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

Olds F36 Engine Compression

Old August 28th, 2017, 10:17 AM
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Olds F36 Engine Compression

My '36 Olds has no get up and go, and tops out at about 40 MPH after about a minute to get there. I bought the car a couple months ago. 6 cylinder 213 cu. in. 90 HP.

I have rebuilt the carburetor and timed the engine. The timing was off, so I thought that would be the biggest issue. Even after that there was no change. So I did a compression test (dry and wet). Each cylinder was between 75 and 85 lbs. The manual says that the compression should be at 111 +/- 5 lbs (At 100 RPM or cranking speed). I can only assume that this means the compression should be at 111 lbs while trying to turn the engine over. I just want someone to verify that I'm reading it correctly. If so, then I assume that the low compression has to be the culprit for the lack of power. Which would mean removing the engine and opening her up. New rings, honing, etc... My guess is that I'll end up with a rebuilt engine and transmission when it's done. Maybe an update to a 12v system with an alternator too...
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Old August 28th, 2017, 11:43 AM
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Yes 111 with the engine rotating 3 or 4 times and the throttle wide open. Try squirting some oil (1/2 oz) in each cylinder, then crank the engine and take a reading. If the compression goes up significantly then it needs rings.
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Old August 28th, 2017, 01:32 PM
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Originally Posted by oldcutlass View Post
Yes 111 with the engine rotating 3 or 4 times and the throttle wide open. Try squirting some oil (1/2 oz) in each cylinder, then crank the engine and take a reading. If the compression goes up significantly then it needs rings.
Thanks for the reply. I did not have the throttle wide open when I did the test before. If do a wet test again and the compression does NOT improve, I assume that means it still needs rings?
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Old August 28th, 2017, 02:09 PM
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That compression isn't terrible bad as it is, but these engines/ cars weren't very quick when new. If you were lucky they would develop about 7 to 1 compression from the factory.

If you are having slow cranking issues with a 6 volt system the first thing and most common problem is a 12 volt ground and hot lead that has been replaced incorrectly in the last 70 years. 6 volt takes huge cables compared to 12 volt.... Tedd
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Old August 28th, 2017, 09:55 PM
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Originally Posted by cozmo3710 View Post

I have rebuilt the carburetor and timed the engine.


I recommend replacing the points and spark plugs . You may very well have ignition problems . Have you checked ( with a flashlight down the carb throat) to make sure the throttle is opening all the way with the pedal to the floor ?

Maybe an update to a 12v system with an alternator too...
BAD IDEA !
As Tedd mentioned most problems with 6 volt systems are when people use "skinny" 12 v cables on them .
Shops that service agricultural equipment will often have people and equipment to service generator systems .
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Old August 28th, 2017, 11:43 PM
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Did you check the vacuum advance to see if it's good ??? 1936 was the first year for it.
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