power boost with choke

[julie4morris]

I have recently fitted a pancake air filter my Morris Traveller and I've found that if I pull the choke out I seem to gain an extra 10 also MPH. The engine and carburettor are all original and I was just wondering with the addition of the new filter would I need to change the needle/ with changing the needle increase power output. I have looked in the Haynes " tuning that a-series engine" manual and it advises using a H6 needle for a rich mixture in a 1098 engine.

What would anyone recommend and where is the best place to buy from?

[bmcecosse]

Pancake air filters are not the best....... The flat face is too close to the carb inlet. You can try a richer needle - but all it's going to do is use more fuel.......

[julie4morris]

mmmm I thought that might be the case but would you say they are an improvement on the original air filter in terms of air flow?

[bmcecosse]

Very marginal - the carb is the main restriction to air flow on a standard engine. The way forward is with a larger 1.5" carb on a good alloy inlet manifold (thus eliminating the power zapping hot spot) and then a good (NOT pancake!) air filter will pay dividends. http://www.ebay.co.uk/itm/CLASSIC-MINI- ... 3a7ee63944

[lambrettalad]

I put a pancake on and took it off pretty sharpish,engine wasn't as smooth and mpg went up.looked nice tho

[daveyl]

Bought and fitted one of these, along with a K&N.
http://www.ebay.co.uk/itm/MGB-AIR-FILTE ... 35bf4c2b1b
A bit pricey, but you get 2. Comes as standard with a spacer block/back plate, supposedly for better flow. And it is a bit quieter than a standard K&N and type, unless you prefer 'roarty'.

[julie4morris]

OK then thank you all very much for your advice, I think I will leave the carb and inlet manifold mods till I replace then engine with a 1275 one. Also just out of interest what is the "power zapping hot spot" that bmcecosse talks of? Sorry if it sounds like a bit of a dumb question

[bmcecosse]

On the cast iron one-piece manifold - the exhaust heat from cylinders 2 and 3 comes through into the inlet manifold at the join - causing a hot spot which heats the ingoing air/petrol charge. This costs a good 3 or 4 bhp - and is often the only gain from fitting 'twin carbs' which don't have any inlet charge heating - and so are perceived to give more power!

[julie4morris]

oh I see thought it might be something to do with that but was not to sure so thank you . I have also heard that you are better off having one big carb than twin carbs, is this so?

[chesney]

Yep.

[mike.perry]

I put a pancake on and took it off pretty sharpish,engine wasn't as smooth and mpg went up.looked nice tho

Two pancakes look even nicer [frame][/frame]

[bmcecosse]

Certainly a single 1.5" carb on a GOOD inlet manifold - is better than twin 1.25" carbs on the hopeless BMC inlet manifold..... Each piston breathes independently - and only sees ONE carb on each breath - so it sees either a 1.25" carb (with the twins) or a 1.5" carb with the larger single. The twins are 'better' than the standard single only because they don't have a hot spot - the cross tube on the manifold doesn't feed ANY flow across from the other carb - it actually disrupts the flow from the carb directly in line with the port. A good single carb manifold has no hot spot (and don't connect the water heating either...) and although the flow has to come down an S bend from the carb to the port - it's still better than the flow from the smaller twin.

[julie4morris]

haha yes 2 do look good ok then sounds like a good plan, I was also working on the basis that it would be less hassle and cheaper fitting one 1.5" carb that having to mess about with twins, with all the balancing and what have you. I have also done some reading up in inlet manifolds and found that the longer straighter ones (such as Janspeed produced) to be more efficient.

[bmcecosse]

I think generally the 'Howley' manifold is considered 'best' - but honestly unless looking for the very last 0.1 bhp - I doubt there is much to choose between them.

[mike.perry]

I have extension pieces on my inlet manifold to clear the exhaust pipes