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One thing to check is whether the cylinder
installation was done right. I am guessing here.
I ones was reading that if the valves are not
closing fast enough (weak springs) or if they are not opening enough (bad
lifter) you'll end up with less power.
Every time I had a cylinder sent to a shop , it
came back with new valves and guides.
Maybe something was not done right
there.
Else you could read at this wonderful site. http://www.sacskyranch.com/eng27.htm
(You might check for an induction leak as listed
on that page)
My experience is to replace the new installed parts
with known good ones to eliminate the bad performing one.
I had it several times that my mechanics followed a
weird road to troubleshoot a problem, because they thought that a newly
overhauled part with a yellow tag must be a good one.
That way the replaced my regulator after putting
in an overhauled generator that had problems. It helped little the
overcharging and I reverted to my old generator/regulator combo that is still
working fine.
Still have that yellow tagged alternator in the
box.
Same with a carburetor. They replaced my old
"dirty" Stromberg with an overhauled new and shiny one from a reputed shop.
There is not much that can go wrong with a Stromberg carburetor, yet that one
was not performing good and I reverted to my old one. Another yellow tagged part
in a box.
So maybe it's just an induction leak.
Hartmut
----- Original Message -----From: heavensoundsSent: Wednesday, June 21, 2006 6:45 AMSubject: [COUPERS-TECH] Short on Power II (Update)----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Thanks to all who have so far provided advice. I truly appreciate this group's willingness to help.Summary of the problem: Perfect run up at 2000 RPM with small mag drops, but the engine does not develop max power. (Please trust me when I say that it is NOT developing full power). This is after pulling out and back in a cylinder to fix a helicoil and after replacing the magneto harness and the right magneto's impuse coupling and drive gear. And after installing 4 new shielded plugs (top).Another symptom I noticed is that after a little while (engine is warm?) attempting maximum static RPM (on the ground), the indicated RPM max out at 2000 and then over a period of a few seconds slowly drop to 1800 indicated, and stay there. All those readings are in the plane's tach which reads higher than a more trustworthy handheld optical prop tach. So the true RPMs are lower than the numbers I quoted above.In response to all your recommendations, we did the following today:1. Checked mag timing. It was good, but we fine tuned it to exactly what the Continental C-75 manual calls for: 28 degrees before TDC on right and 30 degrees before TDC on left. The problem stayed the same.2. Checked compression on all four cylinders. All were good.3. Checked throttle, carb heat and mixture links and range of travel. All good.4. Checked all 8 spark plugs on a Champion tester. All sparked good.5. Cleaned the four bottom plugs, which were not new (the 4 top ones are new) and showed some carbon deposits.6. Replaced one of the bottom plugs with a new one (the thread was not in nice shape). So now I have 5 new plugs out of 8.After all of that, the problem is still the same!!What next? Carburetor?This is becoming a mystery. Any more ideas???By the way, Ed, the prop is a MC Cauley 1 B 90 CM 7351Thanks to allEliacim============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm
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