Upgraded Engine Mounts

With the Southern Kit Car Club European road trip coming up it was time to give the car a check over and look for anything that might present reliability issues during the 1300+ miles.

One thing I've been keeping an eye on recently is the original Tiger engine mounts.  Other Avon owners have had issues with these failing and I suspected it was only a matter of time before mine gave me issues.  Upon closer inspection there did seem to be some metal fatigue setting in where the diagonal tubes meet horizontal plates.  I was not happy with this so decided now was the time to get on with fabricating a more robust replacement.

After jacking up the engine and resting it on some wooden joists I was able to remove the old engine mounts.  Straight away it was easy to see that in their natural rest position these had not been level with the top of the engine rubbers.  Instead they had been inclined and the tightening of the bolts had clamped them down onto the rubbers and had deformed the top of the rubbers over time.  This obviously meant that there was a constant force applied trying to tear the diagonal tubes from the horizontal plates, even before any twisting force is applied by an accelerating or decelerating engine.

With the original engine mounts fitted, the engine was not level.  So using the wood under the sump I raised the inlet side around 15mm to bring the bottom of the engine (sump) horizontal with the ground, when viewed from the front of the car.

Next I replicated the four flat plates.  This time out of 6mm steel instead of the previous 5mm.  For the diagonals I used 5mm thick 45mm box section.  This compares with the 1.5mm tube used previously.

Cutting these box sections to fit was a very difficult task.  Multiple compound angles and all work being undertaken with the engine in situ.  On the exhaust side I was having to work in between the small gaps between the exhaust headers - very difficult indeed.

In the end I got there.  Had them tack welded by Ashby Welding ready for a trial fit.  They fitted perfectly, with the horizontal plates resting on new rubbers, without any clamping and with absolutely no stress applied to the mounts or rubbers.  Back to the welders to have them fully welded up and here is the end result.  A very nice job done by the welder.

These have been painted up, fitted to the car and bungs inserted into the bolt holes to protect from water ingress.

Another long term to-do list job completed and hopefully another piece of reliability added to the car.

Engine Mount Strengthening

The offside engine mounting plate is fixed to the chassis spanning two chassis rails, where they come together in a vee shape.  This is strong enough to take the loads transmitted from the engine.  On the nearside however, it is a very different story.  The flat plate is welded on top of just one chassis rail.  Over time the loads from the engine cause this to droop and eventually this puts an abnormal loading on the engine mount itself, which then fails.

I'd kept an eye on my nearside mounting plate over the months and it had always been fine.  Recently though, I noticed that the non-welded side had drooped around 10mm.  It was on its way to causing the engine mount to fail.

So, I fabricated two triangular fillets from 6mm mild steel and got a local garage to weld these in place, after 'jacking' the plate back into its original horizontal position.  The welds are not the neatest in the world, but they seem to be good enough to be strong.

Denso Alternator

I'd been having some more issues with my Lucas alternator, so I took it apart and ordered a service kit, which included bushes, bearings, rectifier and regulator.  I started to overhaul the alternator, but during the process I decided that I was not really happy with the situation.  I wasn't convinced that I would not have further problems in the future, so I finally took the plunge and ordered a genuine Denso alternator.

The new alternator is rated at 40 amps, so should be more than sufficient for the modest electrical loads that my Avon can generate.  It weights about 2kg versus the 3kg of the Lucas, so there is a nice weight saving too.

When I removed the Lucas alternator I discovered that the lower mounting bracket had failed.  The front lug had snapped off and it was just the rear lug that was holding the alternator on.  It was lucky that I discovered this in the garage and not at the side of the road!

I took the old lower bracket to the local fabricator/welders.  They removed the old lugs and added strong new fixings for the Denso.

For the alternator tensioner I re-used the old upper bracket and connected it to the alternator with two rod ends and some 8mm threaded rod.

The main output connection is a threaded copper post.  I had a proper battery cable made up that had the correct size ring connector for the alternator on one end and the correct size at the other to connect to the starter motor connection (where the car's main loom terminates the +12v).  This arrange should be much better than the Lucas spade connections, which are prone to arcing.  The cable is more heavy duty than the original Tiger alternator output wire, so this can only help.

Cooling System Updated (Again!)

