Lapping in new Black Diamond valves in my A65. One cylinder is done, no bubbles seen in the soapy water when I blow air into the ports. The other side is trouble. I've lapped those valves four times, but I still see bubbles when using this test.
Some years ago i bought a set of those yankee Neway Valve seat cutters, they are bloody great, you don't have to finish lap the valves but i do anyway, it takes a couple of minutes. They do a lovely job, no chattering etc and two tools do the three angles for most britbike heads. Not cheap but a good investment. No dressing stones etc.
I bought an old seat cutting set that uses stones and they work very well. I never lap the seat, and also make sure they are not overly wide. I use a black texta so I can see the angles and seat width easier.
I bought a set of valve seat cutting tools set years ago for about a hundred ( apparently made in England ) but have never used them. However, I have had the local machine shop machine the head seats to match the new valves and had to lap two of the valve/sets in anyway and that was after they had seriously created deep pockets in the head which had to be eased down to get rid of all the hard edges they left behind. Perhaps I should try using the seat cutting kit next time. They are not stones but cutting edges of steel.....
Joined: Sep 2002 Posts: 7,812Alex
BritBike Forum member
BritBike Forum member
Joined: Sep 2002
Yes, the Neway cutters are the [censored], but as kommando says: beware, you will get lots of new friends. I've now done everything from Ariel square four to Morini to Rudge with them... I can think of very few better investments I've made.
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
I need some new friends. Just can't see buying these things for something I rarely do (lapping has always worked in past.) I'll just go see Charlie, he probably has the stones and will cut mine for chump change. Besides, if I had a set I wouldn't be able to find them the next time I needed them .
I bought some Sykes picovant valve seat cutters and they did help to remove the step in the seat, however they took a lot of lapping in of the valve afterwards. Maybe from a worn guide or the pilot wasn't quite the right size. In the past I have put sheets of emery paper over the valve head to take the worst off then lap with an old valve then lap with a new valve ( that way I am not putting a bur on the new valve head) that seems to work better than the steel cutters.
Shops that have expensive machines that cut 3 angles at once can really sink the valves and put big recesses that are not good. I prefer doing my own seats, and if they are recessing too much I have new seats put in, then blend and cut them myself, so I can control the widths. Overly wide seats are not good.
Shops that have expensive machines that cut 3 angles at once can really sink the valves and put big recesses that are not good.
Whether you own a $300,000 Newen valve machine or an old orbital Black and Decker seat grinder you still have to know what you are doing. Is the person doing the work qualified? Few shops today are when it comes to working on Hemi type heads.
Mark, sinking the seat to get that top 3rd angle was the practice with many shops using seat grinding equipment long before the form tool machine (Serdi and others) or computer computer controlled single point machine (Newan) even had been thought of. I have shops ruin heads using Neway cutters. It isn't about the equipment being used but the qualifications of the person doing the job. Remember that Michaelangelo did his best work in stone using a hammer, chisel and file. Burt Munroe did all of his work in a "rose shed" with fewer tools than most of you have in your workshop.
With the fuel available today it is important to toughen your engine against detonation. This starts by using wide valve seats. Those narrow seats are great for performance engines using race fuel, but on the street an engine with narrow seats will eventually suffer from detonation or pre-ignition. Often sooner than later.
Pocketing valve seats on a Triumph typically starts with the removal and replacement of the valve guides. Because of the structure of the head casting surrounding the valve guide is minimal at best, and does not support the guide equally around its circumference, when pounded in the head often goes in at an angle. If you don't want pocketed valve seats insist that the guides be drawn into the head with a proper tool. Also insist that the old guides be machined out of the head to insure oil wont be leaking down the grooves left as you bang the guide out of the head.
One of the things I have learned is an awful lot of the power available is to be found in the head. A lot of this is in the placement and shape of the valve seat. While it was a lot of work to find in the first place, with hand equipment it was even more frustrating to repeat.
It was just as frustrating to copy what you found in one head to an other. By drawing in the guide, thus starting with it perfectly aligned with the valve seat, you could remove a few thousandths from the seat rather than cutting away a lot of metal just to get to the point where you had a full seat. By trying to correct what you did installing the guide there was little chance of repeating the location of that seat that was giving you that increased performance.
Also the shape of the hemi-head itself becomes the basis for the top angle. See Mark's picture above.
Shops that have expensive machines that cut 3 angles at once
When it comes to pre-ground tool bits you cannot use a "one type fits all" approach. Most shops will not go out and buy a "properly" ground tool bit to work on just your Hemi-head. You are not looking for someone who is calling himself an expert, but someone who is qualified to work on the type of head you have and has the proper equipment and EXPERIENCE.
The selection of cutting bits used in Serdi type machines (cut three angles at once) for various heads is extensive (although do not cover all applications), and are expensive. Some one with a Serdi type machine who works on a lot of Hemi-type heads would often have a special tool ground for the application.
Someone with a Newan machine, and is qualified to use it (owning one does not mean you are qualified to use it), is computer controlled single point technology and uses a tool similar to what you would use in lathe. The operator programs in the angles, and diameters (including the shape of the Hemi combustion chamber) so there is no need to sink the area around the seat.
Those exhaust seats look very narrow to me, i tend to aim for about 30 thou on the inlet and 80 on the exhaust, with standard seat material and standard valves. Messing about with seat material and heavier valves helps stop the pinking with narrow seats, but unless on the track is it worth it? Fully radiused seats can be good but it's determining the correct radius eh? (How many heads do you want to scrap?) Back in the UK years ago i did some work for Sunnen, they made a nice valve/head machine. It looked higher quality than the Serdi things around at the time. At that point they had just bought General Hone, a product they were more noted for.