Warbird Information Exchange

My front engine in coughing a bit. Running slightly rough, and not putting out power.
I get the follow readings on a static run up:

1800 RPM. mags OK L+R front and rear engines

Front engine: MP 25 RPM 2500 Fuel Flow 15
Rear engine: MP 27 RPM 2700 fuel flow 18gph

Annual was 4 flight hours ago. The aircraft and all compressions were up. Post annual flight normal. No obvious loose parts. Intakes and exhausts clear. Prop exercises well on runup.

Any ideas?

Thanks

If I remember correctly that aircraft has TCM IO-360's. Remove & check your fuel nozzles. They get gunked up & may need to be (ultrasonically) cleaned. Thats a start & pretty easy to do. Good luck.
Robbie

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Fly Fast Make Noise!

Cough is not as easy to diagnose as a miss. Nozzels are a possibility, if so it would likely be rough at low speed also. If it happened at annual, it is possible they swithched a plug lead or dropped or improperly cleaned a plug resulting in one having a cracked insulator. Can you isolate it to one mag on runup mag check or one cylinder? If mag check is good, but it is down on power, and smooth it could be retarded ignition timing, also some resrtiction in air intake, like a carb heat or alt air door. If it has a definite miss, it is likely to be ignition related. If all else fails blame it on Michael Moore or socialized mechanics, or maybe there is a bleeding heart liberal stuck in the air intake.

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Bill Greenwood
Spitfire N308WK

Real quick, got to get back to work. Explain the coughing a little more, is this turbocharged engine. I assume 25 , 2500 is the most she'll do. Non-turbo check the muffler for obstructions.

or mechanics glove or baseball hat...

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I replied to quick without reading. if the rear is doing 27, 2700 then it's non-turbo. Sorry, I'll give it some more thought.

If all else fails blame it on Michael Moore or socialized mechanics, or maybe there is a bleeding heart liberal stuck in the air intake

Bill, I'd never blame you!

Thanks all for the input. The exhausts and intakes were clear, and the alt air intak and main intake were clear.

With the rpms down and the fuel flow that far off, I would suspect a fuel flow problem. Does switching tanks and/or turning on the boost pumps make a difference? If not, then the problem is downstream of the pumps...ie gascolator, injector spider, nozzle clogs ect.

Fuel flow is related to rpms, if they are down flow and power are down. It can be cause or effect. Make sure you have full travel on the prop cable or arm to the govn, a mech might have conncted it back wrong or some such, or changed limit setting.This would not, however explain". coughing"

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Bill Greenwood
Spitfire N308WK

"Coughing" is that out the exhaust or intake? Lower MP and fuel flow, is it lean? EGT's? Is the inside of the exhaust black or white?

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"There are old pilots and bold pilots but few old, bold pilots."

The boost pumps do not seem to make a difference on the high or low settings.

And the answer is!!!!!

#5 cylinder was cracked!

Thanks everyone for their input.

Now, Where to buy a new cylinder?

Any recommendations?

Remans would be OK, I'm looking for quality at a decent price.

Oscar, the financially challenged