped in the bottem of jar....

with no tube to direct the oil in the jar, no surprise at all that it puffed a bit after 10 miles due to the "wicking" since you did manage to trap 2oz in just 10 miles!!!!

yes,,,it will take some miles for the gas to clean and flush the accumulated oil out of the intake and chambers....

LOL (but serious), 2oz in 10 miles!!!! = make a accumulator out of a "32oz mayonaise jar",,,, even a 8oz jar peanut butter jar would fill up too quick!!!!
footnote:
the "tiny" compressor based accumulator jar worked OK for me because I was only sorting out a slight WOT full rich mix smoke puff, which did turn out to be a pcv baffle problem, oil accumulated in the intake, the rich WOT mix flushed it out....

even done wrong with no tube, the first test does indicate the pcv is very very likely the main oiling source....
the good news!!!!:
that's just a time and patience and no bucks fix to make some baffles out of scrap sheet steel or aluminum and mess with the shape till it works based on where the pcv sits on the cover and the rockers clearance...
the baffle added to those Edelbrock Elite covers in the pic' is approx 3x3", it's tight to the intake side curve on the cover (so oil can't run onto the baffle) and has less than a 1/8" gap along the 3" width at the headers side cover curve with a approx 3/8" lip facing down the curve just for more insurance.....
the sides extend well past the mount screw boss so I could bend them tight to the cover by hand once it was mounted so the only air is from the small gap at the lowest point...
the opening in the pcv valve is small so the open gap can be pretty small and not restict the cfm....
it took me 3 tries to get it right,,,, I stuck the "pretty good" second try under the breather filter because it does sit on a roughly 3" piece of heater hose to catch cool air from the hood opening (FL heat!) so oiling is no problem at all....

dang CRS=there is a way to mount the pcv on the chevy block and get it away from that rocker oil completely but I can't recall how!!!!
it's on this board many times on many threads,,,try using the "search" link
 

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#20 ·
derekg383 said:
No baffles in the valve covers but I do have baffled grommets under the filters. And I guess I was wrong earlier when I said I currently have 3 breather + a pcv. I have 2 breathers in the left and only a pcv in the right but no baffle or anything to stop oil from being sucked up the pcv. My oil pan is a 7qt for sure. I put 6 in and it is at or just below the bottom of the "safe zone". I'm definetly going to look into the pcv system before I go any further.
Until you get a baffle in the PCV valve cover, the PCV valve will be sucking oil. Do you have an aftermarket oil pan? The factory pan is 5 quarts.
 
#21 ·
Yea Miloden 7qt deep sump oil pan. Although it seems I have to fabricate EVERYTHING (I've heard of bolt on but never seen it) I think its time for some new valve covers anyway, this time w/ bafffles. Will any of the popular valve covers w/ baffles clear my rocker arms. They are Comp. alum. roller 1.6 and the cam has .540/.562 lift. Oh and my instruction following skills are not very good :spank:
 
#22 ·
I've got an oil pan that's advertised as 10 quarts and it holds 8. The next time you change oil, put in 6 quarts, start the engine to fill the oil filter, shut the engine down, then check the oil. Keep adding 1 quart until you reach the full mark.

You'll need tall valve covers to clear the roller rockers.
 
#23 ·
I'm sure the last time I changed oil it took 6 1/2 to fill after starting and filling the filter (actually I fill my filter before I put it on). What are the chances of my dipstick or tube being wrong? I plan on tall covers, I really want holes for 2 breathers on the left side (to avoid any customizing) and a hole for pcv on the right. Moroso has the only I've seen but I'm not sure there are any holes in the right side valve cover.
 
#25 ·
derek,
your checking to see that the top edge of the dipstick "tube" length to the top of the oil in the pan is a match for the total length to the dipstick itself marks....

if there is to much oil in the pan the crankshaft throws will dip into the oil (accelerating/decelerating slosh) and throw a hurricane's worth of oil onto the cylinder walls in just an instant....which the oil rings aren't designed to handle....

just comments:
buyin' stuff and just boltin' it on a car isn't "Hot
Rodding" to me....
if those covers aren't warped, they do seal good,,,,give making a baffle atleast a shot.....
so you have money in your pocket to add a windage tray for better oil control or some other power adder that is a bit of a PITA to make yourself....
(as long as you use a peanut butter jar and remember to empty it {LOL, I would forget to!} all is fine while you work out the baffle)

I do like the rubber/steel reinforced cover gaskets,,,with just normal care, you can take the covers off a dozen times and they still will seal good without any help on non-warped covers...
a definite plus while working out the baffle shape...
(they do conduct a bit more head heat into the covers to help cool the chambers versus "excellent heat insulator" cork gaskets)

the baffle design included in many of the aftermkt covers is almost worthless crap (a too small flat piece of sheet with a big gap on both sides)
so shop carefully....
clears the rockers is #1 priority,
the pcv hole "NOT" aligned with the rockers is my #2 (why they do that is beyond stupid!)
do a gooogle search like: "best chevy pcv oil control baffle covers"

have a oil pan custom made for your specific motor for $$$ would be a bolt on,,,the cheaper off the shelf stuff has to "be able to" work for to many different applications...

drive safe, have fun....
Red
 
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