new engine noise ???

[mikesloud]

I have had people look at it , even nissan head mechanic, I don't know if they are lying or just don't know. Weird knock noise from valve train. I just got my motor rebuilt 1400 miles ago , complete ross pistons, pauter rods,jim wolf cams, new valves, stiffer valve springs ,etc and I have had the same damn noise , It kinda sounds like a knock sort of, and goes away some times. I have had three different mechanics look at it they said it wasnt a knock. I first thought it was valve lash but it was all in spec. I have hell trying to figure out the noise. It seems to drive fine and the noise gets a little quieter as it warms up. I hate it , The car has great power but still worries me. What causes piston slap and is that common with forged pistons? what can fix it or what causes it? Could that be it ? No one is very helpful or even cares about hi performance imports here. I spent all this money and it worries me. I wish some one could help us !!

[huguetpj]

Who did your engine build up? How where the clearances between piston and cylinder wall? It could be piston slap, since it kinda goes away when it gets warm... but I'm just throwing ideas into the air here.

[C-Kwik]

Most forged pistons require bigger clearance between the piston walls and the cylinder walls with results in piston slap, especially when cold. As it warms up, the pitsons fill in the space better and the noise tends to go away. Tehre are forged pistons out there that use a higher silicone content which reduces the expansion rate of the pistons. This should have been something you looked into before buying pistons.

[PMan_S13]

Don't know if this is could be your problem, but I had a very similar effect right after I got my rebuild complete. It sounded like knocking on startup but slowly went away as it warmed up. Turned out to be the bolts holding my downpipe to turbo had gotten a little loose. It allowed a small exhaust leak to form which at the time sounded to me like a very noisy valve train. I have a metal gasket so it must have expanded as it got warm.

Got some high temp lock tite and stronger bolts and torqued them down. Sounds fine now. I don't know if that could be your problem but it is something to consider...