never underestimate the possibility of getting the gap out of sequence on the piston rings, this can explain blow by.valve lash on the solid lifter motor is crucial as i have recently found.
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| Compression Test Numbers https://slantsix.org/forum/viewtopic.php?t=8442 |
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| Author: | Daddiojoe [ Mon Feb 16, 2004 8:14 pm ] |
| Post subject: | Compression Test Numbers |
I'm still fighting with what appears to be blow-by (see the "pukin' oil" thread) and recently did a compression test. Numbers go from 100-115 psi, with a high of 140 and a low of 60 (goes up to 80 with oil in the cylinder). What kind of numbers are good ones? Engine has at least 160,000. Maybe 260,000. Many owners. Thanks as always, Joe |
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| Author: | Doctor Dodge [ Mon Feb 16, 2004 8:31 pm ] |
| Post subject: | Re: Compression Test Numbers |
Quote: I'm still fighting with what appears to be blow-by (see the "pukin' oil" thread) and recently did a compression test.
Hate to say that this sounds like a well worn engine. I would like to see readings in the 130 to 140 range with no more then a 10 psi difference between cylinders.Numbers go from 100-115 psi, with a high of 140 and a low of 60 (goes up to 80 with oil in the cylinder). What kind of numbers are good? Joe I would guess that you have a combination of worn rings and valves seats. I need to go check the other thread to find-out what year engine this is, if it has solid lifters, you should run a valve adjustment then re-check the compression. DD |
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| Author: | johnnysix [ Mon Feb 16, 2004 8:52 pm ] |
| Post subject: | |
anything below100 or so is completely unacceptable.My choice is burnt or worn exhaust valve,and don't let anyone tell u that u can't just replace one,because I have many times!! |
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| Author: | Daddiojoe [ Tue Feb 17, 2004 7:32 am ] |
| Post subject: | Background Info |
Doc-- Here's the background: 1971 225 /6 w/solid lifters--I do plan on rechecking after a valve adjustment. Heads have been completely rebuilt with new valves, seats, springs, grind, and even pushrods. It's highly possible that I've done a bad job of adjusting. I'm thinking of buying a remanufactured shortblock and swapping that in. Thanks for your help, Joe |
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| Author: | Doc [ Tue Feb 17, 2004 10:37 am ] |
| Post subject: | |
Recheck the valve lash, tight lash will lower your cranking compression readings. When you do the re-adjustment, keep them on the loose side. DD |
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| Author: | 67 LAWNDART [ Tue Feb 17, 2004 6:40 pm ] |
| Post subject: | piston ring gap |
| never underestimate the possibility of getting the gap out of sequence on the piston rings, this can explain blow by. valve lash on the solid lifter motor is crucial as i have recently found. |
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| Author: | Joug_Fin [ Wed Feb 18, 2004 3:24 pm ] |
| Post subject: | |
I'm just curious, how do you people do compression check??? I have allways done it so that i take out all plugs and turn engine with WOT. First stroke at every cylinder should be quite a good, I don't remember how much (maybe ~100 PSI) and then I turn engine so that cylinder has ten strokes. That is the reading. |
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| Author: | steponmebbbboom [ Wed Feb 18, 2004 4:35 pm ] |
| Post subject: | |
That's how I do it, though I only turn six revolutions. |
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| Author: | Joug_Fin [ Wed Feb 18, 2004 6:50 pm ] |
| Post subject: | |
I think that there really is not very much difference if there is six or ten revolutions, but I live here in finland and we are using metric system 
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| Author: | Eric W [ Wed Feb 18, 2004 7:07 pm ] |
| Post subject: | |
Last time I did a compression test I forgot to take the aircleaner off and open the throttle...ooops. Oh well, I still got readings in the 140-150lb range. 
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| Author: | Daddiojoe [ Wed Feb 18, 2004 9:03 pm ] |
| Post subject: | |
LawnDart-- So is there an _easy_ way to get the ring gaps aligned correctly? Joug--- Liked the metric system joke. I used to live in Minnesota, where there's a fair amount of Finns. One town (whose name I forget) even has a statue to St. Urho. I'm going to try to get the valve lash adjusted this weekend. Will keep you all posted. Thanks for the tips, Joe |
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