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Lycoming SI 1290 for Thru Bolt Leak

avrojockey

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If you see my other post, Divco thinks I have middle main fretting (common) that will likely need rework. Thinking about doing Lycoming SI 1290, reaming and oversizing the thru bolt. Anyone have success with this? I have an -E2D which the SI is applicable, but it was upgraded to 160HP at overhaul in '93. After some searching it appears this can work for 160HP but may not last.

My goal would be to let things squeak by a little longer until a full overhaul is required. Right now everything is running really well but this oil leak is little too much for my liking.
 
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Confirmation please.

Tim, I am skeptical that the illumination is from the oil. Have you checked the fluorescence of the oil on the dip stick to be sure? I tested my oil (aeroshell 15W50) from the original container and it did not fluoresce using a small black light (fluorescent tube type).

[EDIT: I purchased an LED inspection light from Amazon and it indeed causes aeroshell to fluoresce. Thanks to Tim for a straight forward answer to the question. I found the UV wavelength is the issue.]

Case fretting is due to a shearing of the case halves. If progressed, retorquing the case bolts can pinch the main bearing.
1. Have you attempted to retorque the bolt/nut? Was it low?
2. Did the torque to rotate the crank change? (no plugs and measured at TDC)
3. Is a new washer with an ID bonded o-ring approved by Lyc?
 
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Thanks Bill...yes I confirmed its the oil that is UV reflective (Phillips XC). Shines plain as day on the dipstick and the little drops on the floor from my breather. It's pretty cool...even when you wipe the oil up with a shop rag the oily spots glow on the rag.

Divco did warn me about re-torquing the bolt can effect the bearing crush/clearance and cause wear. The bolt was properly torqued to 600 in-lb..checked both sides.

I had that jug off during the pre-buy with rocketbob (checking cam, tappets), so it was re-torqued then. In theory any fretting gap could have been snugged up, however, oil analysis has be great and doesn't point to any premature bearing wear.
 
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It appears that SI1290 you can go to a .001-.002 oversized bolt without reaming if the bore is clean...because that Lycoming reamer is $1300 :eek:
 
One other thing thats worth noting. The rebuild log shows that main had the most clearance with the crank installed...not sure how this is measured except with math using the bearing thickness, but it was .0038 and the others were .0029, .0028, and .0032
 
One other thing thats worth noting. The rebuild log shows that main had the most clearance with the crank installed...not sure how this is measured except with math using the bearing thickness, but it was .0038 and the others were .0029, .0028, and .0032

I read the manual...300 in-lb temp case torque and measure ID of bearing. It also appears the .0038 is well within limits
 
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Just wanted to post an update...did SI1290 and after 4 flights, with temps up to normal, everything is bone dry! Hopefully the tighter interference fit and rigidity keeps things aligned and leak free until the case is split for overhaul.
 
Just wanted to post an update...did SI1290 and after 4 flights, with temps up to normal, everything is bone dry! Hopefully the tighter interference fit and rigidity keeps things aligned and leak free until the case is split for overhaul.
Sorry for the late reply, but where did you find SI 1290? I can find it on the Lycoming site.
 
Sorry for the late reply, but where did you find SI 1290? I can find it on the Lycoming site.
Some of us paid Lycoming money each year to have new paper copies mailed to us as they were published. The paid subscription went away when Lycoming started publishing all new copies to the internet for everyone to have free access to. I started collecting PDF copies of all Lycoming documents while paper were still being published and mailed so I do have a PDF copy of SI1290F that was published July 24, 2009.

The Service Instruction 1290F is only for 'wide cylinder flange engines identified by the suffix "A" or "E" after the engine serial number and incorporating body-fit thru-studs.'
 
Some of us paid Lycoming money each year to have new paper copies mailed to us as they were published. The paid subscription went away when Lycoming started publishing all new copies to the internet for everyone to have free access to. I started collecting PDF copies of all Lycoming documents while paper were still being published and mailed so I do have a PDF copy of SI1290F that was published July 24, 2009.

The Service Instruction 1290F is only for 'wide cylinder flange engines identified by the suffix "A" or "E" after the engine serial number and incorporating body-fit thru-studs.'
I finally found a copy of SI 1290F, but it wasn't on the Lycoming site. Can anyone tell me how to correctly search the Lycoming site for this SI? I see lots of other one, but not 1290F.
 
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Just wanted to post an update...did SI1290 and after 4 flights, with temps up to normal, everything is bone dry! Hopefully the tighter interference fit and rigidity keeps things aligned and leak free until the case is split for overhaul.

Did you ream or just use the .001 or .002 oversized bolt?
 
I finally found a copy of SI 1290F, but it wasn't on the Lycoming site. Can anyone tell me how to correctly search the Lycoming site for this SI? I see lots of other one, but now 1290F.
Attached...
 

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Did you ream or just use the .001 or .002 oversized bolt?
I ended up using P5 and honed with 0.5 brush hone instead of reamed to make sure the bore was nice and smooth. Tools were cheaper but you need a small bore gauge to progressively check the amount to material coming off. You want to maintain the interference fit because aluminum case gets larger than the steel bolt as the engine heats up. Regardless, I reinstalled with Loctite 515 to seal it up good to prevent any path for oil. Stayed completely dried until overhaul.

I have oversized P1 or P5 bolt if you're interested. I overhauled my engine last summer due to a cam eating itself so my case is now modified with dowels and I'm using a standard thru-bolt now. Bolt was inspected and magnafluxed by Aircraft Specialties with all my other steel parts so I have an airworthiness release.

When I split the case, there was some fretting on the middle main. Just enough to allow oil through, and only on the top part of main where the offending bolt was. if you look at this picture I suspect the last overhaul they put POB sealant on the mains (not allowed), which probably caused this.
 

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Thanks, Tim. I might grab the P1 bolt from you. Here's the leak on my IO-360 (top right of #2 cylinder. I've got my conditional in May, so I may try something temporary until then. Engine on has 250 hrs, so I do want to attempt the SI 1290 fix with the P1 bole to get it closer to overhaul.
1709598677189.png1709598677189.png
 
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