Heavy twin engine

An 88 head will fit a 99 ,the fin shapes may not be as standard but it will work, pistons may work work but may need an octane booster with low grade fuel and timing reduced, the old con rods may object to the increase unless you restrict the revs, flat tappets are right ,push rod length needs to be checked, make it work.

The heads with that casting number, 22707 were often found on early slimline Dominators like yours, and the cylinder heads were interchangeable between the 88 and 99.

The Nomad pistons will work with your bike but you will want to set the ignition timing at 27-28 degrees BTDC.

Early Norton Atlas pushrods were the same as the 99ss pushrods used in 1961. They should work okay in your bike, but you will want to do a mock engine build, install the pushrods, carefully turn the engine over a few times then take the cylinder head back off and check them closely for any signs they were rubbing or hitting the inside of the head or cylinder.

All Dominators got the flat tappets for 1960 so they should be the right ones for your bike.

Commando forks are longer than Dominator forks. Dominator fork tubes should be about 21 7/8" long.

The 500 and 600 Nomad ignition timing with the 9.1 compression pistions was 32 degrees B.T.D.C fully advanced. As show on page 64 of the Norton Motor Cycles book by P.L.Garratt, the fifth edition from 1962

I use Commando forks on my Manxman cafe racer. I bought the forks used at a swap meet, they were bent but that didn't matter as I knew I would have to fit Dominator length tubes to make the bike right. Dominator fork tubes are available from all the usual sources, including this club web site for 35 quid a pair.

Might be better to retard the ignition a couple of degrees - 9:1 compression and present day petrol could cause pinking otherwise. Generally, 99 timing is said to be 32 degrees, 88 30 degrees BTDC. Gordon.

As the last Nomad scrambler was made very early in 1960, most of them did not have the cylinder head that a 1961 Model 99 would have which would give one point higher compression than the Nomads had, raising it over 9:1. Dunstall and others recommend later ignition timing with that sort of compression ratio, again in the neighborhood of 28 degrees BTDC.......

If you look at page 60 of Norton publication P106, it explains this and states specifically that the 1960-62 Model 99 will have 10:1 with the Nomad piston.....!

If you are going to use Commando fork sliders with shorter tubes, you also need to change the damping units inside to a set shorter by the same amount as the tubes are shorter.