Discussion
Jhonno said:
stevieturbo said:
Jhonno said:
Well, if he is wrong then that is handy! I can keep my valves.. 
Holy valve shrouding Batman !Not the concern bit, as it obviously doesn't lead to pinking or det, but if in a moment of enthusiasm you were to blend them out, it'd have quite a detrimental effect on your CR at the very least~any waterways in there btw??
Mignon said:
That's about as shrouded as you can get. Hardly surprising it flows better without a valve in the hole.
To be slightly fair to him, I may have misunderstood and he hadn't even looked at the chambers at that point.. It was conversation as I dropped the heads off. So not much can be done about it, without major (£££) surgery..
If you put a tulip valve in there it would direct more air sideways to the shrouded bit and make flow even worse. In this situation you want the air to skip across the shortside into the open part of the chamber. It's pretty clear whoever you are paying knows sod all about port flow, chamber shapes and valve shapes. Now I've explained it to you I guess it seems pretty obvious but that's the thing about knowledge. It always looks easy after the event. But it takes many years to get it in the first place.
Mignon said:
If you put a tulip valve in there it would direct more air sideways to the shrouded bit and make flow even worse. In this situation you want the air to skip across the shortside into the open part of the chamber. It's pretty clear whoever you are paying knows sod all about port flow, chamber shapes and valve shapes. Now I've explained it to you I guess it seems pretty obvious but that's the thing about knowledge. It always looks easy after the event. But it takes many years to get it in the first place.
Yes it all makes sense.. So in conclusion. I've got to live with it.. The valve suits the setup, but is badly shrouded.
Jhonno said:
I was intending to used 13.5-14mm lift, with some extra duration..
I can only go by what the head shop says, and I am paying him for his knowledge. He looked at the heads and one of his first comments was the poor shape of the back of the valve for higher lift.
Flow is barely increasing after 13mm...almost begs the question if it is worth pushing lift further.I can only go by what the head shop says, and I am paying him for his knowledge. He looked at the heads and one of his first comments was the poor shape of the back of the valve for higher lift.
Presumably this will be a custom camshaft or something or are people already using this ? And your springs etc can accommodate the lift you intend to use ?
Is there any room/bore diameter to reduce shrouding ?
stevieturbo said:
Flow is barely increasing after 13mm...almost begs the question if it is worth pushing lift further.
Presumably this will be a custom camshaft or something or are people already using this ? And your springs etc can accommodate the lift you intend to use ?
Is there any room/bore diameter to reduce shrouding ?
This is what I mean.. Is it worth it?! Doesn't seem so really. It would be a custom profile cam, I am speaking to the cam people tomorrow.. I've put higher rate springs in to allow me to run a "bigger" cam.. Presumably this will be a custom camshaft or something or are people already using this ? And your springs etc can accommodate the lift you intend to use ?
Is there any room/bore diameter to reduce shrouding ?
I've gone up to 91mm bore from 88mm so there is 1.5mm available
Maybe a bit more, I'd need to offer the new HG up.. There won't be loads though.Max_Torque said:
Looking at the graph on P1, something happens at 8mm of lift and significantly reduces flow until 13mm of lift. Suggests a seperation that squashes flow. If you could trim that out i reckon there's 10% more flow at the same lift.......
Would it be something obvious..? Stupid question? Kccv23highliftcam said:
Meh.
What's that huge shaft down the middle of the port ?Edited by Kccv23highliftcam on Monday 16th July 01:33
No lightweight race valves there....another way to achieve some degree of reliability.
And of course depends on lift, length of valve, how much guide there is you cannot see etc etc etc
Cutting the guides away like that will do very little to improve flow over a bullet nose anyway. You'd be better with a bullet nose guide and a proper valve.
stevieturbo said:
Kccv23highliftcam said:
Meh.
What's that huge shaft down the middle of the port ?Edited by Kccv23highliftcam on Monday 16th July 01:33
No lightweight race valves there....another way to achieve some degree of reliability.
And of course depends on lift, length of valve, how much guide there is you cannot see etc etc etc
Cutting the guides away like that will do very little to improve flow over a bullet nose anyway. You'd be better with a bullet nose guide and a proper valve.
Ref.. speed pro series, how to build, modify & power tune cylinder heads, ISBN 1-901295-45-1 Ch14 head cases.. if it's still available]
Kccv23highliftcam said:
Actually it's worth (4x2) 8 hp at the wheels according to Burgess/Gollan...
Ref.. speed pro series, how to build, modify & power tune cylinder heads, ISBN 1-901295-45-1 Ch14 head cases.. if it's still available]
And I'm sure fitting some better valves would be worth even more...the stem on those is massive !!Ref.. speed pro series, how to build, modify & power tune cylinder heads, ISBN 1-901295-45-1 Ch14 head cases.. if it's still available]
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