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05-10-2002, 11:50 AM | #1 |
My poor 79 RIP
Join Date: Oct 2001
Location: Suisun City,
Posts: 2,320
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compression values
Here are my (dry) compression values:
#1 119 #2 92 #3 118 #4 117 #5 121 #6 118 #7 115 #8 91 These are really low. Now I know where my horse power isn't coming from. What would cause low #'s all across the board? Bad cam?
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'84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am |
05-10-2002, 06:58 PM | #3 |
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Was the engine warmed up? Was the throttle blocked open?
Forgetting either one will result in false, lower than normal results. Take care, -Chris
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05-10-2002, 07:50 PM | #4 |
My poor 79 RIP
Join Date: Oct 2001
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damn, there is more to this then I thought, lol. I take it then I need to block open the throttle? Also, no, it's wasen't really warm, but now it's cold, and I'm going to do the wet check.
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'84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am |
05-10-2002, 08:19 PM | #5 |
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STOP
You're wasting your time. The results won't mean anything. For accuracy, you MUST perform the compression tests with the engine as close to operating temp as possible, and have the throttle blocked open. You should also do both tests at the same time, dry first. In short: 1) Warm up the engine 2) Disconnect the coil 3) Block the throttle so that it is wide open 4) Remove all 8 spark plugs 5) Install the tester and crank the engine through 5 revolutions 6) Read and write down the results 7) Repeat steps 5 & 6 for the remaining cylinders 8) Add 3 squirts of engine oil into the spark plug hole of the first cylinder you tested, and test it again 9) Read and write down the results 10) Repeat step 8 & 9 for each of the remaining cylinders, but do not add the oil until you are about to test that specific cylinder. Adding oil to all of the cylinders at the same time won't work correctly. Post your results. Take care, -Chris
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05-10-2002, 08:42 PM | #6 |
My poor 79 RIP
Join Date: Oct 2001
Location: Suisun City,
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It takes too long to remove the plugs, it will be cold by then. Same thing as last time. I got it warm, but it cooled before I got them out. They are hard to get out. The headers are in the way.
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'84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am |
05-10-2002, 08:49 PM | #7 |
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Do it anyway. The metal inside retains heat longer than you think. If you do it cold, the numbers are meaningless because the conditions are different. It would be like performing a dyno on an engine with the ignition turned off. The info you would get would have little or no effect on the engine when it was running.
Take care, -Chris
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05-10-2002, 09:38 PM | #8 |
My poor 79 RIP
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Location: Suisun City,
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Crap, well, my day tommorrow is all planned out now-lol
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'84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am |
05-11-2002, 04:08 AM | #9 |
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Think of it as experience!!!
Take care, -Chris
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05-11-2002, 06:18 AM | #10 |
My poor 79 RIP
Join Date: Oct 2001
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Is the motor being warm really going to bring the #'s back up to 150?
Hey, can a cast iron crank)stock 2bbl crank) handle 200 psi? I'm thinking of shaving the heads to this. Or do I have to buy a new forged steel crank?
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'84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am |
05-11-2002, 06:48 AM | #11 | ||
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Quote:
Look, it's your car, time, and money. Do it however you want to. But don't ask my advice, and then act like I have nothing better to do than tell you to do unnecessary procedures on your car. You followed my advice about doing a compression test, but you did it wrong, and the numbers you came up with are meaningless, and don't tell anyone anything. This wasn't your fault, because no one ever taught you the right way to do a compression test, so I did. I'm not mad at you, Kaspar, but please understand that I don't have any reason to instruct you to do things that aren't necessary. If you want my help, you need to supply me with accurate information. Quote:
What kind of compression are you thinking about? Keep in mind that more compression means more octane will be needed to control the compressed fuel mixture's stability, which means running a more expensive gas. If you go much beyond 10.5:1, you should plan on having to use a mixture containing at least 20% AV fuel. Take care, -Chris
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