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Help! My bonnet won't fit.

by Rex Grogan

   
 

From the number of times I've heard this and variations of it, I conclude that it is a common problem made worse when there is the necessity of having a new floor or part of it made. Once the body is off it may be re united with the chassis (and not necessarily the original chassis) in a bewildering number of ways. Not just ‘right or wrong’ but an almost infinite number of variations of ‘almost right’ or ‘good enuff’.

During sleepless nights wrestling with this problem and its consequences on the fit of the bonnet, (read non-fit of the bonnet) I came to the conclusion that I was the only one in the universe to have encountered the difficulty. Two observations have since encouraged me to think that I am not alone.

Firstly I noticed at a recent event, a car with a nicely fitting bonnet (one gets to be very critical about such things) only to find on viewing the other side that the bonnet was a deplorable apology for a decent fit. Big gaps, tapering gaps, skewed locking catches - the lot. Clearly the owner had been having a major problem (I can't think he didn't notice it) and had resigned himself to driving a banana shaped car, "with luck no one will spot it… ". Well they have, and it can be improved. Read on...

Secondly the observation that one purveyor of parts offers to make you a new bonnet to fit your car but you have to leave said car with him while he tailors the new one. Surely in this is a counsel of despair? But it only goes to show.

Given a pristine, undrilled floor, or a body which has only just been introduced to the chassis the unhappy owner discovers that there are four ‘little’ problems

viz: -

1 The body is too far forward or too far back along the chassis. The radiator position is a fixed by the chassis brackets but the bonnet stay has several degrees of freedom ‘cos the holes are slotted and said stay can be fitted, on the top of the radiator and a body brackets, or underneath them, or one on top with t'other underneath, not to mention skewed or right or left, and this is only the start. Obviously the body must clear the engine, but by how much? There's about ⅜” (all metric? Work it out!) float fore and aft. In fact it is only restricted by butting the front against the cylinder block, in which case the rear cylinder head nuts are pigs to remove (been there), or too far back so that the foot pedals have insufficient travel. I kid you not, because I … no, I won't unburden myself further on that score.

2. The body can be skewed. It's not easy to spot this one and you can't rely on the front wings which join the running boards, which join the rear mudguards, which bolt to the rear wheel arch to be precise enough to ensure that are both sides are the same. The bits can fit quite well, apparently, and the body can still be quite badly out of line. You need lots of measurements from the centre line of the chassis, which you have previously chalked on cross members to make sure body and chassis are parallel. You didn't mark the centre lines? Oh dear!


 

3. The body may be up or down. During assembly the body could be, and was; raised or lowered on the chassis by felt pads. These were fitted “to reduce body drumming caused by vibrations being fed from the chassis”, said Austin. Oh yeah? At the risk of being sued for defamation of character I take leave to suggest that much more likely is that this was another "adjustment" available to make everything fit. And it just to confuse matters still further it didn't have to be the same on both sides! The body could be tipped relative to the chassis.

4. This is the delicate one. The body could be tilted up front or back by the judicious insertion of shims, packing pieces, distance blocks, call them what you will, between the chassis and the floor. Austin used bits of wood, "to reduce body drumming". Ha ha. If your bonnet won't fit after you've got items 1-3 sorted, number 4 is likely to be the culprit because, it turns out, it is a very sensitive adjustment which has a profound bearing on the bonnet fit. I needed ⅜” of extra height at the front end to match body and bonnet. But my bonnet was miles out to start with, so it proved to be a very effective adjustment. And of course it doesn't need to be the same on both sides. Have I said that before?

A real codge - but it works if the other 'adjustments' are inadequate . The rubber 'twixt bonnet and at body doesn't have to be the same both sides or uniform all round or the same back and front but it has to look the same.. In fact you can fine-tune the apparent bonnet fit by bodging the holes through the rubber, which take the wires securing this strip to the body, anywhere you like. And no one will notice this because the bonnet, which you have now made to be, apparently, a beautiful fit, covers it over. Easy.

Although the foregoing concentrates on the problems associated with new floors and mismatched body/ chassis combinations, the problem can, and does, arise when bodies are removed and on replacing, don't match. This, I am convinced is because the felt and wood "anti- drumming" pieces have rotted away or compressed over the years. Avoid, at all costs, the temptation to make the body fit back again. It can be done I know, and the two structures can be reunited by pulling down the chassis bolts firmly but the body twists and stresses and it quickly shows up as cracks at the corners of the doors and windows.

The aluminium body of the Chummy or Tophat is very easy to distort but resist that temptation and restore the various packing pieces until a stress-free fit is obtained with the holding bolts fitting without ‘persuasion’.