best spec 1.2 ???

[5_door owner]

alrite then. i've got a mint condition 1.2 engine all on a stand an eveythin in my shed (not jus garden shed lol quite spacious)

so i want to build it up slowly then either use it for track or on road. i'm thinkin of a re-bore to around 1250-1300cc complete with pistons ect..

now over the course of rebuilding it im looking at spending about a grand on it probably more as it will be over the course of a few months(?year?)

so im just wondering what spec i'd be able to get for the money and what power figures.

please can you list all that can be done to the 1.2 and what parts ill be needing,

cheers fella's

(oh and btw i know i could just get another bigger engine and do it to that, but that'd be no fun :twisted: )

[Geth]

Im doing pretty much the same thing with mine. Don't let anybody tell you the 1.2 will be a waste of time. The fun is in trying to get 1.2 to go as fast as it possibly can.

This is what I'm doing at the moment.

Carb
Webber 32/34 twin choke carb. Very easy to come by. I think you need a 1.3 inlet manifold and an adapter to put them together. I got the whole setup all put together from ebay with a K&N air filter (Don't forget the K&N) for less than ?100. You could go for the DCOE twin 40 setup but that will cost around ?700.

Cam
Get a Kent or piper cam kit. A fast road cam will create higher lift and more power between 2000-6000 revs. A complete kit with springs and followers etc. will cost around ?250. Kent cams say you can get around 8-10 Bhp from an AST1 cam.

Outlet
Anything should be an improvment on the 1.2 exhaust system. You can either get a second hand 4-2-1 system of a 1.3 for around ?30 or a new 4-1 performance exhaust for around ?140. Although the 4-1 will require the rest of a 1.3 system anyway as the 1.2 exhaust won't match up.

As for the rebore, I don' know how much you can over bore a 1.2 by (I will find out in a few weeks when I get mine done). If you can take it up to 1.25 you should see a decent increase in power and your compression ratio will inrease aswell. With tthe combustion chamber in a 1.2 being 130cc you will get ratio of 9.6:1 (1250/130 9.61). You can then skim the head to get it up to around 10:1. These figures can be re-jigged depending on how much the engine is overbored but you should get the idea.

I don't yet know how much power you will get out of this as from reading other peoples's experiences, adding up the numbers never seems to be what you get. Give me a month or so and I'll get it on a rolling road to see what it's pulling and set up the carb.

Oh yeah. I'm not toosure how long a 1.2 will last on a track. You might blow it up in half the time it took to build it.

Sorry for the long winded reply but I'm pretty bored/stoned.

[Aragorn]

the 1.2 bottom end is just as strong as the 1.6 etc, its bearings rods caps bolts etc are all capable of the same power levels as a 1600 block and will me more rev happy since the stoke is shorter

for big power u'd need a set of 40's, 1.4SRi head (b+ mods preferably and compressoin ratio calculated and head skimmed to 10:1), 290-300degree cam, decent zorst system, high rev limit (7500-8000?) with arp rodbolts

you should be able to see the friendly side of 105bhp if not a tad more with higher rev limit

[burgo]

to make a 1.2 a 1.3 you use 1.4 crank and rods

[Aragorn]

why bother doing that when u could just buy a 1400 block for pennies

and its 1300 rods and crank and 1200 pistons makes 1403cc engine

[burgo]

why bother doing that when u could just buy a 1400 block for pennies

and its 1300 rods and crank and 1200 pistons makes 1403cc engine DOH :oops: i knew it was a combination of some of them to get something else lol

[Stuart]

so far "we" have a 1.2 head (no stupid EGR crap to fill in) with 1.6 diameter (but 1.2 length) valves cut in with 3 angle seats. (?300 ish) Head porting to suit the new cuts and some ramp porting to try and squeeze a few more CFM of air in due to gas speeds. Heavy skim. nearly 2mm off it lmao, some combustion chanber work but not much as it will upset things like the burn and compression ratio.

