Cam advice sought for petrol XN1 504 engine please

Beano said:
Those blocks ain't getting any younger.
We have previously had debate on this forum about head bolt torque, with some saying that the angle tightening method is best. That is to say, doing it up to a certain middling torque, then turning the bolt a certain number of degrees.

From memory, the infallible :LOL::rolleyes: Haynes manual says 55 ft/lbs torque, which of course is absurd. A local Pug mechanic here used to regularly do them up to 60 or 65, and said that there was no problem doing them up to 70 ft/lbs. And that is what I used to do.

If too much is shaved off the head, the engine is then prone to ping, which is irritating as it sounds metallic. I think that heads started out as 92.5 mm thick and you could take them down to 90 before pinging started, but don't quote me on this. Please somebody correct me if I'm wrong.

Heads can be shaved further but then either an aluminium shim (shaped like a head gasket) is needed (or else two head gaskets, with more torque added, but that's not ideal) . So you are better off with a shim, plus liberal Hylomar squirted on all mating surfaces.
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Angle tightening only on the XN6 which has special stretchy torque to yield bolts which are use once only. These are unobtainable expect they are the same as 205 ones I believe! 11 mm thread too. Use 65 ft lbs.
 
ThanosK said:
I think 70 ft.lbs is a good number, we use 80 routinely on the rally engines with copper gaskets and o-ringed liners.
Pinging is lethal to engines, yet another reason to go with a bigger ham than stock. If your head has been skimmed to 90.8 to 92.0 mm the compression ratio will be 9.5:1 at the most, and the 240 can easily handle that without the need for a shim or two gaskets.
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I took about 30 thou off my 8.8 to 1 SR engine with 112 cam, runs on slightly sometimes after switching off, would have pinged with the standard cam I'm sure, even with 98 octane. These engines are very prone to pinging.
 
You will also need to machine the tops of the pistons to get clearance for the inlet valves if you fit a different camshaft, I had to do this with the 112.
 
GRAHAM WALLIS said:
Angle tightening only on the XN6 which has special stretchy torque to yield bolts which are use once only. These are unobtainable expect they are the same as 205 ones I believe! 11 mm thread too. Use 65 ft lbs.
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Sorry, except not expect.
 
GRAHAM WALLIS said:
You will also need to machine the tops of the pistons to get clearance for the inlet valves if you fit a different camshaft, I had to do this with the 112.
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really I was not aware of that. Can you buy new pistons that take this into account?
 
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