6 replies to this topic

[spaulwill]

Hi folks I have a 1293 running on road/rally cam, 4:1 FD, Aldon Yellow dizzy, lightened flywheel, duplex chains, Mainflow exhaust system (LCB/RC40) and a reworked original S head. I currently have HS2 1 1/4" twins with K & N on them with M needles and red springs. I also have a set of 1 1/2" which have been rebuilt on an osselli manifold. I would like some opions on what the thoughts are on 1 1/4" or 1 1/2" would there be any benefit. The car is to remain period so I don't want to fit 1 3/4" single. I know the works 1275s had 1 1/2" twins. If there is benefit I will swap but if not I will leave things as they are. Thanks

[KernowCooper]

looking at your spec on the engine twin HS2s may well be at there limit especially if there on a standard manifold which were not that good, I always thought 80-85bhp+ was HS2s and anything above HS4s.

[spaulwill]

Thanks Dave my decision made 1 1/2" it is

[Cooperman]

Definitely the HS4's for that spec.

[bmcecosse]

Yes - even on a standard 1275 the 1.25"  carbs are well beyond their limit.....  The 1.5" carbs on a GOOD manifold will make a huge difference. 

[spaulwill]

Thanks everyone, do you think an M needle on red springs would be a good start for rolling road, I know the works 1275 SU's used MME but not sure if these are available.

[KernowCooper]

Here is some information I have if its of any use.

Attached Files

•  HS4 1275s.png   17.01K   12 downloads
•  su_needle specs by car.jpg   71.63K   7 downloads

Edited by KernowCooper, 28 July 2013 - 06:46 PM.