I've got a FWD VQ (Altima) engine here that's making noise.. The valve lash is on the tight side (had the heads cleaned/valves lapped in) @ .006" - .008" on the intake side and .009" - .010" on the exhaust side with the engine cold. I ordered the correct buckets, and will replace them. However, would having lash too tight cause valvetrain noise with this engine? I would think that noise would come from having the lash set too loose.. but, then again, I haven't had to really mess with valve lash on one of these engines before. The engine has JWT cams that are ground on stock base circle diameter.

Any pointers/experiences would be appreciated.. Has anyone else had this issue after lapping valves in?

Thanks..

 

Whats the noise sound like...and is it only on cold starts ?

 

It's a very tone ticking noise.. but, it's defined, and definitely noticeable. It ALMOST sounds like piston slap, but, not quite as loud. This engine has HR pistons in it, as well.

The noise is there at cold start for sure, and gets slightly quieter as the engine gets up to operating temp. But, it is still there for sure.

Travis

 

There's a similar if not almost identical issue w/ the 03-04 DE's... Its the VTC cam sprockets. There a small spring mechanism inside that supposedly wears over time. I'm actually having mine replaced next week. I have the same exact symptoms you do but not as bad. Mine is 3 outta 4 times on cold starts. Do a search for them on the forum, theres like 2 threads out there that talk about this. The only thing that sucks is that replacement OEM ones are not cheap and the labor is fairly involved as well.

 

Can you elaborate on the sound? When I start up my 04.5 it sounds like it's choking for a few seconds (engine cranks fine, fires fine) but then quickly disappears. Only on cold startup.

 

The sound is like how the OP decribed it....a few seconds of what sounds like piston slap ( metal ticking )...that only happens on cold starts.

 

The sound doesn't go away.. I have the engine out, and the sprockets sitting on the bench.. I suppose I could take them down and inspect for damage..

Travis

 

make sure you are using the correct lash specs... JWT are not the same as OEM specs (on the exhaust side anyway for my cams)... if they are set to OEM your might think they are too tight and in reality they could be loose... here's my experience (starts on post #42 – conclusion on post #55)

https://my350z.com/forum/na-builds/383566-cams-3.html

 

That's what mine sounds like, but, it's pronounced when the engine is cold, and seems to get quieter as it warms up. I don't know what to make of it..

My lash was WAY too tight.. though.. I know that. I have 45 degree angled feeler gauges, and measured clearances as tight as .006" on the intake side, and .009" on the exhaust side. The highest clearance that I measured was .013", on one of the exhaust cams.. The rest were all closer to .009-.010". Nothing on the intake side was higher than .011", with the majority being closer to .009".

I have buckets on the way, so, I'll eliminate the possibility of it being incorrect lash.. but, it bothers me that I don't fully know what's going on. Maybe it's a bad chain tensioner? This engine is 6 years old.. and it gave me a good rattle for a second or two, every time I would start it up.

Travis

 

Well, I just went ahead and pulled down the entire engine.. to double check the piston to wall and bearings..etc.. Everything looked fine, with my PTW @ around .001" on VQ35HR pistons. Bearings all looked fine, as did the wrist pin clearance. So, this has to be something associated with valve lash, or the chain/tensions/guides.


Travis

 

GL...keep me posted.

 

Update?

 

My sound completely vanished when replaced the cam sprockets...I put in 04-05 ones in my 03 - same part# but slightly different design. also changed out the belt and tensioner as well. - All is good.

 

Do you have the part numbers please for the sprockets, belt and tensioner?