strange noise at high rpm....please help!!

[E91cpe]

i searched the forum and could not find anything on this. (the car is a 91 240sx bone stock) it runs very smooth during everyday driving but at around 6k rpms and over it makes a weird vibrating noise sounds almost like a sped up ping. i think it may be the heat shields on the stock exhaust vibrating....has anyone experianced something like this the help would be greatly appreciated

[E91cpe]

anyone?

[fun240]

How many miles?

Your timing chain guides could be messin' up. Usually the first thing to go. If you're not feeling the other cams engage at 4k.. And they engage at 6k... Something is really wrong. If it sounds like a ping, Maybe, Marble in a Can. Which is infact, the timing chain hitting the timing chain front cover... Then it needs to be replaced. You'll lose the guide in the motor, then it could be a potential hazard. Timing chain replacement kits from Nissan run about 450 bucks. I wouldn't go with autozone ones, you'll be replacing it once again. Considering the motor is doing it at higher RPMS, i would wait till you crank it up one day, it does it at idling. Then replace. If that's a SOHC just get a DOHC and do a swap. Ya those SOHC motors are good, and ive heard of nice ones that would kill DOHC... but so much easier with something newer.

[E91cpe]

well the engine has 140k on it and from what i know it has never had a timing chain it does make some noise at an idle but im not sure what your talking about by cams engaging at 4 and 6k rpms ...are you talking about their power band?

[corn322]

I don't know what fukin240 is talking about... maybe he's getting the swirl valves confused with vtec. Might take a look at the timing chain guides though. Not an easy task, btw.

My B&M shifter rattles at 6k. It sounds pretty bad. It could be your heat shields. Take