Many thanks for the prompt response Bob.
I had a suspicion it might be a coarse thread. So glad I asked.
This list is just the best............
_____________________________________________
(______________ Alan Bromfield _______________)
(______ \____1957-BN4____/ _______)
(_________________________)
http://tinyurl.com/healeyforum
-----Original Message-----
From: Bob Haskell [mailto:rchaskell@earthlink.net]
Sent: 30 May 2011 19:05
To: Alan Bromfield; healeys@autox.team.net
Subject: Re: [Healeys] Thread size on 29D Engine.
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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