Date: Tue, 31 Oct 2006 21:46:49 -0700
Reply-To: Steve Williams <steve@CELINEANDSTEVE.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Steve Williams <steve@CELINEANDSTEVE.COM>
Subject: Re: AMC heads (part 2)
In-Reply-To: <454816FA.7060405@videotron.ca>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Nope, you aren't the only ones reading all of this!
I learned lapping valves on old Briggs & Stratton lawn mower engines
from my old man when I was pre-teen!
I knew the technique & the goal, but none of the reasoning. Very
interesting. Strangely enough, he was an aircraft mechanic as well!
Thanks for the great info!
Cheers,
Steve Williams
benoit wrote:
> John, very very interesting post, thanks for all that very well written
> information!
>
> The only thing i have to say about airplane VS cars (i'm also trained as
> an airplane mechanic (never really work in it!), and on top, i have
> another 3 years in airplane fabrication). That said, just so you know,
> early pancake (1700, 1800) engine had sodium EX valves, being to
> expensive, they where simply lost with time... in those cheap rebuilt! i
> have in the shop a brand new OEM 1700cc heads (found this one in a scrap
> Bus???) with those valves! this head is now on a shelf as a collection
> item!! :-)))
>
> The 1700 and the very good 1800cc pancake were, i think, the most
> reliable and strong engine in the boxer line... sadly, the 2000 that
> followed was not that strong, any well in shape big valves NON
> hydro-lifter 1800 equiped with a good set of dual carb would beat any
> other generation of VW boxer engine, including a 2.1L... the 2000
> suffer from improper Hydro-lifter (i hate those) system, yes, it work
> great for any normal consumer (no valve adjustment) but they loose power
> just for that reason, also, many 2.0L or Vanagon engine have bad valve
> adjustment! the lifter is there to to compensate some play, but not if
> your way out of the recommended adjustment! you should see some engines
> i see, 4 turns IN, 006 gap out.... bent pushrods, broken lifter, damage
> cam.... no wonder we see all those broken valves, damage heads,
> pistons, rings... Valve gap/opening is EVERYTHING to an engine working
> properly!!!!
>
> Anyway, i don't want to bored anyone with my experiences!
>
> To your questions (not that i need to answer it since you know better
> than me!!! :-)))))
>
> -----------------
> Ben, a question(1)
>
> Can one take those valve stem retainer halves and simply grind them down
> on a surface plate with 400-600 grit wet/dry paper and take off enough
> to get them to fit with the tiny gap-o-sis that is needed??
> -----------------
> That is what i did! BUT, like Dennis told me this morning:
> *****Properly fitted, the valve keepers should allow the valve to
> rotate. The rockers are offset to provide rotation action. Of course, I
> often wonder if they do but that is the plan. ******
>
> Well, Dennis is right! BUT, here we have 2 problems, well, the first
> being that the AMC keeper are to big and we can see the damage, and the
> second is that we can easily grind to much the keeper so they will be to
> small!!! It is almost impossible for the human eye to grind those to
> perfection... and what is perfection! Rotation of the valve is as good
> as rotation of the pistons rings! rings should be place is a certain
> patern and stay like that... and NOT move form that position (VW said
> 180deg to each other), some good mechanic will put them 120deg from each
> other... who care, i did that on many engine, not to say all, but i had
> to re-open an engine that had the ring at the 180deg position, they were
> all mix up after 20k... i should have known better! anyway, now, i don't
> care about ring position! i just care that they have the right gap....
>
> where was I ????? a non rotating valve would result in what?? an oval
> shape big end? maybe a burned valve, a damage seat!! we can live with
> that, but a valve falling into the cylinder....... NO one can live with
> that... so for me know, AMC keeper are going IN to tight! well, maybe
> just ok because i have good eyes.... he he he... but german OEM EX valve
> are the solution... and i have an hand-lapped tool! i will put pictures
> of the 3 different hand-lap tool that i have... one is perfect for the
> VW head.
>
> ----------------------
> Question (2)
> Do you know what metal is used for the valve guides in todays
> engines.Aircraft engines use to use bronze guides. That may have changed
> by now. Curious to know about modern auto engines.
> --------------------
> Nop, aks Bob Donald, he should know... but they are not bronze... and,
> they are NOT the problem, they are hard enough, the AMC valve look if it
> was made out of scrap metal... proof! : today i had fun for a few
> minutes, i put one hold AMC valve and one hold VW valve in a vise, i
> banged them with a hammer as hard as i could! well, what new, i had the
> hardest time to bent the VW one, you wanna see the AMC......
