Valve Guide Reamers

[4-Shipp]

Could someone please post a part number, description, picture or other information on the appropriate reamer for our valve guides?

I have just about 800 SMOH and have noticed a bit of a vibration myself. I would like to be prepared if I should need to do a quickie valve job. Thanks.

Bruce

[4-Shipp]

I spent the last few hours reviewing old posts on stuck valves and the rope trick. It would appear that the 0.437 or 0.4375 reamer is the winner. Of course, I will check the overhaul manual to be sure.

Where is a good source for these reamers?

Next question: is this a treatment for the exhaust valve only or do you do both valves?

I think I will do a little preemptive strike on the valves. Thanks.

Bruce

[GAHorn]

Your vibration might not be a sticking valve at all. It could also be valve springs that have lost their tension. Or any number of other things, of course.
Is it a steady vibration? Or just an intermittent one? Cold or hot?
Have you ever had a dynamic prop balance performed? A good technician can tell you all sorts of things about your engine, including failing springs, lifter or cam issues, etc.

It's not always lead that causes sticking. An often misunderstood factor of sticking valves is improper cool-down. If a hot engine is quckly taxied in and shut down, the oil inside the valve-guide will "coke" or turn to carbon. This has the effect of reducing valve-guide clearances, and can lead to sticking. (After the quck shutdown, the heat continues to build for a few minutes for several reasons, cooking the now-stagnant oil inside the guide. Usually it's the exhaust valve. Intake valves are keep cooler by the onrush of relatively cool fuel/air mixtures.)
After landing, operate the engine at 1200 rpm for at least two minutes, then idle at 800 for one minute before shutdown. It can be done in conjunction with the taxy in. This will bathe the valve stems/guides in fresh oil and help cool the area before shutdown.

Any reputable tool supplier can get reamers for you. Snap On franchisers can order them.

[4-Shipp]

We did a dynamic balance a few weeks ago - 0.05 IPS at 2230 rpm.

I haven't decided if there is a vibration or not. It is subtle but I think it is it is there.

Just trying to be prepared if I do need to do a valve guide. Yea, I try to do all those shutdown tricks, but to taxi for 2 minutes, I have to make 2 extra trips down the runway - usually the taxi is about 20 yards

Yea, I know - I still let it idle for a few minutes.

anyway, one valve or two?

Thanks.

[GAHorn]

If it ain't broke....

[davevramp]

Here is a good source of tooling, very high quality stuff. If you use a reamer you should lap in the valve. Request a catalog and look through it.
://www.goodson.com

This one is for cast iron and will work with our valve guides but give them a call and explain your application to ensure that you get the right one.

http://www.goodson.com/store/template/p ... 3f40478543

dave

[Bruce Fenstermacher]

Bruce

I've never had or seen a stuck intake valve so I would only do the exhaust.

[4-Shipp]

Thanks, Bruce. That what I gathered from most of the post, but wanted to make sure.

Bruce

[bsdunek]

If it ain't broke....

Then break it!

[Bill Rusk]

My understanding is that a reamer may not be the best choice. I have heard there is a ball type hone that does a better job. Might do a bit of research before going this route. Also beware of the rope trick. It is quite possible to break a lifter body which will then require splitting the case. See my post on the subject.

Bill

http://www.cessna170.org/phpBB2/viewtop ... 07&start=0

[mrpibb]

Yes the flex hone is the way to go, I find it easier to control the amount of material I remove.

[blueldr]

Hey fellas! We're talking about reaming a valve guide, aren't we? Where in hell are you going to find a 3/8th in. dia. hone of any kind? Besides that, a reamer will be much more likely to keep the valve guide round and a precise size. All we want to do is remove the gum and varnish out of the guide and maintain the ogiginal dimension of the hole. Any removal of metal will only result in valve wobble.

[Bruce Fenstermacher]

Well from my experience with a ball hone if I could find on small enough I'd use it. OK I just found one here for $19 http://www.brushresearch.com/brushes.php?c1=1

As for the rope trick breaking the lifter body it wasn't the actual rope trick that did that it was the act of removing the push rod which pulled the top of the lifter bodyy out that did that. For this reason I would not recommend, and there is no reason, for removing the push rods when reaming a valve guide.

[Bill Rusk]

Bruce

You are correct re the rope trick. I did not word that very well. Nothing wrong with the rope trick just ment to give a heads up regarding a possible unintended side effect.

I was cautioned about the reamer Vs the hone by a very experienced IA. According to him, the reamer will leave a less than ideal surface in the guide which will then attract or allow carbon to build on the surface more easily than a proper hone job, thus your problem is more likely to re-occur. I don't claim to understand all of this. That is why I suggested doing some more homework before doing it. It is another option and may be better (or worse) but it is worth looking into.

Best of luck, and just trying to help.

Bill

[johneeb]

Below is a picture of what Bill and Bruce are warning us might happen if we remove the push rods while doing the rope trick. Experience (bad ) speaking here.

Bill, unless things have changed engine builders, when installing new valve guides, use a series of increasing size reamers. Some times if they have available a machine like the Sunnen Hone they work with it. Sunnen Hones are very precise how ever they are quite large and it would be impossible to work on a cylinder that is still attached to the airplane.