Here is a shot (sorry for the poor
quality, from my cell phone, well, not so bad after all....)
of a 25k AMC head, so what is the deal! look at the right valve, see the red
line? both left and right (exhaust) valve have stretched, even the intake (center
one) are not even! That said, this is one of my customer who had those
installed in the US 2 years ago.... BUT!!! the late AMC head i have
installed have different valves than the old one!!! are they better? i don't
know! the question is! would you buy 2 AMC heads + VW or better quality
valves/guides/valve seat job on top? I have no answer for you..... just some
facts!
| Ok, lately i had to face some new (to me) problems with those heads (over 24 installed) a near 0 compression was one, lifter noise or just the obvious, stretched valves. Strangly, none of my customers had any of those problems of what i know! The 2 past engine i had to work on had similar problem, but the last one was the worse. Overall, the main problem is cause by a poor valve quality, seating and the worse, VERY poor keeper shape and fitting, | |
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Ok, if you click on this picture you will see one obvious things, the right valve (tip only is shown) is new, look at the arrow and see how thick are the keeper shape groove. The left tip is the worse exhaust valve i had on that particular head with 0 compression... look how thin are those groove, the keeper were almost off the valve... a near disaster. On the left, the keeper are intact! The problem is that the keeper are not well cut, grinded, they are to big and they don't seat properly on the valve, they touch each other before they seat on the valve... so, they are loose!!! |
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Those 2 small keeper are there to hold the valve in place on top of the spring valve, if they fail, or should i say if the valve fail, the spring will pop out and the valve will fall into the combustion chamber... Why the exhaust valve, of course this valve take way more beating, more hot than the intake one, those intake valves and keeper were fine with no streching and no damage to the valve tip. |
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Here is a top view of those 2 shaved keeper , if you look carefully, there is a small gap in between the 2 |
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Here you see the result of a 30K+ miles old valve, burned!!! (center one). Not closing properly due to a poor valve adjustment, stretching and/or poor seating. This is not exactly related to the valve keeper problem... or is it!!!! New German valve on right, old AMC on left, still ok on the steam but VERY bad on the tip! So, the left one as about the same millage and is kind of ok! |
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Here is a clear view of the above picture, the burned center one as the best groove of the 2 old one. |
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There is NO real conclusion,
a new head is way better than any old, reman head... the casting is way
better, and who care if this is true, they are NEW! now, we need to deal
with those valves problems.
Good mechanic like
Bob Donald (from
http://www.bostonengine.com/
) have their way with those heads, Bob gave me
very good advice, many thanks for that! |
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My solution! install them out of the box whit a small modification (shave the Keeper so they seet properly) and have a QUALIFIED mechanic have a look on them once in a wile.... if they stretch, you know what to do! second option is to fit German valve (at least the exhaust one), that imply some work, seat need to be cut at the right angle!
