23 replies to this topic

[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

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.

 

what spec of head would you go for? valve sizes etc

[Paul Wiginton]

Well firstly bare in mind that the HIF44 can deliver enough fuel to supply a 300bhp turbo engine - I know the air is blown in but just talking fuel here.

 

Twin Su's are used to great effect upto around 130 bhp. Weber 45DCOE is really only of use over 120bhp where we start looking at tuned induction lengths as in longer manifolds and long trumpets - My Sprint has 11 1/2" induction length which cannot be achieved with SU's

 

Yes my Sprint was on the cover of MiniWorld in 2001

[KernowCooper]

The secret to power on the A Series is in a good modified head, without it your not going to benefit much from the cam you choose or the Carb, the SU Hif 44 is a excellent carburettor and can provide enough CFM for engines that produce 100bhp+

 

To get a weber/dellorto working at its best on a mini you'll need a longish manifold which will entail a modification to the bulkhead with the modification known as a weber box, to allow enough clearance, have you modified your bulkhead?

Edited by KernowCooper, 18 August 2013 - 11:07 AM.

[karlnz]

ok sorted i got one.

 

http://www.trademe.c...px?id=629020688

 

what needle/spring to you think i should start with gentlemen?

 

the head has actually had some porting done, but valves fairly std

 

i have a bdl here

 

i suppose the 544 will be needing a little more fuel

 

thanks

[KernowCooper]

It will depend on how well the whole combination of head/cam can flow air and its difficult other than a rolling road to get things spot on, but it can be done. When its all together try the BDL which is a standard 72bhp metro needle and work from there.

[Cooperman]

The key, as someone has said above, is the head. ideally with a 544 cam you would do well with 35.6 mm inlet valves and 30.5 mm exhausts, This with a fully and well gas-flowed head and a compression ratio of around 10.5:1.

Twin HS4 or a single HIF44 will work in respect of carburation.

Gas-flow the inlet manifold and match it to the head ports and do this with the exhaust manifold as well.

For the exhaust you need to have a 1.75" internal diameter exhaust pipe from the end of the manifold to the final outlet point with either one or two straight-through silencer boxes. RC40 or Maniflow are the best exhausts for power.

Also necessary will be a distributor with a modified advance curve. This is most important to get the ignition right as the engine accelerated. A lightweight flywheel will be needed and the entire engine will need to be balanced as the 544 will need to be revved to over 6500 to get the power which that cam can give. A centre main bearing cap strap is also advised to prolong main bearing life and reduce the possibility of the crank bending and eventually snapping.

[karlnz]

ok that was an excellent post much appreciated.

 

have 91 and 96 octane fuel here, what are you using in the uk?

 

can i i modify the curve in my lucas 45d, or should i be looking at another dizzy. Have electronic conversion on older A series unit (45d as mentioned)

 

Karl

[karlnz]

how would you explain the term 'gas flow' to someone? ...

[IainStallard]

ok that was an excellent post much appreciated.

 

have 91 and 96 octane fuel here, what are you using in the uk?

 

can i i modify the curve in my lucas 45d, or should i be looking at another dizzy. Have electronic conversion on older A series unit (45d as mentioned)

 

Karl

We use between 95 and 100 octane fuel here (95 being standard unleaded, and super unleaded ranging from 97 with BP Ultimate, to 100 with Shell V-Power)