1.2 8v on twin carbs

[Dirtydog1]

does anyone have any idea as to what sort of power a 1.2 8v engien running on twin 40 webbers would produce?

i also have a cam, and i going to get the head skimmed........or am i waisting my time lol

the engine is going in the back of my mini, i have all the engine parts inc the carbs and ignition system already, thats why i am thinking of using it.

any other suggestions as to gain more power from the 1.2 welcome.

or will it be total bollocks lol?????

[Stuart]

carbs + cam (depending on lairyness) and a goodsetup on a 1.2 I'd say will make 80ish bhp (assuming its a 1.2 carb head of course)

[mowgli]

stick a 1300 crank & rods into it. then you have a 1400 hi comp. engine. then think about head work & a cam....

if you stay with a 1200, you will be lucky to get much more than 70hp without spending big. with the crank mod, it will give about 85hp with a std head & carb. do the head & cam and you will be pushing 100+hp easy

[NOVA-KID-93]

i dunno what power they give out but my mates running a standard 1.2 8v carb engine on 40's and i must say it definately shifts, i also think it would be running around the 70-80bhp mark thats if the engine is standard apart from the 40's!!!

[crash_ndie]

think you will find that the engine will be over fueled with 40's on it. so you will have to jet them down, so i dont think you will get that much gain much more than 70 bhp. you can get that power form the 1.6 as standard an prob cheaper too.

[dellortotwin40s]

hi i run 40s on a 1.2 and they run ok they slightly overfuel but not much once they have heat up they run ok mine are running on bigger jets though. i reckon it will pull between 75-80 bhp

[Dirtydog1]

stick a 1300 crank & rods into it. then you have a 1400 hi comp. engine. then think about head work & a cam....

if you stay with a 1200, you will be lucky to get much more than 70hp without spending big. with the crank mod, it will give about 85hp with a std head & carb. do the head & cam and you will be pushing 100+hp easy

its a single point injection engine at the mo.
ive heard of the 1300 crack and rods mod before! sounds intresting. so do i use the 1.2 pistons still?

i already own a set of twin 40 webbers with the linkage and manifold for a small block.

what head work do you suggest? if i am to use the 1.2 head, can i get it skimmed down as far as it will go and gain compression that way? will a skimmed flywheel make it revvier?

cheers for the advice

[Stuart]

ewwww nasty square ported 1.2i head.... throw it in the bin, get a 1300/1200 head (or a 1.4/1.6 mpi head, better yet get the whole engine lol) on there

[Dirtydog1]

ewwww nasty square ported 1.2i head.... throw it in the bin, get a 1300/1200 head (or a 1.4/1.6 mpi head, better yet get the whole engine lol) on there

fraid so.
i have 1.6 sb block and a 1.4 se head also. could maybe make a combo from the lot?
the block needs pistons though

[Dirtydog1]

ive just been reading up, someone elsewhere has been told a skimmied 14se head on the 1.2 block with a set of 40s and a 285 cam will be around 100bhp??? true?

[mowgli]

ive just been reading up, someone elsewhere has been told a skimmied 14se head on the 1.2 block with a set of 40s and a 285 cam will be around 100bhp??? true?

with solid lifters, a serious porting job, it may be doable, but would be a very peaky power curve......

[Stuart]

with solid lifters, a serious porting job, it may be doable, but would be a very peaky power curve......


agreed. pulling 100bhp from a 1.2 is going to be hard, expensive work

[Sloth]

not with a t25 on it....

[Dirtydog1]

i realy want to make do with what ive got, im being ignorant i suppose, the 1.4 head i have is an se and has already been ported all the valves ground and seated.
if i get it skimmed down to the near maximum with the 40s on and the 285 cam and bolt it on the standard 1.2 block what do you think will happen? you guys seem to know alot more than me? at the end of the day its going to cost me 25 for a head skim and 10 for a gasket.

would it also be worth skimming the flywheel?

