Rajo BB head
 

I just got this head I believe it is the BB head. Has a high serial number in the 12000 range and has a B casted on top of the head under the valve cover. The eight spark plugs threads are all the same. I don't have a 18mm spark plug to check but a lot smaller than 1/2 pipe. The head has been milled to about .980. It has the large intake ports, the rocker towers are a cast bronze. What spark plugs would be recommended and who sells the best head gasket. How do you tell if the valve cover is a reproduction.

Re: Rajo BB head
 

Tough to tell a B from a BB. All the Model Bs that I have seen had embossments for the second set of spark plugs on the intake side so someone could easily drill and tap them if desired. I believe the real difference between a B and BB is higher compression and maybe larger valves..

Fortunately, it looks like your head has not been milled much since there is still a lot of meat between the recessed spark plug holes and the bottom of the head.

It does look like the valves and valve seats have been enlarged because there is very little meat between the two valve heads. From the pictures it looks like they are very close to touching! Be very careful here, especially if you are going to do a valve job or any type of work on the valve seats. This looks very fragile. If you are doing valve work, just gently touch up the valve seats with some hand lapping compound- I wouldn't go anywhere near a valve grinding machine.

From what I can tell, your cover is a replacement. Hard to describe but the originals just have a different look. If the casting is rough underneath, it is probably newer. Not a big deal either way and I wouldn't worry about it.

Looks like a great head. Original exhaust manifolds are hard to find. Congratulations on your purchase.

Re: Rajo BB head
 

It also has dual valve springs, seems like that would be to much tension on the rocker arms.

Re: Rajo BB head
 

The inside of that cover leads me to believe it may be original. Most of the reproductions are pretty rough on the inside.

Dual valve springs seems like a bit much. I have only seen single valve springs.

Re: Rajo BB head
 

From what I just read this head is a 1926-27 BB head with the slanted rear casting for clearance of the firewall and fuel tank. Has anyone seen a B head that's slanted?. None of the spark plug holes are 1/2 npt all are I believe the 18mm thread and look factory threaded. The real race BB heads had 1-7/8 valves from what I read. It seems a lot of information on the rajo heads I'm reading online vary from person to person.

Re: Rajo BB head
 

RE the head gasket; most of the suppliers carry gaskets for the over head. Most all fit the same so don't need a lot of choices.

Re: Rajo BB head
 

The intake valves have not been enlarged in this head- all B/BB/R heads used the same size intake and exhaust valves as what is shown in the pictures here. The head looks to be in great shape. . The cover may well be an original from the looks of it. You are correct the slanted back makes it a later head to clear the firewall/gas tank in the improved Fords.