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Myles Raymond
Myles Raymond
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#556349 08/03/14 9:23 am
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geordie Offline OP
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Hi the exhaust valve seat on my DBD appears to be made of bronze whilst the intake is steel, is this standard? It seems the exhaust seat may need to be replaced


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Hi Geordie .... I have a posting on page 22,fourth from the bottom of the page. Ron replied that the exhaust seat was a high tech. material ... not specified. I had the same question that you are asking.

Good luck.
James.

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In Remembrance
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Some tuners use Copper - Beryllium. Do NOT breathe any dust from it, use a filter mask if doing any grinding or machining of it. That stuff lasts and lasts.. takes heat better than anything..

My cylinder head guy likes to have a lot of interference fit, 0.004 or 0.005". Uses Nitrogen to freeze the insert and warms the head. The seat slides right in..

The intake runs a lot cooler thus any seat material is often used.. but then some guys use the Copper-B for both seats..

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geordie Offline OP
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Thanks for the reply I had the valves and seats recut and the machinist remarked on how tough the exhaust seat was to cut. The work done has resulted in no tappet clearance on said exhaust valve (actually the valve is held open at all times).
Ron I just saw an earlier post of yours (4 yrs old) saying you had some "seat saver" exh valves made up, I find this interesting as I measured the seat insert diameter on mine at 1.75" and got thinking a new bigger valve might get me out of installing a new insert and the problems that might come with that. In fact I am wondering if this is a normal size for the insert, it seems large to me ?? The dbd500 valve as I understand it is about 1.53"
The valve as found appears to be from a different model (65-1644 BB32 350cc) however I think it is the same size as standard 58 model DBD 500cc am I correct ?
[Linked Image]

Last edited by geordie; 08/03/14 8:07 pm.

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Regardless of anything else, I'd be concerned about the age of the valve..


No generalisation is wholly true, not even this one.
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I assume you have the rocker in the loosest position.. It is not easy to tell how much the ex valve is held open, but most likely you can take about 0.015" off the top of the valve stem and get away with it. One way to judge is by the installed valve spring heigt.. if shimming was needed, then that gives an idea of how much to take off of the top of the valve. I would need to look to see if I have any of those valves left. But I got the idea from Pearson and he may have some still, if I don't

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geordie Offline OP
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Yes rocker with marked flat uppermost. I placed .025" shim between the cases and barrel and this gave me .006 clearance so installing a cyl base gasket (which i wasnt planning to do) and rocker cover gasket might just get it there but with no room for adjustment later
Might give Phil Pearson a call, see if he has any bigger valves on hand


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