Carb question

Post by **Bazzalucas** » Mon May 12, 2008 10:47 pm

Hi, all. I have installed a 1275 motor in my 1958 with a 948 engine. Is it feasible to use the 948 carb and intake, or should I stick with the dual carbs that came on the 1275 motor? Thanks for your input!

Post by **aupickup** » Mon May 12, 2008 11:15 pm

larger single carb is good , hif 44

Post by **Bazzalucas** » Mon May 12, 2008 11:34 pm

Hi, thanks, but...the carb I've got isn't an HIF. It says AUC 6070 on the side, and has a separate flota bowl on the side. I think it's original to the 948. Will that one be adequate?

Post by **alex_holden** » Mon May 12, 2008 11:44 pm

I would stick with the dual carb setup. The 948 carb and manifold would probably strangle the performance and you would have to find an appropriate needle for it too.

Post by **Pyoor_Kate** » Tue May 13, 2008 7:53 am

When I fitted the 1275 originally to my minor I didn't have the bits to make up the exhaust (nor airfilter), so it ran with the original carb and exhaust. Around town it was fine, but as soon as you got out on the motorway it was clear the engine was being strangled by the combination. It felt completely gutless above about 50.

Changing to a HIF44 and a larger bore stainless steel (it's whatever comes off an ital) made a huge difference to it.

Post by **bmcecosse** » Fri May 16, 2008 12:17 am

The single 1.25" standard 948 carb is far too small - but the twin carbs may attract insurance problems. An HIF 38 from a Mini would be good, although best is an HIF 44 and alloy inlet manifold from an MG Metro - this will be better than twin 1.25" carbs.

Post by **mike.perry** » Sat May 17, 2008 9:18 pm

Fitted twin 1.25 carbs to my 1275 MG instalation with LCB exhaust. Look traditional but a pig to balance. Probably easier to set up single HIF 44 carb which I am told will give similar performance.

Post by **wibble_puppy** » Sat May 17, 2008 9:22 pm

stoopid beginner's comment here but.... if increasing air flow in to the engine then ensure more air flow out of the engine too, otherwise you are more or less wasting your time. Bigger bore exhaust manifold and exhaust piping.

hope that's relevant and helpful! (I know nothing about 1275 engines

Post by **bmcecosse** » Sun May 18, 2008 9:51 pm

Exhaust pipe bore increase is not essential - but does help of course if you can afford it! Single HIF 38 (on good alloy manifold) will equate to twin 1.25" carbs, and single HIF 44 to twin 1.5" carbs.

Post by **Bazzalucas** » Sun May 18, 2008 10:37 pm

Okay, I must confess my ignorance: what does LCB stand for, and LCB as opposed to what?

Post by **bmcecosse** » Sun May 18, 2008 11:09 pm

Long Centre Branch - the 'sporty' version of an exhaust manifold. Standard cast iron ex manifold has all short branches - all pretty much same length. It's functional - but not made for easy exhaust flow ! LCB is tubular steel and all branches are longer than standard - but the centre one even more so. The two outer branches join together and continue down to meet with the 'long' centre branch a good bit further on - usually almost twice as long as the outer branches. Here's one that was on ebay recently -

Post by **bigginger** » Sun May 18, 2008 11:13 pm

Long Centre Branch - a 'standard' modified exhaust manifold.

Post by **Bazzalucas** » Mon May 19, 2008 12:02 am

Ah, yes!