Cam we have a 285 piper but im binning it in favour of a 300+ cam BUT with the idea of revving to 8K and seeing as benji munched a set of lifters in not long, id look to fit solid lifters (?250 a set). I shall be looking into making my own. An AST1 is a bit of a waste of time if your gunning for "max power", but it might be a bit more driveable low down lol.

the bottom end had a 1mm overbore and some pocketing of the pistons to accept silly lift/duration cam. Also the pistons slightly intrude into the head. the gasket takes up this gap.

bottom end, rods were de seamed and shot peened oh and arp bolts, crank polish new bearings etc.

i belive the bottom end build wasnt far off ?900ish maybe more with full VAT etc.

it will be getting Twin 40's and a modified 4 branch exhaust


couple this to a CR gear box with a >4 final drive and you should see a rather nippy 1.2 lol

i did some rough simulations with GT Power at work and it claims about 130Bhp @ 8K but thats not including proper losses etc so id say more like 120 MAX on a good day with perfect conditions .

TBH if i get over 100 ill be happy.

with a webber 32/34 you WONT see more than about 80 unless your on an iffy RR lol

[w_wall_2001]

i know someone who has a 1.2 block overbored to fir 1.67 pistons and rings, diffrent crank etc, a 1.2 head with i think 1.4 valves, cam etc with twin 40's with a corsa spi rocker cover

[DrivingSpanner]

reving to 8k stu.... I wonder where you got that idea from!!!

[burgo]

so far "we" have a 1.2 head (no stupid EGR crap to fill in) which isn't to hard if you good witha dremel :)

stu i ended up doing the bolt method

[Geth]

1.3 Crank and rods. Didn't think of that, I like it. But if the piston is going to pretrude into the head, won't this give a huge compression ratio on a 1.2 head and how close are the valves going to get to the piston. I suppose the reall question is: can I get an extra thick gasket to lift the head slightly or will I need to put a different head on it? Or have I missed the point?

[alistairolsen]

youve missed a bit. If you take the length from the centre of the crank to the piston crown, it will stay the same, but with the 1300 crank and rods, more of it is crank and the rods are shorter, so they go further down. The blocks are all the same height, and the cranks are in the same place, vaux just used a smaller crank, and then longer rods to bring the piston back to the same place.

[dan-hipgrave]

reving to 8k stu.... I wonder where you got that idea from!!!

My old blue 5door used to be able to rev right off the counter lol it was my little showoff trick..

Its no wonder the headgasket went :lol:

[Geth]

Thanks alistairolsen. I couldn't get my head round it earllier. The stress from working overtime seems to fry my brain. Been down the pub and had a few pints and all is clear now. I think a bit more over time will be required for me to get the crank and rods though. Although I should save some money on getting the head skimmed as I've worked out that the new engine capacity on a 1.2 head will give roughly 10.9:1 compression anyway.

I've come to the conclusion that I work to be able to buy parts for my nova so I can get to work faster. What a strange world we live in.

[burgo]

actually in the haynes it ses they are 9.2:1

[alistairolsen]

burgo, read the thread, its a homebrew engine, no way in hell the CR will be in haynes. I still wouldnt use the 1.2 carb head, its only used to get a high CR on 14nv neinges cos its cheap, its really a fairly poor heab, go for a c14se head, biiger ports and valves. It will need a skim, as it will give alower CR, but thats cheap. Anyway, IMO 10.9 is a little high for carbs, dizzy timing and pump fuel.

[burgo]

sorry kent read lol or is that kent be assed. any way heres a useless fact for you the 14nv cam also has the highest lift of all standard cams :D

[Stuart]

the 1.2 head is one of the better heads actually :p

ok its not got the valve size that the 1.4 SRI/1.6gte/gsi has but its ports still flow damn well etc

10.9 is no where near enough for me ;o)

an overbore will increase CR for those of you not in the know

[alistairolsen]

if you can garuntee fuel quality, and mixture, and ignition timing ie fuel injection and pref one choke pre cyl, you can run sillly figures, IIRC some of the NA cossie boys are running 13.2:1. with carbs and dizzy however you can really top 11 on pump fuel

The 1.2 head is certainly better than the 14nv head, but it is a cheap upgrade and thats it, if your getting work done to it and going for a lot of power the 14se head is so much better

[Stuart]

did you not read what im doing/done? lol

same sized valves as the 1.6/1.4sri head etc blah blah

im not blindly modifying stuff lol ;)

[alistairolsen]

I never made any comment as to your modifications, infact I knew nothing of them, I simply stated the opinion that the .12 head in std form is a cheap way of increasing the sompression on a 14nv, but if you are prepared to get it skimmed the c14se head is so much better, both ports and valves wise.

