Besides the one going through the head ,two more went through the block, these were supposed to warm up the petrol, (exhaust pipe one side of eng. inlet manifold other side} many have now been removed and blocked of regards Brian
probably the same reason they used double the amount of studs and bolts on the front hubs.. overkill .. many of the components on RM Riley cars are overly complicated and overbuilt.. not quite to extent of overkill as used by RR/Bentley.. but things could have been far simpler, .lighter and less complicated and still have done the job just as well.. if one looks at the size and bulk of a riley 1 1/2 litre engine (and many of its contemporaries) ... and a 'modern' 1 1/2 litre engine .. its about 1/2 the size . 1/2 the weight ..and double the power output.. whilst lasting double the mileage.. most of the improvements are due to better metallurgy and computerized machine facilities allowing greater consistency and much better tolerances. also..'normal' petrol 'back in the day was very close to kerosene/parrafin in octane rating.. i.e. ..it was really crappy fuel..hence compression ratios of between 5:1 and 7:1 were common.. compare to today with 9- 10:1 being the 'normal' situation..