I am grateful to Steven Wood for a copy of an LT document showing all the engine codes for RT, RM & DMS buses, together with his explanatory notes.

The document gives engine details, fuel pump types and axle ratios.

I've posted it on the RmOOF website and you can see it by clicking here

My bus number (if any): RM238, RM471 and RM2213

It was not as complicated as you might be led to believe by the chart. 1) A lot of the variants were swept into the main classes over time or were of very small numbers.
2) You got back, in the main what you sent in. The bulk of the RM engines were the EN 45 EN 52 and EN 62, the EN 62 became more and more common over time. The others for RCLs and BEA were of very small numbers in comparison with the other types.

There was a spare engine in the District stores for roughly every 12 allocated buses and this "ratio" was spread and maintained across the fleet as far as possible by Rolling Stock Stores Control. Every 6 months a check was undertaken with Internal Audit assistance to see that the laid down allocations of units was being maintained. If not transfers were made to balance the books, this was particularly important where changes in vehicle allocation and routes had occurred and Districts that had lost vehicles had been "slow" to make the necessary transfers .
With regard to classifications being changed over time, bear in mind the only difference between an EN 54 and EN 62 was the fuel pump, so as more DPA fuel pumps were fitted more and more EN62s appeared and the EN 54s disappeared.

My bus number (if any): RTL 960 RMC 1458 RM 1585 and several RTs

Brian, I wondered if you're able to shed any light on the 'replacement' 590 engine blocks that were manufactured sometime after the delivery of the last Routemaster. I was told that there are generally more sought after since generally they will be less worn and can be readily identified by the serial number on the outer casing of the block being stamped upside down. I've no idea when these were manufactured and in what quantity.

My bus number (if any): RM1699 Eastbourne Regent V 69 (KHC369)

Steve
I am not aware of any particular programme of engine block replacement, but I wasn't at Chiswick until 1973 and then had little to do with the engine overhaul shops. The system at Chiswick was to repair where possible and replace if none of the possible repair processes would effect a viable part. What that meant that each unit was stripped to component parts and then subjected to a process that restored it for use as a component usually in another unit. When an engine block was deemed beyond repair and it would have had to have been bad given the range of repairs possible at Chiswick, it would have been replaced by a block from the new material stores. These would have been bought in economical batches as determined by the supply contract.

My bus number (if any): RTL 960 RMC 1458 RM 1585 and several RTs

AEC manufactured a batch of 590 engines complete with fans at the very end of the companies existence.
The engines were stockpiled at Southall at the same time that the ex LCBS RM types were being assembled there.
The engines were finished in black with yellow fans and were all kept in the front finishing inspection shop.

I went there at the time and was amazed as the parts supply at garages was crippling.

My guess is the engines were made in 1977/8 or 9. I think it was winter 1979/80 that I went to AEC.

Of the engineless wrecks from LCBS, RML2345 stood out. It was missing almost everything, When it later arrived at HL it was almost as good as new. It ran like new but the engine was silver painted, fan and all. and could not be distinguished from any of the others that arrived over that period.
Engines were not my field then and I did not pay much attention to the nuances of the Chiswick mechanical practices.

Interesting John, must have either been an attempt to ease the parts shortage or was it only for the return of the LCBS buses that were by then in a dire state? There was certainly a severe parts shortage around 79/80 which resulted in many buses being against the wall and that continued up to the time that the Metrobuses started to arrive in large numbers and replace the DMSs. I was seconded to RSE Buses about this time to go round all the garages and find out what was keeping buses off the road and see what was really in the stores as hoarding of parts by GEMs and garage foreman was rife. The Garage stores location system was only in its early days at that time and only AR and Q were on it. Typical of what was going wrong Q had several RMs around the district off the road waiting steering side arms whilst Southall which at that time had no RMs in the district had a bin full! A lot of loaned engines and other units were not being returned to their rightful garages either, with storeman being instructed to send in their own "notes" with engines being returned to Chiswick in an attempt to get another engine for their district, often the one that one replaced had the right "notes" sent in with it and was then returned to the rightful owners. Because of this practise the Supplies Office at Chiswick set up a special team to determine where units should go, just sending one in with requisitions did not guarantee getting one back, the no bus available situation determined that.

RML 2345 would have had a silver engine as it was rebuilt and overhauled at the same time and so received the Aldenham treatment.

My bus number (if any): RTL 960 RMC 1458 RM 1585 and several RTs

I just checked the LT identification plate that is screwed to the left side of the engine in RLH 62. The plate states that it is an EN 38, which identifies the A217 engine as fitted to the 2RLH's.

Thought that might be interesting to fill in a little gap in the codes.

My bus number (if any): RLH 62

RLHs were long gone when this chart ws produced Jim, so useful addition. The EN 77 Leyland engine for the DMS is also missing unless there is another page of course.

What I did find odd was that was that according to this chart the same RM Flywheel FF13 could have 3 different ratios 4.8:1, 5.22:1 and 4.7:1. Does that mean that the plate on the diff means nothing in determining the ratio?

My bus number (if any): RTL 960 RMC 1458 RM 1585 and several RTs

Jim, just a point of clarification - I thought that the RLH had AEC A208 engines as opposed to 217.

I don't think that there's a second page to the chart and so am not quite sure why the Leyland DMS engine is missing.

My bus number (if any): RM1699 Eastbourne Regent V 69 (KHC369)

Yes, I noticed this as well. However, I read it as the same flywheel type but mated to differentials of three different ratios.

However, my question was concerning the Flywheel FF13 vs. FF14; was there really a difference between the one for the Leyland and AEC engines ? From memory it is the same flywheel with a different mounting.

My bus number (if any): RM1368

Yes of course Andrew, the diffs were DU numbers and differed by their ratios. I think you are right about the FF13 and 14, probably differentiated due to the different part as opposed to unit number.

My bus number (if any): RTL 960 RMC 1458 RM 1585 and several RTs