Valve guide seals

Why were valve guide seals implemented? Were these all the 850's?

What changed within the motor............or was it driven by environmental compliance?

I think(Not quite sure) it was introduced with the commando evolution with the engine being sloped forward. The Atlas were upright engines. I can definitely say my combat had valve guide seals. I am not too sure when they were introduced. Maybe L.A.B. has the answer.
edit: My 1969 P11 had seals on when I disassembled the engine. I was not the first one in there thou. Others had their fingers in.
Cheers,
Thomas
CNN

CanukNortonNut said:

I think(Not quite sure) it was introduced with the commando evolution with the engine being sloped forward.

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Just look at the part nos: The 1968-70 list still shows the old guide version for both inlet and exhaust. In 1971 they changed the inlet guide.


Tim

Tintin said:

CanukNortonNut said:

I think(Not quite sure) it was introduced with the commando evolution with the engine being sloped forward.

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Just look at the part nos: The 1968-70 list still shows the old guide version for both inlet and exhaust. In 1971 they changed the inlet guide.

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Inlet guides with seals used from serial number 149670.

L.A.B. said:

Tintin said:

CanukNortonNut said:

I think(Not quite sure) it was introduced with the commando evolution with the engine being sloped forward.

Click to expand...

Just look at the part nos: The 1968-70 list still shows the old guide version for both inlet and exhaust. In 1971 they changed the inlet guide.

Click to expand...

Inlet guides with seals used from serial number 149670.

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From Wikipedia: "the first 850 cc machines launched in April 1973"

Based on the part number change date listed above and the referenced manufacture dates for the 850's, is it accurate to say the guide seals were installed on the later 750's?

So the specific question is, what was driving this change?

Dances with Shrapnel said:

From Wikipedia: "the first 850 cc machines launched in April 1973"

Based on the part number change date listed above and the referenced manufacture dates for the 850's, is it accurate to say the guide seals were installed on the later 750's?

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Yes, the initial Norton Service Release (N45) regarding the introduction of inlet guide oil seals is dated May 1971, so well before '850'.

Dances with Shrapnel said:

So the specific question is, what was driving this change?

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From Service Release N45:

.......The seals are introduced to prevent oil passing
between the guides and valve stems and being
burnt, causing excessive oil consumption. Under
no circumstances must the seals be fitted to the
exhaust valve guides.........

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L.A.B. said:

From Service Release N45:

.......The seals are introduced to prevent oil passing
between the guides and valve stems and being
burnt, causing excessive oil consumption. Under
no circumstances must the seals be fitted to the
exhaust valve guides.........

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Thanks L.A.B.

So was this improvement/change to:

• resolve a persistent problem of excessive oil consumption with earlier Commandos (cleaning up their act), or
  an enhancement to meet some emissions requirements (cleaning up their act).

From a historical perspective, is it fair to say that the seals were added in response to the changing environment (market and/or environmental emissions requirements or just wanted to reduce oil consumption) or was there some other change with the motor that necessitated the inclusion of guide seals? My hunch is that it was in response to the environment as noted above.

Anyone with opinions or insights on this?

Dances with Shrapnel said:

So was this improvement/change to:

• resolve a persistent problem of excessive oil consumption with earlier Commandos (cleaning up their act), or
  an enhancement to meet some emissions requirements (cleaning up their act).

From a historical perspective, is it fair to say that the seals were added in response to the changing environment (market and/or environmental emissions requirements or just wanted to reduce oil consumption) or was there some other change with the motor that necessitated the inclusion of guide seals? My hunch is that it was in response to the environment as noted above.

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There's nothing in the Service Release that suggests this was done for 'environmental' reasons, only because of: "....excessive oil consumption...".

An engine puffing oil smoke is an indication of poor design. It's a reputation that no manufacturer wants to own. It's bad enough that Commandos leaked oil like they were designed to, but to also smoke out the exhaust would be unacceptable. Seals may actually have been driven by EPA regulations, but IMO customer expectations played a part too.

I tend to agree with mylar's statements.

But were Norton twins always oil consumers.

We have two distinct changes I am aware of which are:
Changing from a 3 start pump to a 6 start pump with redesigned rocker spindles. (thank hobot for pm on this), and
Engine slope forward commencing with Commando/Fast Back circa 1968. (thanks CanukNortonNut of this from above)

I am just wondering if the older ATLAS (vertical) engines had an excessive oil consumption problem; if not then excessive oil consumption may have been self-inflicted through design changes.....or.....primarily driven by external factors as elaborated on by maylar.

