Twin carbs for 13/60

[Stodec]

Hi Im trying to get some information on setting up my Herald with a twin SU 1.5 carb setup...
I'm under the impression that I can use the same carbs from the 1.3 spitfire on my 1.3 herald, but im not sure if its a straight swap.
I was wondering if anyone could help me with this?

Thank you

[Clive]

Yep, the 1 1/4" carbs from a 1300 spit are a straight swap. May be some fiddlling with accelerator cables, especially if from a mk3 spit (this had a rod operated carb setup)
The 1 1/2" su's can also be used from a 1500, but needles are probably all wrong and the carbs more than whats wanted on a std 1300 engine.

[Stodec]

Ok I will hunt them down then thanks very much!
And with this straight swap do I need to skim the head at all for a higher compression ratio? and if so how much by?

[Deleted User]

yep, other than making up a throttle cable i just bolted a pair on and away we went...a bit of fiddling later to get mixture right, but a noticeable improvement  

[Richard B]

1560 wrote:

And with this straight swap do I need to skim the head at all for a higher compression ratio? and if so how much by?

fit a MkIII Spitfire cam.  :)

[Stodec]

Ah ok sounds good and that will mean the standard compression ratio will be fine with the spit cam fitted?

[Clive]

hmm, its all getting a bit more than a simple carb swap :P
Yes, if the spit mk3 cam then a skim 9.5:1 compression sounds about right but worth checking. Then of course the valves may need unleaded insertd while you are there, maybe later valves, def a 3 angle seat........it is just so esy to get carried away ;D
An alternative may be to find a spitfire head ;)

[Stodec]

Haha yh things just snowball on you...
well I will price it up and see whats cheaper then, my head could probaly do with a overhaul anyway.
Thanks for the help!  

[Clive]

It may be worth trying some of the suppliers for an exchange head. May be cheaper, and if you ask nicely swapping to a spit head may well be OK.

[Stodec]

yeah that might be worth a try can't really afford to buy new head have to keep checking ebay aswell see what comes up...

[Nick Moore]

Twin 1.25" SUs will fit without any other mods to the engine - I did this and got a noticeable power increase and wonderful induction noise as well. The various engine tweaks people have mentioned are also nice to have and will give yet more power, but aren't compulsory.

My 13/60 now runs twin 1.5" SUs, along with a different camshaft, high compression head and extractors, and it's pretty nippy and still does better than 35mpg on the open road.  :)

[Deleted User]

mine, running a pair of 1 1/4 and an overdrive gearbox ,outran a vitesse on the motorways  abroad ..the driver of the vitesse rang and asked us to stop so he could catch up...if it were me i'd just get the carbs ..stick them on and the see how i liked the cars performance . before deciding on any of the other mods

[Nick Jones]

2 x 1.5" are really a bit big for 1300 unless well modified.  On my Herald 1300 with big valve head and TH3 cam I tried 1 x 1.5" SU on a Dolomite/toledo manifold, 2 x 1.25" SU as Mk 3/4 Spit and 2 x 1.5" SU as 1500 Dolly/Spit.

The best all rounder was the 2 x 1.25" SUs which gave away very little to to the 2 x 1.5"unless over 6000rpm.  IN reality the single 1.5" was not far behind and gave best low speed running and economy.

I still have the 1.25" SUs but not the Herald.

Nick