CRANKCASE TIP from the magazine of the Bristol A7 Club

   If you have a Seven dating from 1933 to 1936 you need to take care that the right crankcase is used in your car. Not many people know that there were different crankcases made for high or low frame chassis. If you try to fit a high frame (chrome radiator type) crankcase into a low frame car (painted radiator cowl), then the engine is too low at the back and the starting handle is too high up. This can be remedied fairly easily by putting some extra packing under the rear engine mountings. However, if you put a low frame crankcase into a high frame car then a number of problems become apparent which cannot be easily resolved. The main one being that the back end of the gearbox is much too high and the fabric coupling tends to foul on the propshaft tunnel. The crankcases concerned are the types with two main bearings and rubber engine mountings.

    Identifying the two crankcases is not too easy. They were produced concurrently from mid 1934, when the first Rubies were made, until about the end of 1935 when the last high frame touring models were produced. So, you cannot rely on the engine number to tell which is which. The rear engine mounting feet are positioned at a different height on the crankcase but the easiest thing to see is a square shaped flange on top of the starter motor mounting of the low frame crankcase.  Behind the flange with the two bolt holes, where the starter motor is attached, there is a tea cup sized lump that hides the starter motor bendix gear. On the lowframe crankcases this has a heavy square flange about one inch back from the fixing flange, which looks as though it is a stop for the clutch pedal. On the high frame crankcases this square flange is incorporated into the starter motor mounting flange.

    I only noticed the difference early in 1997, after building a replacement engine for my Opal prior to the run from John O’ Greats to Lands End. After mentioning it to a few people, it seems that there are one or two high frame cars with prop shaft couplings fouling the prop shaft tunnel and the owners didn't know why. So, I hope that helps. By the way, I discovered that the spare crankcases that I have are all high frame ones and I really need low frame versions.

                            Nick Beck