cylinder head torque on Renault 5

[renaultman]

Why does the engine in my Renault 5 make a tapping noise since I replaced the head gasket? Could I put more torque on the cylinder head bolts?

[KebabMeister]

Did you replace the head gasket yourself?  Is it an Over Head Valve or Over Head Cam engine?  Did you adjust the valve clearances after rebuilding the head?

[renaultman]

It's overhead valve, 1396cc, I replaced the gasket myself. I adjusted the valve clearances as well and now I get a ticking which sounds like it could be a broken piston ring - I did one of these repairs before on another Renault 5 and had the same problem, but the ticking went away when I put a bit more torque on the bolts....! Could it be some kind of compression problem and is a little extra torque OK - or is it more likely a broken ring?

[KebabMeister]

Difficult to say without hearing it!

I would recheck the valve clearances, if one has too much of a gap it would make a lot of noise.  Which method of setting the clearances did you use?

[renaultman]

With the engine cold, I set them according to the Haynes manual, by turning the crankshaft and adjusting with a feeler guage - is there another way? The noise seems to be coming from the block, though, rather than the head.

[v64paul]

Get back to basics. why did you change the gasket? was the noise there before? if no, what have you done, retrace your steps as it were. it's very unlikely that torquing the head bolts down more would stop it rattling, more like increase tappet noise cos in theory the gap between the rocker and valve stem would increase by the amount you manage to tighten the head down. any signs of a broken ring? mis-fire, crankcase back pressure? 

[renaultman]

Either the gasket blew because the engine overheated - it's quite common on these cars if you're not really careful - or the engine overheated because the gasket blew! I didn't notice the rattle before this but I'm wondering if a broken ring can lead to the gasket blowing? I've done everything by the book - skimmed the head, used new bolts, reset the valve clearances twice already (so I don't think it's the rocker arms) and this noise is quite loud. The car is not mis-firing - how do you recognise back-pressure?

[v64paul]

back pressure is excessive smoke/fumes  created as compression gases push past the piston rigs into the crankcase itself, run the engine and remove the oil filler cap. old ford owners will know the signs! lots of smoke/ fumes = backpressure. if the overheating has caused a piston to melt, then the rings would break up, but unless you removed the pistons there is'nt much chance the rings would be damaged any other way. 

[renaultman]

Thanks. No, there is no excessive fumes or smoke coming out of the filler tube, just recognisable crankcase fumes which are (mostly) sucked out by the carburettor...I guess it could be something else then (not a piston ring) causing the noise, then...? I'll do the valves again, one more time, and see if it's one of them but, other than that, I'd be concerned that something worse has occured. Thanks to all concerned for the help - this is a great forum!!