>
> I'm sure that we are the only one reading all that stuff!!! he he he,
> but it was fun, tanks for sharring your knowledge John!
>
> Best regards, Ben
> Doing THAT today!
> http://www.benplace.com/paul.htm
> (it's not a joke, i'm oppening engine like any would open a soup can
> each day!)
>
>
> John Rodgers wrote:
>
>> Ben,
>>
>> Interesting stuff on your website.
>>
>> Before I get into this, let me say I AM NOT by any means an auto
>> mechanic, not even close. So what I have to say may not even be quite
>> right or even have application to an automotive engine. Guys (and
>> gals) who work them all the time know what is what.
>>
>> I come from that aircraft mechanic perspective. I was taught on piston
>> aircraft engines the critical nature of valve specs to the engine,
>> it's operation and longevity. In that training we were taught that the
>> intake valve was cold, the exhaust valve was hot, and that told the
>> tale. Exhaust valves suffered a lot from the heat of combustion,
>> because they didn't have the benefit of the cooling of the fuel-air
>> charge coming in past it for combustion as with the intake valve, but
>> the exhaust valve got the full brunt of the heat of the burnt fuel
>> going out of the cylinders. Thus it was that often exhaust valves
>> stems were sodium filled to help transfer some of the heat up the stem
>> to the oil circulating around the cylinder top. The sodium would get
>> hot, liquify, and slop back and forth in the valve stem first toward
>> the valve face, then to stem end, each time transporting heat from the
>> face to the stem end protruding into the circulating oil system.
>> Crucial to the life of a valve was the alloy. It has to be tough,
>> hard, and capable of transferring the heat. Also, such was the case
>> for the valve seats to take the hammering they get under extreme
>> conditions.
>>
>> On the aircraft engines, it was also crucial that the valve face and
>> seat be ground to mate properly. "Properly" for an aircraft engine
>> was a valve face ground with three different facet angles on it, and
>> if I recall, the valve seat was similar. The real trick was to hand
>> "lap" the seating surface of the valve face to the seat. Very fine
>> grinding compound in a moderate lubricant was applied lightly to the
>> valve face, and then with the head at the right angle so the valve
>> stem would be vertical to the floor, a tool was used to rotate the
>> valve back and fourth 90-180 degrees. The valve was then lifted,
>> rotated 90 degrees, then set back in place, and oscillated back and
>> fourth again. This was continued until there was a continuous,
>> non-metallic-glistening lapped circle of the ground surface on the
>> valve face and on the valve seat. The "lap-line" was specified to be
>> approx 1/8 inch wide, and located in the center of the center third
>> of the ground valve face. . The final test of the proper seat was to
>> remove the valve, wash of all grit, re-insert the valve in to the
>> valve guide - with out benefit of springs to seat the valve, The
>> weight of gravity provided the force of the seal between valve and
>> valve seat. The cylinder was then filled with gasoline. If the gas did
>> not leak, then the work passed the test. If the gas leaked, woe be
>> unto us - we got our fannies kicked., an "F" for our grade, plus the
>> luxury of doing a re-grind to get it right.
>>
>> I don't know if auto shops go to this much trouble for car engines.
>> For an airplane, you had to have it right. It's a bit difficult to
>> park on a cloud when there is a malfunction. But I think if auto work
>> was done with such attention to detail, a lot of our V-gon problems
>> would disappear. To me, a proper valve job would include hand-lapped
>> valve seats. It would involve also a check to ensure no variation in
>> the length of the valves - even new valves.
>>
>> Ben, a question(1)
>>
>> Can one take those valve stem retainer halves and simply grind them
>> down on a surface plate with 400-600 grit wet/dry paper and take off
>> enough to get them to fit with the tiny gap-o-sis that is needed??
>>
>> Question (2)
>> Do you know what metal is used for the valve guides in todays
>> engines.Aircraft engines use to use bronze guides. That may have
>> changed by now. Curious to know about modern auto engines.
>>
>> Regards,
>>
>> John Rodgers
>> 88 GL Driver
>> Chelsea, AL
>>
>> Benny boy wrote:
>>
>>> So lately i have worked on some engines with somewhat old AMC
>>> heads... so of
>>> course, i have seen other scary stuff... after some e-mail exchange
>>> with Bob
>>> Donald about those problems... i have uploaded my page to show you
>>> how bad
>>> AMC valve are... or can be, because it's not always the case, that is
>>> the
>>> real main problem!
>>>
>>> http://www.benplace.com/amc.htm
>>>
>>> Cheers, Benny boy (working like a dog)
>>>
>>>
>>>
>>
>>
>>
>>
| 
