36 replies to this topic

[JonnyAlpha]

Hi, having seen a Webber 40 pop up on FB market place, I now find myself considering fitting a Webber to my current 1310 engine upgrade (not finished yet, link at the bottom of this post).
This has led me into a very complicated area of research to identify whether the 40 DOCE will suffice or whether I need a 45. Then on reading Vizards Bible I started looking at Webber 28/36 Carbs and the web of confusion / research to make an informed decision widens.
My engine is based on a 1989 Mk 2 Metro 1275.
Bored to 1310
+40 Heploite Pistons
AC RS Cam
Non Vernier Duplex Timing Gear
12G940 head with chambers taken out to 24 ish cc to achieve CR of 9.75:1 (not yet finished.
Standard or ACs 1.3 Rockers
Metro Valves 35.6mm and 29.2mm (Inlet and Exhaust)
MG Metro 65D electronic ignition
RC40 (not bought a manifold yet)
Should produce about 80-85lb torque (poss more), from what I recall with this cam setup.
Having spent the morning reading Chap 2 and 3 bits on carbs in Vizards bible, I am a bit more up to speed, but still confused.
Fig 7.14 suggests a main Venturi Dia of around 29 - 32mm for a single cylinder of 327cc (1310/4) at between 6000 - 6500 RPM. Which will be absolute max RPM.
This suggest a 40 DOCE.
However fig 7.15 suggests for an engine output of 85HP a Venturi of 34mm which on the previous page suggest switching to a 45DOCE. However it does say stick to the conservative side as fitting a smaller Venturi by even a couple of mm has little or no effect on peak torque and will only reduce top end by 2-3BHP.
So suggests even if I achieved 90HP a 40DOCE with a 33mm Venturi should be good.
I am modifying my head myself as I just cannot afford moser head modding prices, I understand that this will mean I am not going to get the best out of my engine yet, but hey ho.
I have also read several threads where a 40DCOE has been used very successfully on even larger higher performance engines than mine.

So the question - get a cheaper 40DOCE or try and pick up a 45DOCE or heck grab an even older 28/36 and stick a hole in the bonnet (ye ha).
We have a classic car garage here in ND who is apparently a Webber dealer with a RR so I’ll tap his thoughts too.
I also appreciate I need a good manifold and with a 40 or 45 DOCE this will mean a bulkhead box.

Any learned experiences advice will be appreciated.
Also some advice on costa involved e.g. manifold., swapping out parts for the carb, filters etc would help the decision.

P.S The phrase “Speed is a question of money, so how fast do you want to go?” Is not where I am headed!!

Edited by JonnyAlpha, 31 May 2021 - 11:25 AM.

[whistler]

You don't need a hole in the bonnet for a 28/36 DCD. I use one of these as a first start on a rebuild nowadays but used to run a 997 with a 544 cam many moons ago. Very reliable, economical if just 1st choke is used.

 

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[The Principal]

id stick with an SU its a good build but not a fire breather

[The Principal]

oops double post....

Edited by The Principal, 31 May 2021 - 11:33 AM.

[cal844]

Su HS4 all the way, easier to set up and less expensive for parts

[nicklouse]

Having run many carbs on a 1380 with a 286 cam back in the 80s ranging from a 40 - 45 DCOEs and 28-32 DCDs and single and twin SUs guess what carb I would fit?

A Single HIF44 on a well sorted inlet manifold with standard inlet housing with KN element and Calver mods to the housing.

[JonnyAlpha]

Having run many carbs on a 1380 with a 286 cam back in the 80s ranging from a 40 - 45 DCOEs and 28-32 DCDs and single and twin SUs guess what carb I would fit?

A Single HIF44 on a well sorted inlet manifold with standard inlet housing with KN element and Calver mods to the housing.

Interesting- I thought there would be more leaning towards the Webber considering it is supposed to deliver more power than an SU and stay in tune longer.

But in answer to the question 40 or 45 for this build?

[Tones61]

Having run many carbs on a 1380 with a 286 cam back in the 80s ranging from a 40 - 45 DCOEs and 28-32 DCDs and single and twin SUs guess what carb I would fit?

A Single HIF44 on a well sorted inlet manifold with standard inlet housing with KN element and Calver mods to the housing.

Interesting- I thought there would be more leaning towards the Webber considering it is supposed to deliver more power than an SU and stay in tune longer.

But in answer to the question 40 or 45 for this build?

45 Weber,36 mm chokes,long inlet,either alloy or steel, 6 inch minimum

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[Tones61]

^^^^^^
Mines 1380,
Slark head,
12/1 comp,
Newman 300 cam,
45 on long alloy inlet,polished underneath,
Big bore lcb,
Maniflow,
Alden red dizzy,
115 @flyw

[nicklouse]

 

Having run many carbs on a 1380 with a 286 cam back in the 80s ranging from a 40 - 45 DCOEs and 28-32 DCDs and single and twin SUs guess what carb I would fit?

A Single HIF44 on a well sorted inlet manifold with standard inlet housing with KN element and Calver mods to the housing.

Interesting- I thought there would be more leaning towards the Webber considering it is supposed to deliver more power than an SU and stay in tune longer.

