Mgf donor car: building an MG Allegro VVC!

[edk83]

So then after having some fun this summer and getting on the nitrous.

Time for the standard Rover 5000 mile service.... lol



The engine I pulled from the zr after doing about 2000 miles on it with no issues, the previous owner said it had been fitted with an mls gasket so I decided to leave it and just do the belts and pump etc.

The gasket was an elastomer not mls but does look fairly recent, cant see any damage to the bead. The liners all look fine as does the block, the head has some pitting on the firing rings, one I can just about feel so that is going for a skim. I don't think these would cause an oil to coolant leak though.







I've had a new Payen gasket on the shelf for a couple of years ready, just got it out the packet and noticed this.

[edk83]

The head got skimmed anyway, looks good.



Back at it, happy with the belt tension.





All back together Spun it on the starter and got oil pressure, the belts all still line up.
I need to change a coolant sensor thats on order before putting coolant back in.

[Rob Bell]

I have to say that the engine bay on your car looks even better "in the metal" than it does in the pictures Ed

[edk83]

Thanks mate, could be down to the old phone camera and I need to replace a dead strip light bulb!

So now it's back up and running but probably will have to come to bits again. The vvc control shaft is binding at certain points in the rotation, causing no vvc! It's been suggested that as the head was skimmed after bolting it down the journals the shaft sits in could now be slightly different. I'll have to take it out and check it, maybe lap it into them or try another shaft.

The fun continues!

[Rob Bell]

Have you managed to get this sorted yet Ed?

[edk83]

Not yet, I had another look last night and got the plunger running nice and smooth with compressed air, was about to call it fixed and it got jammed again about 2/3 the way down. Couldn't even lever it back up with a screw driver! Took the hcu off and the plunger was still stuck so it's not that, no amount of force would move it upwards but as soon as it's tapped lightly downwards it frees off in both directions.

Messed around with it some more and found that if the vvc mechs are loosened from the head / carrier the plunger is nice and free, as soon as they are re-tightened it starts jamming up again on the upwards stroke.

I took the carrier off and cannot see any damage or anything fouling it at all - it does look quite straight forward to swap the vvc units and control shaft as long as the cams stay on the units. It's been suggested that I should just swap the shaft but with all the resealing effort needed to test it properly I'm very tempted to swap the vvc units and shaft complete from my spare head.

[edk83]

Well after lapping the vvc control shaft into the journals in the carrier it seems to be nice and smooth. I had to drain and clean out the followers as they were jacked up which meant the cams were getting locked up when refitting. After draining it was better but they were still tight and that feeds back through the vvc mechs and makes those tight.

I decided to try some different cams. A 270 high lift exhaust cam with some dva offset dowls and some Mike satur inlet cams that are a higher lift too. Building them up with engine assembly lube certainly helped. The vvc still felt really tight but all the way through not at a certain point in the shaft rotation like before. Decided that's probably feedback from the cams and I should just run it.

Sounded pretty unholy to begin with, vvc works though ! After getting it nice and hot it's now super quiet.

Next job is to get it on the rolling road to remap for the cams, idle is a bit degraded and I can tell there is slightly less torque sub 2k rpm. Over 3500 when the vvc comes in though it pulls hard.

New cams left. Because race car!

[flyingbanana]

How much did the cams cost?

[edk83]

I paid 250 for the cams second hand, they came with known quiet vvc mechs and the dva offset dowls all ready to go, it was in bits at the time I saw them for sale so perfect timing! I've also swapped the control shaft for a clean looking one and lapped it into the journals.

I think these cams are £600 or £450 exchange

Inlet cam 270° duration and 10.08mm of cam lift.
Exhaust Cam 260° duration and 10.16mm of cam lift

Now that it has run I could take the hcu off again and see if the plunger is now smooth which I suspect it will be. It seems to be happy now and all resealed etc so I think I'll just leave it alone!

