When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have an 1970~ Olds 455 rocket bored and stroked to 495 in my jet-boat. With the new racing tolerances and 20W-50 synthetic oil, my boat dumps about a quarter-quart of oil per gas tank of fuel. My machine shop suggested a vacuum pump to keep the oil in and guarantees their seals are not what's failing. Since I have breathers on each valve cover, I am going to remove/replace them with these 12an adapters from Motion Raceworks. I was originally going to plumb one valve cover to the vacuum pump and the other to the relief valve, however I think I'll instead get a few 12an tee's and inline the relief valve and plumb the vacuum pump to both valve covers (I do have a reservoir that is not shown for the other end of the vacuum pump).
My real issue here is the pulleys. The vacuum pump is to be driven at 50% to 66% and the crankshaft pulleys are pretty big (like 6"). I can't seem to find the correct parts whether it be a smaller set of crank pulleys or a mandrel kit.. Has anyone done this or maybe can refer some parts for the remainder of this?
Thanks in advance folks! standard 4-bolt pattern on crank pulleys moroso 4-vane enhanced vacuum pump, motion raceworks adapters, 12an relief valve Jet Pump
In a car that engine would have a PCV valve in one valve cover w a line that ran to the carb. The other valve cover would have a breather. Any oil residue is captured in the PCV and burned in the engine...
oh your trying to capture the oil and drain it back to the engine ?
sometimes in the PCV system if the valve cover doesnt have a baffle excessive oil consumption can result do you get a 1/4 qts worth of residue at the breathers ?
Wow, that sounds like there's some massive blowby. My engine has 50-60 psi oil pressure above 2500 RPM but no oil blowing out everywhere like that.
Yeah, for sure I'm burning white smoke. I was under the impression the vacuum pump was the right path to fixing or at least reducing it though. I do have the low-friction piston rings installed. I wish I had all the tolerances from the paperwork on hand.
Install a PCV valve in one of your valve covers and plumb it to manifold vacuum. That will prevent excessive oil consumption and weeping gaskets.
Well I do understand what you guys are saying about the intake vacuum, but I've already spent the funds for the vacuum pump and I honestly believe the intake manifold vacuum is insufficent.
Is there any others with these same thoughts about the PCV? It seems much simpler if it were the correct fix.
Well I do understand what you guys are saying about the intake vacuum, but I've already spent the funds for the vacuum pump and I honestly believe the intake manifold vacuum is insufficent.
Is there any others with these same thoughts about the PCV? It seems much simpler if it were the correct fix.
Its what the PCV is for...
Id recommend trying it first, as it is very simple and cheap to try. If it works, sell the vacuum pump. If it doesn’t, proceed with it. Not much to lose here.
Id recommend trying it first, as it is very simple and cheap to try. If it works, sell the vacuum pump. If it doesn’t, proceed with it. Not much to lose here.
Well I do understand what you guys are saying about the intake vacuum, but I've already spent the funds for the vacuum pump and I honestly believe the intake manifold vacuum is insufficent.
Is there any others with these same thoughts about the PCV? It seems much simpler if it were the correct fix.
Why not spend $30+/- for gauge and quit speculating. If you have sufficient vacuum then a simple PCV will probably work fine if you have no ring or seal issues.
Why not spend $30+/- for gauge and quit speculating. If you have sufficient vacuum then a simple PCV will probably work fine if you have no ring or seal issues.
I'll purchase this as well as putting a line up to the intake/valve cover before proceeding with the vacuum pump. I'll repost my findings. An expensive lesson if it does work-
Check if your valve covers have baffles in them too this keeps the oil away from the breather or PCV
they also sell a grommet that has a baffle in it if your VCs dont have it
PCV isn't going to solve an oil consumption problem.
A PCV does two things:
1) pulls crankcase vapor into the engine to be burned, reducing emissions (and reducing engine bay mess)
2) moves fresh air through crankcase, extending oil life by reducing contaminants (sulfur and water contamination especially, IIRC)
You won't *see* oil blowby with a PCV, except at WOT, but it still happens and the oil still goes bye-bye.
If oil vapor is blowing out the breathers then you have excessive blowby. Something went wrong in the cylinder bore, hone, or seating the rings. Most guys use the big open filter element breathers like you've got and zip tie rags around them. The rags catch the oil so it doesn't make a mess and you can see how much is coming out.
If white smoke goes out the exhaust then you're sucking oil into the intake charge. I've had no end of problems with intake to head sealing, but that is a hilariously contentious topic for some reason that's beyond me. Or valve guide clearances are too big/stem seals are bad. How do the spark plugs look? Are they smeared with oil remnants?
One somewhat silly possibility is the oil level is too high and the crank is whipping it up. It's a good idea to verify the dipstick indicator level before bolting on the oil pan. I can't tell what pan you have, but note that the "7 quart" or "8 quart" aftermarket pans don't necessarily need that much oil in the pan!
The vacuum pump probably won't help. *IF* you have a blowby problem, then it'll just pull the vapor into the pump and its outlet, along with all the oil. Racers use vacuum pumps because on a healthy engine maintaining some crankcase vacuum (6"Hg? 7"Hg?) can improve ring seal and squeeze a bit more power.
Frankly, unless you're willing to dig back into the engine, should probably just consider this a "feature". Never have to do oil changes!
