23 replies to this topic

[karlnz]

good evening!

 

have a fresh new motor and have got my hands on the above carb

 

will be off to the rollers in due course, but obviously want to get it at close as possible beforehand and run the bugger in

 

can anyone recommend what inital set up to go with, or tell me where i can find out? anyone know where AC dodd is these days?

 

need to know where to start with venturi size, main jet, idle jet emulsion tube etc etc

 

also be keen to find a labelled diagram, i got most of it figiured out but theres some things im not sure of.... whats that little lever on the top, is it the choke? (excuse me its my first non SU)

 

anyway, spec....

 

1275 +60 (1330?)

544 cam

lcb

playmini exhaust

fairly standard head, very very midly ported

 

does not have rampipes, but i should probably get some, also need advice with regards to this

 

any help appreciated thanks!

[oltonlad]

with that engine spec you will be over carbing the engine with the dellorto...............stick with a HIF44, it will be much better, also I would use an SU carb to run the engine in with anyway.

[oltonlad]

I would put a decent head on it first as well, the 544 will not perform very well with a standard valved cylinder head.

[karlnz]

why do you think its over carbing? ive been reading alot of vizard and it seems like a reasonable choice according to him... i'd expect about 80bhp out of this motor? what do you think?  the thing is that i will actually have to go and find a Hif44 (tricky here in nz)
 and why would you use a different carb to run in a motor than the one you intend to use

 

appreciate the post sorry to kick holes in it but im just interested in the what and the why of carb choice etc etc

 

thanks

[oltonlad]

why do you think its over carbing? ive been reading alot of vizard and it seems like a reasonable choice according to him... i'd expect about 80bhp out of this motor? what do you think?  the thing is that i will actually have to go and find a Hif44 (tricky here in nz)
 and why would you use a different carb to run in a motor than the one you intend to use

 

appreciate the post sorry to kick holes in it but im just interested in the what and the why of carb choice etc etc

 

thanks

that's ok, the dellorto and weber carbs are very fussy, and often like to spit fuel out of the back of them, it would not be my choice to run an engine in with a side draught carb, if the carb does decide to overfuel then you will petrol wash the bores and the piston rings will never seal, an SU HIF44 will give you more power than a weber or dellorto 40 with that spec of engine.......as well as much better fuel consumption. 

[Paul Wiginton]

Think of it this way - the engine will only ever breathe through one of the two chokes of a Weber or Dellorto at a time and yours has 40mm chokes. a HIF44 has a 44mm choke so the Dellorto will give less than the HIF but it will probably use more fuel and will make the car harder to drive

[karlnz]

ah thanks, i hear you re head... it needs better flow, becuase the power is higher up the rpm range?

 

what do you mean by 'the back'... the exhaust?

 

good point re the petrol washing of the bores too....

 

the thing about these carb subjects is... you hear alot of things along the lines of 'twin carbs are hard to set up and go out of ballance' and 'webber carbs use too much fuel' but then you start reading vizard for exampe, and it right there in black and white that all carbs work correctly if theya re correctly configured..... why would webber/dellorto carbs have such a long term historical relationship in competetive motorsport with the a series if they were fussy and un economical (obviosuly economy is not an issue, they they are run at max rpm) just thinking out loud.....

[karlnz]

Think of it this way - the engine will only ever breathe through one of the two chokes of a Weber or Dellorto at a time and yours has 40mm chokes. a HIF44 has a 44mm choke so the Dellorto will give less than the HIF but it will probably use more fuel and will make the car harder to drive

hola thanks for the post.... why will it only be breathing through one at a time?...

[Paul Wiginton]

Because only one cylinder is on an induction stroke at a time - therefore it only breathes through one choke at a time

 

There really is nothing wrong with the twin chokes - I use a 45 Weber myself and all this going out of tune talk is just rubbish - they dont, same with twin SU's. This is from my 25 years experience of playing with them on Minis and setting them up on DB4s DB5s and DB6s for nearly aslong.

My point is the HIF would probably be better suited to your engine

Edited by Paul Wiginton, 18 August 2013 - 08:11 AM.

[karlnz]

what spec do you run the webber on?

[Paul Wiginton]

A full on race engine

[karlnz]

ok so its looking like a nice big sigle su (i just need to find one in new zealand)!

 

okay so im defiantly goign to take the advice and swing towards to su... but im really interested how these things work, and im still wondering why the Dellorto wont be suitable? any other reasons why you wouldnt go there?

[Paul Wiginton]

Really just that the SU has been proven to be better upto 90bhp than anything else

[karlnz]

right then.

 

ok this is just hypothetical now becuase im interested, but if you were running something 100+ bhp how would you base your decision on wether to go for a 40, 45, or 48... is it the final power output of the engine, or where you want the maximum power?

 

hey im sure i saw your sprint in a magazine years ago, 9/10 years ago?

 

karl

[oltonlad]

right then.

 

ok this is just hypothetical now becuase im interested, but if you were running something 100+ bhp how would you base your decision on wether to go for a 40, 45, or 48... is it the final power output of the engine, or where you want the maximum power?

 

hey im sure i saw your sprint in a magazine years ago, 9/10 years ago?

 

karl

I don't think that there is an A series engine on the planet that would warrant the use of a 48 weber, the 40 is a waste of time on a mini, the 45 is good for most applications over about 80BHP...........with your spec of engine I would hope to achieve around 65-70bhp with a standard head, the A series loves to breathe and it just cant do that with a standard head........it doesent matter what cam you chuck in it......if it cant breathe then it wont perform.