Torana Bonnet Hinge Refurb

The following procedure applies for LC to UC Toranas and HQ to WB holdens which all share the same style of bonnet hinge and suffer the same wear on the pins.  This leaves them sloppy and they squeak and rattle on their rubber isolators as well as not lining up consistantly when the bonnet is opened and then shut again.

This is my old set of bonnet hinges - I actually got another really good set from a UC to do up whilst these ones held the bonnet on the car but you can see by their appearance half the reason I needed to do something - the chrome was stuffed and was never done properly as they were complete hinges when they were chromed.

First step was to centre punch the middle of the pins on the side with the cross stamped into it so they can be drilled out.  I took a measure of the OD of the pin where it had been stamped so I knew how far I should peen over my new pins on re-assembly.  The heads of the pins need to be expanded to approx 2mm larger than their 'unpeened' state.

I used a 11/32" drill bit and a pin punch to remove the pins being very careful not to mark any part of the hinge as I wanted to HPC coat them and have them look spot on. Timber and plastic are great for cusioning steel items when you are trying to knock the pins out.

3 things to take note of here. 

1. The pins are stepped down because the way they work is they are actually rivetted hard to one piece of the hinge with just sufficient clearance so they can pivot on the other half of the hinge - they do not float on both bits of the hinge - this is important because they would wear quicker if they were just allowed to float between 2 sliding bits of metal as there would be a lot more side loading on them.

2. There are 7 pins per hinge and 2 types of pin.  The pin on the left has a slightly higher step (3.2mm) compared with the one on the left (2.5mm) as 2 of the hinge pieces are made of thicker gauge steel. This is important because if these are not correct, the hinge will be too tight or will have sideplay.

3. There are 3 pins with the 3.2mm step and 4 with the 2.5mm step per hinge. 

The majority of the wear is on the OD of the first step on the pin as that is the bit that pivots in the hole. It would be wise to check the holes in the hinge to make sure they have not worn - if they have, I would drill them to the next largest metric size and make the new pins to suit. Mine didn't need drilling but I did get the pins made very slightly oversize and they were a firm fit and the fine file was my friend for re-assembly on a couple of tight ones.

Once the hinge is all apart, no better time than now to actually get a proper coating job done - I think this is the first properly coated set of hinges I have ever seen.  Whilst they were down in Melbourne getting the HPC coating applied, I had a mate turn me up 14 new pins out of 304 Stainless steel.  The pic above is the coated hinge ready to go with new stainless pins all lined up. Notice the alloy tool that goes under the pin so they don't get marked when the pin is being peened over.

Some close ups of the tool below.

As each bit is assembled, I lubricated it well with Redline Grease on the moving parts. (I'm sure any grease will do but I only use the redline stuff)

Now down to the assembly.

You will need to start with the 2 pins on the little piece of the hinge as they are not accessible when the remaining pins are installed.  Identify where the big sized and the little sized pins go or the hinge won't work like it should.

Make sure the hinge is assembled the right way (you only get 1 go unless you made spare pins) and find a nice young blonde assistant to hold it for you (the hinge I mean :-) )

Place the alloy tool under the head of the rivet and using a nice smooth faced peening hammer (I found flat side best), carefully peen the head of the pin over until you have spread the head out 2mm larger than the hole.  There is no need to worry about going over the top and peening the pin in too tight - it has to be nice and tight on that half of the hinge you are 'rivetting' it to and it is not supposed to move on that bit.  

The 304 stainless only needed very similar sort of hammer hits to mild steel to deform it into the desired shape.  Carefull finishing off with the peening hammer left a really nice smooth finish and I didn't even have to file or polish them.

(Ner ne ner ne ner ner to the rare spares guy who told me I would never be able to peen over a stainless rivet - it was easier than falling out of bed)

There are 2 pins that go on the piece of angle which bolts to the bonnet.  I was very paranoid about damaging the HPC coating so I put about 20 layers of masking tape along the edge to protect it if my swing was a bit wild.  I also used a pin punch to finish off the peening process around those pins because you can't physically swing a hammer in there without hitting the hinge - worked a treat.

The finished products.

One last thing. In the pic below - see how the base of the hinge where the spring hooks around is bent slightly - this is the result of me shutting the bonnet when the hinge bolts were fairly loose - as the spring stretches, this bit of steel can't handle the force and will bend unless the bolts are done up almost all the way.  I had to remove this from the car and re-straighten it because it causes the spring to lose tension and can't hold up the bonnet.  This is worth checking as part of the hinge refurb process becuase I have seen a few of these where people reckon'd their springs had gone weak when in fact the hinge was bent at this point.