blueldr wrote:When the requirement for installation of the single piece venturi came out, believe me when I say that I was not the only one with the rough running engine problem.
Yep. I bought my 170 in 2004, and it had a carburetor overhauled by the manufacturer, with all the "new and improved" parts.
My mechanic helped me find a two piece venturi and old fuel nozzle, and switch it back to the old configuration. It runs much smoother. The manufacturer (which has changed ownership several times) has little credibility with me.
I'm pretty sure they worked out whatever issue there was with the one piece venturis a lng time ago. I exchanged an old carb for an overhauled one through Chief Aircraft 9 years ago, and I'd my engine ran like a top until that Cherokee knocked the float bowl off of the throttle body...
Miles
“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
cessna170bdriver wrote:I'm pretty sure they worked out whatever issue there was with the one piece venturis a lng time ago. I exchanged an old carb for an overhauled one through Chief Aircraft 9 years ago, and I'd my engine ran like a top until that Cherokee knocked the float bowl off of the throttle body...
A little gorilla glue might fix that Miles. My engine runs so well with the old two piece, I just kept it and look at it every annual....so far, so good.
Some years, ago when the single piece venturi AD came out, I bought and installed one in the carburetor on my engine, It ran rough as hell! I contacted the manufacturer of the venturi, Precision, to complain and they sent me a new nozzel assemblyto cure the problem. NO JOY! It still ran rough. I was getting really good at removing and installing the carburetor on the TCM O-300 engine. I borrowed a pin gauge set from a machinist friend and checked the size of the Holes in the new nozzel in comparison to the old nozzel and they ALL were identical.
I sold that engine when I installed the TCM IO-360 and advised the buyer about the carburetor. He reported that it ran just fine with the old nulti part venturi and nozzel and as far as I know it is still that way.
I strongly suspect that some real turkey A&P took one of those carburetors apart, put it back together wrong. sucked some parts into an engine, and brought about that AD. That engine operated for many, many years on various airplanes and types without any problem that I ever heard about on that carburetor.
Murphys Law!
Last edited by blueldr on Mon Nov 23, 2015 2:58 am, edited 1 time in total.
Thanks for the info. I decided if it's not broken don't fix it for now but I will keep an eye on it. It's running great right now but it's good to know the information. Good luck with your annual.
cessna170bdriver wrote:I'm pretty sure they worked out whatever issue there was with the one piece venturis a lng time ago. I exchanged an old carb for an overhauled one through Chief Aircraft 9 years ago, and I'd my engine ran like a top until that Cherokee knocked the float bowl off of the throttle body...
I agree. My single piece venture carb runs just fine with nary a problem.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
In 1995 Precision Airmotive came out with serivce bulletin MSA-8 which replaced a non-atomizing nozzle with an atomizing one to correct problems of engine richness or roughness associated with the one-piece venturi.
I can now answer that question because I just looked at service bulletin MSA-8 that Gary put up in the Maintenance Library! It means that the service bulletin has been complied with. Thanks, Gary!
