"Best"? exhaust valve guide material?

[gbent]

I missed this was an aircraft engine. Generally, racing means life cycles that are measured in the length of one race and rebuilds are expected after the race. Performance degradation during the race must be absolutely minimal. Failure is not considered catastrophic. Pretty much the opposite of an aircraft engine, where performance degradation is allowable, but catastrophic failure can't be tolerated.

 

[kustomizer]

This says "file" hard guides are best though I have never seen them, they could be part of a long list of things I've never seen.

EXHAUST-VALVES AND GUIDES FOR AIRCRAFT ENGINES

Trouble with the exhaust-valves of the Type-J air-cooled cylinder caused an investigation to be made of valve-cooling and of valve and guide wear. A temperature of 1300 deg. fahr. invariably caused fractures of the exhaust-valve stem at the junction of the stem and the neck. A file-hard tungsten-ste

www.sae.org

 

[stephen thomas]

Doug,
There is absolutely no way any automotive engine will survive very long at a 75% loading. They were never deigned to do this. Automotive engines are designed for limited duty applications. Compare any automotive engine design to a continuous duty engine. There are huge differences. This is specifically true in Stephen's case. Please compare his over bored and stroked motor to say a Lycoming aircraft motor.There is a very good reason automotive engines are only rated at peak brake using power pulls rated in seconds as opposed to an SAE rating of work done over time.

Secondly, wear on valves, guides and seats rarely cause catastrophic failure. Even in stock engines, that kind of wear as Stephen specified is very unusual. He should be seriously looking at valve train geometry IE valve length, push rod length and rocker arms. Stephen did not specify if his engine is using after market heads, rockers or cam All of which can drastically effect valve stem loading..

My first line states that it is a 2276 Av conversion.
Originally Great Plains. EMPI heads. Appear to be first run, though heads might not have been refreshed when nikisil cylinders failed, and PO installed steel barrels. This is my first VW in any form. I'm a lot more familiar with small Continentals which i have owned and maintained including flying behind a GO-300 for 6 years.

Back to VW.
As Doug mentions these do cruise at over 75%.
80HP design/dyno at 3600 rpm.
Typical cruise 65 - 70 HP.

Heads (as you are aware) are limited by cooling capacity to about 70HP
They seem to last in this type app for about 250 hrs.
Good bottom ends seem to last "about" 1,000 hrs.

Yes, VW operators more or less say "just get used to changing valves and guides"
Some notes indicate the exhausts get changed anywhere from 2 x to 3x as often as the intakes need attention.

Hence my questions.
& no one has really commented/compared among the 3 commercial solutions.

So far, Ampco 45 keeps turning up from contacts in the industry and so far would probably be my choice if i turn on the lathe instead of buying a solution.

smt, going hiking for the rest of the day.

 

[MrStretch]

As someone that drove both beetles and pre type 4 busses I can say that heavily loaded vw motors (bus) only run for about 50% of the mileage between needing engine work.
It's been many years but I was always happy that engine problems could make it stop at worst, not fall out of the sky.

 

[implmex]

Hi Stephen Thomas:
Have you considered reaching out to AlfaGTA and asking for his opinion?
For those who don't know of him, he is a contributor on this forum whose company rebuilds and restores classic vintage cars of all kinds, and Ross does all the engine work for that company.

He's been doing it for a long time and across a gazillion different exotic types of engines, so he has had exposure to many different material combinations and can probably advise you from real life experience...maybe not for a VW aircraft engine conversion, but for anything automotive internal combustion motor related, he's a great resource.

I had a similar question a couple of years ago, here's a link to the thread:

Automotive valve guides 660 bronze instead of cast iron

Good morning All: This is a question for all you automotive guys. I've been asked to make replacement valve guides for a customer who apparently makes and runs antique race cars. The original guides are cast iron (based on what he's told me...I have no idea what motor this is going into) He...

www.practicalmachinist.com

His response back then was in post #4.
In that instance he recommended Ampco 45 or 642 bronze.

The owner eventually changed his stated desire and we went back to cast iron, but it was a totally different use case...he was going to drive the car to Pebble Beach, and back and then store it in his garage and polish the bodywork after he took it out for a Gentle Sunday Cruise twice a year.
(I originally understood he was going to race it, but apparently the car is way too valuable to beat the shit out of it.)

