14 replies to this topic

[all4sreturns]

Hello all,

I am just putting together a rebuilt engine which will be 1340cc with 276 cam, stage 3 head, but was debating on carbs!

I am stuck between three or four options. Either twin SU carbs or a single weber (as these are similar in price).

If it's to be twin SU carbs, would people recommend the 1 1/2" or 1 3/4" twin SU's with this engine set-up. I've heard twins are better for more direct fuelling?

If it's to be a Weber, would people recommend a 40 or 45? I've been told a weber 45 is a bit too lairy for a road 1340 engine. Plus with Webers, there is the need for bulkhead cutting out, plus the manifold ends up curved not straight into the cylinder head due to lack of space under the bonnet.
Which of these options would you all recommend???

[bmcecosse]

I would go for either single HIF44 - or twin HIF 38s. You could consider twin HIF44s - but really a bit of an overkill for your mild engine spec. Weber 40 can't take big enough chokes to feed a 1340 engine - so would need to be the 45 - be ready to go deaf, and to spend all your money at the petrol pumps!

[Steve D]

Go for some bike carbs

[all4sreturns]

Cheers for the advice!

[bmcecosse]

" Go for some bike carbs " - My bike doesn't have 'carbs' - I have to make it go with my legs!

[WiredbyWilson]

I would go for either single HIF44 - or twin HIF 38s. You could consider twin HIF44s - but really a bit of an overkill for your mild engine spec. Weber 40 can't take big enough chokes to feed a 1340 engine - so would need to be the 45 - be ready to go deaf, and to spend all your money at the petrol pumps!

Afraid i must disagree with that, I run a weber 40 on my 1330 with Morspeed Ph3 cam and it runs fine. Even the weber tuning specialist didn't mention it not coping with big enough chokes!! From memory it runs 36mm chokes but I can't remember to be honest.

But have to admit the weber sounds truly awesome!! Not that deafening either and I have a weber box sitting an inch behind my dash!!

[camp freddy]

I would go for either single HIF44 - or twin HIF 38s. You could consider twin HIF44s - but really a bit of an overkill for your mild engine spec. Weber 40 can't take big enough chokes to feed a 1340 engine - so would need to be the 45 - be ready to go deaf, and to spend all your money at the petrol pumps!

surely if the carb / carbs are set up right they won't use any more fuel unless
you boot it, i'm fitting twin 1 1/2's ...... if your going oversize motor you won't
be too much bothered on fuel consumption..

[Sherlock]

I shouldn't really get involved with this because I always get into trouble, however, Camp Freddy is right, whatever carburettors you have, if they are set up correctly, they do not have to be incredibly thirsty. For example, there is no need for a 45DCOE to virtually blow fuel out of the exhaust, you need someone who has the knowledge to set it up right through the speed & power range. Too many people think that just chucking petrol into an engine will hide all the flat spots which should be dealt with more scientifically. We used to run a 1310 with a 45DCOE (noise, what noise? that was 'music' combined with a s/c box & LCB) in the good old days of leaded petrol & the inside of the tailpipe was always a nice pale grey colour. I don't doubt that a 40DCOE will work on a 1340, but it would certainly not have been as good as the 45 on the engines we used to use, ok on a 998 or 1098. Having said that, with regard to this particular engine, I can't comment as I have no idea what a 276 cam is, I only ever use the Leyland ST profiles. As far as SU's are concerned, I used twin HS6's on a 1330 with a 544 Cam, reworked head (stage 3 if you want to give it a number) they were stunning. I do not like HIF carbs I find them very fussy & more difficult to maintain for no advantage. Controversial, or what? (I better not even mention my icon of carburation, the split webers!)

Edited by Sherlock, 17 November 2009 - 12:26 AM.

[1380rich]

WEBBER BABY!! you'll never go back. fuel wise if correctley set up theres nothing in it!

[Cooperman]

For high air-flow at the top end a Weber is definately the way to go.
For low and mid-range, however, twin SU's are arguably better. The power delivered by either a Weber or SU's is still dependent on engine spec, engine build standard and accuracy of set-up.
It can be more difficult to set-up a Weber and it really has to be done on a rolling road or a dyno. Once set-up it will hold its tune. Twin SU's can be set-up without a rolling road to run reasonably, but a RR is needed to get the best power. They will need minor re-setting sometimes, although I can't remember the last time I had to re-set mine on my '64 'S' from the settings achieved on Peter Baldwin's RR about 3 years ago.

[m1tch]

*has Weber 40s from a race mini sitting on his desk* If carbs are set up properly it should be running optimally for the most power/torque, so if its running rich all over the rev range and drink fuel, it needs tuning

[Calum_Ward]

Hello all,

I am just putting together a rebuilt engine which will be 1340cc with 276 cam, stage 3 head, but was debating on carbs!

I am stuck between three or four options. Either twin SU carbs or a single weber (as these are similar in price).

If it's to be twin SU carbs, would people recommend the 1 1/2" or 1 3/4" twin SU's with this engine set-up. I've heard twins are better for more direct fuelling?

If it's to be a Weber, would people recommend a 40 or 45? I've been told a weber 45 is a bit too lairy for a road 1340 engine. Plus with Webers, there is the need for bulkhead cutting out, plus the manifold ends up curved not straight into the cylinder head due to lack of space under the bonnet.
Which of these options would you all recommend???

If you've got the money go for quad amal bike carbs. They range from £757.46 to £1197.29 on minispares and will probably do better than the su's or webers as they have an instant reaction time and not needing a piston to lift like the su's. They are also more reliable due to less moving parts!

[KernowCooper]

With the engine spec given by the OP I would say from experience and without cutting the bulkhead then a HIF44 would be the way forward.

[timmy850]

Hopefully he has made up his mind in the past 6.5 years 

[vx220]

Hopefully he has made up his mind in the past 6.5 years 

You know how these mini projects drag on, and are never really finished...