But in answer to the question 40 or 45 for this build?

 

It can not give any more power than an HIF44 unless there is a restriction.  Look at a rover V8 what carbs?

 

you will see worse fuel economy with the Weber. You may see slightly quicker pickup as the accelerator pump is just that. While the meters the correct amount of fuel on acceleration.

 

in answer to your question neither. I see nothing to warrant the need for a Weber.

 

again don’t get me wrong. I love Weber’s. 

[alex-95]

 

 

Having run many carbs on a 1380 with a 286 cam back in the 80s ranging from a 40 - 45 DCOEs and 28-32 DCDs and single and twin SUs guess what carb I would fit?

A Single HIF44 on a well sorted inlet manifold with standard inlet housing with KN element and Calver mods to the housing.

Interesting- I thought there would be more leaning towards the Webber considering it is supposed to deliver more power than an SU and stay in tune longer.

But in answer to the question 40 or 45 for this build?

 

It can not give any more power than an HIF44 unless there is a restriction.  Look at a rover V8 what carbs?

 

you will see worse fuel economy with the Weber. You may see slightly quicker pickup as the accelerator pump is just that. While the meters the correct amount of fuel on acceleration.

 

in answer to your question neither. I see nothing to warrant the need for a Weber.

 

again don’t get me wrong. I love Weber’s. 

 

I was just about to write pretty much the same as this, I've never driven a car with a weber fitted but from what I've heard they guzzle fuel and don't give much more power, Someone I knew swapped from a HIF44 to a weber and gained 1 or 2 bhp.

[timmy850]

Weber’s are cool. They sound awesome. They have snappy throttle response. They may use more fuel than an SU - but honestly who cares. If you tune them properly with the same air fuel ratio they will use pretty much the same amount of fuel

You don’t own a mini because it’s the most sensible car. You buy them because they’re fun, so make it exactly the way you want it

I have a Dellorto DHLA40 on my mini. It’s easy to tune & looks and sounds great. I didn’t want to cut the firewall on my Mk1, so I’ve used a redline manifold (not the swan neck) and a 90degree speedo drive. These manifolds have been able to get over 100hp so it was more than fine for my car.

I think for your spec you’d be better off with a 40mm. My friend had a 1310 with a similar spec and the 40 worked great. There’s also a great book by Des Hammil - how to power tune Weber / Dellorto carbs which gives lots of good tuning advice.

[Cooperman]

Having had Minis with a variety of SU's and sometimes a Weber, plus Ford Cortinas and Escorts with twin 2-choke webers, I can't see the benefits of a Weber over either one single or a pair of SU's on a Mini.

Of course, if the aim is to wring as many bhp out of a race Mini engine as possible is the aim, a pair of split webers as fitted to the 'works' rally cars and subsequently to race Minis will gain a bit over even twin HS4's or 6's, but on a road car the difference will not be significant, althought he cost will!

The limitation is not normally with the carb(s), but with the ability of the head/cam combination to flow mixture in and exhaust out. The quality of the head flowing will determine how easily the mixture can get in and the cam will deternine when it gets in and for how long. All the crb(s) need to be able to do is not to restrict this flow at fully open throttle settings. Even a pair of HS2's with only 32mm choke sizes will flow sufficient mixture for an engine up to around 80 to 85 bhp. Flowing the carbs will improve them even more.

Buy, a Weber does look nice and if money is not an issue you will lose nothing else by fitting one. By the way, fitting a twin-choke 45 DCOE equates to fitting a pair of HS6's. I had a 1330 cc 'S' with twin HS6's. but it went no better than with twin HS4's and probably no better than with a single HIF44 on a really good inlet manifold.

[JonnyAlpha]

OK I get it, general feeling is that in terms of power there is no real difference between a Webber and an SU, however I am not in this for all out power (heck I've been driving a 998 HLE for the past 4 years!!

I also understand that the Webber will cost more.

 

However, they look fantastic and sound awesome!!

 

So should (if I decided to get a Webber) get a 40 DCOE or a 45 DCOE.

 

I am currently in line for either, but the 40 is old and looks like all the linkages are missing? (more cost)

Here is the 40 DCOE (£170):

 

 

 

And here is the 45 DCOE £325 (New and unused but signs of storage corrosion):

 

 

 

 

What do you reckon?

Edited by JonnyAlpha, 01 June 2021 - 09:40 AM.

[JonnyAlpha]

 

 

Having run many carbs on a 1380 with a 286 cam back in the 80s ranging from a 40 - 45 DCOEs and 28-32 DCDs and single and twin SUs guess what carb I would fit?

A Single HIF44 on a well sorted inlet manifold with standard inlet housing with KN element and Calver mods to the housing.

Interesting- I thought there would be more leaning towards the Webber considering it is supposed to deliver more power than an SU and stay in tune longer.

But in answer to the question 40 or 45 for this build?

45 Weber,36 mm chokes,long inlet,either alloy or steel, 6 inch minimum

 

 

My engine is not quite the beast that yours is

Looks like the 40 DCOE I linked is missing the linkage kit and the fuel banjo - I wonder what else?

Edited by JonnyAlpha, 01 June 2021 - 09:41 AM.