Diagnose My Rattle

[Strik3r]

So there is an audible rattle coming from my engine... fairly sure its coming from the block and not somewhere in the drive train. Current best guess diagnosis from my mechanic is its piston slap, probably due to the previous engine builder not setting the tolerances correctly on the rings. Am going to find out build specs tomorrow to try and confirm. It sounds a bit like a big end, but I dont think it is cause:

a) it doesnt sound quite the same

b) i've been driving with the rattle for around 3 weeks now with no noticed effects.

c) engine doesn't seem to be using oil

I have a couple of very poor quality recordings that you can listen to... the noise is the sharp rattle that you can hear clearest in the cold recording when i rev it.. its noticeable just before the 'vroom' comes.

UPDATE: Video -> http://www.youtube.com/watch?v=dRd5DGmGzpY - slightly easier to hear..

http://users.bigpond.net.au/Strik3r/car_cold.mp3

http://users.bigpond.net.au/Strik3r/car.mp3 (once warm after 15 minute drive)

I know its impossible to actually 100% work out whats wrong from that, but I'm just after some ideas that I can ask my mechanic to consider.

The recordings were taken with my phone held about 20-30 cm from the engine block.. i'll try and take another recording tomorrow with the phone held a bit further away so you can hear a bit better.

cheers

Gervase

[DjeMz]

bottom end?

hope not

[dangerman4]

do a compression test on it before you run it again.

and is it a build motor with forged pistons or just cast pistons?

sounds like a piston has let go causing exessive slap. ie broken skirt or ringlands etc allowing the piston to rock in the bore.

sounds more like a diesel tractor in the vids. lol..

[Strik3r]

yea complete rebuilt motor. N1 block, extended sump, cp race pistons, tomei rods, poncams and lifters.

I'm starting to think along your lines.. a ring or skirting causing 1 piston to slap like crazy... in which case i should probably not be driving until i can get a comp test done.. if the piston grabs it'll punch a hole in the block.

[Strik3r]

having said that, if it was a ring / skirting, the engine would be sending so much oil out the back i wouldn't be able to see the road behind me...

I'll check the catch can when I get home. Any other ideas ?

[Strik3r]

new video..

http://www.youtube.com/watch?v=dRd5DGmGzpY

OR

http://users.bigpond.net.au/Strik3r/car_cold.avi

after talking with people today and another chat with the mechanic, we think it might be a little end bearing.... any other ideas would be appreciated, else it looks like engine is being pulled down next week.

sux2beme

[dangerman4]

link dosent work

[Strik3r]

Right click -> Save Target As

SAU has some wierd linking to AVI files.. so cant straight click it.

[Duncan]

no bearings at the little end so it wont be that. gudgeon pin could come out if there was a problem with the circlip i guess.

[Strik3r]

there is no bearing between the rod and the piston ?

[Duncan]

well kind of there is a bush on the little end of the rod. its a single piece press fit though, nothing like the big end and mains

[Strik3r]

ah ok. what do you think of the noise ?? The curious thing is that aside from the noise, the car seems to be driving fine (although ive stopped driving it now for fear of doing more damage). No flakes in the oil, no blow by, no white smoke..

[Duncan]

sorry mate I'm not brave enough to try and guess about something like this over the net. I have killed a couple myself over the years but I don't want to guess wrong and have yours die. best to talk to a good workshop.