1.5 or 1.75 SU

[YMJ]

Morning,
The mudplugger motor (950 bored out to 998) is coming on. We have a tickled 295 head and an Evo001 cam from Minispares. I have the luxury of many carb setups to choose from, so bearing in mind we’re looking for a nice tickover with low-med grunt and top end power unimportant, do we go for 1.5HS4 or a 1.75HIF?
Also any thoughts on manifolds? I have a couple of Metro inlet/exhaust manifolds to hand but that is all.
There are a few single carb manifolds on eBay right now
Cheers

[GraemeC]

I can't see a 998 benefiting from a 1.75". I'd think it would actually be detrimental, especially at WOT as the gas speed will slow down.

[mk1]

I agree with Graeme, on the face of it an HS4 will be a better bet than the bigger 1 3/4 jobby

[YMJ]

Right. So HS4 it is.
Manifold suggestions?

[Exminiman]

Maniflow steel with 1.4 inlets to keep gas speed up ....https://www.maniflow.co.uk/index.php?vi ... oduct=1098
would serve well

[YMJ]

How about a standard Metro or even better an MG Metro, sawn off with an LCB? I’m looking to use what I can drag out of the shed/hedge!

[GraemeC]

MG Metro used a HIF44 so the manifold would be too big.
Standard 1.0 Metro manifold would probably work but wouldn't be as good as the Maniflow.

[YMJ]

I have just dug out Des Hammill’s excellent “SU Carburettor high-performance Manual”...a single 1.5 SU will be perfect. He and Vizard also confirm that you can over-carb a manifold without too much loss in efficiency but not the other way around. So I’m tempted to fettle up the 1.75” Standard Metro HIF6 manifold. BUT, it’s bloody heavy and an ally aftermarket job might just be better

[111Robin]

When I ran a single 1-3/4 HIF I used the mini spares torquemaster manifold, seems to be a popular choice.
I still have it somewhere if it's of any use to you.

[YMJ]

For what its worth I'm going to use the Metro inlet/exhaust manifold with a 1.5 HS4. It's a bit heavy but its what I've got to hand.
The only issue I will have is the hotspot where the inlet touches the exhaust raising intake temps. If it turns out to be "that bad", I've got another damaged one that I can saw off to use the inlet part with an LCB or similar.