16 replies to this topic

[BADM1N]

Hey guys,

 

Ive got a series of Qs re the weber 45s on minis.

Im a mini noob when it comes to the technical details so forgive any wrongful terminology lol

 

Ive recently got my hands on a 1340cc motor courtesy of one of my friends friend leaving the country. Came with it two carbs - twin SU's and a Weber 45 both complete with manifold etc. See pics.

Based on my uncles (a old school mechanic) instructions ive started bolting on the weber which he believs is superior to the SUs. Since my lack of techincal knowledge ive got the dilemma of which to install and so ive come to the experts!

 

My queries go:

 

1 - Weber 45 or Twin SUs?

2 - If Weber how to go around the vacum advance from the dizzy as the weber has no allowance?

3 - Electric fuel pump or standard mini mechanical? Fuel filter? Fuel regulator?

4 - anything else that may need doing with either setup feel free to adivse?
 

Ive got a bunch of receipts outlining the works etc carried out on the motor by the past owner, some makes sense to me others dont! Feel free to ask any details that you may need.

PS ill be using it for fast road purposes so not too worried with fuel consupmtion etc!!!!

 

 

 

 

 

 

Cheers guys, your help is much appreciated!

 

 

[Bungle]

you haven't said what you want from this engine

 

is it out and out power to brag down the pub or a nice engine to drive every day with good MPG ?

 

i know deli's have a vacuum take off and thought webbers being very similar did too

 

can you drill a take off into them ?

[BADM1N]

umm at this stage power

 

Not too sure about delis but the weber ive got doesnt seem to have any purposely built vacuum take off that I can see with my limited knowledge!! Ive been doing a bit of online reading and have seen that "Dellorto UK" do sell a takeoff bit as an accesory but not to sure where to fit - manifold or carb and if suit weber?

 

http://www.dellorto....artsectionID=59

 

Midget and Healey forums suggest either take off from manifold or replacing with dizzy without vacuum takeoff? Not too sure tho for my application

 

There is an exisiting bolt on each leg of the manifold which i could possibly remove and use as a takeoff spot?

[patricksouth]

I am fitting a 40 on mine and also interested in what to do with the vac advance....sorry to jump on The thread...lol

[The Principal]

You need to provide some more info about the engine, as a rule of thumb power modifications need to work in harmony with an end game in mind. From the pics that looks like an 11 stud head so what work has been done on the head i.e valve sizes, compression ratio, rockers etc. What camshaft, pistons are you running etc the more info provided will generate more feedback.

 

45 webers are very noisy (which some people like) and are suited to highly modified set-ups. To answer your question re vac advance, change the dizzy for an Aldon Yellow but again you need to consider any mods with respect to the overall engine design and balance. The down side could be you push all the power up the rev range creating a car thats very hard (and annoying) to drive around town. 

Edited by The Principal, 21 April 2014 - 09:32 AM.

[Bungle]

these are the twin deli 36's on my VW engine to help show where the van take off needs to be fitted

 

 

you can see the take off port just above the manifold on the same line as the throttle spindle and butterfly

 

 

this is the right hand bank carb on my engine and you can just see the vac take off blocked off, the 2 bit's sticking out that look like air take off's are balancing ports

 

[gazza01]

I have a 45 weber on my 1330 and I love it. You can remove one of the bolts on the manifold and get something to adapt it for the vacuum from a plumbing shop. You can just blank the vacuum off if you want to but I find it
better attached. You don't need a facet fuel pump to run the carb either, keep the mechanical one it will supply the carb no problem and you don't have any safety issues that you would with a facet. I manage 116bhp without a
facet. You will need a fuel regulator set at 4psi, they are cheap and a doddle to fit. Go with the Weber mate,
you won't go back to SU's if it's power you want, once you hear the roar and feel the extra grunt. Then once its tuned properly, (which you MUST get done on a rolling road) there is no more faffing about with dashpot oil and
needle selection and main jets becoming worn etc.
When the Weber is tuned and jetted properly that's it done. You don't have to touch it again.

Edited by gazza01, 21 April 2014 - 03:57 PM.

[KernowCooper]

You need vacuum advance on any road car, unless its a full race engine in which case it will have a totally different distributor curve to suit. Regards to extra grunt from a weber, setup correctly there will be little difference between a pair of SUs of 1 1/2" (yours in the picture by the way are 1 1/4s and would restrict th bhp on a well sorted 1330) and a weber 45 except at the very top end of the rev range. Check Vizards book on the graph and its only a few bhp were talking about.

 

So back to your question it depends on what the spec is of your engine, if its built to 1275s spec and about the same BHP (75) then the SU 1 1/4s will be ok and fitting the weber will do little, if on the other hand your motor is built and your expecting 100bhp then the weber would not be restrictive like the little SUs

 

The vac take off is quite important as if its sited in the inlet manifold then its subject to a higher vacuum then if its sited slightly behind the butterfly as per SUs and in Bungles Dellortos above. They started fitting later cars with the vacuum takeoff in the manifold for emission reasons as at a given rev it produced more vacuum advance which was a attempt to clean up emmission readings. The problem with it being in the manifold is induction pulsing which upsets idle and the sportier the engine the worse it becomes. Your problem is the Weber was sold as a racing carburettor and is not drilled for a ported vacuum take off, which is only there to aid economy.

[patricksouth]

Ok so vac is needed so what is the best option tap the manifold or try and get one before the butterfly.....again sorry to hijack the thread but in doing mine this week?

