Topic: CB750 Cyl Hd oil jets

[01Thomas]

Hi
We know that these heads came out with two versions of the oil jets; I'm talking about the jets that meter the oil flow to the cam bearings etc.
There is the smaller one with a diameter of about 5mm; let's call it Type 2.
There is the later version with a diameter closer to 8mm; let's call that Type 3.

However, I have just come across a head where there is no inserted jet. Instead the oil flow seems to be controlled by a narrow passage between the head surface and the stud cavity. The head surface is recessed by about 1 mm. Anybody come across this before? Can we call this Type 1?

I've attached photos, the first is as found and in the second photo I've pushed a pin into one of the two passages.

regards
Thomas

[01Thomas]

Last night I had issues with my ISP so my first photo didn't come through but here it is now: this is the oil jet/metering orifice without an insert of any sort, and without my bent-open safety pin in it. The round recess in the head is obviously to take a o-ring and it's only about a millimetre deep. The head has been badly stored and is quite dirty. It is very obviously an early head as it doesn't have the extra bolt-hole in front.
Has anybody come across such a CB750 head before? Is this a sandcast head, or maybe a prototype? Frank? Mrieck?

[fire113]

...I have a sandcast head and the oil jets looking like a drilled hole, nothing to remove or to insert, just a small hole.

EDIT ...found a picture of the firs insert type.
 
 

[MRieck]

Last night I had issues with my ISP so my first photo didn't come through but here it is now: this is the oil jet/metering orifice without an insert of any sort, and without my bent-open safety pin in it. The round recess in the head is obviously to take a o-ring and it's only about a millimetre deep. The head has been badly stored and is quite dirty. It is very obviously an early head as it doesn't have the extra bolt-hole in front.
Has anybody come across such a CB750 head before? Is this a sandcast head, or maybe a prototype? Frank? Mrieck?

Quite possibly sandcast.....it is the earliest example of 750 heads.

[01Thomas]

Thank you, Fire113 & MRieck
Do these heads have any value?

[MRieck]

Thank you, Fire113 & MRieck
Do these heads have any value?

Yes