Next job is to rewire the fuel pump, at the moment I'm using the factory zr circuit via the inertia cut off and the relay in the engine fuse box. After a while the fuel relay gets hot and then the ecu refuses to prime the fuel and errors with 'Fuel pump primary circuit failure'.

Swap the relay and it will work again for a while, my 044 pump draws 14a and the factory circuit fuse is 20a - so I thought it would be ok, maybe not - the long wiring run to the pump is 40a cable and my dash switch is rated at 25a, I'm only using a short bit of the factory wiring but either that is failing or the yellow relays are not rated very highly. When it fails the pump still runs when cranking but will not prime, very odd I wonder what the ecu is looking for - voltage drop on the relay terminals maybe?

I could just swap the pump relay for a better one but I might as well make the entire run decent. I've got a couple of the zr fuse box outputs spare so I'll run one of the 40a ones to a new 30a rated relay and use the old wire for the trigger, its adding anther circuit but the switch will also have some load removed, I just find it's handy to be able to kill the pump when needed.

[edk83]

Well not a picture update but this weekend I rewired the pump and swapped the generic front brake pads for some Mintex 1144 compound.
There is defiantly more bite and braking effort on them now, so pleased as they are not cheap!

Still looking into a rear disc conversion for the winter months, my 2nd hand obp fluid pots are weapy at the bottom seals too which is annoying. I have a new set that look to be a better design to go on but that means pushing all the fluid out and rebleeding, another job for the winter.

I'm booked in on a rolling road day with the MG club at Saws tuning in a couple of weeks so that may be worth a photo! Should be able to tweak the map for these cams and check the afr on the nitrous too - and maybe a bhp number!

[talkingcars]

Still looking into a rear disc conversion for the winter months,....

ZR160 rear H frame?
Or does the Allegro have a full subframe?

[edk83]

The Allegro has a rear beam but the suspension is horizontal like a metro, so no shock towers.

I'm planning on mounting Corsa sri rear stub axles inc hubs to the Allegro trailing arms

The Corsa package is the correct overall width and pcd, comes with modern wheel bearings and caliper mounts all on the stub axle.
The wheel offset would remain the same with the whole package being within 2mm width as the Allegro drum setup.

Mounting it will need some fabrication and thought though, the Allegro stub axle is not bolted to the arm like modern ones are.

[flyingbanana]

Steel Top Hat shims each side machined I/D and O/D to allow the new stub axles to be bolt in. I'm assuming the allegro ones are fitted by heating up the arm to expand the hole?

[edk83]

Possibly, removing them might be fun. They are an interference fit with a circlip in the back to retain them. The corsa stub axles simply bolt onto a flat surface on the end of the vaxuall beam. The Allegro beam has the hole where the stub axle lives plus a raised part which holds the rear section of the wheel bearing. That will need to be removed to make a flat surface to mount the Corsa stub axle to, this also provides the correct wheel offset.

Mounting it won't be as simple as drilling 4 holes as the casting at the Allegro arm rear would be in the way. My plan is to fabricate a spreader plate that mounts to the Allegro arm correctly and the Corsa stub axle can be machined and welded into it. I may use the 3 drum brake backing mounting points but drill them out for thicker bolts, these pickup the arb on the other side so need to be retained. I could also weld the spreader plate with stub axle to the arm for extra strength, if these 3 bolts are not enough. - Not like you end up replacing stub axles often

[flyingbanana]

If the arm is cast, welding is not that straight forward - how about fabricating a cds arm to replace the cast one?

[edk83]

Anything is weldable with the correct wire

Plan A is to make them bolt on anyway. I've been looking at the rover 100 setup but they have separate hubs to the drums.
Allegros have drums with built in hubs and separate bearing races so quite different

[edk83]

It went for a thrashing on a dyno yesterday.



I'll take that for a little K series I think

[Barbour]

That's insane!

Pocket Rocket, love that colour too.

Great project.

[edk83]

Thanks Check out the torque curve on the nitrous

[Bazzajay]

That's awesome!