James Gasek

Heard after running 7 psi and hitting 2 step a little too hard.. anyone ever heard anything like this on a nb? I know the lifters usually aren't a big issue on nbs like the na's, could the VVT be causing issues? Really want to figure this out.

Car is a 2001 Canadian se

Video:
https://photos.app.goo.gl/hjYQWg7jodiYddev6

hks_kansei

So it didnt make noise.
you bounced it off the limiter
Now it does make noise.


Valvetrain noise is usually a result of there being too much lash between cam lobes and lifters.
HLA often make noise because they pump up with oil pressure to reduce the lash, when they clog they dont pump up as fast, and get noisy.

NB uses solid lifters, so they dont have that issue.


Either lifter type can still get noisy for other reasons:

wear
busted valve spring
chipped cam lobe
etc.


Short answer, take off the rocker cover and have a look at everything in there.

James Gasek

Yep, hate to be that guy but that's what happened. Tommorow I'm gonna go down to the shop and look under the valve cover. Appreciate the helpful reply. Definitely sounds valvetrain related to you though right? No weird vibrations or anything just that awful noise.

Thanks,
James Gasek

curly

iTrader: (25)

I did that once, turned out it was the piston skirts contacting the crank counter weights.

James Gasek

As in you bent a rod?

hks_kansei

I'm at work, so cant listen to the noise.

But i'm assuming it's like the typical lifter tick sound.


A rough way to help narrow down the source of sounds is to take a screwdriver and put the end of it on the rocker cover, and then put your ear against the handle.
The sound will travel up like a ghetto stethoscope.

try a few places around the engine and see where it's loudest.
it's not ideal, since there's a lot of background noise, but can help at least trace the bigger noises to some degree.


I'd still track the issue before continuing to drive it much.
if it is excess lash from a busted spring, or worse, it spat a shim, then you may chew up a cam lobe, which would mean having to source a new cam (or have the current ones reground if there's enough meat left)

James Gasek

It sounds like the typical lifter tick from the videos I've heard but it is pretty loud.. I'm going to compression test to make sure all cylinders are making healthy compression and make sure everything else is in check then do the ghetto stethoscope, then pull the valve cover. Just have to wait and see I guess.

Gee Emm

Bent rod contacting the bottom of the bore ...

sixshooter

iTrader: (12)

Race cars that use a "2 step" have a forged bottom end and are rebuilt every 50 hours of runtime or less.



Sounds like you might get to do both also.

We've got really weak rods known to stretch or bend and very poorly balanced engines that are prone to harmonics related failures. Treated with some empathy they can survive being boosted for quite a while.

A stretched rod due to over-revving can cause contact with a valve. A slightly bent valve will not seat properly and there will be excess valve train noise due to the additional lash created. It is also possible to burn a valve using a two-step.

hks_kansei

Just had a listen.

that sounds a bit more severe than lifters with too much lash.
But not like knock.

I'm leaning more towards big head issue (like a spit shim) or as others said, maybe bent rod clipping something.

sixshooter

iTrader: (12)

Just listened. Does not sound like lifter tick.

It also sounds like the frequency is a bit too often. Remember, the pistons cycle twice for every movement of the valve.

James Gasek

Wouldn't it have to be bent pretty severely to be contacting the bottom of the bore? Or is the clearance really that tight.. the engine is still very smooth and I don't hear any weird vibrations.

James Gasek

I was just guessing some sort of lifter tick because I knew they were common on the older NA's. It didn't sound like it was coming from the bottom end or anything. I could see it being the rod making some contact with something though. Definitely sounds like it's coming from the head but I'll have to look more into it today.

sixshooter

iTrader: (12)

If the rod stretches the Piston can hit the head or the valves

codrus

There is very little clearance between the piston skirt and the counterweights or the oil squirter.

--Ian

James Gasek

Quick update:

Pulled the valve cover, didn't see any damaged loves or anything, all the springs are intact.

Video of everything just in case I missed something obvious:
https://photos.app.goo.gl/DStXDFivNxvwHstF8

Compression test next...

Thanks to everyone for your time and help. Looking more and more like a bottom end issue now that I checked everything out and talked with a few more people. If I did bend a rod or something the plan is to put some forged rods in and have it ready to rip for the spring or late fall.

James Gasek

Cylinders 1-3 were around 130-140 psi, cylinder 4 (where I think the noise is coming from) is around 120. Could be slightly lower as a result of not reading TDC due to a bent rod. At least I have good compression!

dglb99

I don't have nearly as much experience as some of the other people on this forum, but isn't good compression more like 180+ PSI?

Your numbers sound pretty concerning to me.

Midtenn

iTrader: (15)

See other thread about motors with poor compression. The test is as only as good as your tool. Percent difference is a big indicators on cheap tools.

James Gasek

I just ran to AutoZone and got a loaner compression tester, and I only cranked it 3 or 4 times to get the reading which is probably why they are so low. They were pretty consistent and I thought they were reasonable enough. Didn't know Miata motors had such high compression honestly. Not too concerned because they were pretty consistent other than the hurt #4 cylinder, and even that was only like 10 psi off.