[Healeys] Thread size on 29D Engine.

[Bob Haskell]

Alan,

5/16-18, 5/8" long with a copper sealing washer.  If you need to chase 
the threads with a tap, fill the flutes of the tap with grease to catch 
the swarf.

Cheers,

Bob Haskell
AHCA 3000 Mk I registrar
http://www.ciahc.org/registry_3000mk1.php

On 05/30/2011 01:22 PM, Alan Bromfield wrote:
> Team.
> I have fitted my BN4 project with a 29D engine that has been subtly upgraded
> to a spec that is similar to the BJ8.  The engine was fired up for the first
> time last weekend and all initial checks seem ok.  Unfortunately I have this
> afternoon traced what appeared to be an oil leak to a couple of tapped holes
> on the generator side of the engine that are open to the crankcase.  I don't
> know if this is common to all 29D engines but there is a flat mounting face
> that would accomodate a mechanical fuel pump in other roles.  The two
> mounting bolt holes (for a pump) are drilled and tapped but strangely the
> square window for the actuating arm doesn't exist - solid casting.  Why the
> holes were drilled and tapped beats me.
>
> My question is, what thread form would these tapped holes be?  It is tricky
> to get to see down there and I can't get a 5/16-24 UNF bolt started into the
> tapped holes.  A 1/4 bolt drops in and hardly touches the sides.  It may
> just be paint in the threaded holes that is preventing the bolt starting.
> My worry is, If I chase this through with a UNF tap only to discover
> I should be using 5/16-18 UNC I could wreck the threads.
>
> Paint peelings and perhaps cast iron swarf into the crankcase is a secondary
> worry.  I wish I'd noticed this while the engine was out of the car.
>
> Thanks.............