Oil drain hole Domi 88

Remind me please, Wayne - are you still rebuilding the 88 ?  Has it got the scavenge return oil feed to the rockers etc ?  Are you using a 6-start oil pump gear or an SS oil pump ?   The larger drain hole for oil from the head aims to remove the excess pools caused when different combinations of the above are used.  Eventually the excess oil can flood all the galleries in the head and pour down the guides making smoke and sprouting leaks.  Even a hollow dowel in the existing hole will restrict some oil passage so I usually carefully increase the diameter and provide a gentle lead-in staying away from the edges.  Be careful when opening up the hole through the head gasket, base gasket and crankcase.  With the scavenge feed, an SS pump and 3-start oil pump gearing you will not need to bother.   Good luck, Howard    

So, Wayne worry not.  Does the oil pump have an S stamped into the front of the casting ?  That signifies an SS oil pump, in which the scavenge gears are twice the width of the feed gears.  If it doesn't have the "S" then it is more than likely a standard Dominator pump.  So assuming no "S" then, in the build-state you have there will not be any over-oiling in the head so you don't  need dowels, larger drain hole nor "O rings."  From the image you show it does look to me that your 500 has the stronger late crankcases - there seems to be a shadow along the cases towards the join lip, just above the copper breather pipe.  Is your engine a late (1961) 88 ?  Whatever, you seem to be building a good motor.  Good luck, Howard  

Hi Wayne again, I don't want to be a 'party pooper' but that engine number looks like a 122 P to me. The serial number beginning with 76___ also tells me that it is earlier than 1960.  The P says 1959. If your documents show that it is 1960 who am I to contradict ?  C would signify that a Coil ignition set was fitted at the build stage in the factory.  It looks like you're using a Manual magneto which is great.  Regards once more.  Howard 

Hi.  59/60 was  a time of changes, lots of coil ignition bikes were built , lots of engines built in 1959 were fitted to the  DL series and sold later as 1960 bikes ,this was normal practise, ,plenty of DL  machines hung around for a year or so in dealers showrooms . They were not liked much by the "fast" guys . Guys that really  rode and went places fitted panniers and Avon fairings  , their passengers appreciated the  panels as something to grip with the legs and kept them away from the muck.Lots of these enclosed bikes including many of  the  very few 650DL's made  went to eastern Europe  at a special price, never to be seen again . Anyone know where one is ?.Or ever seen one ?.

The P  indicates a 1959 made motor, the P in later engines  from around 1963 indicates made in the AMC Plumstead factory .  AMC did not seem concerned that they were making a mess of the Norton  dating system ! . They had very little respect for what went on in the antiqated and outdated victorian Norton factory.  When they tried to replicate the quality of machine that came out they filled skips with substandard parts . It took a while to catch up with those talented Bracebridge st engineers that got laid off. 

The engine numbers posted by Wayne have too many digits.
If the bike was first Registered in April 1959 with engine number 9112153 then this should be just a 5 digit number.
Likewise, engine number 763531 122R should also be a 5 digit number.
All the Heavy Twin engines up to late 1961 had 5 digits. They then went to 6 digits but not as high as 763531.  The last Commandos were only around 330000.

Adding to the confusion......the number on the rear of the crankcases 271 is too low for any Model 88. The first Model 88 being 122 47300 built in 1952. This has SN T7978.
The only engines that I can find with shop number 271 are a 1952 Big 4  and a 1949 Model 7.  
The Model 7 SN being prefixed with a letter 'T'. ie T271.