1. As advised by Tiger I originally ran the car with no thermostat and no bypass plumbing.  I understand this is a fairly standard set up for race cars.  However, if quickly became apparent that the engine was being over cooled.
2. My next configuration had a thermostat with a 3mm hole in it as a bypass.  This worked very well all summer - the engine stayed at a constant 88oC, unless the fan needed to cut in.
3. Once the cold mornings of autumn arrived the engine started to run cool again.  Things were fine at lower speeds, but once there was a significant air flow through the radiator the coolant temperature struggled to maintain 80+ oC.  So I decided to introduce a full bypass pipe and fit a thermostat with no bypass hole.  To do this I had to fit a thermostat housing from an earlier Silvertop Zetec.  This was necessary in order to fit the coolant temperature sensor in a place where it would get a reading prior to the thermostat opening (as the Blacktop Zetec housing has no sensor holes and I'd previously had the coolant sensor in the main pipe to the radiator).  This set up generally worked very well, but there was one problem: somehow air from the expansion tank would make its way to the top of the radiator, which is higher than the pipe that feeds it from the thermostat housing.  A little bit of air would get trapped there each time the engine was run until there was sufficient air there for the flow of coolant to break down - not good.
4. So one more modification and hopefully the final configuration.  A 8mm hose barb was welded on to the top of the radiator and plumbed into the pipe joining the thermostat housing to the expansion tank. Now all works well.  Any air can return to the top of the system and an added bonus is that the hole coolant system is now self bleeding, which will help when I come to renew the coolant at future services.

Here is a schematic of my final cooling configuration:

8mm hose barb welded in to the top of the radiator.  It is just above parallel with the ground.  This is to allow it and the pipe to fit under the curvature of the nosecone.

Full routing of the new pipework (apologies for the poor quality mobile phone pictures, must use the proper camera next time).

C-shaped brackets were fabricated from aluminium strip.  These were fixed under the camshaft cover bolts and rubber lined p-clips were riveted to them.

Radiator Leak Repair

Since first getting the car on the road there has been a very slight leak from the radiator bleed bolt.  I'd tried tightening it up a number of times, including using PTFE tape on the threads, but it always continued to leak.

I tried one more time, but unfortunately this time I overtightened the bolt and stripped the thread in the radiator - turns out the tread is just tapped into the aluminium so is very weak. My solution was to re-tap the  hole to a larger size (M10 x 1.5mm thread) and use a spare cap head bolt of the same thread that I just happened to have spare.

Once the bleed bolt was fixed I could get back to investigating the leak.  Upon closer inspection it was not the bolt that was leaking at, but a pin hole in the weld around it!  With the engine running drops of coolant would slowly form.  I decided to leave this for a while as the coolant was only coming out very slowly.

Many miles later I got a coolant overheat warning from the Webcon ECU.  Turns out there was air in the top of the radiator and the coolant was no longer flowing properly.  The cause was air being sucked back in through this tiny pin hole each time the engine cooled down.  Something had to be done to fix this. I took the front of the car apart and removed the radiator.  This was when I discovered that the pin hole had turned into a crack, probably about 10mm long.  The body of the radiator was starting to split.

I quickly took the radiator to the friendly local welders who re-made the weld over the area where the crack was.

I'm happy to report that after a few hundred miles of use there is no longer a leak in the radiator.  This gives me added confidence for longer runs, particularly with another trip to northern France booked for later in the year.

Gear Lever

After reluctantly taking the angle grinder to the £60 Rally Design gear lever I took it down to the local welding shop.  Really pleased with the result and only cost £10.  They had to dip it in water to keep it cool so as not to melt the plastic ball joint inside.  This now clears the dash nicely with the gear knob fitted.

MoT Booked

MoT slot and car trailer booked for Friday 13th January.  Fingers crossed!  Final jobs to do including cutting an angle into the gear lever and getting it welded up.

Exhaust Welding Completed

Got the welded exhaust parts back from Tiger.  Looks like a good job and after a trial fit the alignment still seems to be correct.  Will fabricate a bracket for the silencer next and get the exhaust fitted.

Cutting the Exhaust Pipes to Fit

Before getting started on this I realised that the lamda sensor boss was missing from my Webcon Alpha Pro4 kit.  I called Webcon, and as before, they were extremely helpful.  A replacement was posted first class and with me the following morning.

The various exhaust components were fitted together.

Problem was that the curved pipe between the cat and the silencer would not have enough metal showing.  This is a problem as where the bend is in the pipe the profile changes from round to oval(ish).  This is okay where the pipe is to be welded to the cat, but would not be okay where it is to be push fitted into the silencer.  To attempt to solve this the silencer was moved back a little, but there is not much room to play with as it is already near to the rear wheel arch.  In the end I removed about 25mm from the end of each exhaust header and this allowed just enough of the curved pipe to be showing.  The curved pipe was cut to the final dimensions and everything assembled.

All permanent joints were marked up for alignment ready to post to Tiger for them to weld, including the installation of the boss for the lamda sensor.