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By cbass139 - 13 Years Ago
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So the truck ('58 292, Mallory dizzy) has been running like a dream thanks to everybody here but lately I have noticed a lot more fumes coming out the down draft tube so I decided to do a compression and leak down test to see what was going on, kind of wish I hadn't. The compression was right around 100-110 across the board but I was thinking that my gauge might not be working right because it would jump up to that number and right back down to 0, I never had to release the pressure. Then I did the leakdown test with 80 psi it would drop to around 20 on the cylinder side and my little compressor had a hard time keeping up with the amount of air that was rushing by. Had it at tdc, with the choke closed and accelerator plate wide open, no air cleaner on. It sounds like the air is going passed the rings and or the valves (I know "really narrowing it down") because I can hear it coming out the dipstick I think. My question is, with the numbers could I really have the truck running so nice, it sounds like clockwork? Thanks to all in advance.
Regards,
Cbass (Sebastian)
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By hjh - 13 Years Ago
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cbass 139 Information for what it`s worth on my 60 Merc. Monterey the last time I checked the leak down on it 4 or more years ago & 1000 or more 1/4 mile passes it avreaged only holding presure 49% to the good on all 8 cyls. I would hate to see what it is now & it still works, when they get loose they run easier & yes there is blow by.Maybe some day If I live long enough it it will get a new motor Harry Hutten
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By cbass139 - 13 Years Ago
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Thanks, that does make me feel a lot better. I am in the middle of a kitchen renovation that I am trying to get done before my 8 month pregnant wife bursts, which is exactly when I start Paramedic school. The absolute last thing I want to do is rebuild a engine but I love this truck and will do whatever I have to to keep it running well. Plus I really don't have the money saved to do it the way I am hoping to (two year plan). If somebody things different please let me know.
Regards,
Sebastian
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By Hoosier Hurricane - 13 Years Ago
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The immediate drop in pressure on your compression gauge is because the valve in the gauge is faulty, not your engine.
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By PF Arcand - 13 Years Ago
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Seb: Your blurb states that the choke was closed..believe it should be open for the test..
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By cbass139 - 13 Years Ago
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Had the Choke off, is this right? It is a manual choke. Let me know, right now I am planning on saving through the winter and doing a complete rebuild on it next summer. I will be driving until then, let me know if anybody thinks this is a terrible idea.
Regards and thanks a ton
Sebastian
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By pegleg - 13 Years Ago
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I'd keep driving it until it smokes or the oil consumption gets really bad. You'll know when to quit.
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By Ted - 13 Years Ago
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The throttle needs to be in the wide open position when performing a cranking compression test. Squirting some oil in the cylinders and comparing readings with and without the oil will also give an indication of how much ring wear you have. Here’s a link to a past thread giving more details on what’s involved in a cranking compression test. http://www.y-blocksforever.com/forums/Topic43536-3-1.aspx
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By cbass139 - 13 Years Ago
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Hey Ted, I had the throttle, wide open and I did do the wet test as well with slight gains but when I did the leakdown I can actually hear the air moving in the crank and in the valve cover, so I know that they are pretty worn and I am going to start saving to do a rebuild but want to know if I am going to do some real damage by waiting until next june and driving it until then. I also wanted to know how it could be this tired and run so well? I do appreciate the link because now I am certain that I did the test correct. Thanks for the help.
Sebastian
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By Ted - 13 Years Ago
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cbass139 (7/12/2012)
...... but when I did the leakdown I can actually hear the air moving in the crank and in the valve cover, so I know that they are pretty worn and I am going to start saving to do a rebuild but want to know if I am going to do some real damage by waiting until next june and driving it until then. I also wanted to know how it could be this tired and run so well? ....Reminds me of that old adage, “Runs the best right before it breaks!”. But seriously, as long as all the cylinders are hitting equally, overall performance will be reasonably good even with worn rings. The engine will obviously run better with all the cylinders sealing better though. With the engine only using some oil and making some additional blowby, then running it until you can actually work on it will not be detrimental to the short block itself assuming the oil pressure is good during this time frame. If it gets bad enough to start fouling spark plugs, then the time has come to make plans for a more immediate tear down and correct the problem(s).
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By cbass139 - 13 Years Ago
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Thanks for the response Ted, that is what I was hoping to here. I am going to hook a oil pressure gauge up to it this weekend and see what I get. By the way, what should I get for a good range on the oil pressure? I can look it up in the manual if nobody knows off hand. Thanks again.
Regards,
Sebastian
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