Back cut valves
Discussion
No, not what I meant!
Just to add a small 30/32° chamfer to lead out of the exhaust seat surface.. Possibly in on the inlet to, depending on how it sits on the valve seat (need to check with engineer's blue)..
Picture is just to show the shape of both valves.. Reference to the exhaust valve was because it is has a much more defined ridge after the seat surface...
It seems to yield some decent results on various engines, looking at flow figures.
Apparently I need to work on my communication skills in this forum!
Just to add a small 30/32° chamfer to lead out of the exhaust seat surface.. Possibly in on the inlet to, depending on how it sits on the valve seat (need to check with engineer's blue)..
Picture is just to show the shape of both valves.. Reference to the exhaust valve was because it is has a much more defined ridge after the seat surface...
It seems to yield some decent results on various engines, looking at flow figures.
Apparently I need to work on my communication skills in this forum!
Edited by Jhonno on Tuesday 17th July 19:36
Please don't shoot this person down, this forum should be a valuable source of information to people who know less about engines than some on here(Some who work professionally).
Inlet yes if its a dog of a valve, you will usually increase air flow across the flow range, don't take it for gospel that 30º is the angle you need, its often less(numerical). Of course you should also spin polish them because that will show loads of CFM and BHP and credit points.
Exhaust, no, usually doesn't work, infact keep the exhaust seat area (the 45º bit) on the valve, twice as wide as the seat in the headto shift flow through the port rater than round the back of the valve. Exhaust valves from many high flowing heads are a lot fatter on the back than you would expect, number of reasons for this.
The only way you will find out is with a couple of old valves on the flow bench.
I wish my Mac would stop autocorrecting valve to vale, my spelling and grammar is bad enough already.
Inlet yes if its a dog of a valve, you will usually increase air flow across the flow range, don't take it for gospel that 30º is the angle you need, its often less(numerical). Of course you should also spin polish them because that will show loads of CFM and BHP and credit points.
Exhaust, no, usually doesn't work, infact keep the exhaust seat area (the 45º bit) on the valve, twice as wide as the seat in the headto shift flow through the port rater than round the back of the valve. Exhaust valves from many high flowing heads are a lot fatter on the back than you would expect, number of reasons for this.
The only way you will find out is with a couple of old valves on the flow bench.
I wish my Mac would stop autocorrecting valve to vale, my spelling and grammar is bad enough already.
Edited by 99hjhm on Tuesday 17th July 20:03
jhonno,
what you suggest is part of the 'three-angle valve cut' concept. See http://johnmaherracing.com/tech-talk/3-angle-valve... and many other references.
John
what you suggest is part of the 'three-angle valve cut' concept. See http://johnmaherracing.com/tech-talk/3-angle-valve... and many other references.
John
tapkaJohnD said:
jhonno,
what you suggest is part of the 'three-angle valve cut' concept. See http://johnmaherracing.com/tech-talk/3-angle-valve... and many other references.
John
John, what you suggest is part of the 'three-angle valve cut' concept. See http://johnmaherracing.com/tech-talk/3-angle-valve... and many other references.
John
Yes, this is indeed the theory I've been reading up on.. I'm yet to find a negative result for it.
stevieturbo said:
No it is not worthy of another new thread.
And no, I would not randomly be removing lots of materials from valves...especially exhaust valves.
I did my apprenticeship with a lad who tried to waist the valve stems in his Escort Mexico using an old lathe in our machine shop. The material was so hard that even carbide tools struggled, and he ended up with a terrible finish with some nasty ridges and grooves. Needless to say, one of the valve heads dropped off within a few days of using it, trashing the engine.And no, I would not randomly be removing lots of materials from valves...especially exhaust valves.
Mr2Mike said:
stevieturbo said:
No it is not worthy of another new thread.
And no, I would not randomly be removing lots of materials from valves...especially exhaust valves.
I did my apprenticeship with a lad who tried to waist the valve stems in his Escort Mexico using an old lathe in our machine shop. The material was so hard that even carbide tools struggled, and he ended up with a terrible finish with some nasty ridges and grooves. Needless to say, one of the valve heads dropped off within a few days of using it, trashing the engine.And no, I would not randomly be removing lots of materials from valves...especially exhaust valves.
Ouch! I hope I'm not at that level!Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff