whats quicker

[Damogolfgti]

which head would make the engine quicker1.2on 1.4sr block or 1.4sr head on1.4sr block cheers

[Dicko]

not much in it, the 1.2 would raise compression

dpends on other mods

[Damogolfgti]

soz but wat does raise the compression mean and what other mods could u do to the 1.2 heads ive got both just need some info mate

[nov4]

a good friend of mine put a 1200 head on his 1400 bottom end, it worked a treat, and woz Fast as Fcuk. used a 1400 cam aswel, it workes perfectly, and gave out so much power.

use the 1200 head on the 1400 block!!! trust me, you'll luv the result!

[Damogolfgti]

so u say 1.2head on 1.4block on that will be quicker any modds with that u no of mate

[Jim]

Theres a guy that goes by the name of "Novanutter" that comes on Novaload. He's just had a 1200 head put on his 1400. I think he's had other mods aswell, but it'll be best to send him a private message and ask what hes had done.

Jim

[Snowface]

isn't the diameter of the Pistons on the 1.4 bigger than the 1.2? or are the 1.4 pistons longer?

[Will]

lol, jim, my engine is 1400 sr with 1400 head, didnt do the 1200 head thing in the end, its a possibility for the future, but yes the valves are much bigger and the compression will be raised, if you know wot ur doing etc (i assume you do) then stick the 1200 head on the 1400.

When Vauxhall had 1300 engines they were 69bhp odd as standard and when they switched to 1400 in 1990 it was only 72bhp standard, they made the head very restrcitive hence the lack of power and the debate of "which is faster 1.3sr or 1.4sr"

Stick the 1200 or 1300 head on, i think they are practically the same. Hopefully you should see some nice gains :)

Good luck

[rgv_stu]

will
the valves are the same on the 1200 1300 and 1400
so it aint much different ;) trust me i have had both 1200 and 1400 heads apart ;)

ps. i have a weber 32/34 , 1300 manifold and a 1200 head in my shed at the moment ;) can you guess whats coming :)

[mikeoxford]

will
the valves are the same on the 1200 1300 and 1400
so it aint much different ;) trust me i have had both 1200 and 1400 heads apart ;)

ps. i have a weber 32/34 , 1300 manifold and a 1200 head in my shed at the moment ;) can you guess whats coming :)

valver?! :lol: :roll:

[Nova-Boy]

Seeing as knowone as answered your question about what is raising compression i will have a crack.

If you bring the cylinder head closer to the top of the pistons by skimming the head or from using a head with a smaller cut out in the bottom you will reduce cc slighlty. The space in the combustion camber is smaller and a bigger explosion will occur using the same amount of petrol/air so you increase power slightly.

(i think) :D

Was that any good boys? Did i miss much?

[Aragorn]

:/ kinda missed the whole point

the CC is the piston stroke

when the piston draws in the 1.2litres of air/fuel, it shuts the valves and squeezes it, the compression ratio is the ratio of the squeeze

u take 1.2 litres of air and squeeze it into 120cc of space u get 10:1 compressoin (that should all be devided by 4 really since the 1.2 is split over the 4 cylinders)

now if u take a 1.2 head - the space in the head is sized to provide the correct compression for the 1200/4.. 300cc of mix that will be drawn in

if u take a 1400 uve got 350cc of mix and squeeze it into the gap for 300 u get more compression (assuming compression of 10:1 you'd have 33cc of squish space, squeeze 350cc of air in there and your gonna get 11.6:1 comprssion) bigger bang, more force, more power

[Nova-Boy]

Yeah ok. CC is cubic capacity stroke x bore not just piston stroke but i knew what you were getting at. What i meant by reducing cc is that you do reduce the cc when you skim the head or put a head with a smaller cut out in the bottom but only ever so slightly. Basically wasn't on the ball with the fuel air ratios.

[Benjoyce]

i've got a gte head valves cam etc on my 1.4sr, its defo quicker coz i reced one before it came off the road due to misuse by my brother.

[Stuart]

changing the volume of the ehad wont affect the overal capacity of the engine, and if it does it will be by such an insignificant ammount.

and you'd be better off measuring the volume of the two heads so that you can CALCULATE the CR accurately. rather than take the haynes manual to be gospel with regards to the compression ratios in there.

[Nova-Boy]

Starting to think i should have bothered trying! :oops:

Almost as difficult as explaining the off side ruel or torque! :lol:

[Aragorn]

umm i never tried to claim that u could work it out from haynes

i used a theoretical compression of 10:1 in the example and the example was correct albeit oversimplified

u need to measure piston dishes im both engines, head volume and gasket volume and prolly some other things too

but my example assuming the values i used (ie 300cc and 33cc total clearance and 10:1 compression to begin with) would produce the CR or 11.6:1 if the capacity was increased to 350cc

these numbers are not exact - neither engine is 10:1 to begin with and 300/350cc are both rounded up compared to their actual values but it was an example and a correct one at that :o

[Nova-Boy]

Piston dish? Is that what i was on about? The cut out in the bottom of the cylinder head?

[Stuart]

i only saw into a gm block for the firs time on monday lol. but the pistons have a dish cut/machined into them (with valve pockets too). this makes a slightly larger combustion area.

ive come to the conclusion that the dish in the piston can be ignored in the calculation since its the same at the top and bottom of the stroke. ie if there is a constant volume at the top and bottom of the stokr it can be ignored. same as the head gasket can be ignored (unless you change the thickness)

[Damogolfgti]

Cheers 4 replys but what should i do

[Aragorn]

prob is camb

we dont know that the dishes on the 1200 are the same size as on the 1400

therfore we cant ignore them as a constant

im guessing the 1200 head would work fine lots of folk have done it

[rgv_stu]

the piston dishes on a 1.2 and 1.4 are totally different as is the head chamber shapes

[kieran]

will a 1.2 head still fit on a 1.4 block and work ok

[Nova-Boy]

1.2 head on a 1.4 should work fine, even better than the 1.4. the 1.2 and 1.3 heads ar practically the same.