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Mistery bolt hole in tappet block

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Patersoncm
Posts: 27
Joined: Sat Feb 13, 2016 1:20 pm
Location: Rugby

Mistery bolt hole in tappet block

Post by Patersoncm »

image.jpg
Am gradually progressing an engine rebuild for my SP250 and would like to know the purpose of a small bolt hole in the tappet block just below the Rev counter connection on the distributor. There is a thread in the engine block but insufficient room to fit a bolt to prevent oil escaping.

Any ideas?

Many thanks.

Vortex O'Plinth
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Location: Gloucestershire

Re: Mistery bolt hole in tappet block

Post by Vortex O'Plinth »

Are you sure there's a tapping in the block below this hole? If the hole itself is threaded it's one of the jacking screw holes to facilitate removal of the tappet block. If it is one of these it's tapped 5/16 - UNC.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

Patersoncm
Posts: 27
Joined: Sat Feb 13, 2016 1:20 pm
Location: Rugby

Re: Mistery bolt hole in tappet blocke

Post by Patersoncm »

Nick.
Thanks for your email.
Mistery solved. I have just had a Eureca moment. It is not one of the two jacking points it is a locating dowl that must have gone missing whilst the block was having a re- bore. Fortunately I have managed to take one off a spare engine and tapped it into place.
I was worried that I may have needed to take off the tappet block with all that that entailes.

Regard



Chris

tjt77
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Re: Mistery bolt hole in tappet block

Post by tjt77 »

seems the 'mystery' was solved.. there are 2 locating dowels in the tappet block..one left rear..one right front..
unsure if anyone else has come across this :- some tappet blocks have 2 additional bolts along the middle section ..these bolt through into the camshaft towers and are 1/4" NC rather than 5 1/6" NC that secure the tappet block around its perimeter .. I believe this is a feature of early saloon engines .. Ive not seen enough SP250 engines to know of it was part of the original design.. but all of them seem to have the casting designed to take these additional fasteners..

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