Hmmmm. OK I've got a bad feeling about this but would like any opinions ...

Following on from my previous posts the new heads barrels and pistons were fitted to a replacement engine, and finally got the last of it all together this afternoon with all of the ancilleries fitted.

Turned over the engine with oil down the barrels, then new plugs, all electrics connected and it started on the third try. Excellent. But.

A very loud tapping noise coming from the engine Its difficult to locate where the noise is coming from but seems to be the nearside of the engine, or towards the rear near the flywheel.

Rechecked the valve clearances of course, all fine, heads torqued as per spec.

I've tried the trick with the long screwdriver held up to the ear on various parts of the engine, but can't locate where its coming from. I can hear the tappets tapping away happily in the heads.

The engine is "full of beans" feels great with tonnes of compression and fires up really easily, but for this dratted noise it'd be happy days.

The noise is in time with the engine revs, a loud metallic clack, doesn't seem to be louder when revving up or down. I've a horrible suspicion what it might be - top or bottom end of a con-rod buggered. Which would mean another engine needed and a lot of extra work time required.

Any ideas or thoughts welcome for other causes or things to check.

Many Thanks,
Chris

Chris,
any chance that one of the pistons is in back to front, with the arrow on its crown pointing towards the flywheel instead of the fan?

ken.

Thanks Ken,
We were pretty meticulous both Matt and Me checking the piston arrows before we 'closed'. So don't think so, but given that anything is possible, does that fit the symptom? would that mean the piston would be hitting the head? Is there any way of telling the orientation of pistons without deheading? (a keyhole surgery fibre optics set would be handy obviously)
Or could it be anything else causing the racket?
Thanks,
Chris

I might be way off here, but it's not the cowlings hitting the flywheel is it? It doesn't completely match the description you've given, but it might be something simple like that.

Seems the Argy pistons have a habit of contacting the heads there was a bit of murmering about with some of the engine builders at Snet this year

solution is to take heads off and look for witness marks and relieve the piston crown in that area

which of course is forbidden in race regs as it comes under the "not permitted to machine grind or polish..."

Sean

Russell I will check the flywheel and look for some physical contact happening around there, good idea.

Sean, Very interesting, they are argie pistons and barrels. When you say 'relieve' do you mean to file or sand or grind away that area of head? Not planning on racing so no worries there! Thanks for that.

Cheers for the feedback so far guys Anyone else got any more ideas?

yup... but on the piston rather than the head
80 grit emmery should do the trick or a burr in a die grinder( dremmel)

the metal is quite thick (but stop when you can see the top of the con rod )

also if you didnt hear the donor engine run before the build up it could be bearings. Check for any back forward movement of the crankshaft by hauling back and forth on the fan while your assistant feels for movement at the flywheel,while not necessaraly the same thing the end float gives an indication of how tired the the bottom end is.

Not very positive sorry. Maybe small end cracked.
How did the new gudgeon pins feel like.

It's that Concannon. You should never have let him near it - it's BOUND to be scrap now. He's a jinx.

Viking,
Thats my fear too: small end problems. But the gudgeon pins felt fine when they went in. And the noise started from the moment the engine started. I still think it could be this though worst luck

Sean,
I'll try to check the crankshaft 'end float' the way you said, I did run the donor engine in the car for a time, and the reason I kept it in the shed was because although it had no compression (why I changed it) it was a smooth runner. Or so I thought ... maybe I was wrong about it ... but I don't think it had horrific wobbly top end problems when taken out.

2many - I won't hear a word said against The Matt.