1967 Norton 650SS heat isolators under valve

Hi William,

Inlet springs run massively cooler than exhausts as they have a nice cool (relatively) air fuel mix passing underneath them. In addition,  most engines have more valve lift on the inlets compared to the exhaust. Without checking the profiles though, I don't know if this is true for the SS cam.

With this in mind, if you wish to add the isolators,  be careful to ensure that the springs don't get coil bound at max lift.

As to oil drain, I feel you would be better served with enlarging the chamfers on the cam followers. 

Personally, I went back to scrolled spindles and low pressure feed precisely because my 650 engine couldn't get the oil out of the head at the rate the high pressure 'upgrade' supplied it at. Now, everything works as it should.

Regards, George. 

On the 650 engine there are four HIWs.....one for each valve set.  They are very necessary on the 650 engine as it gets pretty warm with a throttle happy pilot on board.

There were two versions of this washer. The difference being the thickness. There were also two versions of the valve spring cup that sits on top of the washer. Again thickness being the difference.

Make certain that your four HIW washers are near identical and the same for the spring cup washers. Unless you are planning on racing the bike using thinner chunks should not cause an issue, But.........after 650 engine 125871 the valves got slightly longer stems which would suit the thicker alternatives.

According to the 1966 to 68 Master Parts List here are the Part Numbers for HIWs - 23392   & Spring Cup Washers - T2073

George in his posting is quite correct......The rear oil drain hole, under the inlet valve spring cup was fighting a losing battle once pressure fed rockers arrived. The feed rate being around 12 gals/hr to the rockers at 6000rpm and the 1/8" drain hole just cannot cope. On my 650 I checked the HIW for fit in the head and then nibbled away enough of one section to ensure an unobstructed flow. Some superglue stopped the washer turning. 

Once the oil is over the washer it will no longer do its job as it has effectively been shorted over by the oil. Worth fitting on the exhausts on an upright twin, but the inlets it very much depends on the cam and valves you are using, and it is not to hard to work out the installed seated spring pressure, ideally aim for 80-90lbs, this should then give a respectful pressure at full lift.

Norton loved high valve spring pressures, but these are not always desirable and you can get a point where you lose power to actually have control.

Hi William, 

When I got my bike, it was fitted with the return line low pressure feed, but I was persuaded by a certain dealer in the midlands that the high pressure supply was an essential upgrade. After fitting the plain spindles and revised pipework, all my bike did was smoke heavily and pink a lot after 5 or so miles. Reverting back to scrolled spindles/low pressure supply means that the bike is usable once again. Some 'upgrades' that were introduced by AMC were good, but I feel that this one was brought in as a cost saving, not a functional improvement to the bike.

Other members may have different views, but I do know that I'm not alone with this view.

I feel a lot of people worry about insufficient oil 'upstairs', but my 350 Morini has no oil supply to the valve gear, relying on mist from below condensing and dripping where needed, and it is now at 97,000 miles on its original rockers and shafts. The valves and guides were renewed at 70,000 miles. Make of that what you will.

Regards, 

George. 

Hi William,

Mine has the 3 start gears.

Again, there are arguments for and against 3 vs 6 start gears -  but stopping an upright engine over oiling its head with a full pressure feed is a bit of a black art it seems. People with a far better understanding than me will say what is and isn't true, but my understanding is that the tappet blocks got a larger chamfer after the high pressure engines were introduced, also that the drain hole increased in size (may have been 750 only?) - both to help oil drain. What wasn't mentioned by the original seller of the high pressure kit to me was that it wasn't a good idea to use new plain spindles with used rockers (probably as you needed a second mortgage to buy new ones at the time I was building mine up) as the extra clearance from any wear resulted in more oil flowing through them. 

I wasn't prepared to mess around with reduced sized holes in the banjo bolts or other similar mods and decided that what wasn't broken didn't need fixing, hence my return to the original system.

Hope that this helps,

George.