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These are my compression numbers. I thought they looked great for an original 1969 455. My plan since I have the car was to get it on the road, drive it for a couple summers, then do a complete restoration. I do not have the equipment for a leak down. From what I read it is a vetter test, but not sure if it will tell me anything that would tell me it needs to be rebuilt. Would like your thoughts. I have had my engine running a couple times, less than 30 seconds each time. I started it yesterday and fuel started pouring out everywhere. Like it was filling up from the bottom up. My thought was a float stuck. But since it sat for 20 years, and is all original i suspect the carb needs rebuilt. Again. Any thoughts would be appreciated. Also opinions on rebuilding, switching to some injection setup, or newer carb. Would love to learn some options.
I agree, the carb needs a rebuild....as for the compression, a more thorough “dive” into the motor would be helpful. You might try getting a leak down tester on loan from an auto parts store. When it’s time to rebuild there are a good number of quality resources on this site (Cutlassefi-Mark Remmel, or Bill K.) to name two.
If the engine has been siting along time, I would bet the compression improves. Blow all the carbon out of the rings, the crud that has most likely accumulated in the combustion chamber, surface rust, etc. most people don’t store engines the way they should. I prefer to pour oil or transmission fluid down the carb while it’s running, enough to slowly kill the engine. That will coat the backside of the install valves, intake, etc with oil to prevent rust. Remove the plugs, pour some more oil inside, turn the engine over, then reinstall the plugs. Lastly, loosen all the rockers. That will close all the valves. Once the engine is put back into service it will smoke like a freight train for awhile, but nothing will be stuck or corroded.
Do the compression numbers concern you? I also noticed this... Notice the plug on the back left. Clean as a whistle. I assume #8 is not firing. I thought the engine sounded amazingly smooth when it ran, apparently not.
The Olds Chassis Service Manual says the compression on the lowest cylinder should be not below 80% of the highest cylinder, and none should be less than 100 pounds. Yours qualifies, and as mentioned, will likely improve with use.
If it were mine I'd do a careful rebuild of the carburetor you have. If it's structurally O.K., that should make it run better.
For now I wouldn't worry too much about the plugs. None look serious. Be sure you've got everything right to deliver full voltage to #8 and be sure the plug is O.K. It doesn't look "wet".
Those compression numbers are fine. That plus the fact that the engine runs smoothly as you say says why fix what ain't broken? Drive the car and enjoy it.
Yes, the carb needs a rebuild. Get a kit for $20 and do it yourself. I rebuilt the quadrajet on my '78 Toro on the bench in my garage. There are good videos on youtube that take you through the process step by step. It is not at all difficult, and it is very satisfying to have done it yourself.
As far as the spark plugs, it's difficult to say much without knowing their history. How long have they been in the engine? How many miles on them? The not-firing plug could be due to a bad plug wire. If the history of the wires is unknown, or the wires are at all suspect, replace them. As far as the plugs, I'd put new ones in, drive the car for 1000 miles, then pull them out and take a look.
Rebuilding an engine is not without its own potential problems. The list of people who come to this site after they get their rebuilt engine back from the rebuilder complaining of oil leaks or coolant leaks or whatever would stretch the length of your arm. If your engine has a problem, fine, rebuild the engine. But don't rebuild the engine just because it seems like a good idea if it is otherwise giving good compression readings and runs well.
Here's the video I used to help me rebuild my carburetor.
I have had my engine running a couple times, less than 30 seconds each time. I started it yesterday and fuel started pouring out everywhere. Like it was filling up from the bottom up. My thought was a float stuck. But since it sat for 20 years, and is all original i suspect the carb needs rebuilt. Again. Any thoughts would be appreciated. Also opinions on rebuilding, switching to some injection setup, or newer carb. Would love to learn some options.
I agree. Rebuild you carb. My '71 had sat for several years when I bought her. One of the first things that I did was buy a rebuild kit for my quadrajet (cost $25 on Amazon). Took about a day to do. Runs like a top now.
November 4th, 2018, 08:22 AM
