Taking my good old CMI headers off for testing, form 525's.
Don't see any issues, but if I do a compression test on the cylinders, which is a lot easier then a leak down, and the compression is OK, Can I assume that the motors are OK? Or do I have to do a leak down also to be sure that motors are OK.
Is there anythingI can discoonect on the 525 EFI's when I do the compression test so I won't get a spark?
Or just remove all spark wires.
Thx
P
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11-21-2009 04:38 PMLife is: what happens... when you plan something else.
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11-21-2009 04:47 PMCompression tests are good to tell you if you have a problem- one cylinder being different than the other. Leakdown is only truly useful if you started early in the engine's life and recorded your results. It allows you to track deterioration. If tou see anything out of the ordinary, I'd go to leakdown.
When I do leakdown, I do measurements at TDC, 90 and 180. I had a circlip come out once. Scratched the cylinder wall. But below the TDC range there was no flaw. Had I not done what I did the engine would have definitely been severely damaged.
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11-21-2009 04:55 PM
Thanks Chris.. I will do the compression, and hope all is well. If I have a problem, I will have to do the leak down, but I assume that if the compression is OK.. then I'm good to go.
Taking these headers off is a pain in the behind.Life is: what happens... when you plan something else.
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11-21-2009 05:02 PM
I do only leakdowns and with a warm engine.
A WTCC/ STW Audi back in the day had 18% leakdown cold and was a bottle hot...
I donīt do the 90 degree test but I compare BDC and TDC leakdown #īs just for the fun of it.Offshore Racing wasnīt designed to be a spectator sport, it's for people or companies with's lots of money to push the envelope of endurance technology and hopefully put a trophy on a mantle. It's man vs the elements, not like boats with like engines running in circles.
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11-21-2009 05:11 PM
Believe me I think it fun to wrestle around in the engine compartment.. or go places people smaller than me couldnīt get to.
Did I tell you I almost always sparr with heavyweights also ?
Because after that a pound for pounder is mincemeat...
But hey thats just me, when you tell me not to work on the boat/racecar I get ****ed really fast.
So whereīs my plane tickets?Offshore Racing wasnīt designed to be a spectator sport, it's for people or companies with's lots of money to push the envelope of endurance technology and hopefully put a trophy on a mantle. It's man vs the elements, not like boats with like engines running in circles.
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11-21-2009 05:51 PMOnce the headers are off it is easy.. Heck a couple Sutphens I worked on you could not stand in the bilge. Pull the center manifolds off and it became tolerable.
Peter the comp test will give you a good idea what you got. If one is low a leak can help tell you why. You don't have to take the headers off to pressure test.
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11-21-2009 07:04 PM
Two is out, two more to go. I have to get the tail pipes off to get new flappers in the tips. So I figured mind as well take off the headers.. look into the exhaust ports. (so far so good, no rust.) Easier to get to the plugs and do the comp. test, I have some bilge cleaning to do and one of my bilge pumps strainer is off. Can't get to it with the headers. So it just made everything easier. New header gaskets are not that costly. Better safe then sorry. More bilge time in the AM.
Life is: what happens... when you plan something else.
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11-21-2009 07:27 PM
I got the standard Merc. gaskets.
Thanks George. Will talk on Monday.
PLife is: what happens... when you plan something else.
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11-21-2009 11:49 PM
Paradox,
I generally do a comp. test if I don't think anything is wrong and I just want to check it out. What I look for is equality from one cylinder to the next. If I see a difference of more than 10 psi from the highest to the lowest, then I will leak the lowest hole. Make sure you do not have any liquid (gas, water, etc) in the cylinders because it will give you an inflated comp. reading for that hole. Good luck.
Eddie
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11-22-2009 12:39 PM
Send the headers back to CMI. I am told for $150/pair they will check the headers and polish them. We are doing this to a couple of ATs this winter.
Brian Tillett; Active Thunder Factory Representative
wwwActiveThunderBoats.com
brian(a)activethunderboats.com
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11-22-2009 06:31 PMAt 90 degrees its much easier with two people.
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11-23-2009 09:20 AM
The fun part is getting them hot and THEN trying to get the headers off fast enough to do a warm leakdown test. Better off pulling them and doing it on a stand.
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11-23-2009 06:09 PM
Headers off??
Never done it that way.Forget Lightspeed go straight to LUDICROUS SPEED!!
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11-23-2009 06:27 PM
Headers off I believe helps to pinpoint if the exhaust valve is leaking, although I'd imagine you can hear a small leak with your ear at the tailpipe in a quiet shop??? Not sure.
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11-23-2009 07:44 PM
At 90-180 degrees ATDC I would think that the intake valve would be off of the seat resulting in 100% leakdown, unless you completely loosen the rocker arms.
But I could be wrong.
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