Please explain mushroom head tappet adjusters

Just not sure what these do or how they work. Thanks.

supposed to cure this;



This is what they look like.



They are supposed to give a larger contact area on the valve ends to reduce the pitting of the small adjusters beating a hole in the end of the valve ends.

They usually can't be installed from the top, so you either have to take the head off or remove the rocker spindle to get them on. Your mileage may vary.

Dave
69S

Often the mushrooms are made lighter than factory to ease valve train loads per rpm. Here's a source of them
http://www.britishbikeconnection.com/parts.htm

I like them for the metallurgy. They don't seem to scuff or chunk out (spalling?) like the stock ones. Don't know what the stock ones are made out of but every one of mine with some miles on them were pretty beat up.
Dave, great rocker geometry on those valves, centered and short excursion of the adjuster path across the stem. The one on the far left is a little funny though. I went though a box of old valves I have and they all seemed to be pretty soft on the stem face. I could cut them with a file, even the Black Diamonds. Didn't they at some time put a Stellite face on there?

DogT said:

supposed to cure this;

Dave
69S

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Hardened lash cap are worth while I hear but need valve and push rod trim attention of course.

bpatton said:

I like them for the metallurgy. They don't seem to scuff or chunk out (spalling?) like the stock ones. Don't know what the stock ones are made out of but every one of mine with some miles on them were pretty beat up.
Dave, great rocker geometry on those valves, centered and short excursion of the adjuster path across the stem. The one on the far left is a little funny though. I went though a box of old valves I have and they all seemed to be pretty soft on the stem face. I could cut them with a file, even the Black Diamonds. Didn't they at some time put a Stellite face on there?

DogT said:

supposed to cure this;

Dave
69S

Click to expand...

Click to expand...

The Black Diamond valves have a stellite pad welded on the top. About .080" thick. Stellite can be cut with a sharp file. If the valve has been shortened then you need to use a lash cap because the stainless valve stem is a very poor wear surface. However I have not found lash caps to wear as well as the stellite tips. They are just hardened tool steel. Maybe we need some carbide lash caps. $$$ The mushroom adjusters do seem to help spread the load a bit. Jim

comnoz said:

The Black Diamond valves have a stellite pad welded on the top. About .080" thick. Stellite can be cut with a sharp file. If the valve has been shortened then you need to use a lash cap because the stainless valve stem is a very poor wear surface. However I have not found lash caps to wear as well as the stellite tips. They are just hardened tool steel. Maybe we need some carbide lash caps. $$$ The mushroom adjusters do seem to help spread the load a bit. Jim

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I'm waiting for you to get bored and make some rollers. :mrgreen:

Thanks for the explanation guys. So, with head off what would be the procedure to replace the tappet adjusters with the mushroom type?

You just have to screw them in the rocker arms from the bottom. As you can see you can't get the mushroom head through the rocker threads. No problem with the head off. Just make sure they are centered on the valve ends, you might have to adjust the shims on the rocker arm shaft, I did, just like Mick said in his DVD. Some people make special bronze washers for the rocker shaft. Funny I didn't have to adjust my originals to center them, but I did replace one rocker arm. It might have been that one.

Dave
69S

swooshdave said:

comnoz said:

I'm waiting for you to get bored and make some rollers. :mrgreen:

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Click to expand...

Don't think I haven't thought about it. Making them adjustable is the hard part. I think pivoting adjusters like a porsche would be more practical though. Jim

Yellow_Cad said:

Thanks for the explanation guys. So, with head off what would be the procedure to replace the tappet adjusters with the mushroom type?

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You need to remove the valves first... or the rocker shafts (valves are easier I think).

I could be wrong, but as I remember if the push rods aren't in the way, you can just push the arms up and thread them in. It becomes an issue if the head is installed and I seem to remember I could get either the intake or exhaust on, but not both. In that case you either have to remove the head or remove the rocker shaft. There was a thread on this when I was doing it, it's still back there somewhere. As I say, I could be wrong, I'll see if I can find the thread.

Here it is. installing-mushroom-tappet-adj-t8649.html?hilit=mushroom

Dave
69S

I would have thought that a wider contact area would affect the valve lift.
Imagine the rocker arm at full lift, the edge of the mushroom will be touching the valve stem tip instead of the small contact area of the normal adjuster, that would make it lift the valve a fraction more.......wouldn't it?

It depends on the head casting whether you can get the arm up high enough to get the adjusters started without either blocking the valve open or removing the arm. Some heads you can and some you can't.
I figure the change in valve lift would be very small. Jim

I'll bet ya dew drops to doughnut Old Brits did theirs so they screw in from above like factory. I need a set, now, so will ask, before head put on, just in case ya I am mistaken.

hobot said:

I'll bet ya dew drops to doughnut Old Brits did theirs so they screw in from above like factory. I need a set, now, so will ask, before head put on, just in case ya I am mistaken.

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Make that a case of chocolate covered donuts. You know my address.

comnoz said:

swooshdave said:

comnoz said:

I'm waiting for you to get bored and make some rollers. :mrgreen:

Click to expand...

Click to expand...

Don't think I haven't thought about it. Making them adjustable is the hard part. I think pivoting adjusters like a porsche would be more practical though. Jim

Click to expand...

As you know I'm no engineer but here's one exotic way to do them:



Pushrod side would stay the same. For adjustment a worm screw and gear teeth in an eccentric bushing. Turning the screw would adjust the clearance and because it's a worm screw it shouldn't move. I bet with all the machining they'll be $500 per. :mrgreen:

Stellite is a reasonable choice for stem ends, properly applied of course. I have not checked the hardness of a Stellite faced stem but expect it to be Rc40 or thereabouts. Will cut fairly easily with a file.
This is not hard by any means. Rc above 62 would be fairly hard in my book.
The last valve stem I did check out of curiosity in my infancy was from a '67 Ford 170 ci six banger and I remember something in the low Rc 50's. Murder on a bandsaw blade, that's why I checked.
But, one must consider may variables when specifying materials and hardness is not super important here.
Wear and impact resistance is what is desired and Stellite or even maybe Tantung are reasonable choices.
Carbides, while hard like 90-100 on a comparison converted Rc scale, which is the wrong scale for that range, tends to be brittle when with <about 20% Co.
The TCE will affect the joining method and in a friendly world will match the stem material. This is rarely the case though.
I'm done rambling, the end product would be of little improvement when we replace the valves because they are rocking and look closely at the stem and it's barrel shaped but holy mackeral those tips are like brand spankin' new.
I will use the Stellite tipped valves with coated stems when the time comes for replacements. Or maybe I'll just clean the ends up on the old ones on the cheap. Mechanical things wear, I can live with that as long as we all wear out together.