The round shape ports offer superior gas flow over any of the other port shapes, hence why 1.4SRs with twin 40s can gain another 8 - 10bhp with just an SRi head on :wink:
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The round shape ports offer superior gas flow over any of the other port shapes, hence why 1.4SRs with twin 40s can gain another 8 - 10bhp with just an SRi head on :wink:
you are rong my dear friend i shall try to explain. as the air passes threw the port the air that travels around the top of the port travels alot faster than at the bottom of the port, this creates more turbulence therefore slowing down the flow of the air. now with the cathedral shape it makes the air at the bottom of the port travel the same (ish) speed as the air at the top, therefore you get less turbulence and a better flow.Quote:
Originally Posted by SKoob
I can garuntee you its the round ports that make the SRi/GSi/GTE heads that bit special, otherwise vauxhall would of stuck with the cathedral ports :wink:
doesnt turbulance create a better fuel air mix so you get a better fuel atomisation? hence a better more efficient bang??
To be fair mate a lot of people i have spoke to have used sri heads with t40's on j series engines so there has got to be somthing right about them, although i am not distputing tat the 1.2 head is better than the 1.3 1,4 sr ones
sri head is the one you want. it got me 12bhp just from changing the head
on a sr after full exhaust and k+N
if added a sri head then would it make a postive or would you need more
it would give you a postiveQuote:
Originally Posted by Boro'Nova
in standard form the sri head is better yes ok i agree but if you put the same valves into the 1.2 that would be better
ive done flow bench testing on a 1.2 head and found that if you build up a 3-4mm layer of material and blend it down to the valve you gain about 4% more air flow, ok 4% isnt much but its a gain from reducing the port size and making it nearer round.
read vizzards book on ford sohc tuning as the heads are baically the same
ok.
1.2 / 1.3 have same Cathedral shape inlet ports which are better than the 1.4 Sr's Square Ports.
SRi head has round shape ports and is better than both of these.
1.2i and 1.4i have same bad square shape ports as 1.4sr head.
GSi has Round ports like Sri.
Quote:
Originally Posted by benji