Hi Bob. The issue is that when the plugs are screwed in, and
tightened, they don't go in far enough for the end of the plug to go
into the combustion chamber - as it does on all other Westlake
designed heads. The plugs are up to 200 thou away from the roof of the
combustion chamber in the 960 head.
So you machine the plug seat, on the outside of the head, where the
plugs screw in. By removing metal from the head where the plug screws
in and seats, you allow the plugs to be able to screw down so they
reach the roof of the combustion chamber, as Harry Westlake originally
designed it, and as the pics of other Westlake designed heads show.
Obviously measure each one.
Best
Chris
Sent from my iPhone
On 22/09/2011, at 1:07 AM, Bob Spidell <bspidell at comcast.net> wrote:
> I couldn't get from Chris' page what the 'solution' is; mill out the
> plug hole, or the inside of the chamber?
>
> Bob
>
> --------------------------------
> Bob Spidell - San Jose, CA
>
>
>
> Chris & Mark,
> Thanks for the information. I checked my two 960 heads & they both
> have the
> plugs recessed in the combustion chamber as per Chris' information &
> photographs.
> If this is a machining mistake it is still a mystery why they never
> corrected
> it. And why the BJ8 is the only model a greater advance.
> Gary
>
>
>
>
> Chris and Gary,
> also have an original works head. It too has the AEC 721 number
> ast into the top.
> s an aside, I was told long ago that the heads were made 'after
> ours' when production had stopped for the day. They were apparently
> ade from recycled diff. heads that had been melted down.
> 've not done a side-by-side comparison of the 721 and the 960 or
> lue-printed either of them, but I have been told that there is also a
> light difference in the squish area in the heads, the 721 being
> onsidered the better designed one.
> ne of our racers here in NZ actually replaced the 960 on his BJ8 with
> he 721. He reckoned it gave him a marginal improvement in
> erformance. I don't know how scientific his analysis was . . . that
> as back in the 70s.
> Cheers
> ark Donaldson
> uckland. NZ
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