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Lead free valve seats

Puddle jumper

Well Known and Active Forum Website User
Non-VOC Member
Hi Gang,
What are your views on lead free valve seats, do I need to change the original valve seats if they are in good condition and would you recommend changing the valves as well ?

Cheers Paul
 

Ken Tidswell

Well Known and Active Forum Website User
VOC Member
Hardened valve seats and valves

Given that the automotive industry and the petroleum companies care nought for old bikes or cars, and put allsorts of oxygen containing compounds in their formulations for emission control and injection systems. And may go even furthur in the future on formulation,You can use additives to mitigate the effects of modern fuel on valve seat recession, or even modern two stroke ashless oil. But the valves sold by Vinparts are made by a Formula 1
part manufacturer are are a better shape than the originals with regard to flow.
You pays your money and make the choices, also the time to get the job done is now, I speak as an independant observer and have no commercial interest, in any spares manufacturer. If you use the bike for short distances and keep off the freeways and motorways , don't use them much, them the additive should suffice. I have bought a set for a 636 Comet currently in a foreign land and in the process of being fitted for the same. If i should live so long.
 

timetraveller

Well Known and Active Forum Website User
VOC Member
I'm with Mr Boggler on this. On the ex-Cecil Mills bike I used Millers Additive and Octane Booster for several years and found that I was having to slacken off the tappets. I was only doing about 6,000 miles per year. Bill Turner from Hove, who does a lot of miles and used to regularly travel between Hove and Liverpool stuck with it for several years and then changed his valve seats. The old ones were warn about half way through. I still have one here somewhere if anyone would like a photo. In the VOC we have one member who has a PhD in automotive engineering and he did some calculations a few years ago into rates of valve seat wear. It seems that there is a combination of valve seat pressures, revs, temperatures etc which can be used as input to the equation to work out under what conditions maximum wear will occur. Guess what! A Vincent twin at normal motorway speeds, 3,500 rpm, is right in the worst place for rapid wear. This might explain why when this problem surfaced over here we had some of our American friends telling us it was not a problem as they had theoretically been limited to 55 mph for years. Both my experience and Bill's suggests that if you are going to keep up with modern traffic and do several thousand miles a year then, whenever the bike is apart, take the time to insert lead free seats.

How did I know that mine were wearing? I have a habit of turning the engine over a few times with the valve lifter used to get the oil circulation started and then just testing the compression on both cylinders before I try to start it. Just as well as every few months I would find that the compression was not what it should have been and slackening the tappets cured the problem. :)
 

john998

Well Known and Active Forum Website User
VOC Member
Valve seats

Being a tight Yorkshire man I have used unleaded from it first appearing.
Neither of my bike have suffered any problems with seat eroding, over something like ten to fifteen years. Admittedly my average mileage is only around 3000, split between the two machines. I feel that unless you have a machine with an iron head and no inserts it is not a problem. John.
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
valve seats

According to K.T.B. exhaust seats are made from austinetic iron, the same as used by Jaguars. I have literally hundreds of clients using unleaded feuels super+regular. If there were problems I would have ques of head jobs. As none of them have materialised I can only assume that there is no need to worry on this score. The majority of vin mettalurgy was worked-out pre ww2[pre leaded ] Don't worry, be happy! Roy.
 

clevtrev

Well Known and Active Forum Website User
VOC Member
According to K.T.B. exhaust seats are made from austinetic iron, the same as used by Jaguars. I have literally hundreds of clients using unleaded feuels super+regular. If there were problems I would have ques of head jobs. As none of them have materialised I can only assume that there is no need to worry on this score. The majority of vin mettalurgy was worked-out pre ww2[pre leaded ] Don't worry, be happy! Roy.
Having worked on several hundred heads, I have NEVER seen an austenitic seat in the exhaust position, inlet yes, most of them,only the later ones having bronze. Only ever seen bronze for the exhaust seat.
And if you do fit lead free seats, increase the amount of interference, as they do not expand at a similar rate to bronze, and have been known to drop in.
 

Ken Tidswell

Well Known and Active Forum Website User
VOC Member
unleaded valve seats

As far as I am aware only early heads were fitted with austenitic iron, I have only seen one pair of heads with same.I am using Castrol additive. But if you are using old guides in the head the oil may do the trick, but the coke formed from the combustion of the oil when thick enough detaches itself, and will sometimes lodge between a closing valve and the seat. This hammers the bronze seat and causes indentations . a poor sealing ovf the valve.
 

Puddle jumper

Well Known and Active Forum Website User
Non-VOC Member
Valve seats

Hi Guys,
How much interference do I need to give lead free valve seats in the Vincent ali head?
Cheers Paul

 

timetraveller

Well Known and Active Forum Website User
VOC Member
If you want your valve seats to look like this then by all means stick with leaded ones. Otherwise fit lead free items. This is one of Bill Turner's and was not the worst but it the only one I can find to take a picture of.

PIC_0823.JPG
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
valve seats/time traveller

looks like it came out well[nice one] , I would personally ,have refaced that seat ,it looks in the pic to be too good to replace. It appears from the colour to be made of some sort of bronze, which should have suffered better on unleaded. not knowing the history of the motor makes further comment difficult. Roy.
 
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