On Tue, 7 Oct 2008 13:10:26 +0000 (UTC),
wrote:

Hey all. I posted a week or so ago about low power in my Cherokee, but the signal-to-noise ratio
was low with all the things we've tried in the past. We're basically at the point of asking if
mismatched hydraulic lifters could cause chronic low power. The overhaul was done before we bought the
plane by a shade-tree mechanic, so I would not be at all surprised if the lifter bodies and plungers were
mixed and matched. Last year, we swapped out pushrods to get dry tappet clearance correct, and that
seems to have corrected an *intermittent* power loss at the first takeoff of the day we had then I was
skeptical that the lifters would be inadequate to make up the difference, but it hasn't done that for a
year so it seems to have fixed the intermittent problem.

SO, I was thinking that maybe if the lifters were mismatched, they would still pass the Service
Instruction 1011 we did last year, but not have correct bleed-down rates. We checked lifters for being
straight, no stuck ball valves, and they'd spring back when assembled dry.

Can lifters with marginal bleed-down rates truly be responsible for what I'd guess is ~10 hp
at full power? I can see making it idle badly, but the time for bleed-down is much lower at max RPM.

Thoughts? Opinions? Without some definative reasoning, it seems silly to spend $600 in an experiment?

Thanks,
-Cory

your prop has 6 bolts. all symetrical. the prop can sit in many
positions relative to the piston positions.

I remember a thread about a dozen years ago where the prop position
was found to have a noticeable effect on the power out of the engine.
something to do with the coinciding of the blade wash across the inlet
at the time of air suck. (substitute your own technical terms)

you look to be heading to my sort of insanity (my carby fix took 18
months and $2,500 but by hell I understand the bugger now)
comiserations!

try changing your prop position relative to the crank. a spool of
lockwire and some lockwire pliers should be cheaper than $600.

Stealth Pilot