An Entertaining & Informative Vintage Automobile Internet Magazine

Replicating The North London Garage 1909 J. A. P. Engined Record Holder – Part IV

In our last installment, Pavel Malanik, who is building an incredibly interesting machine powered by a 165.62 cubic inch (2,714 c.c.) J.A.P. engine, finished up machining the valve and port housings for the V-twin. Just (above), you can see one with the newly machined valve guides, valve keepers and retainers and the packing nuts for the intake manifold and exhaust stacks installed.


An unusual feature of this engine design can be seen in the first thumbnail (above). While the valves are installed in the valve and port housing, they extend beyond the bottom of that component into the closed top of the cylinder where the valve seats are located (see cutaway drawing, below, of a smaller engine of similar design).

There are no head gaskets, per se. During final assembly, the valves are installed up from inside the cylinder into the valve guides and the valve and port housings are bolted to the top of the cylinder. Earlier photos of the cylinders in  Part II  show the tops of the cylinders and give you a clearer idea of how it all fits together.

Below you can see one of the two flywheels being turned in the lathe (left). The second image shows it being bored and spot-faced for the crankpin. The third thumbnail illustrates the fork and blade style connecting rods, the roller bearings with hardened races and the crank pin. When installed on the crankpin between the two flywheels, the rod (blade) at the bottom of the photo fits into the upper (forked) rod.


Our last photo shows the almost completed rotating assembly. A second flywheel will be attached to the crank pin when it’s done. Next time around we will show you more of the completed lower end and crankcase, the sleeves for the cylinder barrels, the patterns he made for the pistons and the pistons that Pavel machined from the castings. You can see Part III  and Part V showing the construction of this very special motorcycle here on The Old Motor.

6 responses to “Replicating The North London Garage 1909 J. A. P. Engined Record Holder – Part IV

  1. Hello David,

    Is the cylinder top a separate piece ? It does not look like a very good way to cool an exhaust valve seat.

    • Paul, No the cylinder is closed-ended at the top and and the valve seats are on the bottom side of this top.
      Follow the link in the text back to photos of the cylinders being machined and it will all be clear.

  2. I ran a contemporary 50 degree 980cc version of this engine on a Morgan in the 1980’s. It had proper exhausts though, they were not sneaking between the push-rods. It probably came from the same designer as the V8 air cooled JAPs that are about, they have several common features. The engine came from a motorcycle called the Shorts JAP, and I have contacted the daughter of the creator of the bike, but have little more info. I found it very fast, very noisy mechanically and quite economical. The heads used to glow red in the dark. I added a bit of methanol to the fuel, it is supposed to help it run cooler.
    The insides are quite barbaric compared with this new engine. It’s resting now, cracks between the valve seats and crumbly cast iron in the valve & port housing. Oh that I was a good enough machinist to make the new bits necessary. Eventually it will run again.

  3. The technical drawing is of a “90 Bore” JAP, and shares teh same valve arrangement as this (earlier) engine. I have never understood why JAP thought it was a good idea to have the valve seats in a different component from the valve guides. It makes it almost impossible to align the seat and the guide, and valve life must suffer as a consequence. Moreover, when the valve has to be replaced it can only be done by removing the barrel. Am I missing some touch of genius in the design, or was it really just an almighty clanger? (But all credit to Pavel for a wonderful piece of work!)

  4. It was even worse than that, The valve guides must be unscrewed before the valves are removed as they are pocketed into the cylinder wall and won’t come out otherwise.

Leave a Reply

Your email address will not be published. Required fields are marked *