Kerias

ok i know i've pulled some stupid stunts with my car lately but i have yet another question to ask! i have a knock... it dosnt happen when its cold but only when it warms up fairy loud. i also know i have and exhaust leak at the gasket. how do i tell if its the exhaust or rod? and if its the rod how can i tell if its the barring or the pin... also can i tell if its a valve? the exhaust leak is on the #1 cylinder on top in between the water outlet and intake.... please have good news! the sound is very "pingy" not like a hollow knock. also only knocks at idle. acceleration and de-acceleration its just quiet

NismoPick

I have a video on youtube of my 280zx turbo when it had a rod knock. Search for "280zx rod knock" or it might be "280zxt rod knock". I'd post the link but I don't have access to youtube at work.

It's a fairly unmistakable sound. Usually quiet at idle, loud when revving.

Exhaust manifold gasket leak is also an unmistakable sound... it's a chugging open exhaust sound.

Kerias

if you will be on here im uploading a video in a few min

Kerias

Rod knock??? Or exhaust leak? - YouTube


the best knock is at 1:42

ThaPimpShrimp

NismoPick's L28ET 280ZX Turbo Rod Knock - YouTube

Watched this a while ago

Pretty mean sounds exhaust there haha.

ZZzzz

haha, thank you Nismopick! i do NOT have a rod knock. awesome!

Kerias

so what the diagnosis on my car???

NismoPick

Dunno... that was a really really crappy video and only one second of the noise.

I suggest checking the valve rocker clearance and timing chain guides.

ThaPimpShrimp

After doing what Nismo said, see if you can feel the exhaust leak from below the engine.

That sounds exactly like what my engine sounded like when I had an exhaust leak.

Jack up the front of the car and stick your hand up to the manifold (carefully) to see if you can feel any exhaust. Use a flashlight! Also if you have it, a trick I've learned is to take a piece of hose and put one end to your ear, and put the other end up to the manifold and move it around. If there is a leak you'll know it, you'll hear the air loudly in the hose.

Good luck!

Edit: I misread these posts. I thought you didn't know if you had a leak or not. Honestly, I suggest you go ahead and replace the gasket now and see if what Nismo said is correct. It'll be a lot easier to diagnose without all that noise.

Kerias

ok so change the gasket... the check valve clearance... then check timing chain guides. ok is there any way to ensure the main bolts dont break?

ThaPimpShrimp

On the manifold? Take your time, use a product like PB Blaster and let them soak. If they are hard to get off don't force them too much, use more PB Blaster and wait a day or more. Also using a pneumatic ratchet can help if you put it on a low setting. The hitting motion of it breaks the bolts loose.

Oh and here if you haven't seen this.. https://www.zdriver.com/forums/240z-...-gasket-18779/

WanganDevilZ

This is mine, just got it started tonight

Datsun 280zx resurrection startup... Rod Knock - YouTube

ThaPimpShrimp

Ouch

I got mine started today though! Sounds good. The engine itself is a lot quieter and the muffler is louder

Tomorrow I am doing the catalytic converter gaskets and cleaning up the distributor cap.. I am having an intermittent idle drop because of ignition, I figure since it was off for so long and it rained it probably could use some cleaning.

Sorry for jacking your thread haha.

NismoPick

That sounds like a valve train issue (out of spec or stuck lifter), not a rod knock. A rod knock wouldn't be going that fast at idle.