Tapping/cracking Noise, help !

[minirace]

Have had Chimp 430 for 4 years, has had a slight tapping noise when under extreme load, has recently got very loud, a sharp tapping/cracking sound a bit like when I strapped cards to my bike as a kid and the spokes flicked them,but much louder. Only when under load, i.e. constant if in 4th @ 2000 revs and foot to floor.
I assumed manifold gaskets, I changed both sides on Sunday, (5 out of 8 had split). But noise still as before.
Anyone got any ideas ?
Thought possibly dodgy injector ?, or plug leads (a bit hopeful !), head gasket or valves (have had pressure test all v.good when cold).
THanks all, you have always solved problems before, looking forward to relies.

[trefor]

Camshaft? problems with the valvetrain? Not unknown in the Rover V8.

[boosted ls1]

Check the plugs are screwed in properly, exhaust gaskets are tight. Also keep an eye on the coolant level. Check exhaust pipe connections. If it's none of those then the engine could be pinking so I'd check the timing as well.

[GreenV8S]

Have had Chimp 430 for 4 years, has had a slight tapping noise when under extreme load, has recently got very loud, a sharp tapping/cracking sound a bit like when I strapped cards to my bike as a kid and the spokes flicked them,but much louder. Only when under load, i.e. constant if in 4th @ 2000 revs and foot to floor.
I assumed manifold gaskets, I changed both sides on Sunday, (5 out of 8 had split). But noise still as before.
Anyone got any ideas ?
Thought possibly dodgy injector ?, or plug leads (a bit hopeful !), head gasket or valves (have had pressure test all v.good when cold).
THanks all, you have always solved problems before, looking forward to relies.

If it's been blowing for a while, it could be the sealing faces have been scored so the new gaskets aren't sealing.

[minirace]

Thanks for your comments, manifold & head face are fine all so used assembly paste. Noise is too sharp/rasping to be pinking also Mole valley checked timing with it was only a slight noise (which they said they couldn't hear at all).
Doesn't really sound like a tappet sort of noise.
Cann't find any exhaust leaks.
Should I try the HT leads and those caps over the spark plugs ?

It's driving me mad.

Thank's again to all those that take the time to help.

[boosted ls1]

This might sound like a long shot but has the box been off the car? It's not the inspection plate catching the flywheel is it? Are you sure it's the engine? I've had similar problems over the years so know it can be hard to make an accurate diagnosis.

[2 sheds]

A small Exhaust manifold Leak is only noticable under load, and will make a metallic tapping noise, check for any black carbon deposites around manifold to head area. recently we saw a chimaera with these symptoms and found a hairline fracture in the "Y" piece (main cat) seam
9/10 it will be as simple as this, hopefully yours will be
Tim

>> Edited by 2 sheds on Tuesday 1st April 21:35

[ribol]

minirace said: manifold & head face are fine all so used assembly paste.

You say you used assembly paste, if it was too thick(eg Holts Firegum) it will leak more than if you had not used any. If that turns out to be the case Loctite make a VHT silicon sealer that is perfect for the job and cannot burn.

Ivan

[minirace]

Ivan, your right it is holt's firegum, oh shit, do you think I should change the gaskets again, I am not sure I can face that.
2 Sheds, I hope your right, where are you based, I am in Sunbury on Thames, maybe you can sort it for me. Do you service Chimps. I usually go to Mole Valley but its getting a bit expensive. Also thinking of David Batty in Compton This time.

Could the noise be severe cam of follower wear ?

[2 sheds]

minirace said: Ivan, your right it is holt's firegum, oh shit, do you think I should change the gaskets again, I am not sure I can face that.
2 Sheds, I hope your right, where are you based, I am in Sunbury on Thames, maybe you can sort it for me. Do you service Chimps. I usually go to Mole Valley but its getting a bit expensive. Also thinking of David Batty in Compton This time.

Could the noise be severe cam of follower wear ?

Would happily listen to it for you, but don't repair or service cars only engineer / manufacture stuff. i could supply gaskets and any reasonable mechanic could fit them assuming this is the problem.
i'm 5 mins from Sunbury, west Twickenham, email / phone for directions.
Tim

[ribol]

If it blowing again, the job will have to be done again before you do any damage to heads/manifolds. If you have only just done it then the gaskets should still be ok but would not like to say if it is worth risking re-using them.
Might be worth getting a second opinion before spanners come out again.

Ivan