[KernowCooper]

I'd be inclined to try a vacuum take off in the manifold rather that try and drill a port in the webers body Patrick, and then see if it pinks on the transition from cruse to power initially, I searched the web and they all advise against drilling the weber body. whats the spec of your engine by the way and what distributor do you have now?

Edited by KernowCooper, 21 April 2014 - 09:03 PM.

[BADM1N]

You need to provide some more info about the engine, as a rule of thumb power modifications need to work in harmony with an end game in mind. From the pics that looks like an 11 stud head so what work has been done on the head i.e valve sizes, compression ratio, rockers etc. What camshaft, pistons are you running etc the more info provided will generate more feedback.

 

45 webers are very noisy (which some people like) and are suited to highly modified set-ups. To answer your question re vac advance, change the dizzy for an Aldon Yellow but again you need to consider any mods with respect to the overall engine design and balance. The down side could be you push all the power up the rev range creating a car thats very hard (and annoying) to drive around town. 

 

 

You need vacuum advance on any road car, unless its a full race engine in which case it will have a totally different distributor curve to suit. Regards to extra grunt from a weber, setup correctly there will be little difference between a pair of SUs of 1 1/2" (yours in the picture by the way are 1 1/4s and would restrict th bhp on a well sorted 1330) and a weber 45 except at the very top end of the rev range. Check Vizards book on the graph and its only a few bhp were talking about.

 

So back to your question it depends on what the spec is of your engine, if its built to 1275s spec and about the same BHP (75) then the SU 1 1/4s will be ok and fitting the weber will do little, if on the other hand your motor is built and your expecting 100bhp then the weber would not be restrictive like the little SUs

 

The vac take off is quite important as if its sited in the inlet manifold then its subject to a higher vacuum then if its sited slightly behind the butterfly as per SUs and in Bungles Dellortos above. They started fitting later cars with the vacuum takeoff in the manifold for emission reasons as at a given rev it produced more vacuum advance which was a attempt to clean up emmission readings. The problem with it being in the manifold is induction pulsing which upsets idle and the sportier the engine the worse it becomes. Your problem is the Weber was sold as a racing carburettor and is not drilled for a ported vacuum take off, which is only there to aid economy.

 

Hey guys,

 

Have attached the receipts that came with the motor as im not too sure of the info, if you could highlight the key points it would be grt!!

 

[BADM1N]

I have a 45 weber on my 1330 and I love it. You can remove one of the bolts on the manifold and get something to adapt it for the vacuum from a plumbing shop. You can just blank the vacuum off if you want to but I find it
better attached. You don't need a facet fuel pump to run the carb either, keep the mechanical one it will supply the carb no problem and you don't have any safety issues that you would with a facet. I manage 116bhp without a
facet. You will need a fuel regulator set at 4psi, they are cheap and a doddle to fit. Go with the Weber mate,
you won't go back to SU's if it's power you want, once you hear the roar and feel the extra grunt. Then once its tuned properly, (which you MUST get done on a rolling road) there is no more faffing about with dashpot oil and
needle selection and main jets becoming worn etc.
When the Weber is tuned and jetted properly that's it done. You don't have to touch it again.

 

 

Ok so vac is needed so what is the best option tap the manifold or try and get one before the butterfly.....again sorry to hijack the thread but in doing mine this week?

 

 

I'd be inclined to try a vacuum take off in the manifold rather that try and drill a port in the webers body Patrick, and then see if it pinks on the transition from cruse to power initially, I searched the web and they all advise against drilling the weber body. whats the spec of your engine by the way and what distributor do you have now?

 

 

 Hey Patrick, thats absolutely fine, the more the merrier!!

 

So is it better to head down the replacing dizzy with Aldon yellow as suggested by ThePrincipal or simply taking vac takeoff from manifold? Any key advantages? I did a search for an Aldon Yellow dizzy on minisport and they are rather $$$$, if not really needed id love to avoid lol

 

Also Gazza01, how do i check if my weber is jetted and setup correctly for my motor?

[patricksouth]

So im running a 1380,266 cam,stage 3 head,double valve springs,lightened and balanced fly and crank and now running a 65dm4 dizzy with vac takeoff....well my plan was to tap the blanking cap for the servo off and run that until i can afford either a megajolt or mappable dizzy...

[Bungle]

taking the vac from the manifold wont work

 

take for example your going down hill with your foot off the throttle, a vac port on the manifold will see a lot of vacuum as the pistons try and suck air in but the butterfly is closed

 

where as a vac port on the carb in the same situation will see little vacuum as the throttle butter fly is blocking it

 

now as you reach the bottom of the hill and start to put your foot down a vac port on the manifold will see the  vacuum drop a little as air can now be sucked in

 

where as a vac port on the carb in the same situation will see the vacuum increase as the throttle butterfly isn't blocking the vac port and more air is being sucked into the engine  

[The Principal]

Hi - looking at that list it appears to be a modest set up similar to the MG Metro spec, with that in mind keep the weber in the garage for a future upgrade and use the SU's and your Vac advance problem goes away. Looks like a thorough rebuild from the comprehensive receipts should be nice to drive round town.

 

You can run a weber without Vac advance by changing to a Yello dizzy or ECU you can pick them up second hand but ... looking at your spec the weber is too big it would be much more enjoyable to drive with the SU's

Edited by The Principal, 22 April 2014 - 07:45 AM.