Gearbox mount to chassis - bolts up or down? - does it matter?

[CO2MAX]

I have an engine hoist lined up for Thursday this week and was hoping to drop my engine/gearbox assembly in that day. However…..  I tried dry fitting the gearbox mount to the chassis and found that, whilst the bolts could be fitted from the top on the RHS (photo 1) on the LHS (photo 2) they refused to drop beyond the waisted section below the bolt head (photo 3) even using an Allen key to try and thread them through. Both sets of bolts will go all the way home when fitted from the bottom and I’m pretty certain I’ve cleaned out any heat tape excess. In my background reading I seem to remember reading that one IVA inspector insisted bolts should go through from the top  but the new manual (Duratec v2.3) shows them from the bottom.

My question then is: does it really matter which way round they go and, if they have to go from the top, can I afford to just run the Dremmel round the holes?

Cheers, Craig.

 

 

 

[lapsedtheorist]

Mine went in “top down”, photo attached. I seem to recall they took a bit of pulling through with a plain nut before actually fitting the proper nut. I chose that way because I didn’t want to faff about with IVA questions.

[Miker7]

Instinctively I'd go down so if one but fell off the bolt would still be doing something to stop any twist on the bracket.

I've not done iva but wouldn't expect it would make much difference to them if it's up or down as long as the nuts are nyloc. Practically, how easy will it be to get a spanner or socket on a nut if you go upwards with the bolt?

[CAT170]

I would also go top down. Main reason (from experience) being it was much, much easier to hold the bolt head in position with a hex key from above than to try and tighten and torque a nut from above. You might be able to use a hex socket which would be better but I couldn't get one to fit in the tight space available. Note also if you do it this way that placing a thin piece of hardboard/plywood between the end of the Allen key and the foil will help protect it when you inevitably haven't held it tight enough with your hand!

Another tip is to check beforehand that your engine mounts actually fit on the chassis in the correct position with holes aligned (many of us had to file down the edge of the mount as the chassis welds can interfere) and that the M8 bolts will go through the chassis holes (usually have to drill out or file the aluminium skin). Clean out the rubber from the chassis mount threads too and make sure Caterham have supplied you with the 4 Schnorr washers that you will need under the heads of the large imperial bolts that go through the engine mount brackets into the rubber mounts. 

And don't tighten ANY nuts or bolts until every one of them is loosely in place. Enjoy, as it's a great feeling when the engine and gearbox are in 🙂

[CO2MAX]

14 hours ago, lapsedtheorist said:

Mine went in “top down”, photo attached. I seem to recall they took a bit of pulling through with a plain nut before actually fitting the proper nut. I chose that way because I didn’t want to faff about with IVA questions.

Problem solved thanks Ben - I’m not sure why I didn’t think of using a plain nut to try and pull them home yesterday (possibly because the other side went in easily). I’m slowly learning that there’s a fine line between “won’t fit” and “tight fit”.

[CO2MAX]

11 hours ago, CAT170 said:

I would also go top down. Main reason (from experience) being it was much, much easier to hold the bolt head in position with a hex key from above than to try and tighten and torque a nut from above. You might be able to use a hex socket which would be better but I couldn't get one to fit in the tight space available. Note also if you do it this way that placing a thin piece of hardboard/plywood between the end of the Allen key and the foil will help protect it when you inevitably haven't held it tight enough with your hand!

Another tip is to check beforehand that your engine mounts actually fit on the chassis in the correct position with holes aligned (many of us had to file down the edge of the mount as the chassis welds can interfere) and that the M8 bolts will go through the chassis holes (usually have to drill out or file the aluminium skin). Clean out the rubber from the chassis mount threads too and make sure Caterham have supplied you with the 4 Schnorr washers that you will need under the heads of the large imperial bolts that go through the engine mount brackets into the rubber mounts. 

And don't tighten ANY nuts or bolts until every one of them is loosely in place. Enjoy, as it's a great feeling when the engine and gearbox are in 🙂

Problem solved! The bolts pulled through using a plain nut. Thanks for the other useful tips which I’m sure will come in handy to tomorrow🤞

[richy]

Standard practice in a corrosive environment - orientate the nut where it is easily accessible should you need to split it for removal. For example - can you access it with a hammer & chisel?