looks like what mine did when it was clean (except i totally forgot to knife edge the inlet split lmao)
ah well, it will be off again next year no doubt.
Its a turbo head so dave went the conservative route, but it helped me gain about 30 odd bhp inc cams at a calibra rolling road day.
Other than head and cams, and decat the car is std running std chips and .8 bar boost. I think port enlargement was 2mm on inlet and 1.5 on exhaust, but it has helped no ends especially the torque through the rev range.
Also having looked on daves website it looks like he's gone into business, i`d recommemnd him to anyone for head work.
you dont have to sell Dave A to us, his reputation totally preceeds him. nice pictures too, saved.
oh yeah and this another tick on the 11mm guides in turbo coscast heads debate. (gte16v had 13mm guides in coscast head)
Where the single port on the inlet side of the head divides into two, to go to each inlet valve.
pictured in the third picture up there.
To Knife Edge it, well, a knife is something you stab somebody with. i.e. it's sharp. So instead of the rather thick split. You thin it out, and the start of it is like a knife!
From:
.__
/..\
to
./\
/..\
sorry about the .'s but the message poster takes out consecutive spaces...
heheheeh.. no Brian, your explain is so easy to understand..
Well, my opinion about the knife, i think is two.. Because if you make the knife, you will improve power in high revs, because will have less restric for flow, but in low, you don't will have turbulence, and badder emulsification mixture(when the gas mixture with oxigen), but if you keep route, in high revs you will lost power, but get better power in low and mids, and better fuel economy. I will make a knife in my 16V head.. heheeheh..
The trumpet is operating differently, as air is not approaching it from one direction. As tghe low pressure is created by the inlet valve, air is drawn in through the inlet. At the trumpet entrance, air rushes from everywhere surrounding the trumpet exit. This is where you need a smooth run for all the air. Once in the port, it's uni directional. so all the air is heading directly towards the split.
This makes it different to the trumpet entrance where air is being drawn from all angles.
ah well. Best not do any more headwork until my head modding books arrive lol!
WHAT IS MEANT BY THE TEARM PORTED, DOES IT BASICALLY JUST MEAN CLEANING THE INLET AND OUTLETS FROM THE VALVES TO COMBUSTION CHAMBER ETC... I THOUGHT PORTING MEANT TO CREATE A HOLE TO INCREASE THE AMOUT OF AIR FUEL / RATIO.. CORRECT ME THO PLS I MAY BE CHATING SHITE... I AM SO GOD DAMN KEEN TO LEARN,,,,
it´s your head´s
and if you don´t wab´t to max it out then don´t listen to me..
but here´s a piccie to maybe convince you..
hem.passagen.se/hitmeharder/pics/topp/Image-02.JPG
As you can se the edges are round and smooth at the 'bulges' that the valve stems are going in..
BUT!!
at the 'backside' of the 'bulges' the edges are knife edged.
This Head is a CNC-Ported Nascar chevy smallblock.
and they got about ~750hp with only one carb.
Well, it's a 2-valve per cylinder head, and TBH I can't really see the bit your referring to. But I have not read too deeply into air flow dynamics. I just used common sense, which isn't always right
youre trying to convince us that knife edging is bad by using big capacity v8s as ammunition. i would think torque is more on the agenda of nascar boys, which rounded split would benefit.
hmm iirc i'm sure i've heard something about 2v per cylinder being different due to layout etc that they shouldn't be knife edged as it obstructs flow
could be wrong tho i'm reaching far back into my memory bank here
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Vauxhall Owners Forum
4.7M posts
72.6K members
Since 2000
A forum community dedicated to Vauxhall owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, reliability, maintenance, and more!