Overhaul review, Jewell Aviation and powerflow exhaust

[aaronk25]

I have about 6 hours on the jewell aviation, kennet mo overhaul. http://www.jewellaviation.com/overhauls.htm. Anyway, I went with Sam and David Jewell because I wanted a high quality overhaul but didn't see the value in spending another 5k on a large shop that has higher overhead. Sam is probably in his mid 60s and has been overhauling engines most his life and pretty much dedicates all of his time to overhauls.

We elected not to replace cylinders because Sam said all the barrels still met factory new specs! I was surprised as many of you know how hard I run! He said he would be happy to supply new but since I keep the CHTs under 380 degrees, the heads probably won't developed cracks and will most likely make it until the next overhaul cycle. He did want to replace exhaust valves, guides and hone up some pitting, which was a result of the previous owner letting the plane sit some.

The price for this overhaul was $16,100 and it included overhauled mag with new harness, fuel servo overhaul, fuel pump, oil pump gear, new Pistons and rings which he balanced and bearings and a bunch of other stuff.

I posted these pics before but it obvious quality is top of these folks minds:

I almost ordered a factory motor, but literally hours before I was going to place the order with airpower I had a conversation with a guy who had 2 overhauls on his twin continental powered bird from Jewell aviation. He never had any issues and told me that Sam and David Jewell are "straight shooters". The rest is history. I was glad not to do business with lycoming as the factory lycoming cam shaft I had failed after 2 years and 400 hours, the factory reps at Oshkosh were to busy talking to each other and left me waiting for 20 mins and I don't care for they way they treated my friend who has a factory motor that's in warranty that's making metal.

I went with remfg/reground cam and lifters since Buldoc and Jewell avaition both said they have had significant problems with factory parts. I really didn't want to go this route but after I had a factory cam fail, and to top it off lycoming told me they don't have cam failure issues! Both shops told me they would be glad to install factory parts and there really wasn't much of a up charge either, so it wasn't about money. The theory is that if a cam and lifters make one engine cycle there a proven part and can be used again. The parts came from ASL. I met with ASL at Oshkosh and they talked to me for 45 min and taught me a lot about the re-man business. The only cam and lifters they use are ones that require less than three thousands cleaning up and then they even put them back though a re-hardening process, similar to the factories, but with a claimed higher quality control process. It wasn't a easy decision, nor was it money motivated, time will tell.

The engine when inspected showed it was presided well and honed beautifully.

So how did it run? Purrrrrrs. We also added a power flow exhaust so I'm not sure which contributed to the increased performance but when I ran a 4 way gps speed test at 6,500ft it turned out 167kts! This is after 6 hours so it very well may improve....maybe not.

It seems I've picked up about another 100ft per min in the climb and it's almost impossible to get the egts in to the 1500 range. Now it's a given that there is some variation in mounting probes but as far as I can tell there in almost the exact same spot. On average egts are down 60-70 degrees, which I believe is a function of the power flow exhaust. The power flow system routes all exhaust stacks into a collective 4 where the mooney muffler basically pressurized a can and I believe this makes it more restrictive so the cylinders don't evacuate as much exhaust so why the exhaust does leave the cylinder it's hotter. That's why I believe the egts show cooler. Chts are also cooler by about 30-40 degrees and if more exhaust is getting out it might lower the chts as there wouldn't be as much heat contained in the cylinder.

The other interesting thing is I ran 50 degrees Rop for about 5 mins at full throttle 26" at 2500 rpm and the hottest the chts would get is 360. We didn't change any baffles, left the cowl doors in the same position too but prior to the power flow system I'd be at 380-410 depending on OAT...the day I ran this test it was at 18c at altitude. I never run 50 Rop but I wanted to see if I could actually get the temps up, and I couldn't. I think this power flow is a nice system....although at 4, expensive.

So it's my opinion but I think the speed increase is more of a function of the power flow exhaust, but not sure. Anyways I'd like to hear others thoughts.

[MooneyBob]

Very nice article.

[ArtVandelay]

I'm curious, what made you do the overhaul in the first place? Was it results of oil analysis, bore-scope inspection, TBO?

[aaronk25]

Whoops left that out.....started noticing pin head size pieces of metal in filter....barley detectable, but because oil was getting black after 10 hours and oil burn was up to a quart in 3 hours and #4 cylinder intake tubes and exhaust and spark plugs showed signs of oil I wanted to have #4 pulled as I thought for sure it would be a broken ring. It turned out to be the rings were shot. The slight pitting in the cylinder barrels wore the rings out. Also the intake valve guide was worn.

As soon as the cylinder was off I looked up at the cam and lifters, just out of curiosity. Then we discovered the cam lobe was worn and lifters starting to become damaged as a result of the failed cam. Hard to tell using a mirror, but Jewell confirmed this.

This was a big hit because I planned on running this engine to 3,000 hours total time as I felt confident since it was just inspected and flys a lot!

[Mooneymite]

Great review! Thanks. Sounds like you've got a winning combination!

[Oscar Avalle]

Thanks

[carusoam]

Aaron,

I hope the glowing reviews keep coming for the next few years.

What is your break-in plan?

Best regards,

-a-

[aaronk25]

I talked with Peter's buddy Ed from Camguard and his recommendation was to dump the oil, but leave the filter installed at 3 hours or so to get the high prowear blowby contamination that's suspended in the oil out of the oil. Given that temps are back down and oil consumption seemed to stabilize I elected to refill with 20w-50w blue bottle phillips.

