1275 engine question

[mmjosh]

would a 1275 engine be ok with a 1098 carb and manifold on just for know

[bmcecosse]

Yes!

[mmjosh]

thanks bmc will it still have a good speed with a 4.22 diff in

[bmcecosse]

Yes!!

[Stig]

I remember Kate saying she ran her 1275 with the 1098 carb initially and said it felt a bit strangled on motorways. It won't harm the engine though if that's what you're worried about.

[hotrodder13]

i tryed running mine with a smaller carb and it run like a bag of nails, put bigger carb on and it glides now

[mmjosh]

i dont know what sort of carb to put on when i have the money whats the one with the dash pot in the middle of the big air filter

[RobMoore]

Josh, I have 1275 with a small carb HS4 i think its 1 1/2" and whilst my engine seems a little strangled at times I can easily cruise @70mph although the revs are a little on the high side so for me a diff change is my route fwd before I source a better carb/manifold etc.

[bmcecosse]

If you are going to modify the 1275 even slightly - fit the larger HIF 44 carb. If you want best economy - fit an HIF 38. But it will run on the standard 1098 carb - just won't give any more power than the 1098!

[mmjosh]

do i need a 3 branch manifold for them

[bmcecosse]

You don't 'need' a 3 branch manifold - but it helps! You can just use the standard manifold - with the inlet section cut off and thrown away. Again - that manifold and the small bore exhaust that goes with it will limit the power from the engine to not much more than 1098 figures - but it will run.

[mmjosh]

so can you tell me what will give the best power please

[bmcecosse]

Modified head with larger valves - camshaft upgrade - HIF44 on MG Metro inlet and 3 branch -long centre branch - exhaust manifold with large bore straight through silencer system! You can of course bore the engine out to a larger capacity - but the gains of this are much exaggerated - the power is usually limited by the ability of the cylinder head and the inlet system to pass air into the engine.

[mmjosh]

how about this http://cgi.ebay.co.uk/MG-Sprite-Morris- ... 4cf0a6699c

[bmcecosse]

Slightly worrying in that the description says it will fit both Sprite and Minor - which is not possible. It could be a Minor one, but hard to tell from that single picture. Minor LCBs are usually more swept away from the manifold flanges - not cutting back as these are. The price is right at the moment - but now you have alerted everyone to it.............

[Kevin]

Josh you should get a copy of this it will answer many of your questions, it also proves that an 1 1/2" carb is only overtaken in performance at speeds over 70mph by the 1 3/4" which uses more fuel.
http://cgi.ebay.co.uk/Tuning-A-series-e ... 2eaedfa4e2
If you decide to go down the route of maximum performance you can end up with an engine that is not nice to drive in town with a lumpy tickover, personally I prefer more torque with a smoother engine but the choice is yours.

[bmcecosse]

I did say earlier to only use the bigger 44 carb if modifying the engine. However - Rover deemed it necessary on all but the most basic 1275 Minis - and on the 1275 Marina/Ital......... If set properly - the larger carb doesn't use more fuel - that's the beauty of the SU carb - due to it's very clever variable choke it adapts to however much air the engine wants at any time and delivers the correct amount of fuel if the needle profile is correct of course. My 2 litre TR7 engine has twin 1.75" SU carbs, yet delivers almost 40 mpg when driven reasonably - ie at the speed limits!

[MarkyB]

at the speed limits

Did you let "her indoors" drive it then?

[Kevin]

If set properly - the larger carb doesn't use more fuel

Well that contradicts your own posting

If you are going to modify the 1275 even slightly - fit the larger HIF 44 carb. If you want best economy - fit an HIF 38. But it will run on the standard 1098 carb - just won't give any more power than the 1098!

Well a few years ago I had a 1275 fitted with a Minor 1 1/4" and it developed quite a bit more power than the standard 1098 with a lot more pull up hills but was at its best when an 1 1/2" was fitted later on.

[mike.perry]

Have you checked your insurance premium before you modify your car?