IMO the 1.2 head really isnt worth using, as for twin 40s or TB's you will be wanting to use a round port manifold off a gte or gsi. I dont see why you have gone to the effort of fitting bigger valves, and their associtade valve guides, and somehow gone about accounting for the different stem lengths into and inferior head, why not simply use the 1400 head and get it ported properly??

The only disadvantage with the 1400 head is the lack of off the shelf manifold for single carbs. None of the others will fit without work.,This is naother reason why the 1.2 head is more commonly used.

IMO the 1.2 head is an ideal lo budget compression upgrade with better flow for single carb applications, and the 14se head is the best small block head for big ish power, esp if using 40s or TBs.

[Stuart]

hence why im ramp porting the 1.2 head ;) makes the a bit more round, BUT the gas tends to flow mostly round the top of the port where its round anyway.

the valves ar e"special" ones that are the same length as the 1.2 ones but with the 1.6 head size. the guides didnt need changing due to the stem being the same as the 1.2.

TB's on an 8V will make for a mega peaky engine that will probably be a biatch to drive under about 4K

i mean mine will be a total cow under about 3-4K due to large valves, small bore/valve ratio and the silly cam but hey the chokes on the carbs might be able to compenstate for that.

we used the 1.2 head to prove its doable and that most 1.4sri heads are a little tricky to get hold of.
IMO the 1.2 head with appropirate work is NO worse than a worked 1.6 head. you just need to have the nerve to do it etc. We also wanted to keep the head with a 1.2 casting on it ;)

[j1400]

No to be silly, but why spend hours modding a 8v head?? when you can just stick a 16v head on and get bigger gains?? esp if you're runnign TB's on it :wink:

[Stuart]

iu guess thats swings and roundabouts

youy'd need to convert the 8v block to take the cam tensioners etc. its not hard granted but it does cost

and then there is the effort of getting the ign sorted. is there a dizzy that fits the small block 16V head?

i was gonna go down the TB's 1.2 16V route lol but that idea got shafted at the stupid stupid cost

[j1400]

Well a dizzy mount could be fabricated seen it done on a x20XEV, but you could just use the std ign, then cut away the inj loom and put in the correct resitors, mount the TPS on the carbs, and the MAP on the vacum line. and leave the rest of it alone, and vola. you have a small XE ready for carbs. Been thinking abotu it to stick it in runabout nova.

:)

[Snowface]

in an ideal world a 1.4sri head is better, in standard form.

But how many C14SE engines/heads do you see around compared to 1.2's?

1.2 head is the best out of all the nova heads after the mpi ones.

make sure you at least put a 1.2 head on with a bit of work, don't keep the 1.4 head!

[alistairolsen]

yeah, there are a lot of 1.2s around, if you want to do it as a cheap tuning exercisa, but if I was putting money into porting work etc, it seems a little defeatist to start with an inferior casting, just to put bigger valves etc into it.

As for the 16v idea, with the cost of a complete 16xe engine, its really not worth it, either way you need cambelt, tensioners etc, but the 16xe comes complete with no machining needed, on injection.

[j1400]

You can pick them up for around the 100 mark. it depends what you want. a 1.6 xe on carbs will make 140 with no other work on it. so it costs more but you have to spend less for the same power. take it a step futher, and you get 285deg cams on regrind 160, verniners 160 and pocket the pistons, then you'll be looking at a reasonable 170-175bhp engine.

[alistairolsen]

I want to know where you find 16xe's for 100 quid mate?? about 250-300 normally, but its still a lot cheaper than buying a head and then fucking around to make it all work.

[Stuart]

nice to see youve bought lots of pessimism over form mig ;)

[j1400]

Just keep your eyes open really. Yeah they usually go for the region of 200-250, but you can always find a deal. there's plenty of MK3 astra dieing of rot now. there's a 1.4 16V on corsa sport at the mo fo only ?100 too.

