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Discussion Starter #1




guess I could snap some pix of what an untouched one looks like

should be good for at least 5 mph more on the top end
 

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Discussion Starter #2
could be the subject title appropriate for a bike build

what's been done to the pushrod tube bore and why?





anyhow, more modern sealing and loss reduction

glass shadows

 

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Discussion Starter #3
could be the subject title appropriate for a bike build

what's been done to the pushrod tube bore and why?





anyhow, more modern sealing and loss reduction

glass shadows

 

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quote:Originally posted by HackAsaw

could be the subject title appropriate for a bike build

what's been done to the pushrod tube bore and why?



Uhhh, the ore has been radiused to allow the pushrod o-ring to compress rather than be sliced during assembly? Bonneville head, correct? Set screw holes drilled and tapped for exhaust spigots?
Do I win any old bike parts?

-James
 

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quote:Originally posted by HackAsaw

could be the subject title appropriate for a bike build

what's been done to the pushrod tube bore and why?



Uhhh, the ore has been radiused to allow the pushrod o-ring to compress rather than be sliced during assembly? Bonneville head, correct? Set screw holes drilled and tapped for exhaust spigots?
Do I win any old bike parts?

-James
 

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Discussion Starter #6
ummm 66 bonneville head....... that is not the right answer as to what has been done to them or why. the lead in chamfer was done by the
factory

but yes on the spigot thingies

hated the idea of throwing that head away and it did take a bit of carving to unshroud the valve without giving up too much compression

I've also never been too thrilled about how sloppily and off center the british cast in the valve seats


those of you that have had Japanese and other better Euro Iron apart will recognize how miserable these castings are in this area alone

really takes a lot of work to make them useful

lap and full polish next


shiny may actually be my favorite color

 

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Discussion Starter #7
ummm 66 bonneville head....... that is not the right answer as to what has been done to them or why. the lead in chamfer was done by the
factory

but yes on the spigot thingies

hated the idea of throwing that head away and it did take a bit of carving to unshroud the valve without giving up too much compression

I've also never been too thrilled about how sloppily and off center the british cast in the valve seats


those of you that have had Japanese and other better Euro Iron apart will recognize how miserable these castings are in this area alone

really takes a lot of work to make them useful

lap and full polish next


shiny may actually be my favorite color

 

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Discussion Starter #10
yes and pressurized feed to the tappets is not needed so I block that off too
 

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Discussion Starter #11
yes and pressurized feed to the tappets is not needed so I block that off too
 

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quote:Originally posted by HackAsaw

ummm 66 bonneville head....... that is not the right answer as to what has been done to them or why. the lead in chamfer was done by the
factory
Damn, a loser again! Maybe next time.
I agree oil sealing could be improved on 650 twins, but I understand it also has something to do with poor crankcase ventilation and both pistons moving together rather than 180 degrees apart.
As for un-shrouding the valves, it looks like you basically smoothed out the chamber around the circumference of the valve, no? Any before pics? I wonder how yours compared to my later '71-72 heads in this area before you started work.

-James

-James
 

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Discussion Starter #13
I think I have some but the actual seats were recessed so the 30 degree cutter is used much more than I care to in order to ease a path from the seat into the chamber

the edges will be hand blended before it's all polished and bolted on

a pristine and perfect hemi head will have the 45 degree seat high enough and only needing very lightly topped with a 30 and then 15 to preserve low lift flow

they are both within a half a cc of the other so I'm ok with it

I open the crank case breathing and run it to a one way valve

try to find at least 10 inches of vacuum

your 71-72 heads have nearly identical pushrod tube bores...... the 66's don't

now how many different tappet blocks and pushrod tubes did they make until they got some that had a chance of sealing?

several......... the later tubes (type 3) are the only ones to use
 

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Discussion Starter #15
probably going to bolt it on a fresh long block that is here

I may have others, what are you building?

Probably have one with welded spigots and large bored ports if you want to go fast
 
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