I'm under the impression that I am needing more vacuum than that.
The valve cover breathers have baffles and it's spewing maybe a palm-ful out of each valve breather, each run.
I am at around 50+ oil psi at full throttle, trying to offset the pressure with vacuum it so it's not dumping synthetic oil each run.
I can see leakage from the seal between the intake manifold and the block on each end and spewing from the breathers, possible additional leakage.
thinking about this some more. Oddball asserted that possibly your intake manifold isnt properly sealed. They can be problematic. Besides the parts we cant see there are the two end seals that are prone to squish out and leak, this sounds like it might be happening to you. Current wisdom when installing the intake is to make a good wall of sealer like the “right stuff” at the ends and throw out the rubber end seals. Then let it cure 24 hours. Many intake oil leaks are at the front and rear end seals. Also a thin bead of similar sealer around each water port ensures no leaks there. People have opinions on the best gaskets to use on the intake, i used a turkey tray and the above sealer w no issues others say the individual gaskets are better, but many still use part of the old turkey tray to keep oil off the bottom of the intake.
i think if you redo the intake and eliminate leaks there, then try a PCV valve set up you might be ok w the oil use.
im no expert but 50 psi full throttle is common
running 20-50 is not uncommon on engines w larger clearances i dont know enough about the topic to comment more than that tho.
i also agree w eric pick up a vacuum guage and see what it reads ....
Location: Colorado Springs Colorado/Thousand Oaks Ca
Posts: 1,722
Originally Posted by oddball
PCV isn't going to solve an oil consumption problem.
A PCV does two things:
1) pulls crankcase vapor into the engine to be burned, reducing emissions (and reducing engine bay mess)
2) moves fresh air through crankcase, extending oil life by reducing contaminants (sulfur and water contamination especially, IIRC)
You won't *see* oil blowby with a PCV, except at WOT, but it still happens and the oil still goes bye-bye.
If oil vapor is blowing out the breathers then you have excessive blowby. Something went wrong in the cylinder bore, hone, or seating the rings. Most guys use the big open filter element breathers like you've got and zip tie rags around them. The rags catch the oil so it doesn't make a mess and you can see how much is coming out.
If white smoke goes out the exhaust then you're sucking oil into the intake charge. I've had no end of problems with intake to head sealing, but that is a hilariously contentious topic for some reason that's beyond me. Or valve guide clearances are too big/stem seals are bad. How do the spark plugs look? Are they smeared with oil remnants?
One somewhat silly possibility is the oil level is too high and the crank is whipping it up. It's a good idea to verify the dipstick indicator level before bolting on the oil pan. I can't tell what pan you have, but note that the "7 quart" or "8 quart" aftermarket pans don't necessarily need that much oil in the pan!
The vacuum pump probably won't help. *IF* you have a blowby problem, then it'll just pull the vapor into the pump and its outlet, along with all the oil. Racers use vacuum pumps because on a healthy engine maintaining some crankcase vacuum (6"Hg? 7"Hg?) can improve ring seal and squeeze a bit more power.
Frankly, unless you're willing to dig back into the engine, should probably just consider this a "feature". Never have to do oil changes!
One thing about boat engines is they operate under full or at least 3/4 throttle almost all the time. Whereas a car gets up to speed and cruises using maybe 30 HP to stay at 70 MPH, a boat needs lots of power to stay on plane. If you don't think so, try it next time you're in a boat. As soon as you let off throttle the water slows you down fast- no brakes needed on boats. Anyway that is why there is no vacuum advance on boats, they never easily cruise like a car does. So a speed boat engine works very hard and uses lots of fuel!! I don't know what a allowable amount of blow by would be under that type of use- surely more than in a car! I 'm guessing the shop is recommending the vacuum system to help the rings seal better ( as it is supposed to do in race cars) so there is less blowby under load.. Sorry no solution here just my thoughts! Good luck on it!!
Do you need or have an crankshaft/oil pan windage tray? I wonder without one, the crankshaft can whip up oil and thrown it up all over the place, creating leaks and other issues.
Some guys cut out the valve cover baffles so they can fit aftermarket rocker arms but by doing so, the breather then gets inundated with motor oil and dumps oil everywhere.
Last edited by pettrix; September 28th, 2020 at 01:56 PM.
One thing we're all missing here is this is a marine application. You want to control all vapors in the bilge.
How many run hours on this new build?
Did the builder put it on a stand and do some break-in runs?
Did an Oldsmobile guy or a Chevy guy do the machine work?
You could be pumping all the oil up into the valve covers at WOT. That means some internal oil control is needed in the form of top-end oil circuit restriction???
Step one is a wet and dry compression check, (School yourself on how to correctly do both).
Step two is a leak-down check.
Step three what do the spark plugs say? Read them. Oil soaked or dry?
I do agree some form of negative crankcase ventilation should be installed. The engine should produce enough vacuum to utilize a PCV of some form. I'm not sure about the marine requirement for said system. Speak with a knowledgeable marine shop.
Don't toss parts at it do some solid troubleshooting. More importantly, you need to concern yourself with safety...bilge fumes.
Find the source of the blow-by and control the oil and gas fumes or you risk a fire and maybe a life.
September 24th, 2020, 11:01 AM
Vacuum Pump for Olds 455 Rocket
