Carb coolant/heater pipework

[toopy]

Said pipework is currently plumbed in on my engine, however ive removed all the external hoses
for a flush through after the thermostat housing bolt sheared and i thought i might as well dismantle the lot at that point!

The pipe between the carbs is blocked, no surprise there really. I assume for colder climates
it was essential, but in the UK not so much. Have most people blanked it off and then removed the metal
pipe that bends round the back of the engine?
I believe there is a thermostat housing out there that doesnt have the outlet for the swan neck pipe,
that feeds into the manifold, and so would look neater than a blanked of stub as i would have to do?

 

[AliK]

I think I read somewhere it was for colder climates for warm up phase and to stop the carbs icing in normal operation!?

The correctness of the latter I'd love to hear about from the people on the forum who are fonts of knowledge. Are these carbs susceptible to icing due to the pressure drop across them!?

My carbs will never ice with all the heat in the engine bay

 

[toopy]

I think I read somewhere it was for colder climates for warm up phase and to stop the carbs icing in normal operation!?

The correctness of the latter I'd love to hear about from the people on the forum who are fonts of knowledge. Are these carbs susceptible to icing due to the pressure drop across them!?

My carbs will never ice with all the heat in the engine bay

I should imagine most of the pipes on these cars are now blocked or at the very least partially blocked
and lots of people, me included have been driving around just fine!

 

[AliK]

That is a great point!!

 

[MaximG]

Mine was blocked and I removed all the pipe work when I rebuilt the engine a few years back.

 

[cosworth415]

I have my flat top carbs, inlet manifold and thermostat housing off at the moment seems to be a lot of half clogged up pipe work, looks a bit like a boiler house. Would love to get rid of it all if its not doing anything.

 

[Farmer42]

I don't think I have ever heard of SU style carbs icing up especially in this country. As Ali has mentioned, there is enough heat in the engine bay to prevent that happening anyway.

I have however heard that if SU carbs get overly heated, it causes 'needle drop' where the carb body and the jet expands causing the needle to drop and thus making the mixture too rich.

I wonder however whether this would also cause pre-ignition or 'pinking' where the fuel gets too hot and ignites before getting into the combustion chamber. I have been trying to get rid of my pinking for quite a while & have tried everything. My valves & head are fine with no pitting on the seats and I have nudged the timing back to around 6 degrees BTDC. I am also using Millers VSPE additive to increase the octane on unleaded fuel but all to no avail.

Maybe the heat from the water pipes is having an effect?

 

[jonbills]

I don't think I have ever heard of SU style carbs icing up especially in this country. As Ali has mentioned, there is enough heat in the engine bay to prevent that happening anyway.

I have however heard that if SU carbs get overly heated, it causes 'needle drop' where the carb body and the jet expands causing the needle to drop and thus making the mixture too rich.

I wonder however whether this would also cause pre-ignition or 'pinking' where the fuel gets too hot and ignites before getting into the combustion chamber. I have been trying to get rid of my pinking for quite a while & have tried everything. My valves & head are fine with no pitting on the seats and I have nudged the timing back to around 6 degrees BTDC. I am also using Millers VSPE additive to increase the octane on unleaded fuel but all to no avail.

Maybe the heat from the water pipes is having an effect?

I wouldn't think slightly hotter fuel in the carb is going to make any difference to the combustion temp and pinking. I'd be looking more at compression level and a very lean mixture.
Do you know what compression you're running?

 

[Farmer42]

I wouldn't think slightly hotter fuel in the carb is going to make any difference to the combustion temp and pinking. I'd be looking more at compression level and a very lean mixture.
Do you know what compression you're running?

I have no idea but that's the next stage. Just managed to get hold of a compression testing kit and found the compression stats for the L20A engine that I have in mine.

The spark plugs look ok i.e. the right colour - not glazed or sooty and if I adjust the mixture either way, it doesn't run very well.

Might have to invest in taking it to an SU carb specialist to run diagnostics & get them tuned properly as they will have all the right equipment that I don't have. Wouldn't be surprised if jets and/or needles are worn.

Might try by-passing the inlet manifold with the heater pipe first to see if it really does make a difference. No harm in trying!!