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.............
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