Replacing the headgasket, what have I missed?

[R500 CYA]

The car:

 

SLR with standard VHPD head and cams, polished inlets and roller barrels, mbe ECU. Head has been skimmed a further six thou after gasket replaced and timing has been confirmed as unchanged.

 

The symptoms:

 

Ran the car for 15 mins with the nose in the air to remove all airlocks and bleed system. Temp gauge sat happily at about 70 degrees (88 degree thermostat fitted)

Drove the car for a few gentle miles to bed everything in and make sure nothing leaked, all seemed well.

Increased rpm to about 5000 revs after 15 mins or so and all continued to look normal, water temp rose to about 80 degrees.

After a few more miles started to use full throttle, the car pulled cleanly to just above 6000 rpm and then misfired aggresively, reminding me of the older style rev limiters where the car would jump.

 

In a panic returned home at a gentle pace, all temps and pressures looking normal, and put car in the garage. Quick check of the oil cap (dry sumped engine) revealed a large clump of white sludge.

 

Question:

 

Are the two related?

 

Is the white sludge a result of water in the oil wells after the head was removed? Will a gentle drive clear this problem? Or is it something more terminal?

 

The cutting out seemed to be consistant around 6400 rpm. It feels like an electrical problem, perhaps the heavier demand for a spark at high rpm is causing a breakdown. Any ideas?

 

Or perhaps the two factors are related: I would be surprised if the head gasket had failed again, it's an uprated DVA one and I was very meticulous in the torquing and installation procedure as per the haynes guidelines.

 

The liners are flush with the block, not raised six thou as DVA suggested they should be, but Minister had built the engine that way and it had worked for the previous four years so I don't understand why it should make a difference now.

 

Any help really will be appreciated as I am runing out of ideas.

 

Cheers,

 

Nick

 

ps. Dave, if you read this it is by no means I criticism of your advice, you have helped me immensely, I'm just desperately trying to work out what I have done wrong!

 

 

[John Howe]

Nick, sorry to read about your troubles. I'm afraid the sludge is an oil/water mix.

 

Did you use up any water on your test driver, or could water have got into the sump when you lifted the head?

 

Assuming the water/oil problem it is head gasket related - did you measure heads bolt length before refitting them and could water on the plugs relate to you misfire?

 

Where about in deepest darkest Sx are you

 

JH

 

 

[R500 CYA]

Hi john,

 

Not worried about oil/water sludge, I'm fairly confident it is probably a by product of the water that seeped into the wells when the head was removed.

 

Morer concerned about this misfire, which I'm sure must be electrical, just don't know where to start!!

 

I'm in Storrington by the way!

 

Nick

 

[Peter Carmichael]

I would advise you reexamine your coolant system anyway as your temperatures don't make sense.

 

Running at standstill for 15 mins at 70 degrees with an 88 degree thermostat? Not possible. It means airlocks or buggered sensor. Means you don't know what temp you have been running your newly rebuilt engine at. Means yoiu mustn't run it again until you can confirm temperatures.

 

Drain oil and coolant. Flush cooling system. Renew with cheapy oil and engine flush to flush out remaining emulsion. Sacrifice a filter to this task. Carefully flush the dry sump tank and hoses.

 

Then start again with new filter, new oil. Only then will you know if newly appearing emulsion is a problem.

 

*thumbup*253 bhp, up and running