At long last, my Rajo head made it from California to Alaska (via the machine shop). Actually it came on Monday but this is really the first chance I have had to open the box. It is either a B or a BB. Take a look at the pictures and look over the following data. The head has a “B” cast on the top. It has that flat on the back to fit the 26-27 cars and the serial number places production in 1926. It is drilled for 8 plugs and they are all 18mm (standard T plugs are too big and 14mm too small). The shop took 9/1000 off the deck. The pockets in the head are 1.015 deep and the webs between the bottom of the plug pockets and the deck on the side not drilled on the B are 0.20 thick (in the pictures it’s sitting on a soft rubber pad that makes them look thinner).
Here is your chance Rajo experts, tell me what I have.
Rajo “what is it?”
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Reno Speedster
Topic author - Posts: 573
- Joined: Tue May 26, 2020 6:23 pm
- First Name: Morgan
- Last Name: Blanchard
- * REQUIRED* Type and Year of Model Ts owned: 1926 Model T Speedster Project, 1922 Runabout Pickup
- Location: Anchorage, Alaska
Rajo “what is it?”
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Mark Chaffin
- Posts: 4343
- Joined: Sat Jan 12, 2019 12:11 pm
- First Name: Mark
- Last Name: Chaffin
- * REQUIRED* Type and Year of Model Ts owned: 1911 Speedster, 1927 Lake Roadster
- Location: Lake Elsinore
- Board Member Since: 2001
Re: Rajo “what is it?”
Looks to be a modified model BB as it has the heating duct port between the intake ports. The intake ports appear to have been enlarged and are oversize. Stock depth on the BB cylinders as it came from the factory was 1.250. The BB also only came with the plug access on the intake side; however, they did have bosses present on the exhaust side for the addition of a second set of plugs as was used on the BBR. Since alot of these heads were modified over the years, details can be a little sketchy. One thing is for certain, it started out as a BB.
On a side note, back in the 60's and 70's the late (sloped rear) model BB head was reproduced in cast iron. I have had two of those heads over the years which look very similar to yours. Lastly, I'm not aware of a source for RAJO serial numbers indicating when a specific cylinder head was manufactured. If there is such a source, please do tell.
On a side note, back in the 60's and 70's the late (sloped rear) model BB head was reproduced in cast iron. I have had two of those heads over the years which look very similar to yours. Lastly, I'm not aware of a source for RAJO serial numbers indicating when a specific cylinder head was manufactured. If there is such a source, please do tell.
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Reno Speedster
Topic author - Posts: 573
- Joined: Tue May 26, 2020 6:23 pm
- First Name: Morgan
- Last Name: Blanchard
- * REQUIRED* Type and Year of Model Ts owned: 1926 Model T Speedster Project, 1922 Runabout Pickup
- Location: Anchorage, Alaska
Re: Rajo “what is it?”
Interesting. From what I read, I thought the B head had one plug and the BB two. Now you put me on the spot. I ran across some numbers on line and now I have to remember where it is…
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ThreePedalTapDancer
- Posts: 1631
- Joined: Sun Nov 24, 2019 2:29 pm
- First Name: Ed
- Last Name: Martin
- * REQUIRED* Type and Year of Model Ts owned: 1914 Touring, 1909 Touring
- Location: Idaho
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Mark Chaffin
- Posts: 4343
- Joined: Sat Jan 12, 2019 12:11 pm
- First Name: Mark
- Last Name: Chaffin
- * REQUIRED* Type and Year of Model Ts owned: 1911 Speedster, 1927 Lake Roadster
- Location: Lake Elsinore
- Board Member Since: 2001
Re: Rajo “what is it?”
A general determination regarding the B series is as follows:
Model B - No heating port between intake ports. Single set of plug holes on intake side. Cylinder depth 1.250 factory.
Model BB - Heating port present. Single set of plugs on intake side. Cylinder depth 1.250.
Model BBR - No heating port present. Dual plug capability. Cylinder depth 1.00. Much heavier duty rocker assembly with roller bearings and not bushings.
To make matters more complicated, the predisessor to the Model B was the Model 31. This head was used by Knowl Bullock in his famous Pike's Peak hill climber. It is identical to the Model B; however, it had a recessed flange along one side for short cylinder head mounting studs. Similar to the later RAJO Model C35 which was a totally different animal. The Model 31 heads are quite rare as they were soon replaced by the more common Model B.
Like mentioned before, alot of these heads have been modified over the years. Ports enlarged, milled down to raise compression, second set of plug holes added on the driver's side. Rocker assemblies replaced. The main thing is enjoy what you have and have fun!
Model B - No heating port between intake ports. Single set of plug holes on intake side. Cylinder depth 1.250 factory.
Model BB - Heating port present. Single set of plugs on intake side. Cylinder depth 1.250.
Model BBR - No heating port present. Dual plug capability. Cylinder depth 1.00. Much heavier duty rocker assembly with roller bearings and not bushings.
To make matters more complicated, the predisessor to the Model B was the Model 31. This head was used by Knowl Bullock in his famous Pike's Peak hill climber. It is identical to the Model B; however, it had a recessed flange along one side for short cylinder head mounting studs. Similar to the later RAJO Model C35 which was a totally different animal. The Model 31 heads are quite rare as they were soon replaced by the more common Model B.
Like mentioned before, alot of these heads have been modified over the years. Ports enlarged, milled down to raise compression, second set of plug holes added on the driver's side. Rocker assemblies replaced. The main thing is enjoy what you have and have fun!
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Reno Speedster
Topic author - Posts: 573
- Joined: Tue May 26, 2020 6:23 pm
- First Name: Morgan
- Last Name: Blanchard
- * REQUIRED* Type and Year of Model Ts owned: 1926 Model T Speedster Project, 1922 Runabout Pickup
- Location: Anchorage, Alaska
Re: Rajo “what is it?”
That is definitely the plan. I am making new push rods, need to do some fiddling and adjustments to the rocker alignment (side to side so the pushrods align with the rockers and clear the cover) and am waiting for a copper head gasket to be available. Manufacturing manifolds is also on the list. Looking for a proper carb for it.