I've been running 65-75% power varying rpm every 3 min or so anywhere from 2350-2700rpm. Chts have been under 350 with the exception of the first climb out where temps ran up to 380ish full rich, full open cowl flaps but after 1-2 min they dropped and never got that high on subsequent take offs. We uncowled it a couple times double checking for loose items and/or leaks.

My best guess is it took about 2 mins on climb out to mostly break in the rehoned cylinders.

Temps dropped of a slight amount durning the following 2 hours, but for the most part the drop off in CHTs was barley noticeable.

Might be different with a new set of cylinders but given these still met new specs and received a hone, I'm guessing new cylinders wouldn't be much different. It burned 1/2 qt of mineral oil in the first hour then there wasn't any measurable amount of oil consumption.

I think break in is done, or mostly done so I'm going to switch back to normal 65-75% lop cruise with the exception of adjusting rpm every 5 min or so.

Sorry about the Peter comment I couldn't resist!!!!

[Bob_Belville]

Can you call this a zero SMOH engine while keeping cylinders?

[aaronk25]

Yep....but original time stay with the engine...but it does count as zero since major overhaul.....if you get a factory reman then you count it as zero time. If it's a factory overhaul, same rules apply as a field overhaul.

[helitim]

Did you do the R&R or fly down and let Jewell do it?

[aaronk25]

Engine r&r at local shop, drove down to MO.

[Guest]

Can you call this a zero SMOH engine while keeping cylinders?

Hi Bob,

Lycoming SB240W calls out required parts replacement at overhaul. Exhaust valves, intake and exhaust guides are required but not the actual cylinder.

Clarence

[Bob_Belville]

Hi Bob,

Lycoming SB240W calls out required parts replacement at overhaul. Exhaust valves, intake and exhaust guides are required but not the actual cylinder.

Clarence

Clarence, thanks, I did not know that, and i think 2 engines shops have misrepresented to me what it would take to turn a tear down into a zero overhaul. But I may have misunderstood them. 

[N601RX]

That gets very tricky. It depends if it is an A&P doing the overhaul or a repair station. If it's an A&P then their going to use the lycoming overhaul manual as their approved data. If I remember the language of the overhaul manual correctly it only recommends following SB 240. If it's a repair station they may not have as much leadway as they are going to have to follow their operations manual. If their op manual says that x,y and z must be one for it to be an overhaul then that is what they have to do.

Keep in mind that most real overhauls are going to include a lot more parts that what SB 240 calls for.

[Guest]

SB240 is Lycoming's version of what must be replaced during an overhaul. Many of the better shops are doing much more than this. The actual process of replacing would be laid out in the appropriate overhaul manual.

http://www.lycoming.com/Portals/0/techpublications/servicebulletins/SB%20240W%20(02-23-2012)/Mandatory%20Parts%20Replacement%20at%20Overhaul%20and%20During%20Repair%20or%20Maintenance.pdf

Clarence

[Yetti]

I may have missed it, but what was the history and hours on the engine?

[aaronk25]

I may have missed it, but what was the history and hours on the engine?

1999 factor overhaul. Propstrike in 2011, new main bearings cam and lifters. June 2014, 400 hours after new cam, cam failed one lobe wore down.

[OR75]

Kept the D mag ?

[aaronk25]

Kept the D mag ?

Yes kept the dual mag the only economical way to convert from the dual was going with a factory overhaul, but at a cost of 29k compared to 16.1k, for me the choice was clear. As I think it would be impossible to recoup the factory engine cost at time of sale, given what has been reported for 77j selling price. The Jewell overhaul also came with a lot of new parts. Also wanted roller engine, but with the goal being to make 2,000 hours, I think either motor would most likely accomplish this.

[flaflyer]

I'm curious about the powerflow. Do you know your 4 way speed at the same settings/conditions prior to the ovh and the powerflo?

[aaronk25]

I did several runs at 6,500 during various times of the year abs the fastest I could ever obtain was 162kts. I also did this test after a mag overhaul last year and the 4 way pass repeated the 162kts number. Power settings used was full throttle, 2,700rpm 80 ROP, for best power.

Supposably, according to power flow, the system is optimized for 11.5k, an altitude I haven't flown at yet as I have been trying to keep the power setting higher than that during the break in time.

[dhc]

I have the same engine and Powerflow. I don't think your CHT deltas are due to the PF. I'd suspect difference in mag timing before and after the OH.

But heck, when all the numbers are better, just enjoy it...

[jetdriven]

I did several runs at 6,500 during various times of the year abs the fastest I could ever obtain was 162kts. I also did this test after a mag overhaul last year and the 4 way pass repeated the 162kts number. Power settings used was full throttle, 2,700rpm 80 ROP, for best power.Supposably, according to power flow, the system is optimized for 11.5k, an altitude I haven't flown at yet as I have been trying to keep the power setting higher than that during the break in time.

You should be be able to get 165-168 knots when it's rigged real good, doors close tight, etc.

[kmyfm20s]

This is a clip from when I was breaking some new cylinders on my old "J" I sold which was a pretty well rigged plane. You can see on the MX-20 that GS was 170 kts and if you pause the clip the KTAS was 172 kts. The GS fluctuated between 170-174 in different direction so I felt it was correct but didn't do a formal 3 way. You can also see it was calm water in the Salton Sea. They are cylinders I had LyCon rebuild, port and flow balance which seemed to work.

I was considering the Powerflow but had no real reason to pull the trigger. If I needed to replace the exhaust I would have probably done it. The Powerflow exhaust 11.5 altitude optimization I felt was good since it would be DA. In the summer when I fly DA can easily meet or exceed 11.5 at cruise altitudes of 8.5-10.5. I cant remember anytime I haven't had a DA increase except for a few ski trips but I live in the South West. It's been hot out here:)