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Not being one to leave well enough alone , I've been thinking about triple inch and quarter su's on my grey motor. It has mild head work, 30/70 cam, extractors and twin strombergs at the moment. Is anyone running su's and are they better response wise than the strombergs? They seem to be the popular "Performance" choice in the sixties.

Please don't bother telling me for good response put a red motor in (I know that) I just love dinasour motors

Mick .

Mick,
SU carbs are the racer's choice of carburettor for a grey motor. The major advantage of an SU setup is the variable choke design - the choke increases or decreases according to engine demand. This keeps the air velocity at the venturi point constant, allowing a very precise mechanical metering of fuel. I have heard it said that properly set up, SUs are the next best thing to EFI. Unlike triple Strombergs, there is no need to install venturi sleeves to maintain air velocity at low engine RPM. The benefit of triple Strombergs is better fuel distribution. Both the grey and red motors suffered from inadequate fuel distribution (i.e., most of the intake mixture going into bores 3 and 4 rather than evenly spread). With the SUs you solve that problem too.
I'd go for it but I would get the carbs professionally rebuilt otherwise you could be in for a painful time pointlessly trying to tune and balance them. This guy describes how to tune them http://oldjohnno.id.au/page401.html
I think Theo (thropzed) runs twin SUs in his grey powered EK; and gazrat did in his FB until he went the triple Stromberg path.
But you'll need more than triple SUs to catch my grey
Andrew

Andrew,

I see you are running yours through a reco crashbox (syncro on first gear is over rated ), what clutch / pressure plate did you go with? Thanks for the tuning SU's link it will be handy reference info.

Mick

Mick,

I think I'm using an early red motor clutch (EH). I wanted to keep the crashbox to stay within the "EK Sports" category. If it blows, I'll try to con my father out of one of his spare Riley 2.5L 4 speed gearboxes. These were a period modification for grey powered Holdens and worked a treat. Eric uses one these in his So Cal racing car, which he had a mate close ratio for him.
Are you still interested in those triple 1 1/4 SUs that Hamish has, or do you have your own set now?

Andrew

I've scored a manifold already and I'll make up my own linkages, I just needed to know about carb sizes and if they are an improvement over multiple strombergs. I was concerned about going to far with the carburation side of things considering the relatively mild motor that I have, learnt the hard way years ago with hot clevo's and windsor V8's that biggers not always the best way to go.

Mick

They are superior to multiple strombergs as they more precisely meter the fuel and the choke size varies with engine RPM (which makes it hard to over-carb). Windsors and Clevelands use fixed choke carbs, so your experience with them is not relevant to multiple SUs on a grey. Having said that, here's a webpage that displays a graph which recommends the size and number of SU carbs as a function of engine bhp and capacity http://www.sw-em.com/su_carbs.htm
For a warm 138 making between 80 - 100 bhp, you'll see the graph recommends triple 1 & 1/4 inch SUs. This is consistent with what I have been told is the ideal SU set up for a grey.

Andrew,

Your better than a Google site for information, thanks for the link its great

Mick

I picked these up last night , they have been serviced and are set up for a 186 - for $250

Yeah Blacky, for some reason you tend to be able to pick up a set of red motor triple SUs more cheaply than a set for a grey.

Great score, for that price you'd be grinning I'm guessing they are 1 3/4". I've got a manifold already and am now hunting for 1 1/4" carbs to recondition, I visited a local guy whos into Morris Minor 1000's and checked the su out on his "monster". I said I'll have to start looking on early Morris forums to see if I can score some that way, I want to go through the carbs myself if I can so I get a good working knowledge of how to set them up.

Your never to old to learn.

Mick

Nice score Blacky.
I got the latest "just parts" mag and there is a set of twin SU's on a manifold for $1300 .

Been offered a grand for 'em already

Tin ass

Blacky wrote:Been offered a grand for 'em already

Nail his feet to the floor and get his cash.

They are nice,but they aint worth a grand.

If I sell 'em I hafta find something else so why bother ???