Grumman Tiger Performance Problem

[Maintenance Officer]

We have an AG5B with a O-360-A4K which is pretty typical for the Tiger. Our Tiger has a newly overhauled engine, new prop, overhauled carb, new mags, new plugs all with less than 50 hrs. New prop at 63 degrees which is mid range between cruise and climb props.

We just cannot get the performance we used to get at 135 knots. We can barely get 2300 rpm on take-off. We cannot get 2700 rpm on straight level flight at full throttle. We had the air box rebuilt when we found issues with damper allowing hot air into the carb. We saw a little improvement there, but not enough compared to when we first bought it. Multiple mechanics have looked at it and cannot resolve the issue.

We also have found it runs near the top of the green on cylinder head temp. We hear of others who don't have an issue with Grumman's running hot, but we are perplexed.

Thoughts and recommendations would be appreciated.

 

[bnt83]

Crankshaft to camshaft timing correct? Verified without a doubt?

 

[AdamZ]

Can't say as not an A&P but I was going to suggest airbox but you have addressed that. If Brian's suggestion does not reveal anything you might want to contact Fletch Air, which IIRC is outside Houston. I assume you have put this out there to the AYA and Grumman Gang.

 

[Maintenance Officer]

Crankshaft to camshaft timing correct? Verified without a doubt?

Yes, checked camshaft timing. He also checked the opening distance of the valves to be sure the lobes were properly opening the valves.

 

[Maintenance Officer]

Can't say as not an A&P but I was going to suggest airbox but you have addressed that. If Brian's suggestion does not reveal anything you might want to contact Fletch Air, which IIRC is outside Houston. I assume you have put this out there to the AYA and Grumman Gang.

No, I am not familiar with AYA or Grumman Gang, but it appears I need to be. Does AYA stand for something?

Thanks...to both of you thus far for responding

 

[Skip Miller]

AYA = American Yankee Association.

 

[kgruber]

New prop? 63 degrees? What is that?

Props are measured by number of blades, length and geometric pitch (inches).

How are you determining the RPM? With the tachometer, which is virtually useless, or an optical tachometer?

Sounds like the basics have not been covered yet, before complaining.

 

[Van Johnston]

We have an AG5B with a O-360-A4K which is pretty typical for the Tiger. Our Tiger has a newly overhauled engine, new prop, overhauled carb, new mags, new plugs all with less than 50 hrs. New prop at 63 degrees which is mid range between cruise and climb props.

We just cannot get the performance we used to get at 135 knots. We can barely get 2300 rpm on take-off. We cannot get 2700 rpm on straight level flight at full throttle. We had the air box rebuilt when we found issues with damper allowing hot air into the carb. We saw a little improvement there, but not enough compared to when we first bought it. Multiple mechanics have looked at it and cannot resolve the issue.

We also have found it runs near the top of the green on cylinder head temp. We hear of others who don't have an issue with Grumman's running hot, but we are perplexed.

Thoughts and recommendations would be appreciated.

Why did you change props? 63" is the standard pitch from the factory on the AG-5B. Overhauled engine plus new prop = prop strike? Maybe old prop was pitched 64 or 65" for cruise. Any difference in climb performance?

Get ye to https://mailman.xmission.com/cgi-bin/mailman/listinfo/grumman-gang tonight, before you go to bed, and sign up for the Grumman gang. It's free. Ask your question there, tell everyone what part of the country you are in, and ask for a referral to a Grumman guru.

Tomorrow, go to AYA.org, and sign up. This one costs money.

Wednesday go to grummanpilotsassociation.com and sign up. It's free too.

 

[zaitcev]

We just cannot get the performance we used to get at 135 knots. We can barely get 2300 rpm on take-off. We cannot get 2700 rpm on straight level flight at full throttle.

It's been a couple of months. What's the outcome?

 

[Maintenance Officer]

The recently overhauled carb was running too rich. Sent it back to Marvel and they reworked it under warranty and leaned it out.

 

[Pork]

Maintenance Officer - found your thread. Think I may have the same problem. Has your problem disappeared with the repaired carb?
I ferried the plane from the East coast to the West coast - no issues whatsoever until i had to ise higher altitudes toward the West coast. If i leaned the engine, it smoothed right out but the CHT climbed to 450. If I enriched it, the temp would drop but it ran rougher.

 

[1RTK1]

We also have found it runs near the top of the green on cylinder head temp. We hear of others who don't have an issue with Grumman's running hot, but we are perplexed.
.

The recently overhauled carb was running too rich. Sent it back to Marvel and they reworked it under warranty and leaned it out.

Thought you said it ran hot, that wouldn’t make it run cooler.

 

[1RTK1]

Maintenance Officer - found your thread. Think I may have the same problem. Has your problem disappeared with the repaired carb?
I ferried the plane from the East coast to the West coast - no issues whatsoever until i had to ise higher altitudes toward the West coast. If i leaned the engine, it smoothed right out but the CHT climbed to 450. If I enriched it, the temp would drop but it ran rougher.

Have someone that knows about baffling look at your baffling.

 

[Pork]

Have someone that knows about baffling look at your baffling.

Good call - The Grumman Pilots videos all seem to point to baffling problems. That is my first starting point!