Afternoon folks

Does anyone know the specifications for the 5.0 SC engine components?
I'm replacing a piston and need to know the piston ring gaps and the torque settings for the head bolts, and big end bolts!

Thanks in advanced

(P.s I've looked at the workshop manual and there's no mention of these anywhere)

 

Anyone got any ideas?

 

Since there are no engine internal service parts available from JLR, there are no published specifications for ring clearances and torque values for many components.

Due to the similarities between the AJ-V8 Gen 3 and Ford 5.0 litre modular V8, you may want to investigate the internal specifications and materials used by Ford to determine if the same torque specs may apply.

I'm quite sure the piston ring clearances are going to be different for each of the three rings fitted to each piston of the AJ-V8 as they're made from different materials.

Wish I could be of more help.

 

Thank you for the info man

Looks like this is going to be harder than I first thought!

 

One additional thought: the connecting rod and cylinder head bolts may be designed as 'one-use' due to stretching.

The cylinder head bolts are M11 X 178mm, part number is AJ812892. The connecting rod bolt would need to be matched elsewhere.

 

Search for Dave Tibbs on the XF forum. He is one of the few to have rebuilt his engine.

 

As for piston rings, there is a formula used to figure out the gap. I'm sure I have it saved somewhere, I'll go look for it.

EDIT:
Yeah, I'm surprised I didn't remember it,
Cylinder Bore (in inches) times 0.004 = ring gap (in inches)
Slightly larger gap for Nitrous and Turbo installs. Superchargers don't really need more, but you COULD sneak it up a thousandth or so.

 

Perfect! Thank you
Now what is the cylinder bore lol or is that something I'll have to measure when it comes to putting a new piston in?

 

Each cylinder bore is 92.509mm +/- 0.009mm

Be careful with the ring clearance gap as each of the three rings is made of different material and may have different clearance due to cold to hot cycles.

 

With a title like 'engine rebuild' I hope you put some pics with your progress!

 

Thank you for that! I've just seen that in the specification Page Haha

Is there anyway I could find the correct info on this as i don't want to damage anything further!

On that specification sheet I see the torque settings for the conrod bolts and it doesn't say any angles, still need to find out what bolts they are!

 

From the Workshop Manual:

'The diameter of each piston is graded and precisely matched to each cylinder bore to help reduce noise.'

How are you determining the correct piston for the one you're replacing?

 

I've found a range rover sport piston designed for the 5.0 S/C. Being the same engine I imagine it's the same piston?

 

What the quote means is each piston is matched to each cylinder to provide the optimal fit.

Is there a grade marking on the piston that's being replaced that you can use as a guide or starting point?

 

Oh I see, I haven't got the piston out yet, will post on here if there's any form of marking. Surely that would be a really expensive way of building these engines?

 

It's not for engine assembly as there are pistons of various grades available.

When you have the piston removed from the block and cleaned, post pictures too if you can as it may help someone else later on.

 

Also, remember to have the connecting rod cap and piston in the correct orientation prior to fitting the gudgeon pin.

 

"gudgeon pin", man, I haven't heard that term in like fifty years.

 

The OP is in the UK and that's what we've always called them. For the American audience, it's a 'wrist pin'.

 

So the engine is out and all the bits are off.

The piston has a big chunk missing. No idea where it went, but it didnt damage the head, valves or the bore. I must've got super lucky!! But while it's out I've ordered a new water pump, thermostat, timing chains, all new gaskets, new head bolts. So should be like a new engine!