SU shortening

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texpis
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SU shortening

Post by texpis » Sun Jan 19, 2020 7:29 pm

Hi all
Hopefully you can help I have an MGB V8 which I want to fit SU on an aftermarket copy of the trouser manifold unfortunately the carbs are about 10mm to high.
When looking at the internet noticed a firm selling shortened SUs. I could do this my self if I knew the procedure. Anyone know what’s required. I’ve attached a picture and there description

You are looking at a HIF 44 SU Carb. The carb has been modified to suit a 1275cc MG MIDGET / HEALEY SPRITE The Dashpot and Piston have been machined to reduce the overall height of the carb and it is fitted with a flat topped damper. This reduces the carb height by approx. 15mm and allows fitting to most aftermarket inlet manifolds.
1EA021F7-2E38-4C3B-8EA2-F435CC22C8F6.jpeg



minorv8
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Re: SU shortening

Post by minorv8 » Mon Jan 20, 2020 1:56 pm

You can get different dampers, e.g. http://sucarb.co.uk/damper-19098.html. That alone should gain close to 10 mm reduction in height. The threaded section at top is machined slightly lower, moderate machining should suffice. Same amount from the piston top if even required.

A bit hard to tell but looks like they took some material off the flange also. There is not that much to begin with, I would not touch that at all.

All this top of my head, it´s been some time since the last time I had a HIF apart.

texpis
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Re: SU shortening

Post by texpis » Mon Jan 20, 2020 2:48 pm

Thanks for the reply minorv8. I have ordered 2 of them which would probably be fine but the Dashpot comes up through the hole hence the deeper damper top. I guess I will have to machine the Dashpot top to get full travel is that okay to do?

Mick

minorv8
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Re: SU shortening

Post by minorv8 » Tue Jan 21, 2020 1:18 pm

Do you mean the piston, like this ?
SUhif.jpg
SUhif.jpg (10 KiB) Viewed 284 times
Some pistons have circlip, some don´t. I think that HIF44 does whereas HIF7 does not. Anyway, check if you have enough travel when the carb is assembled. You can machine the dashpot top lower, there is plenty of thread for the damper. If required you can take a same amount off the piston top. You may also need to adjust the length of the damper in case it bottoms out in the piston bore and prevents full travel.

Have you considered machining the intake flange/trouser manifold to lower the whole asembly ?

texpis
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Re: SU shortening

Post by texpis » Tue Jan 21, 2020 10:37 pm

Thanks for the reply minorv8
Yep that’s the one, I’ve been looking at shaving the manifold could be possible shortening the SU would be easier I’m going to shorten the Dashpot and use a flat top damper and see how it works. If it doesn’t run well it’s not to painful to return to normal.

Thanks again

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