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Ok, so you've seen the good and the bad. Now for the ugly -the part I hate to even mention.

travel trials
travel trials


The Webcam 312a that has been in my motor for ~150,000 miles is dying. I had sent it back to Webcam to be refreshed around 30,000 miles ago and I re-installed it with new Andover followers. This was the first time I had used the new followers in my motor.

The cam and followers are being sent to Webcam for analysis. Webcam says they will take care of the cam regardless but my limited testing is telling me there is more to the problem than just the cam.

The pad on new followers is definitely different material than the old follower pad.
 
In response to Jim about plugs:
Interesting. I d say mine are similar one slightly darker than the other and I mean slightly. However the colour is
also slightly more on one side of the ceramic centre than the other.
Gas analyser. Gosh another space age tool I dont have.
In reponse to ludwig: well spotted, easy to over look things that are
staring us in the face.
 
ludwig said:
mm.. doesn't look so good to me .
compare the markings of the 2 LH bolt recesses : one is filled with crud .
RH also . Why ?
Signs of leaking into the pushrod tunnel ..
Click to expand...

No question that there are hot spots under the exhaust ports and in the thin area at the pushrod tunnels. There always will be.

Look again. The space between the outer o-ring and the combustion chamber rings is open to the oil as there is no o-ring around the pushrod tunnels or the oil return passage. [there is no room for one]

Oil trapped in this space has burned in the hot spots and traveled in to the barrel bolt holes, but nothing has escaped past the outer o-ring or the copper combustion chamber ring.

There has been no leakage on to the top of the barrel in 13,000 hard miles. It is as close to perfect as it will ever get.

Does this look better. All I did was wash the burned oil off in the solvent tank.
 

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Hi Jim, thanks for posting that, be interesting to see which failed first , new followers, cam or oil?
Am I right in seeing that the O rings around the studs have perished due to heat?
If that is so, what sort of head temp are you seeing to cause that?
Regards Mike
 
Also, with the new followers , did you carry out one of your hardness tests prior to installation?
Any coincidence with Ken's (FullAuto) cam/follower failure?
Regards Mike
 
Brooking 850 said:
Hi Jim, thanks for posting that, be interesting to see which failed first , new followers, cam or oil?
Am I right in seeing that the O rings around the studs have perished due to heat?
If that is so, what sort of head temp are you seeing to cause that?
Regards Mike
Click to expand...

I suspect the silicone o-rings were falling apart from a combination of heat and oil. Silicone rings are generally good to ~500 degrees but they are not so good with oil.
They did still seem to be doing their job however.

On a fast highway run -like extended speed between 80 and 100 the temp at the head to barrel joint between the cylinders runs right around 450 degrees F. I suspect the temp is higher under the exhaust ports.

I may try viton rings next time and see how they do. I have a good supply of both.

I have some data on the cam/lifter problem and I will share it soon. Jim
 
comnoz said:
No question that there are hot spots under the exhaust ports and in the thin area at the pushrod tunnels. There always will be.

Look again. The space between the outer o-ring and the combustion chamber rings is open to the oil as there is no o-ring around the pushrod tunnels or the oil return passage. [there is no room for one]

Oil trapped in this space has burned in the hot spots and traveled in to the barrel bolt holes, but nothing has escaped past the outer o-ring or the copper combustion chamber ring.

There has been no leakage on to the top of the barrel in 13,000 hard miles. It is as close to perfect as it will ever get.

Does this look better. All I did was wash the burned oil off in the solvent tank.

View attachment 5923
Click to expand...
Jim,
Looks like the silicone o-rings around the studs and the center bolt are really taking a pounding. Mabe use copper? Just thinking out loud. I know your bike is highly modified. Fullauto beat me to the right type of oil. :D tongue firmly planted in cheek.
Just keep on keep'n on.
Cheers,
Thomas
 
150,000 miles in an old AC engine that gets flogged hard?
It has every right to die a peaceful death, no autopsy should be performed.
It's not a Mazda 3!

Glen
 
worntorn said:
150,000 miles in an old AC engine that gets flogged hard?
It has every right to die a peaceful death, no autopsy should be performed.
It's not a Mazda 3!

Glen
Click to expand...

Read it again, the cam was re-welded and ground back to new just under 30,000 miles ago. It should not have failed in this short a time.

Maybe I should have said "renewed" in stead of "refreshed"

I did some more digging. The cam was purchased in 1974.

This was the second time it had been refreshed. The first time was in 1981 and it ran over 120,000 miles between that and the second refresh.

And at the second refresh it was still in good condition. I just had it redone so I could install a new set of barrels and lifters. I do not like to install new lifters on a used cam as that may cause the cam to fail.

The cam is on it's way back to Webcam again where they will weld it up and regrind it again. There is no limit to how many times it can be done as long as the bearing journals are still good.
My bearing journals do not wear out because they have a hardened race that fits over them and the race runs in needle bearings. Jim
 
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Jim, with the reduced diameter cam journals, this does not affect its strength or ridgidity? or you increased the cam tunnel diameter?
 
madass140 said:
Jim, with the reduced diameter cam journals, this does not affect its strength or ridgidity? or you increased the cam tunnel diameter?
Click to expand...

It has not caused any problems for the last 30 some years.
Here is the setup. The journals are both ground down to .7505 for a snug fit for the inner races. There is a needle bearing pressed in place of the LH bushing. No mod to the case for that.
The RH bushing bore is bored out to a snug fit for the large OD of the roller bearing. The bronze retainer holds the bearing in place in the case and provides the thrust face for the sprocket. Removing the bronze retainer allows the cam to come out without splitting the cases.

travel trials
travel trials
 
Sorry, my misread.
Read it in a tired state after a hard day dragging toes and whatnot down some really twisty Oregon mountain roads.

Glen
 
Try the Miami-Foley road from Girabaldi to Mohler while you are in the area. Beautiful road, seldom traveled.
 
Evening Jim
Shame to see the damage to the cylinder head.
I've never been happy with the amount of thread engagement that the ring nut has into the cylinder head. Even when i bought my MK3 i wired both the nuts together before i rode it home from the vendors house (he said you don't have to do that, its never been a problem....)
Once home i cut the wire off and replaced it with two loops of stainless wire and a strong tension spring (robbed off a fold up chair)
Later, when removing the exhaust and fully appreciating the space taken up with the exhaust gasket, spherical seat, flared end of the header pipe and split collet its no wonder these things have a habit of coming loose. The MK3 must be the worst in this respect.
To help matters i turned up much thinner spherical seats and collets and have increased the nuts thread engagement by at least 75%.

Large gap, few threads showing the amount of ring nut thread exposed when nipped up onto standard collet, header and spherical seat.
(set up with spare head and used header pipe)


Small gap, no threads showing. On the bike itself.


The anti-undo spring


The Mother of all C spanners (cut out of 1/2" plate)
 
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