Note: This subject is also partly referred to in Neil Cairns XPAG Engine Rebuild Day 12.
I have noticed that it is rare to see a Y type with a perfectly fitting bonnet. All our cars must at some time, have had their radiators removed and more than likely they have been refitted before the bonnet was replaced, resulting in misalignment.
First it is advisable to check the condition of the rubber buffers that cushion the rear of the bonnet, if they are perished or hard it is best to replace them (Y register shop supply the side buffers). There are also thick rubber radiator mounts that fit above and below the cross member that the radiator sits on, if these have also gone hard and become unfit for purpose they should be replaced.
Drain the radiator and loosen the hose connections that hold it in position. Check that the top hose is not too long causing it to hold the rad in an abnormally high position also check that the adjustable engine mounting stay is allowing the engine to line up centrally with the rad.
Unfasten the side stays at the radiator end and loosen the nuts that hold the rad down below the cross member. You will now be able to manoeuvre the rad to a position that gives the best fit at this stage. When the bonnet sides are clamped down it should fit equally on each side. Washers can be added front or back to the ends of the long central pivot pin to minimise end float.
If the vertical gaps front and back are not parallel to the main body and chrome radiator cover, the rad will need to be made higher or lower to achieve an even gap. The chrome pivot at the radiator end can be lowered with washers for a small adjustment, otherwise the radiator will have to be removed and rubber or metal shims can be added to give more height. If it requires lowering, you will need to be more drastic and replace the top rubber buffer washers with handmade thinner ones.
With the sides clamped down and all rad fixing points left loose you should now have the best fit possible. Unclamp and lift one side ensuring the radiator does not move. Adjust the side stay by screwing it in or out so that there is a clean fit for the nut and bolt which is then replaced and tightened. Re-clamp this side and do the same on the other side. Now all the hose clips can be tightened. Finally, lightly tighten the two bottom fixing nuts and secure with lock nuts.
All our cars are different in small ways and I found that the fit of my bonnet was compromised by the uneven line of the back of one of the top panels. This meant that it was not possible to achieve a small gap down the sides. However if you follow these procedures you will have done the best you can for your car.
Stand back and admire your work.