Top Overhaul - need advice!

ptynning · Post by **ptynning** » Sun Jul 09, 2006 8:34 pm

Cylinder #1-0 #2-40 #4-55 #6- 71 and #3- 72 was overhauled 2 years ago and has only 140hrs

Engine total time SMOH 1,062 and overhauled 23yrs ago with all basic's done plus new camshaft,bearings,lifters and crank plus case magnifluxed.

7 years of good oil analysis for the engine and aircraft hangered in Socal.

I would like to just do a Top Overhaul?

Should I just have the 5 cylinders overhauled with all new parts or?

Get all 6 new cylinders?? and Which brand type, ECI-Superior or Continental new generation??

I VALUE ALL OPINIONS! PLEASE SPEAK UP!!

Thanks

Pete

Sun Jul 09, 2006 11:26 pm

Pete

If the newest cylinder is just an overhauled unit and not new then if I was to buy new I'd by all 6 and be done with it.

If it was new then I'd go with 5 new of the same make and the newest one you have.

cessna170bdriver · Post by **cessna170bdriver** » Mon Jul 10, 2006 12:02 am

Are you saying that those 5 cylinders were overhauled only 2 years ago?

I'm assuming the check was done with the engine warm?

It's difficult to make a diagnosis without more information. You didn't list #5 so I assume it's OK. #3 and #6 appear to be in good shape too. Personally, I would just keep an eye on #4 for a while and see where it goes. Since your lowest ones are at the rear of the engine, you can suspect overheating. Take a good look at the baffling and make sure it's in good shape.

Have you looked inside #1 to see if anything is missing? Any signs of cracks (usually from the spark plug hole to a valve seat)? How is the engine running? If it's very rough, you could just have a have a stuck valve. You can tell a lot by noticing where the air is going during the compression check. Air out the exhaust or intake system would indicate that respective valve not seating. Air out the breather tube would indicate worn or stuck rings (in the past this has been the problem with mine when compressions came out in the 30's and 40's).

With only a mid-time SMOH and good oil analyses, I'd just pull #'s 1 & 2 and let their condition dictate whether to overhaul or replace. If it's just stuck rings and the cylinders and barrels are in otherwise good shape, I'd hone the cylinder, install new pistons and rings, and keep going. If the barrel dimensions are out of spec, or the guides, seats, and/or valves require replacement, I'd consider new cylinders. These days, new cylinders cost little enough more than overhauls to take the chance with old cylinders. As to whether to go with Continental, ECI, or Superior, that probably comes down to personal choice. Do some research (search these forums for "ECI and Superior") and decide for yourself. There are good and bad experiences with all three.

Miles

Post by **GAHorn** » Mon Jul 10, 2006 1:37 am

A buddy of mine was preparing for a top overhaul on his C-90 engine due to low compressions (two cyls were at zero). I got curious about it because the airplane really didn't fly all that much (J-5 Cub) so I suggested he bring it over to my place and let's pull the cylinders off. (The air was leaking out the breather/oil filler tubes.)
It was stuck rings of course. We didn't even install new parts. We soaked the pistons overnight in penetrating oil (WD40 which I buy by the gallon) and the next day we carefully peeled the rings off the pistons. Beadblasted the pistons to clean them and the lands up, reinstalled the rings, and put it all back together. That was 4 years ago and he's flown it all the way up to Seattle and is still flying that engine without any problems at all. Total cost: 2 sixpacks of Becks and a slab of ribs for the smoker.

ptynning · Post by **ptynning** » Mon Jul 10, 2006 7:44 am

bruce,miles and gahorn thanks for the reply

#3 cylinder was overhauled with all new parts and has good conpression.

#1 cylinder 0 even after we staked the valve and #2 opposite side down to 40psi. both mostly blowing by exhaust valve

I am now leaning towrds all 6 new cylinders

I will decide after a more thourgh investigation.

thanks!

wa4jr · Post by **wa4jr** » Mon Jul 10, 2006 11:25 am

George...you are in violation of good A&P practice

Should have been Guiness instead of Becks

lowNslow · Post by **lowNslow** » Mon Jul 10, 2006 6:37 pm

wa4jr wrote:George...you are in violation of good A&P practice Should have been Guiness instead of Becks

Bottled Guiness is just not the same. It has to come from tap to taste right.

spiro · Post by **spiro** » Mon Jul 10, 2006 10:08 pm

1,062 and 23yrs SMOH: Take a good look at the cam and lifters after pulling a front jug. I wouldn't spend the $ on a top if the bottom end's about to come apart.

N1277D · Post by **N1277D** » Wed Jul 19, 2006 7:53 pm

Leaking exhaust values can also be cured sometimes by reseating the exhaust valve in place. You remove the rocker arms and springs. Attach a piece of poly tube to the valve stem. Use a mild valve compound on the valve seat and turn the valve by hand against the seat using the tube. You can also speed the process by using a drill attached to the tube to rotate the valve as you pull it into the seat. Your mechanic should be able to do this in about an hr per cylinder.

blueldr · Post by **blueldr** » Thu Jul 20, 2006 2:22 am

I believe that if it was mine, I'd pull all six cylinders for a good cleaning and inspection and go from there.---either a top, new cylinders, or an overhaul.

bradbrady · Post by **bradbrady** » Fri Jul 21, 2006 3:09 am

[quote="N1277D"]Leaking exhaust values can also be cured sometimes by reseating the exhaust valve in place. You remove the rocker arms and springs. Attach a piece of poly tube to the valve stem. Use a mild valve compound on the valve seat and turn the valve by hand against the seat using the tube. You can also speed the process by using a drill attached to the tube to rotate the valve as you pull it into the seat. Your mechanic should be able to do this in about an hr per cylinder.[/quote

This works

I know for a fact, but you wouldn't get my signutuar on an annual using this prosess, but there are other ways around the problem. (that is the signature problem)

brad

mrpibb · Post by **mrpibb** » Fri Jul 21, 2006 2:23 pm

Last annual I had a cylinder that checked good at first, then when i went to recheck it, it read zero. checked again good then zero again. being I had to remove the cylinder in front of that one due to a wrist pin cap that was no more, I pulled the cylinder and tore it down to find a out of round valve guide. Aparently it was not seating correctly each time, if I didnt recheck the compressions I would of not found it untill the next annual or worst yet sooner.

Ps. We have been having pretty good luck with superior, The others are fine too.

Post by **GAHorn** » Sat Jul 22, 2006 1:01 am

I've also had an exhaust valve-guide which was cracked that allowed a valve to seat differently/erratically and gave different readings from time to time.
The crack was not evident until the cylinder was removed and disassembled. (IO-520 engine)