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+--- Thread: Three angle valve seat (/showthread.php?tid=5178)
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Three angle valve seat - Tom Coates - 02-11-2020
I have got the block off for a bit of porting, decoke and valve grind. I was thinking of doing a three angle valve job with one of the chinese tools available on eBay. Just a light cut to the top and bottom of the seats before grinding in. Is this worthwile or a recipe for disaster?
RE: Three angle valve seat - John Mason - 02-11-2020
Tom my penny worth is if you just run your car for pleasure and not for competition why move away from tried and tested ways. If it is for competition then others will no doubt advise the +and - of things.
John Mason
RE: Three angle valve seat - Paul N-M - 02-11-2020
Hi Tom,
When it comes to tools such as valve seat cutters I would always buy well engineered quality such as Neway. They sell single and double sided heads so you could do the throat and seat then finish the top angle by hand. Or just do a single angle if your not trying to improve flow but as you have gone to the trouble of doing some port work you might as well help round the valves as well.
Yes more expensive that Chinese imports but as in everything you get what you pay for. I gave up on Chinese eBay tools thinking they could not be too bad but regreted it every time so no more! We also need to look at the bigger picture and support engineering/manufacturing nearer home and preferably in the UK if at all possible.
RE: Three angle valve seat - Ruairidh Dunford - 02-11-2020
I can add another endorsement for Neway cutters - mine came from America, I think.
Again, a light touch and practise is the key.
RE: Three angle valve seat - Tony Betts - 02-11-2020
valve seats are not supposed to be over 2mm across the flat.
when you recut the seat this face gets bigger.
ill probably be corrected, but the 2 and three angles are to reduce the width of the seat. after cutting.
wheather you will gain an advantage by having three angles. im not so sure.
if there is a gain, it may end up being very very small. or due to the seat being corrected to below a 2 mm seat?
i guess it doesnt hert to do it, as there is nothing lost. the valve just sits a little lower in the seat.
tony
RE: Three angle valve seat - KAS750 - 02-11-2020
I have experience of tuning vintage OHV and sidevalve motorcycles and have had good results by carefully profiling the seat of the head and valve.This is particularly fruitful on old engines with small amounts of cam lift.
RE: Three angle valve seat - Tom Coates - 02-11-2020
Thanks all, I assume it is only recommended on the inlet valves for a road car?
Neway seems to be the business, but not sure I can justify forking out 300 quid for a tool I'll probably use once per decade at most!
I'm looking at Indian carbon steel cutters on eBay which would probably last long enough to cut a set of inlet valves. There are a few second hand ones, of better quality but maybe completely blunt.
RE: Three angle valve seat - Charles P - 02-11-2020
You can spend an awful lot on single application tools that are rarely used.
I like to have a shed full of tools and tackle many things but tend to let the machine shop who bore blocks for me do this type of work.
Charles
RE: Three angle valve seat - Steve Jones - 02-11-2020
(02-11-2020, 05:29 PM)Charles P Wrote: You can spend an awful lot on single application tools that are rarely used.
I like to have a shed full of tools and tackle many things but tend to let the machine shop who bore blocks for me do this type of work.
Charles
+1. Always do the same.
Steve
RE: Three angle valve seat - Bob Culver - 02-11-2020
See my comments under valve refacers.
Only the actual seat determines the valve depth so should be touched as little as possible.. The more narrow the seat the more rapid recession but this seems neglegible on the average Seven. Great care is necessary with the inside dia as once ermoved cannot be readily recovered by setting the valve deeper.The pattern on a much refaced valve is deceptive.
With a tiny cyl block that can be rolled around on the bench and with valves on an open surface, the careful can do much with files or scraper and engrs blue.
Very wide seats, extending to and above the valve rim, and with the extensively refaced valve face extending way below the inner port dia, restrict breathing. Valve heads can be turned/filed back below the seating.
If the seating is pitted do the bulk of correction using an old valve.