Vintage Oldsmobiles Curved Dash, Limited Touring, Models 40, 53, 66; Series 60, 70, 90

Can I Feed the Blowby Back into the Engine

Old November 19th, 2017, 05:27 PM
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Can I Feed the Blowby Back into the Engine

It has been a while, but my '52 Super 88 took its' first drive in over 40 years.
I rebuilt the hydramatic myself. Besides holding a bit long in low, it shifts great and pulls like a tank.
I pulled the valley cover and replaced all the lifters and cleaned, cleaned, cleaned sludge. Had sat for 40 years in a barn. Replaced three rockers and all new p rods.
Doesn't smoke a bit from the exhaust, but I have blowby out the downdraft tube. I can see it when I turn my head and look behind at 60mph. No knocks. 45lbs at startup and 30lbs hot down the highway. Running 10-30
Any ideas on how to recirculate the blowby? Make a fitting on the pristine original paint valve cover? (shiver). Feed it back into the air cleaner?
Would surely appreciate any pointers on this.
Was so cool to drive the old beauty. Never lifted away from 185-190*. Even on a steep grade. Nice.
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Old November 19th, 2017, 06:28 PM
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Try unclogging the rings with solvent in the cylinders followed by an oil change they may be clogged from the sludge in the engine.

Next do a search on "oil catch can" and try to build one.

And...thank you for not drilling into that nice valve cover
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Old November 19th, 2017, 07:10 PM
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You can setup a PCV.
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Old November 20th, 2017, 07:05 AM
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I ordered an oil catch can off the internet. Pretty cheap. I will research putting a pcv on the engine. I did a seafoam treatment a while back and the piston tops are so clean I can see the machining marks on the tops.
The odometer reads 34,000 and may well be original. The bottoms of the pistons were really clean when I removed the pan to clean the interior of the block and the oil pickup screen.
My buddy says just drive it a lot of 50s cars were like that, but I would like to try and rebreathe/catch some of that oil.
The 10/30 is pretty light weight. My original manual says to run 20wt. I wanted to run the lighter oil now to help clear oil passageways. I did have some starvation to 3 of my rockers. Replaced them after disassembling the rockers/shafts to soak and clear. Lots of oil up there now.
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Old November 20th, 2017, 08:00 AM
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Keep in mind that you don't have a sealed system like newer cars do. If you seal up the down draft tube with a PVC valve I would bet that the oil filler tube would leak vapors and probably stink worse than what you are experiencing now. If mine I would run some Marvel Mystery Oil in it for one oil change and see if it improves,you might only have a stuck ring or two.

Back in the day when 394's with their high compression got tired it was common to adapt a PVC valve and change the oil fill tube to help on this . Late California cars had this already done from the factory... Tedd
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Old November 20th, 2017, 09:11 AM
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The less pressure in the crankcase the better because it may cause leaks e.g., at the rear main seal. Crankcase pressure will also cause power loss.

Good move on the thinner oil for a while, perhaps a 15W-40 in time may help the blow-by a little.

Try re-seating the rings by warming up the engine thoroughly, accelerating at full throttle from 20-50 MPH and then decelerating at no throttle from 50-20 MPH. Repeat this ten times.

Please keep us posted about how the catch can works out.

Good luck!!!
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Old November 23rd, 2017, 04:41 PM
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I've put 80 miles on the car since the cleanout and using 10-30 with Marvel.
Nice drive up the California coast highway after lunch. That motor has some power. It wants to do 80 right now. But I kept it at 60 and let off the throttle a bunch. Then back up. Smokes good at the stoplight, but it never climbed above 195* and used maybe 8oz oil. Never below 30lbs running.
Drained the oil after sitting for 20 minutes. Nowhere near as dirty as it used to be. So, I'm thinking Delo 15-40 and one bottle Marvel.
Seems to get better the more I drive it. I can get used to the bit-o-smoke until I ring it. I think the old beauty is just happy to be back out on the open road after 40 years in a barn. I know I would be.
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Old November 23rd, 2017, 06:30 PM
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Instead of Marvel use Rislone Engine Concentrate.
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Old November 23rd, 2017, 06:57 PM
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N i c e ! ! !
Keep driving it for a while. Is the smoke from the exhaust, the breather or a little of both? Smoke from the exhaust at idle could be valve seals. I honestly don't know if they even used them, anybody??? Tedd???
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Old November 23rd, 2017, 07:34 PM
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Originally Posted by Sugar Bear View Post
Smoke from the exhaust at idle could be valve seals. I honestly don't know if they even used them, anybody ???
Yes , they did . Part #565809 . They fit all 52 thru 56 with "top hat" type valve seal .
If this car has the original 65 year old seals , they are probably "toast" .

Last edited by Charlie Jones; November 23rd, 2017 at 08:04 PM.
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Old November 26th, 2017, 06:58 AM
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I installed a new filter element. Had not been changed since the major sludge cleanout. I used four quarts of Delo 15-40 with one quart of Rislone.
Initial start-up was very clean. Drove down the highway about six miles, then back up the hill around six miles. Much cleaner when I got back. 2/3 of downtube smoke gone, maybe more. Higher oil pressure too. Gained five lbs.
The stem seals may well need replacement, but the smoke does not appear to be exhaust as much as downtube. For an og 50's car, I find the smoking at this point to be acceptable. I replaced all the lifters. The cam should be replaced too, but I've seen worse. Just want to get some fun driving time in.
Easy to go back in at some point if I wear out the lifters. USA made set at $140 from an online site. Seem well made. Now some new tires. These bias plies are more than 20 years old! Already went through brakes and wheel bearings.
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