E: Engine Exhaust valve not right

[vibrac]

Count me out on that one David -I always replace them one Comet standard issue is
two sets valve springs, two valve collets and three valve circlips (top guides etc to order)

 

[nkt267]

Count me out on that one David -I always replace them one Comet standard issue is
two sets valve springs, two valve collets and three valve circlips (top guides etc to order)

I replace the top collars as well as I have had a set of collets pull through the collar, thankfully the rocker collar stopped the valve dropping into the cylinder

 

[stu spalding]

Keep an eye on the collar ET37, some were machined with insufficient material in the region of the spring recesses. In the past I've had one fail but, like John's, ET35 was a good fit on the stem and the valve didn't drop. Cheers, Stu.

 

[chankly bore]

Anybody know what the top guide is made of ?, I know it's a kind of alloy, But it must sort of self oiling,
Even after years of an engine standing, It's not practical to take the upper frame off and lube, Before getting an engine going again.
And I have never seen this before.
Some people seem to put things together, With out lube !.
I was always told to assy' with oil or grease or something !.
Cheers Bill.

According to Eddie Stevens, top guides are Hiduminium 4L25

 

[chankly bore]

Bill, Cheers mate, do a search under "HIDUMINIUM" the original specs. are all there, and no, it ain't self-lubricating.

 

[Bill Thomas]

I just thought maybe these top guides were made by someone we don't use, Bit like the mega cams using the wrong stuff for the cam bushes.
We have also had bushes made of bronze instead of oilite. Cheers Bill.

 

[chankly bore]

Yup, you never know how many species of primate have been at these machines from leaving the Works until the present. I am a mechanical ignoramus, but I've seen the glories of Argentinian resurrectionists and some Colonial fencing wire and three-inch nail mechanics. The instruction drawn from these observations has been salutary.

 

[Bill Thomas]

Chankly, That stuff's a bit Special !, If it's good enough for Concorde and Rolls Royce, It's good enough for me.
Cheers Bill.

 

[davidd]

So which spring should I buy, the one from Coventry or search for the Gold Star spring?
Should I replace intake spring at the same time?

Jerry,

You can use the stock items. I just wanted to note that I was showing you something other than stock, but that all the springs do change through use.

David

 

[ClassicBiker]

Following this thread and Chankly's #34 post I got a little curious and looked up Hiduminium 4L25 and found this link for composition; http://silverbiplanes.com/SPECIFICA...inium_DTD_British_Standard_specifications.pdf
and compared it to various aluminum compositions on https://www.onlinemetals.com and came up with 2024-t351 as a good match. It's mainly used in the aerospace industry. I found a really good data sheet here http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=ma2024t4. It seems to be rather tough stuff and a 2 inch diameter piece 12 inches long will cost you just under $44. So it isn't in the realm of unobtainium if you needed to make something special but it is a pricey. The same size piece of 6061-T6511 is only $20, but has only about a 2/3 the yield strength and 3/4 the bearing strength.
So I'll second Bill's statement in post #38.
Steven