NH 350 inner timing cover dowel fitment

[dennis.t]

I bought a '56 NH350 engine without an inner timing cover. The crankcase has dowels (see photo) do these locate the timing cover? And if so can an older timing cover be used (photo)?
A supplementary question. The parts list shows the part number for the inner timing case as 2000-56. The part identifier cast into the timing case is A7/507 P. How can you cross reference the parts list number with the code cast into the part? This is the case for many castings.
Many thanks, Dennis
PS. Sorry, for some reason the photos, like Miss World winners, are in reverse order!

[will_curry]

I've cheerfully swapped cases with only two areas of concern. One is the state of the quill feeding the
crankshaft and the other is how well the camshaft bushes will align. There are all sorts and variations
of timing case with the earlier ones having external rocker-box oil feed and sometimes oil pressure
regulators none of which you need.

2000-56 isn't a part number, it's a spares number. Earlier versions are 2000-41 etc. with the last two
digits being the year of introduction. As far as I'm aware there is no cross-reference listings for the
later spares numbers.

Out of interest, the three digits stamped into the crankcase half make up the assembly number for the
engine with the other crankcase half and the timing chest having the same three digits.

[Roger Gwynn]

The 'Do Not Use' part numbers are listed beside the spares number in the parts books until 1956, although I did once see a 1956 FH export parts book with the part numbers listed. I tried and failed to obtain a copy. the Part numbers were used within the factory and are the ones to be found on drawings and were in use as early as the 1920's. The spares numbers were introduced in 1930.
As Will says there are lots of different gear cases (in Ariel speak) but most can be interchanged with little problem, I can't see enough of the features to identify the one you have but the lack of dowels will not be a problem.

[dennis.t]

Thanks both.
To be clear, I was supposed to ask if the correct inner timing cover has locating holes for the dowels on the crankcase to aid locating and add strengthening?
Good to know that an earlier inner case can be used.
My question about part numbers versus casting codes is how do we, or the part suppliers, know that the part number in the parts book equates to a particular casting if they have no way to cross reference them? Is it perhaps just the year code on the casting?
Dennis

[nevhunter]

The Pivot pin for the CAM followers helps line up the case. AS Will noted those 3 parts crankcase halves and cover have the same number stamped on each so it's wise to check alignment of the camshaft bearings IF not matched numbers, The stepped faces of the mating parts also assist alignment if they're not damaged..Nev

[Pete.Silson]

... does timing cover has locating holes for the dowels...

I believe so - as per picture above. However I don't know the exact year of this cover.

Pete

[Roger Gwynn]

The dowels were added in 1955, unfortunately Ariel forgot to list the new case in 1955 although the dowels and new gasket are listed. The new case is listed in 1956 erroneously as 2000-56 and without any drawing number. If you search Draganfly's site using 2000-, in amongst all the other stuff you will find lots of numbers for the gear case, due to Ariel's excellent part numbering system all singles gear cases are 2000-yy. Frequently the part will change but the drawing number doesn't as the same part can be made from the same casting, so beware and assemblies will be made up from several parts that each have their own part number and the assembly has another plus a spares number. I did start a project to list all the differences but it stalled. I did get as far as listing all the numbers and applications, there are 15 for the vertical singles (covering 32 years), 2 for Slopers and 3 for inclined. 2 of vertical singles versions didn't get a new number, probably because they were interchangeable with the previous version.

[dennis.t]

Roger, thank you for your reply and your advice.
Pete, the photo is a great help as I can see how and where the dowels mate with the inner casing.
Regards,
Dennis