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Mystery head.

Cyborg

Well Known and Active Website User
VOC Member
A NOS head that has been collecting dust for 65 years or so. Purchased by my brother in the 70’s from a small shop that as far as I know had no real connection with Vincent. It is ported to 32mm and has the drainage groove for the intake. The groove, porting, and polishing all appear to have been done prior to the guides and retaining rings being installed at the factory. The original stake marks are on the retainers and there are no signs of tool marks or movement subsequent to installation. There are witness marks around the 4 cylinder stud holes from being attached to a jig, but no marks on any of the other mating surfaces ( including the rocker oil feeds) other than some shelf patina. The number stamped into the intake flange is a bit of a mystery and I’ve never seen another on like it. I have seen #’s stamped into a combustion chamber to note oversized seats, but nothing on intake ports.
Any thoughts on what the number might represent?
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Last edited:

Cyborg

Well Known and Active Website User
VOC Member
Bill, you had previously mentioned the position of the drainage ditch. Maybe they were just starting to explore using this and didn’t want to remove all of the oil? Maybe this head, (although it is a front head) was meant to be used on the rear cylinder?

DDE33A56-142A-4D63-A367-DA3F738E617B.jpegBCF4C259-B2D4-42AE-9380-8E419E173286.jpeg
 

Bill Thomas

Well Known and Active Website User
VOC Member
I am not sure, I have not played with a head for a long time, But I thought they all had that groove,
For me it doesn't go close enough to the guide to do any good.
 

GBewley

Well Known and Active Website User
VOC Member
The valve positions are at 32 1/2° from the centerline of cylinder heads on the Vincent. The cylinder heads are at 25° from vertical. This means that the rear exhaust and front intake are 7 1/2° to vertical when installed whilst the rear intake and front exhaust are 57 1/2° from vertical assuming the engine is actually level to the ground when installed. I always grind the grooves so that they, as a whole, are at or below the bore of the valve guide and it’s retaining groove when installed. This essentially drains all oil but there’s plenty of mist floating around to oil the valve stem and guide without having it remaining as a pool.


I am not sure, I have not played with a head for a long time, But I thought they all had that groove,
For me it doesn't go close enough to the guide to do any good.
 

Cyborg

Well Known and Active Website User
VOC Member
The valve positions are at 32 1/2° from the centerline of cylinder heads on the Vincent. The cylinder heads are at 25° from vertical. This means that the rear exhaust and front intake are 7 1/2° to vertical when installed whilst the rear intake and front exhaust are 57 1/2° from vertical assuming the engine is actually level to the ground when installed. I always grind the grooves so that they, as a whole, are at or below the bore of the valve guide and it’s retaining groove when installed. This essentially drains all oil but there’s plenty of mist floating around to oil the valve stem and guide without having it remaining as a pool.
Have you ever seen #'s stamped into the intake flange like that?
 

GBewley

Well Known and Active Website User
VOC Member
Not that exact stamping. That said, I have seen many odds stamping on many parts over the years of working on Vincents. The first thing I would look at is whether or not this is the B head because if it is it is possible that whoever did the porting wanted to indicate which machine (engine/frame number) it was meant for, or it could just be an identifying mark for a job number or whatever.

Have you ever seen #'s stamped into the intake flange like that?
 

Cyborg

Well Known and Active Website User
VOC Member
Its a later head. BA 70798, so a front head with the bridge between the fins.
It's the porting (out to 32mm) and polishing (prior to installing the guides) that makes me wonder about the number. Also wondering if it was prepped to be a replacement for a Lightning or Flash, or perhaps ordered from the factory that way to upgrade someone's Comet?
It came from a strange source. It was sitting on a shelf at Wiens Cycle in Winnipeg. He was a NSU, Jawa, dealer. North West Cycle was the Vincent outlet and Robin's Cycle had a few odds and ends, so who knows how it got there. It had a layer of dust on it when my brother bought it.
The story will always stick with me. He (my brother) was exiting the dealership cradling the head like it was a Faberge egg and he slipped on the ice. Basically knackered himself, because he refused to let go of the head to cushion his fall.
 

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