multi angle valves/seats

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etsjw
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multi angle valves/seats

Postby etsjw » Thu Dec 20, 2018 9:21 pm

Wondering if anyone has tried using multi angle (3/5 angles) valves and seats to try to improve flow and engine performance?
If so, did you think it was worthwhile?

Jordan
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Re: multi angle valves/seats

Postby Jordan » Sat Dec 22, 2018 8:25 pm

Mr Scurria said this in 2012:

I can tell you what works for me.
If you have access to cutters or stones for a three angle job---30, 45, and 60 for the seat and 45 for the valve.
If you only have 45 degree cutters or stones, 45 for both seat and valve, and do the rest carefully by hand. Seat width about .060".

Frank

double diamond
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Re: multi angle valves/seats

Postby double diamond » Mon Dec 24, 2018 6:21 am

The valve only has one angle:45. Because of the architecture of the Ducati combustion chamber, a traditional 5 angle seat (15,30,45,60,75) can’t be cut. The port side can be cut to 75,60 but the factory type valve seat can accommodate just one relief cut after the 45 due to the shape of the combustion chamber. On heads I’ve seen. Effort seems to be directed toward opening up the combustion chamber around the seat.

Matt
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marsheng
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Re: multi angle valves/seats

Postby marsheng » Thu Jun 04, 2020 4:44 am

From the photo it looks like you have bronze seats. Is this what they are ?

I have 3 heads here and all have very worn seats. I'm guessing the originals were cast iron insets.

I'm about to redo one head and was thinking of using the new 'carbide' inserts. If I cant get the size as they are really quite big ones, I presume aly bronze would be an option.

Any suggestions?

Cheers Wallace.
1964 - 250 MK3 ... 1980 - 900 SSD ... 1977 - 500 GTL Parallel twin ... 1980 - 500 Pantah ... Plus a 'few' others.

ducwiz
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Re: multi angle valves/seats

Postby ducwiz » Thu Jun 04, 2020 6:09 pm

I have never seen a w/c head with cast iron seats.

Hans

marsheng
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Re: multi angle valves/seats

Postby marsheng » Thu Jun 04, 2020 10:26 pm

ducwiz wrote:I have never seen a w/c head with cast iron seats.

Hans

These look like cast iron. I drilled one and the swarf confirmed my suspicions. Powder not strings came off. A standard drill went in quite easily.
1964 - 250 MK3 ... 1980 - 900 SSD ... 1977 - 500 GTL Parallel twin ... 1980 - 500 Pantah ... Plus a 'few' others.

double diamond
Posts: 555
Joined: Thu Apr 28, 2011 1:20 am

Re: multi angle valves/seats

Postby double diamond » Sat Jun 06, 2020 7:50 pm

The head that is pictured has bronze seats.You might have a narrow case head which all had cast iron seats. You could certainly install bronze seats. The trick would be finding the right size unless you intend to make the seats yourself.

Matt

Jordan
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Re: multi angle valves/seats

Postby Jordan » Sat Jun 06, 2020 10:21 pm

I think the original seats, as supplied, had some milling done to them to blend in with the shapes of the ports.
I guess it could be done with a die grinder after installation, if needed.

LaceyDucati
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Re: multi angle valves/seats

Postby LaceyDucati » Sun Jun 07, 2020 1:59 pm

The original seats did have scallops cut in the edge and more bizarrely back cutting into the port, resulting in reducing the face available to support the seat. This In my opinion has always been very poor practice.

As the seat recess is always out of round when the seat is removed it would always be best practice to skim the recess minimum to clean and fit a custom made seat. It should also be noted that when fitting seats it always pushes up material on the squish and head sealing face due to the interference. It is therefore generally advisable to either skim or lap the sealing face after fitting new seats. As I always skim absolute minimum from the sealing face, I would therefore remove any protruding sections of the seats and any pushed up material on the squish band at the same time. I would guess you are looking at 2 or 3 thou (0.05/0.075mm) but it's enough to effect head sealing and catch the piston if you are running a tight squish.

Seats can be removed by tig welding around them. When you complete the rose weld they generally fall out or you can weld a piece of metal across the throat and tap it out via the guide hole. Steel wire works well enough to effect a shrink on a cast iron seat and bronze wire works on the bronze seats. Not everyone has access to tig welding but it does work well and reduces the chance of damaging the seat recess through drilling and chiselling.

The original seats are rather large and not really ideal in theory as far as radial depth is concerned for retention. As has been mentioned, modern sintered seats are not readily available in these sizes so I tend to just use Aluminium bronze as it's easy to custom make any seats I require. If I weld up a head or i'm putting in larger I/D seats then sintered seats are a good option. To be honest unless it's a "special" head, I just farm out valve seat fitting to someone I trust, who does it day in day out and has the specific kit to do it. For me as a business, "times money" and I can't justify some specialist equipment that turns a days work into an hour or two! Mind you even then I only ever have basic rings installed as I prefer to do all the machining, some do like the die grinder.... Always watch out for those using die grinders to finish the squish area as I've seen many seats clipping the piston pocket edge.

Regards Nigel

Jordan
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Re: multi angle valves/seats

Postby Jordan » Sun Jun 07, 2020 10:52 pm

Thanks Nigel - great to know this.


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