i guess it's safe to say your springs were to heavy for that poorly welded valve. maybe it was made by the ANTOINETTE CO.
rob ronky #10507
I just thought I'd give you some of my expreience with broken valves.
At the end of May, I raced the vintage mile at Springfield, one of my bikes a 500cc single cylinder Royal Enfield a hemi head push rod engine (I think I'll start calling it a piglet). This was not the bike I was riding but one of my riders. He Pulled off the track at the end after running secong place between 2 KRs, and when he came back on the throttle in the pits it was dead.
Upon dissassembly the head of the exhaust valve was laying on top of the piston.
Luckely it happened at low RPM (my tell tale recorded 8,600 rpm) as there were only about 6 bad gashes in the head and piston. Obvisly I had to replace the valve and piston but was able to save the head.
valve guides were hour glasssed (3 seasons of racing) center was .004 clearance which is what I set it up with but at the top and bottom they were .010 larger.
This is the 3rd valve I have broken and have similar wear on the guides, 2 at low rpm.
I know this is a racing situation but I believe the causes are similar.
The valve shows the same type of break as in the first picture, very clean and straight.
Look at the secong photo and you will see that the guide is worn out of round and offset, also the valve seat in narrower at the 3:00 and 9:00 positions the 6:00 and 12:00 are wider. his tells me that the valve was hitting the seat off center and sliding to center by spring pressure. .020 oversize is way past rebuild limits.
Each hit (2,500times a min) bends the valve just a little and causes fatgue.
It will fail!
Take a straightened paper clip, put it in a lathe then push the tool post against it
.010. Spin it at 2,000 rpm. see when it breaks. That is dead soft steel , not hardened or hot.
My valves are the best I can buy, manufactured to my specs from Manley and Ferrea. The heads are forged in 1 piece from stainlelss steel. I may be wrong but I don't think any manufacturer of quality valves has used a welded 2 piece valve in many years, thats kind of like the slot in the head so you can grind them in. I am willing to bet that all the distributors supplying valves are buying them from someone else.
Just my thoughts,
AHRMA dirt track # 67J
You are correct about the hour glassed guide wear, I did not measure the big end but it was a lot, my guess about .04".
I have a clear mind and can not deny the valve was under unusual stress that is responsible for the fracture. That said being in the manufacturing world I will stand strong on my beliefs. A valve should never break, bending is another issue. If a valve breaks, lose guide or not you need to go to another valve manufacture no matter who you are currently using. I may be wrong but if I had a choice a bent valve is better than a broken valve and the engineers who design and engineer valves take that into consideration.
Bruce have you broke either a Manley or Ferrea valve?
MeanGene Are you still monitoring this article? We all agree the reason for the break is the loose guide bore. What is your opinion of a fracture V bend ?
And if you've never seen a broken high-mileage (or hours) valve before, you'd led a pretty sheltered life
Of course it is my intent to replace the bad guide no soap opera. The issue here is , a broken instead of bent valve. I work with metal for a living I understand flex and failure.
MeanGene " I have a Severe Duty Manley that kissed a piston in one of my 427's at 7800 RPM, just tweaked it a bit, actually shattered the lifter when the valve stuck in the guide, also a few Ferreas I pulled out of a set of used Edelbrock 427 heads that are also tweaked"
THIS is what I am looking for, valves that bend not break I have my answer, thank you.
Mean Gene "And if you've never seen a broken high-mileage (or hours) valve before, you'd led a pretty sheltered life"
I have seen plenty of broken parts, what I said is I haven't broken a valve myself.
The pan actually ran good, cold and occasionally hot starts became an issue though (valves not seating properly). I knew a tear down was in its near future because the loud clattering noise. I thought the noise was just an issue of a motor being built by someone who forgot to install the pan cover felts.
With my busy schedule on other projects this motor went a little to far. Strange thing is it didn't use much oil and appeared to burn fairly clean. I do remember the last valve adjustment was a little strange getting it right. It now is starting to make more sense, things to watch for.