2.5 manifold

minecab · Aug 23, 2020

I have the weber twin choke carb on a 2.5 in my series 2a and it has given me nothing but trouble, will the manifolds from a 2 1/4 engine fit. I am not looking for performance but reliability. Or is there another carb that will fit on the 2.5 manifold.

ExMil109 · Aug 23, 2020

Yes, the manifolds from the 2.25 will fit the head no problem, but there may be a clearance issue with the starter motor. The exhaust downpipe on the 2.5 manifold is slightly further forward than on the 2.25. I'm building a 2.5 engine at the moment, but haven't got as far as fitting the starter, so can't confirm if it fits or not. No doubt someone on here will know...
I think ACR do an adapter to fit an SU carb onto the 2.5 inlet manifold, but it involves some grinding out of the manifold.
What's the problem with your Weber DMTL? I was planning to use this carb on my new engine, so I'm keen to find out if it has any known issues.
EDIT: The 2.5 SU adaptor is made by HNJ Engineering.

minecab · Aug 25, 2020

had lots of problems with blocked jets and flooding.

Hicap phill · Aug 25, 2020

minecab said:
had lots of problems with blocked jets and flooding.

Are you using the swirl pot?

Dippypud · Aug 25, 2020

minecab said:
had lots of problems with blocked jets and flooding.

Do NOT poke anything in the jets, soak in fuel and blow with air-line or your mouth ... yes, you get used to the taste ...

minecab · Aug 25, 2020

Hicap phill said:
Are you using the swirl pot?

do you mean fuel pressure regulator ? no I am on manual pump .

minecab · Aug 25, 2020

Dippypud said:
Do NOT poke anything in the jets, soak in fuel and blow with air-line or your mouth ... yes, you get used to the taste ...

always use mouth. must have consumed many litres of fuel over the years.

minecab · Aug 25, 2020

may try electric pump and pressure regulator.
when it runs well its great with lots of power

Hicap phill · Aug 25, 2020

minecab said:
do you mean fuel pressure regulator ? no I am on manual pump .

These engines run electric pump into a swirl pot allowing pressured petrol into the carb.
This allows for for no fuel starvation On wide throttle openings.
Iv not run 1 of these engines without the swirl & standard pump.
Could your set up be causing your problems ?

minecab · Aug 26, 2020

found a broken wire from coil to carb intermitent when I touched it I heard a soliniod click. pulled the wire and it broke, fitted new wire now it drives great again

2.5 manifold

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