Carburettor spacer

[bazjude2998]

Hope you can advise / help.
I,m fitting a pair of SU carbs to a 1622 MGA Engine.The carbs have a spacer block approx 30mm thick ,would there be any probs in increasing this to a 43 mm spacer .
Thanks

[GreenV8S]

Throttle/choke cables and fuel line would need to reach the new position and obviously you would need to check you've got space for the carb and whatever filter/intake is connected upstream. Apart from that I wouldn't expect any problems assuming the bore inside the new spacer matches the manifold and carb. Increasing the runner length would tend to increase torque at lower revs but 15mm doesn't sound like enough to matter for an engine that isn't highly tuned. Just out of curiosity, why do you want to move it?

[bazjude2998]

Thanks for your advise & prompt reply I need to bring the carbs foreword so the piston under the carb clears a chassis tube on its downward stroke
Hope that makes sense

[Steve_D]

As has been said the spacer will make little difference.
The 'piston' you refer to is the main jet which is moved downwards by the choke mechanism to increase fuel flow.

Steve

[stevieturbo]

If moving helps...then move it. You certainly do not want that part contacting bodywork...ever. And some engines can move a fair bit if they have soft mountings, so make as much clearance as you can.

[Steve_D]

stevieturbo said:

If moving helps...then move it. You certainly do not want that part contacting bodywork...ever. And some engines can move a fair bit if they have soft mountings, so make as much clearance as you can.

A double consideration here where the engine movement will likely be highest when running a little rough on choke/cold.

Steve

[bazjude2998]

Thanks for all replies
You guys have got me thinking,what would be the safe maximum increase from the current 30mm thickness
Thanks

[GreenV8S]

bazjude2998 said:

what would be the safe maximum increase from the current 30mm thickness

Whatever it takes to get it to fit. Physical clearances will trump any other considerations.

It needs to be stiff and strong enough to physically support the carb, which might become an issue if the spacer was massive. Increasing the spacer thickness will increase the overall runner length which will have some effect on the tune, but you can get some idea how much of an effect you're dealing with by looking at the change as a fraction of the overall runner length i.e. from the throttle to the valve; the sort of changes you're describing here are small.

[Sardonicus]

Simply put that spacer/insulator increase on that old low tech 4 banger no noticeable change IMO , like mentioned though correct material essential for long term reliability

[bazjude2998]

Thanks for all replies