The International Cessna 170 Association

I'm no A&P, but I would definitely not pull a cylinder for a compression test of 66. That's a normal reading. I'd fly it a few hours and re-check it if I were worried, which I wouldn't be over a 66.

Are there any ADs to comply with upon pulling a cylinder?

I remember hearing about a die penetrant test on the rockers or something but can't remember.
I could be totally wrong but it rings a bell for me.

DaveF wrote:I'm no A&P, but I would definitely not pull a cylinder for a compression test of 66. That's a normal reading. I'd fly it a few hours and re-check it if I were worried, which I wouldn't be over a 66.

That seems to be a general sentiment, but it's coming off anyway. As I mentioned before, looking through the log back to the 1950s #5 has come off before, has been welded, and has always been markedly lower than the other cylinders. There must be a reason. I agree that you can go lower on compressions - unless it is a leaking valve. I'd leave it alone if it were, say leaking by the rings, but it's not. Leaking valves don't get better - they keep leaking burning gases past them while the engine is running which further erodes the valve seat.

Also - #5 is in front and quite easy to remove and I would prefer that the valve, honing, whatever be done away from the block - I suspect that the labor difference will be minimal. Lastly - I will be interested in having a look from above at the bottom end of the engine. Also as mentioned before, this work is really being conducted to determine whether the original C-145 is appropriate to keep flying, or bite the bullet now and go with a O-360, which will eventually be installed.

As always - thanks to all for the input and opinions

Jim

Those are good reasons to pull a cylinder. Good luck and let us know what you find.

Short update - Cylinder is at engine shop. Mags are off getting price to either rebuild or by reworked set. Borescope looks ok - some pitting on shaft part of camshaft - lobes generally look ok. Plane looks pretty forlorn at this point sitting in hangar. Will deal with gear alignment and tail wheel issues once we get the front end in running order.

At least I don't have to worry about what to do with my bonus check this year

Regards

Jim

Another Update

# 5 cylinder is ready to go back on - resurfaced the exhaust valve and seat, replaced the exhaust valve guide, honed cylinder and installed new rings. Getting a completely rebuilt set of mags. Hopefully be back together in a week

Jim

Just use someone elses plane and fly it like you stole it...oh yesand wear those gloves

Hmmmmmmmmmm, well not too sure about that

Besides - always have the trusty TR182 ready to roll. Goal is to get both going at the same time!

After magneto o/h, rebuilding carb, and going through #5 cylinder, 90D is back online. Adjustments of the friction nut on the Scott 3200 seems to have taken care of the nasty Tailwheel shimmy.

However, I am still having adventures keeping the aircraft aligned wi the runway on touchdown (180 gear legs and large tires). It is VERY sensitive to being even slightly off alignment with the runway and difficult to bring back. I have flown 170s previously and this is MUCH more difficult

I am going to make sure that the mains are properly aligned, but am considering going back to standard gear

Thoughts from others?

J

I'm going to bet the gear is out of alignment. I wouldn't swap the gear unless there is something wrong with them.

But if you do swap the gear, I might trade you your 180 legs for my lady legs

jimnh20 wrote:After magneto o/h, rebuilding carb, and going through #5 cylinder, 90D is back online. Adjustments of the friction nut on the Scott 3200 seems to have taken care of the nasty Tailwheel shimmy.

However, I am still having adventures keeping the aircraft aligned wi the runway on touchdown (180 gear legs and large tires). It is VERY sensitive to being even slightly off alignment with the runway and difficult to bring back. I have flown 170s previously and this is MUCH more difficult

I am going to make sure that the mains are properly aligned, but am considering going back to standard gear

Thoughts from others?

J

J are you landing on ashpalt or unimproved? Ashpalt with larger tires has a higher drag coefficient. Make sure your tires are aired up a little higher then if you were unimproved. How is the tire wear pattern? what does it look like. You can tell a lot from the wear pattern. What kind of load are you carrying? Do not do anything to the gear geometry till your report back.

Asphalt strips. The tires may be a little under inflated. The wear seems uniform, other than the spots I have created catching myself from a premature runway departure. Generally a few hundred pounds under gross.

Jim

jimnh20 wrote:Asphalt strips. The tires may be a little under inflated. The wear seems uniform, other than the spots I have created catching myself from a premature runway departure. Generally a few hundred pounds under gross.

Jim

Jim, if you over 800x6 you will have fun on asphalt. I run 25 to 28 in mine and then 35 in the tailwheel.In the dirt I air down to 18 and 25. Doug

I'll check pressures. I know I have plus 35 in the Tailwheel. They seem to roll pretty easily on the pavement

J

No offense Doug but i run 22-23 in my 800x6's and have never noticed a problem on pavement... even after changing from 600x6. I aligned the gear a few years back and that is what made a big difference in ground handling at touch down. No doubt higher pressures would be a bit easier on pavement but I bet alignment is the culprit. Jim, I can get you in touch with a mechanic at FUL if you need. Glad to here you're back in the air!