[Dirtydog1]

not with a t25 on it....

not on this one mate! trying to build up a little revvy lump on carbs to fit in the back of my newly bought mini! lol

[Sloth]

ahhh what bout a 1.2 16v on bike carbs? they rev well

[Dirtydog1]

not much between them and 40s tho is there?

[chimp007_uk]

agreed. pulling 100bhp from a 1.2 is going to be hard, expensive work

Stuart, Didn't you build a mental 1200???

As far as i remember, it never got finished.

[mowgli]

a 1200st from a mk1 would be a far better starting point compared to the later 1.2

[Dirtydog1]

a 1200st from a mk1 would be a far better starting point compared to the later 1.2

are the blocks/internals different or is it more down to the head?
im keen to use the 40s on it as they are just chilling in a box at the mo.

[greg1.4]

i have a HIGH spec 1.2..

the block is a 12ST, 1300 Lightened and Balanced Crank and Rods, ARP rod bolts,Blydenstein ported/big valve head (skimmed), Irmshcer Inlet manifold with BRAND new weber carbs, Pipercross socks, Kent AST1 cam (want to change to a AST2 though), Kent Vernier Pulley, 4-2-1 Manifold, Magnex full stainless exhaust system..

i am hoping for about 100bhp. it doesnt seam that fast out on the backroads, but it is running 16'' wheels and a 3.9 cwp also..but feck me it sounds awesome, revs to about 8.5k happily..(ask vaughanmc what she runs like lol )

would be chuffed if it made anything over that. cant wait til i get it on the rolling road..

[Dirtydog1]

cool, im planning on fixing this one in the rear end of a mini! lol
i just wanted something cheap easy and light weight! not to mention the fact that i have a tonne of bits just kicking around!

[Stuart]

i have a HIGH spec 1.2..

the block is a 12ST, 1300 Lightened and Balanced Crank and Rods, ARP rod bolts,Blydenstein ported/big valve head (skimmed), Irmshcer Inlet manifold with BRAND new weber carbs, Pipercross socks, Kent AST1 cam (want to change to a AST2 though), Kent Vernier Pulley, 4-2-1 Manifold, Magnex full stainless exhaust system..

i am hoping for about 100bhp. it doesnt seam that fast out on the backroads, but it is running 16'' wheels and a 3.9 cwp also..but feck me it sounds awesome, revs to about 8.5k happily..(ask vaughanmc what she runs like lol )

would be chuffed if it made anything over that. cant wait til i get it on the rolling road..


thats rather low spec :p lol but atleast yours runs :D

[greg1.4]

its a high spec 1.2 compared to most..

has other **** done to it, but god knows that..

[mowgli]

the 1200st is a large bore, short stroke engine that was designed to run on carbs, and has a good flowing head.

the later 1.2 is longer stroke, small bore & was designed with emissions & economy in mind, the head is not very good.

[matt_vaughan]

So a 12NV isnt a good base to use then?

[mowgli]

So a 12NV isnt a good base to use then?

not really.

[Stuart]

the NV is still short stroke as it was still a carb engine. its the ghey SPI's you want to avoid like the plauge

[matt_vaughan]

Well I have an NV in the car now, relatively good engine, so using that would be ideal. May be easier to build an engine from an ST though in the garage while I still use the car. I've put up a wanted for an engine anyway.

Seriously determined to do this myself now. Got a Kent AST1 and Vernier in the garage too, and a 4 branch. I'll take it for a rolling road readout at DayTuner afterwards to see what happens :D

[mowgli]

the NV is still short stroke as it was still a carb engine. its the ghey SPI's you want to avoid like the plague

the 12st is 77.8 bore, 62.9 stroke
the 12nv is 72 bore, 73.4 stroke
the 14nv is 77.6 bore, 73.4 stroke

the gudgeon pin diameters are different between the 12st and the later engines

[matt_vaughan]

So no go on the NV. Right, how about heads? We should get enough info together to make a guide (maybe)

I'm assuming heads are interchangable fine? Is it really necessary to have the pistons pocketed?