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 Question regarding weber carbs.....

 Created by: TDirkdiggler007
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 Posted: Jan 24, 2023 05:17PM
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"......Off course twin webers will not fit a five port head, unless split.."

Unless your 5 port was modded by Bill Quine ;) ..... But then I suppose you could argue that they were really 7 ports..

Cheers, Ian

 Posted: Jan 24, 2023 04:04AM
 Edited:  Jan 24, 2023 04:06AM
TK
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AU
Not correct, a 'big hole' doesn't need to be cut. Choose the manifold wisely Off course twin webers will not fit a five port head, unless split

 Posted: Jan 24, 2023 04:01AM
TK
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AU
A Weber 45dcoe is for flat out performance on a very modified 1275. Do as I do, either a nice HS6 SU (OA6 needle) or a set of brand new HS4s. That single HS6 will provide enough go for you.

 Posted: Jan 21, 2023 03:10PM
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The answer to your question, as the posts above say in more words.... .NO.

Paying someone who knows what they’re doing (which may be difficult depending on where you live) to tune what you have will more than likely produce a better result than that proposed by your current mechanic.

“Dual carbs” are not difficult to tune (if you know what you’re doing).. And you’re not getting dual carbs anyway - you’d be buying a two barrel carb. You can fit dual Webers to a Mini but you will need at least another zero on your estimate.

Go and get a copy of David Vizard’s “Tuning the A Series....”. That will answer all your questions ...and explain the options ..in 300 pages or so.

Cheers, Ian

 Posted: Jan 21, 2023 05:59AM
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CA
AMEN to what 6464s has written.

Did your mechanic mention the firewall may also need to be modified for clearance? That means a big hole and a metal box right where your speedometer probably sits. It would have to move too.

You mention you have a stock carb. Can you be more specific an say what you have?
HS4 (HS38)
HIF4 (HIF38)
HS6 (HS44)
HIF6 (HIF44)

With the right tuning a HS4or HIF4 can fuel a 1275 sufficiently. An improved air filter system may help, though the carb tuning will need adjusting.

If you go bigger to a HS6 of HIF6, it would do well too, but the rest of the engine's breathing needs to be improved. The intake manifold needs to be sized for the bigger carb and the entire exhaust system from the head out needs to be optimized for the engine size and state of tune. A properly sized exhaust actually aids intake/power as it helps clear the cylinders of combustion products by scavenging, which tends to leave a reduced pressure in the cylinder when the exhaust valve closes and the intake begins to open. Too small an exhaust and you have excessive back-pressure, Too big and the scavenging effect does not work well.

In between the intake and the exhaust lie the valves. An older stock 1275 may need larger intake valves to improve breathing. That usually means an up-rated head. Then you need to actuate the valves better. An older stock 1275 engine probably has a fairly conservative road cam. An up-rated cam modifies the timing and duration of when the valves open and close, for better power but worse fuel economy. High-lift rockers do open the valve further, but then you run the risk of them contacting the pistons = very not good. If not, you will likely need up-rated valve springs or you run the risk of the valves not closing quickly enough, resulting in valve float.

So there's better places to spend your money than on twin Webers. And you can do it incrementally.

My otherwise stock 1275 A+ high compression engine breathes quite nicely with a HIF44 on an alloy intake manifold and a Cooper Freeflow exhaust header connected to a RC40 exhaust system. The stock head has slightly larger exhaust valves and the cam is stock - designed for the displacement and valving. It also make the right noises!

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jan 21, 2023 05:14AM
 Edited:  Jan 21, 2023 09:40AM
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First, you have to ask yourself "what is my goal?" Is it to go faster, reliability, getting it to start. Just dumping more gas into the engine is not going to be the solution. If you want to go faster, drive it in 3rd gear. Step on the gas pedal. There will be plenty of power for you to get yourself in trouble. If racing, you want the engine to breathe better at higher RPMs, change to 1.5 rockers and step on the gas pedal. There will be plenty of power to go off road. If you want to be competitive, open your check book.

Blasting down a straight road with the pedal floored is fun And that is your thing, then do it in a lower gear. Driving fast on curving road, do it in a lower gear, you'll find that you can easily over drive you grip.

Second, if $1500 is absolutely meaningless to you then it's a starting point. If you got something else going on, then it's best to address those issues, like poor starting, etc.

The people who choose to do engine swaps or add other developments ( turbo charging, twin cams, etc. ) in the pursuit of more power find they exceed the four TINY contact patches between them and the road for power and stopping. With the large influx of HP, it may make the mini undriveable or less fun. Driving the smaller engine minis are a lot of fun because you can floor the heck out of them. I do prefer the 1275 engine for their torque. It all depends how you drive should determine if the money is going to be well spent, not being told by a mechanic who does not own one. 

 Posted: Jan 21, 2023 01:46AM
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I have a 1969 Australian built Morris mini that has a 1275 engine with a stock carb. My mechanic tells me I should put a dual Weber carburetor to get max performance and horsepower out of the car. Would I really feel the gains in HP and performance that could justify spending $1400.00USD for Parts/installation and would it be worth the cost? Iv'e heard dual carbs can be a headache with tuning and adjusting.