[Healeys] SU HD carb - one issue found

goldengt at cal.net goldengt at cal.net
Sun Sep 10 15:12:07 MDT 2017

I found the old email in the archives:I got new HD8's in 2001 and as I recall they were fine out of the box. I
no longer remember my initial setup mixture adjustment techniques, but
after last year's engine rebuild I couldn't seem to get an idle via the
slow run screw. A good overall mixture was achieved on the engine dyno,
though, using oxygen sensors. A few months ago, I wanted to get back to
basics which is having the jet flush with the bridge and then richening
the screw 2.5 turns. I could not get the jet up high enough to be flush
(instead was .035 down). Thus I asked this list about what depth below
flush corresponds to 2.5 turns. I think I got one response but I dug up
an old HD8 and 2.5 turns corresponds to .060 depth which also
corresponds to a 1:1 lever ratio with a screw pitch of 40 threads per
Yesterday I found out the two reasons I couldn't get the jet flush and
they are unique to these new reproduction carburetors, not withstanding
using "SU tooling".
1. The Burlen jets are very short. They are 1.145 long. The old SU and
Moss supplied jets are 1.177. That is quite a bit.

2. The lever that holds the mixture screw is not shaped properly. It
interferes with another part of the casting so that the mixture screw
lever doesn't get full travel in the lean direction.

Another area of difference to the original HD8 SU's is the use of metal
throttle shaft bushings and push on rubber seals instead of Teflon
sleeves. After 10 to 15 thousand miles, there is way too much slop in
these bushings, requiring attention. One bushing has quite a large burr
on it and the adjacent rubber seal has lots of cracks that the three
don't. That seal won't last much longer. The bushings are of a split
design, so I guess they have to leak a little bit.

Conclusion: might as well get your old HD8's rebuilt.

Ken Freese
65 BJ8
----- Original Message -----
From: Engl <engl at accesscomm.ca>
To: goldengt <goldengt at cal.net>
Cc: healeys at autox.team.net
Sent: Sun, 10 Sep 2017 12:13:31 -0700 (PDT)
Subject: Re: [Healeys] SU HD carb - one issue found


No luck in the archives [probably not using the right search parameters].

Not sure if the carbs on the car are Midel carbs but the car only came with the carbs on the car so hopefully I can make some adjustments and get it running like a top.

Bob England
On Sep 10, 2017, at 9:28 AM, goldengt <goldengt at cal.net> wrote:

I had the same issues with the Midel SUs. See the archives. I went back to my original carbs.Ken Freese 65 BJ8

Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Bob England <engl at accesscomm.ca>Date: 9/10/17 7:27 AM (GMT-08:00)To: healeys at autox.team.netSubject: [Healeys] SU HD carb - one issue found
Hello All

Thanks to all who provided me with their thoughts on the problems getting my engine to run properly.  It has been really great to be able to get some thoughtful feedback on my trials and tribulations.

I have found one item with the carbs that I thought I should pass along should anyone else have the issue.  You may recall I could not get the jet to come up to the level of the cab bridge – it seemed to hang up 1.6mm low.  Yesterday I discovered the problem – the lever that has the jet fork on one end and the mixture screw on the other is too thick.  Being too thick it hits the mixture screw lobe piece, not allowing the forks to rise, which holds the jets 1.6mm-1.5mm low.

These carbs are not original carbs and obviously casting for the fork/screw lever too thick.  Going to do some filing on the piece this afternoon (or maybe take a dremel to it if laziness sets in).

Still not confident this will help too much on the rich mixture or 30 degree timing sweet spot, but we shall see – it certainly wont hurt!

Bob England
’65 BJ8

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