Lycoming Morning Sickness

[learaviator]

My plane was showing signs of sticking valves, including an occasional hiccup while I was flying it. Got the fixture and performed SB 388, the infamous wobble check, basically Lycomings way of putting the burden of a poorly designed oiling system on the aircraft owners back. Decided I did not like what I saw, so I pulled the cylinders and sent them to Lycon in California. I also sent the carb as I had doubts about it due to what I was seeing on the EGT. All of the cylinders were cracked in the exhaust ports and the valves were pretty bad. So I ended up buying first run nitrided cylinders, taken to .010 over , and had them do their magic on the ports and valves and flow them on their bench as well as installing gapless rings. The carb had issues as I suspected, so 895.00 later they rebuilt it and flowed it to match the heads. Installed them today and found all of the pushrods were now too short, I was getting dry valve clearances in the .070's and .090's. So I am ordering new pushrods on Monday to fix that. I am told that from there experience on the dyno, I should be seeing about 3 hp per cylinder increase, can't wait to check that out. So far about 5500.00 in parts. Plane had been down a month, I am missing the great flying weather!!

[canav8]

Hey Lear, out of curiousity, the gapless rings, are those the ones out of PHX? I didnt think Lycon was using them. What is the lowdown on that. My experimental buddy swears by them. The company also installs them in Continentals. Just worried about PMA. Got any advice? Doug

[learaviator]

I will have to check with Ken on that, I will let you know. I got my cylinders and carburetor on. While checking the dry clearance on the valves they were all in the 60's except 4, those were .078. .079, .082, .082. So I got 4 -35 pushrods (mine were all -34's), and all of the clearances came out great. I finished up the break in on them today, two hours flying, first hour 75 % cruise and then second hour changing back and forth from 65% to 75% power. I was at 5000 msl and the highest cylinder temp was 350 and EGT was 1320'. Flew flawless and at 75% power was indicating 130 mph, true was 143 mph. 65% gave me about 7 mph less. Book showed 10.5 gph and after two hours exactly, it took 21.1 gallons. Was really happy with it, will be hitting the short strips shortly! Only getting 2600 rpm on takeoff though, need to fix that.

[GAHorn]

... Only getting 260.0 rpm on takeoff though, need to fix that.

You wanna fix that typo?

[minton]

A little BTW: Take off RPM or Max RPM check is part of a post engine maintenance inspection/run up. This is accomplished to avert a potential "Overboost" (under RPM) or RPM overshoot "Overspeed" condition on takeoff/@takeoff power. Don't trust your Tachometer reading to provide you that number. A quick review of potential damage will underscore the need for such a check.

Spring is on the way for "short field practice".

[learaviator]

Oh thats right, I am getting 26000 on takeoff, no wait, 26 on takeoff, no thats not it either, oh yeah it is actually 2550, checked it today, put my prop balancer on it and flew it, tach is right on the money.

[minton]

And?? What RPM does the MFG and STC require at max power??

You will get far better takeoff performance when producing the correct RPM.

[learaviator]

Well, the engine wants to see 2700 on takeoff, going to adjust the screw on the front of the prop this weekend and see if I can get it higher, if that does not do it I will go to the governor.

[GAHorn]

I don't know what kind of prop you have or what kind of screw you intend to adjust on the prop but..... It sounds as if you are attempting to change the low-pitch setting of your prop.. a decidedly unwise thing to do without proper data and a basis of approval.

Most adjustments to takeoff RPM are made at the governor, and should be adjusted to meet the specifications of the TC or STC for the installation.

[minton]

Scarry!!

This whole post has me steaming!

You need an A&P with some experience to get you under control! Owners without certificates can only "Work" on their planes while under direct supervision of certified mechanics. That screw has nothing to do with take off RPM

This Goat rope underscores why I do chime in.

[GAHorn]

Your diligence is appreciated, minton.

I would like to continue this discussion with regard to the shop's promotion to learaviator that he can expect a 3 hp increase per cylinder after their work. That's a pretty fuzzy claim to make and I imagine they have complete confidence that no customer will take the time/effort to prove them full of poop.

I'd like to point out that a lot of shops put out a lot of hype. If an original engine mfr'r certifies an engine to produce 180 hp at 2700 rpm... then any alteration of the engine that changes that output is in conflict with the type certificate of the engine. (Assuming there actually IS such an improbable increase.)
If RPM is increased to achieve greater hp, then a basis of approval for that alteration must also be obtained. (Increaseing hp output of an engine adds additioal stress to other engine components....and all other accessories on that engine, not to mention the airframe and engine mounts....the list goes on....) Who approved that?

To make more power, then higher fuel consumption, more heat, more rpm, ....some or all of those.... will have to occur. (Even a simple compression increase will raise heat and stresses, not only on pistons/rings, but cylinder-heads, cranks, bearings, etc etc. Reliability will most likely suffer. Who authorized that? And who wants that? )

If that shop says that their work will provide you additional horsepower.... see if they'll put that in writing.

And when they do, take that document to your local FSDO, and save some money by stop-payment on your insurance premium check.

[mod cessna]

Holy cow fellers. I think there would be a lot more action in these forums if guys did not get hand cuffed for every post. Any time someone experiments or paints an airplane some color not in the parts book they are bombarded with insurance this, FSDO that, photo copy and post your licenses bla bla.

Lear i think its pretty cool to see the neat things you are doing to your 170.

That looks like a nice polish job lear. Most friends that i have talked to did not see a noticeable change in performance from getting the ports polished so i would not expect too much.
Will the engine make 2700rpm in level flight or is it only low during a static run?

[canav8]

Lear, could you get back with me on the gapless rings please? I am curious to know. Thanks, Doug

[GAHorn]

Excellent point, modcessna. Please be aware my comments were/are not intended to discourage folks improving/maintaining their airplanes....

My comments are intended to lend a little reality to the situation and assist in seeing past the wild claims and anecdotes that sales people make in regard to their untested and unproven (and often illegal) claims.

(Example: How many are aware that TCM does not approve of aftermarket polishing and removal of material from their cylinders? And further, has made public their position that such constitutes unauthorized modification of their product? It's a similar situation that some "blueprinters" make when they claim to offer increased "balancing" of pistons, rods, etc etc which they subsequently claim makes for more hp, etc. In fact, there's no basis for those claims and TCM has consistently substantiated their factory specs already balance the components within the maginitudes that produce virtually all the achievable gains of that activity. Just, FYI .... save your money. IMO)

[learaviator]

Scarry!!

This whole post has me steaming!

You need an A&P with some experience to get you under control! Owners without certificates can only "Work" on their planes while under direct supervision of certified mechanics. That screw has nothing to do with take off RPM

This Goat rope underscores why I do chime in.

Well, I have to say that I trust Ottosen Propellor in Phoenix, and that is who told me to adjust the low pitch stop screw in the front. And it does affect t.o. rpm according to Hartzell. It is right in their troubleshooting guide. And I never said I was not a mechanic.