[alistairolsen]

cool, I obviously need to look more. Im planning on breaking a vectra for mine as I want some other bits. Re pessimism, Im from RB originally mate, and agin, the prices were an opinion, just like yours. Just curious.

[Aragorn]

The vectra 1.6 16v units are X16XEL and im sure have different cylinder heads and different compression ratio to the corsa gsi unit (c or x16xe)

they certainly only make 100bhp vs the 109/106 or c/x16xe's

it MAY just be the mapping, but im not sure

[DrivingSpanner]

lets get one thing clear guys stu (camb) isnt spending all that money to have the fastest engine/car in the world of novas he's doing it to prove a point that a 1.2 can be made to go damn quick.

Yes it costs but would me more satasfying than just sticking a 1.6 GTE motor in and going the same speed....... plus it'll get some attention!!!

[j1400]

the C16XE runs a CR of 11:1 and has a different head design, although I can't say I can see it between that and a X14/16XE head. the inlet is also different and the exhaust down pipe seems different aswell.
If you are going to be flowing the head then it really doesn't matter much.

[Aragorn]

c16xe cant be 11:1????

i thaught XE stood for ~10.5:1 MPi

11:1 would have a different identification letter

[j1400]

Check your haynes manual then :lol:

[Aragorn]

lol thats at home and im not - i'll have a look when i get home tho

11:1 on pump fuel must mean the knock sensor is retarding like fuck

i should try some superunleaded and ecu reset i think

[j1400]

well 11:1 is the limit I think, but static CR doesn't relate to dymaic so much, like saying I have 14:1 but on 300deg cams it's ok.
But yeah they run better on SUL.

[alistairolsen]

the engines are pretty similar, there are slight differences in the heads IIRC, but with future headwork this is irrelevant. The manifold on the x16 is more restrictive, but deeing as any of these manifolds is an absolute joke they wont be staying long!! Ill be fitting it in place of a mildly tuned 1400 lump, so the difference between 106 and 109 isnt really a stumbling block. The eventual plan is motorbike TB's and megasquirt managment, so all the differences go. Im only taking this route as I can get a complete vectra for 300 quid and plunder it for spare whels, tyres, brakes, dash for future project, engine, ecu, immob, remote C/L, alarm, etc, then sell what i can to get some money back to replace belt, idlers, plugs, leads etc before I fit it.

I can understand why someone wants to do a 1.2, Id do it if I had money to burn, but Im after the most economical route to power. I still like discussing tuning options for the smaller engines. Fair play to Cambridge and his project, I was merely observing that i would have used the 1400 head if I was going to spend that much time and money on an 8v head.

[Richyb]

fuck it man, if u wana have fun tuning your 1.2 just get nitrous system with some 45-50bhp jets that will certainly get you the best bang for your buck, ur engine wont last very long but u will certainley produce more torque than all of the other 1.2's! i ran nitrous on my 2lt turbo we tuned engine up to around 325-335 then dumped in 100bhp from a wet nitrous system, it was running a lil lean at the time of rooling road but it produced over 425lb of torque!

[Nick]

c16xe cant be 11:1????

i thaught XE stood for ~10.5:1 MPi

11:1 would have a different identification letter

X is > 10.0 to 11.5

and as you said E means MPi

[robb]

TBH the cost of getting a 1.2 to the same spec as a standard GSi/GTE motor is expensive and the cost will easily cover the extra on insurance and tax. (Plus you only need to swap a motor and wire it in).

A 1.2 shell/car with a GSi/GTE motor is fairly cheap on insurance

My ponit is just to get everything into perspective.

Although Camb 1.2 will be a bit of a spectacle when complete, respect for doing it!

Also I am having a great time in France and anyone looking for a holiday in the snow should come to here as it is the best place to stay and eat, for example I met the GLC a month ago had a great time (although Adam Hussain smoked all my smoke), and Super Fury Animals will be in the area soon. What a place!

[Aragorn]

Ritchyb - i'd be willing to bet a std 1.2 bottom end with shotpeened rods and some arp bolts could take upto around 160-170bhp with no other work if not more (via high level of tuning + nitrous)