Wierd and annoying rattling noise

[Knudsen]

Ive got this wierd noise comming from my engine. It sounds like theres something loose inside the engine. Its not present in idle, but if i rev the engine to ex. 2000 rpm its there. Its not disturbingly loud, but its im still a bit worried. The engine pulls hard and doesnt make other bad things. The head is milled 1 mm, and after assembly the engine ran perfect - untill now approx. 1500 km after.
Anyone have an idea on whats wrong with my damn engine? If its dead, im going GZE so dont hold back

[robokill]

Hmmz would almost say the valve springs maybe. Engine would get space in the pistons. While revving you could get a rammling noise.

Why bother buy a GZE fix it up and keep running the engine till it dies.

[Knudsen]

Yeah, it could be the valve springs. I changed the head to one with unknown milages. The original had 140000 kms on it when the headgasket blew. Then i changed the head with one i had laying around that raised the compression... Perhaps that wasnt to clever a move, cuz now it uses a bit more oil and sounds wierd. (but pulls alot better)

Ill guess i just wait and see what happens. If im lucky the engine just keep going and going, even if it keeps rattling.

[Ivan141]

How's the oil pressure and amount of smoke/pressure coming from the crankcase ventilation? Best keep an eye on those 2 things since it might be a piston ring going bad. My engine didnt sound right before it started dying on me either, they do seem to pull strongly before they give up alltogether.. piston slap (pivoting piston? dunno what to call it exactly) seems to be a common problem on aging 4age's..

[Knudsen]

The oil pressure is a bit lower with the "new" head, but still in the OK area. I guess that can be caused by the head if it has alot of miles on it. I havent checked the pressure from the cranckcase yet... But ill do it next time i go for a drive.

[Ivan141]

Just check it when the engine is warm, pull the rubber tube and check how much it's blowing..especially when applying a bit of throttle.
Usually oil pressure gets much higher when the pistons are leaking pressure

[Knudsen]

Okay i have just been out for a little ride... When the engine is hot, it blows a little bit from the crankcase... Is that good or bad? Its just blowing enough to feel it, and no oil is spraying out. As said before, the oilpressure is not either high or low. The needle is in the middle when ideling @ 950 rpm, and if i really hits it, the needle goes to the next line in the oilpressure gauge.

I also have a leaking manifold gasket, it could be that whos making the noise... Atleast it sounds like its leaking.

[Ivan141]

Sounds like the pistons are okay, valve seals are probably also reasonable if there isnt a lot of blow-by gasses. Oil pressure should always be between the 2 lines on the scale though. About 3/4 of full scale in practice. My current engine only drops pressure under the first line at low idle speeds, I dont like it when it does that. If it runs at middle of the pressure gauge while driving I would seriously start saving up for a new oil pump. Also oil pressure usually starts dropping a little bit on high speed runs (continuous high revs) but that's somewhat normal.

Before going worrying to much though, make sure oil level is in order and check the connector on the oil pressure gauge since they come a bit loose sometimes causing weird pressure readings.

[NoHachi]

Try listening and finding out where the noise comes from. Usually a little attention and a long piece of hollow tube can help you out here. At the formula student team we used to have a sort of stethoscope for these things. I remember we bought it cheaply from an ordinary carparts store. Its just a hollow plastic tube with earplugs at the end. It really helps with listening to isolated parts of the engine like bearings and injectors etc.

It could always be a bearing letting go. These tend to rattle.

[Knudsen]

Regarding oilpressure: Ill take some photos tomorrow, its a bit hard to explain how much pressure it makes in idle and in "high" revs...