Fabricating a Weber Carburettor Manifold Flange

[Dave SParticipant @daves59043]

Low 12s is low 12 second runs on a 1/4 mile drag strip most likely.

The turbo metro hif44 was sealed and run blow through.

Long time since I tinkered with Minis, but Vizard had a lot to say about suck vs blow IIRC

Dave

[HillclimberParticipant @hillclimber]

I must admit that I am stuck, imagining how to rejet a DCOE at the back of that engine compartment? You could be in the position of a major, multiple dismantling exercise as you work through the possibilities – the world's longest rolling road session could be your record.

Might be worth reconsidering your choice, simply on that basis?

Cheers, Colin

[Dave HalfordParticipant @davehalford22513]

Here's a man to emulate with an A series, no photo of the original metallic green version. The only 1300 that had to run against cars 3 times the capacity.

[William Harvey 1Participant @williamharvey1]

Posted by Hillclimber on 22/01/2022 13:41:48:

I must admit that I am stuck, imagining how to rejet a DCOE at the back of that engine compartment? You could be in the position of a major, multiple dismantling exercise as you work through the possibilities – the world's longest rolling road session could be your record.

Might be worth reconsidering your choice, simply on that basis?

Cheers, Colin

So here's a Mini with an Eaton M45 SC fitted with an SU suck through:

So here's a Mini with an Eaton M45 SC fitted with an injection throttle body suck through:

And here's a Mini with an Eaton M45 or 65 SC fitted with a Weber DCOE suck through:

[Oily RagParticipant @oilyrag]

I'll repeat what I said earlier – A suck through system with an Eaton type charger is a poor application, the Eaton cannot tolerate fuel going through the rotors as it will wash out the rotor bearings. This will require the supercharger to be rebuilt on a pretty regular basis (1500 to 2000 miles). If you do go down this route then remember that this is an external compression machine and the manifolding down stream of the charger needs to be 'non restrictive' as the boost is generated downstream of the charger not within the charger (that is why it is called an external compression machine). Centrifugal chargers or taper rotor chargers are better suited to tight manifold applications as they are classed as internal compression machines. For a internal compression charger look for a Comprex or Rotex machine.

It amazes me that those pictures you show are remotely driveable with the volume of the induction system from fuel supply point to cylinder. Blow down is far better from every point of view.

You haven't said what you are going to do about strengthening the drop gear – any plans to address that problem?

Martin

[Nick WheelerParticipant @nickwheeler]

Posted by Oily Rag on 23/01/2022 18:59:33:

It amazes me that those pictures you show are remotely driveable with the volume of the induction system from fuel supply point to cylinder. Blow down is far better from every point of view.

Consider just how utterly crap the A-series is in standard form; it's next to impossible to make it worse

[Old SchoolParticipant @oldschool]

What hp are these blown engines making be interesting to see how it compares to my lads turbo mini with fuel injection.

[Oily RagParticipant @oilyrag]

Power specifics for naturally aspirated engines are generally very difficult to improve over a level of about 16HP/ litre / per 1000rpm. For forced induction that specific increases to around 25HP/ litre / per 1000 rpm (there are extenuating exceptions to this such as the 'qualifying' engines used in F1 in the 1.5litre F1 era which managed 60+ HP / litre / per 1000 rpm but only for 3 laps! ). Probably the best forced induction engine was the WW2 Napier Sabre H24 series 5 which managed a specific of 31HP/Litre/1000 rpm, this was considered as the pinnacle of the 'Hyper' aero engines. For 2 stroke engines you have to take into consideration the fact that the piston 'works' both above and below the crown so needs to be rated at twice the volume. A Wankel engine works on all 3 sides of the piston but is then geared to 2/3rds crank speed so needs a correction factor of 1.66.

The best 'A' series was the 970 'S' from 1965 – this was a short stroke unit which could be made to rev to 10,000 rpm and gave around 105BHP in race trim (an 850cc variant I built for a race car which ran in the Triplex Saloon car series was dyno'd at 96BHP at 9000 rpm a specific of 12.5 HP/ litre / 1000rpm ) – BL only made 5,000 of these as 'homologation specials' (worth a fortune if you have one ). I ran a 1275 (well 1310 actually) 'S' in rally trim in the late1960's with a Jim Whitehouse 'Arden' 8 port alloy head – fitted with 4 32mm Amal carbs. Given the car was a Group 'C' and was substantially lightened down to around 9cwt it performed sufficiently well to give an Escort Twin Cam or even a BDA Escort a good run for its money. The engine was giving about 130BHP; its 'transient' torque and the response with the multi carbs allowing short intake to valve head was vastly improved over the standard 5 port head, but the gearbox was always a problem even with straight cut de-speeder drop gears, TR bearings for the intermediate drop gear, and a full straight cut 'dog box'. Probably the major reason for my acute deafness now!

Martin

[Dave HalfordParticipant @davehalford22513]

Posted by Oily Rag on 23/01/2022 21:57:40:

I ran a 1275 (well 1310 actually) 'S' in rally trim in the late1960's with a Jim Whitehouse 'Arden' 8 port alloy head – fitted with 4 32mm Amal carbs. Given the car was a Group 'C' and was substantially lightened down to around 9cwt it performed sufficiently well to give an Escort Twin Cam or even a BDA Escort a good run for its money. The engine was giving about 130BHP; its 'transient' torque and the response with the multi carbs allowing short intake to valve head was vastly improved over the standard 5 port head, but the gearbox was always a problem even with straight cut de-speeder drop gears, TR bearings for the intermediate drop gear, and a full straight cut 'dog box'. Probably the major reason for my acute deafness now!

Martin

I remember that one Martin – respect.

[William Harvey 1Participant @williamharvey1]

Posted by Old School on 23/01/2022 19:43:13:

What hp are these blown engines making be interesting to see how it compares to my lads turbo mini with fuel injection.

Don't have the figures for the blow throughs, but this 1293 with a DCOE and Suck through Supercharger is kicking out about 150 – 160BHP apparently?

**LINK**

My Mini currently has a stock 998 HLE, which was about 34BHP out of the factory. The 1310 in its naturally aspirated form is forecasted to output 85BHP, a massive improvement (albeit not the same engine). Once the SC is on, it is forecast to output about 120BHP.

[William Harvey 1Participant @williamharvey1]

Posted by JasonB on 21/01/2022 15:33:41:

That would certainly give a smoother flow due to the longer transition from the Weber shape to the SC, ideally you would do a lot more shaping of the 40mm block. if you draw each have on either side of the block and then use the loft function of the CAD package that would give an idea. Assuming the extra 30mm does not put the intake end of the carb in the way of anything

Edited By JasonB on 21/01/2022 15:43:56

So I found a CAD file on the web for a DCOE flange. I have printed this and I can now use it as a reference to make a better one.

[Nick WelburnParticipant @nickwelburn]

Looking good, have you mocked it all up in the engine bay? Its going to be quite a tight fit.

[not done it yetParticipant @notdoneityet]

Its going to be quite a tight fit.

That is one I liked with my twin DCEO40 carbs on my 1650 Cortina, many years ago. Plenty of space under the bonnet!

[William Harvey 1Participant @williamharvey1]

Posted by Nick Welburn on 06/02/2022 09:37:34:

Looking good, have you mocked it all up in the engine bay? Its going to be quite a tight fit.

Not yet.
I still have to chop the Supercharger and then I’ll be able to put this 3D printer Flange up against it and work out exactly what needs to be modified. Then make the changes to the 3D file and re print, then mock up and test fit.

[Author]

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