Tappet screws

for those with Series MM sidevalve cars produced between September 1948 and February 1953
ian.mcdougall
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Tappet screws

Postby ian.mcdougall » Mon Jul 08, 2019 10:42 pm

Hi all
Does any one know if new tappet screws/bolts can be bought new .
The reason i ask is i was doing the tappet gaps after a de-coke as well as grinding the valves and seats, i was having difficulty getting a gap even though i could move the follower up and down, so took out the valve and spring i was having a problem with and took out the adjuster screw/bolt, someone before had a problem with wear in the shape of an indentation caused by the valve and they had filed the top of screw/bolt and it has worn a indent again.I assume that filing the bolt top went through the hardened surface .i had a spare parts engine and took the best of the bolts to replace the filed one they all had indent but not as bad as the others.If new ones cant be got what is involved with grinding the screws/bolt head flat and re-hardening them . Or has someone had some new ones made in the past. I also noticed that there was very little adjustment available as if the valves were too long is that possible,the valves are not sunk into the block. the block has been bored +40 in the past and i assume new valve were fitted . i think there were numbers on the end of the valve shaft but will have to wait till tomorrow to look.
Sorry its a long subject by the way.
Ian


Murrayminor
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Re: Tappet screws

Postby Murrayminor » Tue Jul 09, 2019 6:21 am

Proud owner of my first Morris Minor

RobThomas
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Re: Tappet screws

Postby RobThomas » Tue Jul 09, 2019 6:36 am

USHM valve stems are 7mm but it is possible to use a reamer to open out the guides to 5/16 and use BMC valves. Plenty of options. I make valve guides from scratch so can stick in almost any sized valves with larger heads and larger stems. Possible that someone has done the same to yours.
Seem to recall adjusters were metric again so would be easy to source bolts which would then need flattening and hardening.
Cardiff, UK

ian.mcdougall
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Joined: Tue May 20, 2008 9:24 pm
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Re: Tappet screws

Postby ian.mcdougall » Tue Jul 09, 2019 6:22 pm

@ Murrayminor
Sorry they are for overhead valve not side valve engine, actually a bolt.
@ Rob Thomas
Thread size is 8 x 1.0 metric so yes could find bolts have them flattened and made thinner, but what hardening (hardened and tempered or case hardened)
does anyone know


sirrom918
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Re: Tappet screws

Postby sirrom918 » Sat Jul 13, 2019 12:42 pm

The original spec for Series MM valves were:
Head Diameter: 28mm
Stem Diameter: 7mm
Stem Length: 89mm


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