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Terry Prince Top End Kit


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This is what a Terry Prince top end kit looks like. It is a 600cc conversion and includes all the pieces seen in the photo. I did not have the intake manifold in the photo, but it is also included.

This is not mine, but I have looked at it carefully and I think I can answer questions if there are any.



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You are a braver man than me with a Standard Burman Box.
The only time I actually stopped Ben from using the Comet Racer was after seeing the inability of the box to reliably 'be there' when under hard retardation for a hairpin. However anoying (and it certainly is) the oft repeated fault of a slow changes and wide ratios is not a danger issue
Its worth looking for a Norton Box -or getting clever and spending lots with a Burman inside

chankly bore

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You are probably right there- it was a matter of "needs must when the Devil drives". The 'bike is for road use only and I am spending some time getting the gear change, particularly top to third and third to second, smooth and reliable.


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Interesting. Not what I was expecting, it all looks very recognisable as Vincent parts. Oil holes in the rocker feed bolts look big, do they use metering wires? What are all the studs to?
The photos look more impressive on this new look forum.


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Running a 636cc Bob Dunn conversion, 90x100 with 34mm Mikuni, Conways (Honda?) clutch, I find that the Burman box is excellent. This leads me to believe that many of the complaints about running with Burman boxes, rather than actual mechanical failure, are actually caused by problems with Burman clutches not operating cleanly due to hub and basket wear.
My major complaint is that the Mikuni has no tickler and as it has two floats I can't see a way to add one.


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Looks like a better way of piping the oil to the rockers and less chance of leaks without ET189 rocker feed bolt washers. Looks as if it may be drilled and tapped for twin plugs too.


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Hi Ed
Yes, the Prince heads are two plug. It has been suggested to me that there is zero advantage in having two spark plugs firing, but from my reading that is not the case. If you take your standard new Porsche back to the Porsche factory for a power upgrade, they insist on changing to a twin plug ignition. The main purpose of this change is to eliminate the detonation which would surely happen with single plug ignition and a boosted compression ratio. The two plug ignition allows the timing to be pulled back about 5 degrees or more. Additionally, the two flame fronts add three to five percent to the power band. The extra power is greatest with engines which use a domed piston (Vincent) to acheive a high CR.
Another feature of the Prince heads are the generous squish bands designed into the combustion chambre. Drag racers call this type of head a "quench head" because the squish area cools the combustion chamthisbre if set up with proper very tight clearances. This effect also aids in preveion of detonation while adding a lot of hp, particularly in the midrange.
Terry has also added a lot of fin area to give more cooling, again
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