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[DDoug]

Doug,
There is absolutely no way any automotive engine will survive very long at a 75% loading. They were never deigned to do this. Automotive engines are designed for limited duty applications. Compare any automotive engine design to a continuous duty engine. There are huge differences. This is specifically true in Stephen's case. Please compare his over bored and stroked motor to say a Lycoming aircraft motor.There is a very good reason automotive engines are only rated at peak brake using power pulls rated in seconds as opposed to an SAE rating of work done over time.

Secondly, wear on valves, guides and seats rarely cause catastrophic failure. Even in stock engines, that kind of wear as Stephen specified is very unusual. He should be seriously looking at valve train geometry IE valve length, push rod length and rocker arms. Stephen did not specify if his engine is using after market heads, rockers or cam All of which can drastically effect valve stem loading..

Okay fine there Zippy.....
"There is absolutely no way"
Lovely how you are so "absolute" in your reprimanding me.
The requirements are 100% power for 5 minutes, and 75% for the duration of the flight.

 

[Dan from Oakland]

My biggest concern would be a stuck valve and not wear. Bad mojo in something with wings I would imagne. Do you run any kind of top oil in the fuel to help lube the valve guides? just a thought.

 

[72bwhite]

Just a thought but what does continental or lycoming use
one of those times where reliability is king.
really kind of different from a race application, not going to be winding it up
unless you do like rotax and use a gear reduction.

all said and done not sure that ci guides wouldn’t be best

 

[rogertoolmaker]

Stephen
You now have the consideration of advice on materials to use for the valve guides. I 'm interested in what you are going to do!
Roger

 

[DDoug]

You now have the consideration of advice on materials to use for the valve guides. I 'm interested in what you are going to do!
Roger

Fly it over your house first.....

 

[michiganbuck]

I briefly talked to my son Matt simply asking what he thought to best valve guide material and he answered Bronz
Tomorrow I will talk to him for a longer time so he may have more to add to that.
Matt is a UTI graduate and has education and experience in just about everything from race to diesel engines.

 

[Bill D]

Can a plane owner make his own valve guides on a aircraft engine. Can he use other then original alloy for the parts he remakes. Can a aircrft owner take an engine apart and work on it to this extent. I thought this was all highly regulated.
Bill D

 

[michiganbuck]

Here is part of the rule
Likely my son would not be able to perform work that requires a certified mechanic.
But the OPS questing was "what material"
By the following, it would have to be of the material listed in the maintenance manuals
*Making his own valve guides on an aircraft engine would likely not be allowed.
FAR Part 43 specifies who may do what to an aircraft in the way of maintenance, repair or alteration. It requires that only properly certified mechanics work on aircraft and "okay" them for return to service. However, it does allow preventive maintenance to be performed by a certificated pilot, holding at least a Private certificate, on an aircraft owned or operated by that pilot, provided the aircraft is not used in commercial service. The responsibilities for a pilot performing preventive maintenance are very similar to those imposed on the certificated mechanic performing other duties. The FARs require that anyone who works on an aircraft must have the appropriate maintenance and service information available. This means quite simply that before you set about performing preventive maintenance items on your airplane, you must first have the proper maintenance manuals available.

A list of "preventive maintenance" allowed is specifically listed in FAR 43 appendix A (4) c and is copied below:

 

[stephen thomas]

Can a plane owner make his own valve guides on a aircraft engine. Can he use other then original alloy for the parts he remakes. Can a aircrft owner take an engine apart and work on it to this extent. I thought this was all highly regulated.
Bill D

Yes.
If you read above, this is an E/AB AW.
You can put gerbils on a treadmill in the nose; though if that was a complete new re-power, you would have to fly off the negotiated number of hours in the negotiated test area before going cross-country. Changing valve guides would not fall in that category (significantly different power plant)

There's lots to digest from above, and from emails.
I wore myself out hiking in Letchworth today. Much appreciate the information & will respond to other posts in a day or 2.



smt

 

[DDoug]

Here is part of the rule
Likely my son would not be able to perform work that requires a certified mechanic.
But the OPS questing was "what material"
By the following, it would have to be of the material listed in the maintenance manuals
*Making his own valve guides on an aircraft engine would likely not be allowed.
FAR Part 43 specifies who may do what to an aircraft in the way of maintenance, repair or alteration. It requires that only properly certified mechanics work on aircraft and "okay" them for return to service. However, it does allow preventive maintenance to be performed by a certificated pilot, holding at least a Private certificate, on an aircraft owned or operated by that pilot, provided the aircraft is not used in commercial service. The responsibilities for a pilot performing preventive maintenance are very similar to those imposed on the certificated mechanic performing other duties. The FARs require that anyone who works on an aircraft must have the appropriate maintenance and service information available. This means quite simply that before you set about performing preventive maintenance items on your airplane, you must first have the proper maintenance manuals available.