Oil in the intake will have dire consequences to the octane rating/pinking resistance of the engine. Intake seals, properly acting oil control rings, and reducing oil thrown by the rod main bearings are just three of the areas of focus in that respect.

L.A.B. said:

...the introduction of inlet guide oil seals is dated May 1971, so well before '850'.

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Does this date have any coincident with the Combat engine (I'm too lazy to look into that during lunch break...)? That could have been a response to the higher compression utilized in the Combat.

Nathan

Nater_Potater said:

L.A.B. said:

...the introduction of inlet guide oil seals is dated May 1971, so well before '850'.

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Does this date have any coincident with the Combat engine (I'm too lazy to look into that during lunch break...)?

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No, too early for Combat,

Interesting point on excessive oils suppressing of effective octane. I had first-hand experience with one of two omega pistons I installed but failed to notice the oil drain back holes were not drilled for the oil ring groove. I drilled the one piston and problem solved.

Were there any bump ups in Commando compression ratio preceding the introduction of the valve stem oil seals? Were there any changes to the availability of higher octane fuel during that period? The oil embargo on the states was 1973-1974. Catalytic converters for cars were circa 1975 but a total ban on Tetra Ethyl Lead was in the 1990's.

Dances with Shrapnel said:

Were there any bump ups in Commando compression ratio preceding the introduction of the valve stem oil seals?

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No, the compression ratio (as stated in brochures, manuals etc., pre-Combat) was 8.9:1 (or 9:1).

Once upon a time many many decades ago in my youth when I just HAD to fit the many tuning (go slower normally) modifications available (and recommended by the exspurts flogging them) to my Dommy one was the 6 start worm oil pump drive. Friends following reported I was laying down a smoke screen, nothing like as bad as a Ariel Arrow you understand or a destroyer laying down a smoke screen to protect a convoy but noticable. So one day while spending yet another weekend working in the workshop of a certain ex AMC race shop mechainic TRYING to learn (i was testing AC and DC electric motors and generators the rest of the week) we investigated by running the motor and removed the inlet rocker cover (I would guess he knew exactly what the problem was)...Luckily the motor was running on FREE 'R' that was given to me by the competition manager of a certain oil company (There is a tale there!!) The oil went everywhere...over me..over the ex race shop mechanic...over the rear of the bike...etc.....however the cause of the smoking motor was obvious. If you fit a 6 start oil pump along with a pump with the later wider gears in it then oil supply to the head increases SIGNIFICANTLY. The inlet oil return hole through the head barrel and crankcases was not big enough to return it ....oil was building up in the head, covering the inlet guides with some flowing down the guides with the rest flowing over the hump between the inlet and exhaust sides and returning via the cam followers. I drilled out as far as I dared the inlet oil return through the head barrel and crankcases but ended up shoving an external return from the side ofthe head below the valve guide level into the timing chest.WARNING NVT found out how close that return hole comes to the timing side inlet tract...there was a PILE of new near perfect heads with the holes broken into the inlet that were VERY cheap after NVT went base over apex. £20 each If memory is correct..but the castings were crap with more holes than aluminium alloy and a pain in the bum to weld. Ever heard the tale of the porous head problem?The accountants thought casting heads was so easy they could do it themselves cheaper...probably the same clever person who had the Commando frames made in Italy to save money...which then had to be put right by Reynold Tubes and Renold Tubes made more profit per frame than they did in making the frames correctly in the first place..SO I HEARD......
Of course I could of modified the inlet valve guides and fitted valve seals thus increasing valve and guide wear?? I bet NVT 6ook the cheapest, simplest and requiring little brain option which was to fit valve seals.
Was not the Dominator engine originally designed with the rocker feed oil taqken from the slight restriction in the return pipe tote oil tank. In which case the return hole inthe head barrel and crank cases would of been perfectly adequate......... RAMIFICATIONS.......clearly a word AMC / NVT did not know.

If too much oil is going to the head, why not reduce the size of the hole in the oil feed banjo bolt at the rear of the timing case . This would reduce the amount of oil pumped to the rockers. Or would this be a bad idea.

The oil as well as lubrication also helps to cool the head, and the head is the hottest part of the engine especially close to the exhaust valve.