A list of "preventive maintenance" allowed is specifically listed in FAR 43 appendix A (4) c and is copied below:

You've spent allot of time on a post that is answered with one word "EXPERIMENTAL".

 

[michiganbuck]

QT:Stephen (I wore myself out hiking in Letchworth today.)
Ot: Stephen I hope took your gold pan
Just down past a narrow on the inside bar, in the ledges and cracks. (but you may need a permit to sluce, perhaps panning is Ok (?)
There seems to not be much gold in NY , but just finding some is a fun family activity. A few weeks ago I spent most of a day in waste deep water in a Michigan creek, testing a new device, and found Zero gold.
*It Looks like A beautiful place.
Buck

 

[dian]

stephen, you are asking a question mankind has been wondering about for over 100 years. here some random thoughts:

1. clearance is closely related to roundness (id and od). i recently saw some data for reamers/hones. quite revealing.
2. if you guess the wear is abnormal, first investigate cooling system, head temp, concentricity to seat, valvetrain geometry (no, dont do midlift/square), oil quality. is there evidence of overheating like discoloration or baked in oil residue? what seals?
3. its useless to simplify alloys by "nicknames" like: cast iron, bronze, copper. same for bronze categories like manganeese, aluminum, phosphorus. nice ones are tin-bronze and copper-bronze. a "silicon" bronze might have more antimony, zinc or iron than silicon.
4. the condition of the alloy matters: heat treat, cold work
5. currently guides are being made of various sintered components (e.g. fe+c+cu+mos2+caco3+kenolube, or nickel). they are cryo treated, tempered, lube infiltrated and coated with thermal interface materials.
6. its always a pair of specific materials. many combinations work, many dont, for reasons mostly unknown. the hard on soft requirement is not generally true.
7. surface finish matters. 30-80 ra on id, bronze on smoother side. "plateu" finish is used as are textured stems.
8. "indestructible" materials: durabond series, fm-615e, fm-615n (fereral mogul), ms150, ms97 (perf. alloys, number referring to conductivity), wankesha 88 for ss stems. not monel because of low conductivity.
9. its a matter of price and availability. maybe look at cheprecision?
10. for tribological performance i would prefer a randomly/uniformely dispersed second (/third) phase. therefore cast is better as compared to wrought full of elongated stringers.
11. non-heattreated/cold worked is better as these will dereriorate at elevated temps.
12. then there is the issue floating around of "moly" (e.g. modtc) attacking "bronze". maybe use a moly free oil like castrol 0w-40 (the exact designation eludes me right now).
13. if you have some 905 or 934 around, make them out of that. use a carbide reamer. give them 0.002 press fit
14. originally these engines used "copper" guides and changed to "silicon bronze" later (in the 90ies). whatever the designations exactly mean.
15. regular stems (30-40 hrc) wear out fast on 862/863.
16. maybe remove exhaust seals?

does anybody know what alloy is used when they call it silicon bronze? maybe some leaded type? and what the functional reasons are? si-bronze is primarily for door knobs and statues, no?

 

[DDoug]

QT:Stephen (I wore myself out hiking in Letchworth today.)
Ot: Stephen I hope took your gold pan
Just down past a narrow on the inside bar, in the ledges and cracks. (but you may need a permit to sluce, perhaps panning is Ok (?).
Buck

I dunno why he didn't just use the bridge....much easier walking across eh ?...

 

[michiganbuck]

Question: Does anybody know what alloy is used when they call it silicon bronze?
I don't, but it lied not very hard in some matching videos.
My Think SS (some grades )would be more wear-resistant but that is just my casual guess.

 

[Hbjj]

https://www.ferrea.com
https://www.google.com/url?sa=t&sou...AQFnoECA4QAQ&usg=AOvVaw0dNeQPPbdOrqYXHwt-CS3O
We put what they recommended in a turbo 2332 sand car with good results.