odonnell

Replaced all rollers, water pump, timing belt (of course) and installed a cam timing advance key. No balance shafts as you can see in the video. I set the tension using the latest Arnnworx tool, and didn't have any issues with it - tension seems reasonable.

Does this match any tell-tale culprits, to you very experienced 944 wrenchers? It sounds like a bearing to me but am curious to hear what others think. It sounds like a supercharger whine (almost... a little quieter and more ghetto sounding) starting just under 3k RPM. Under the hood, it was much more pronounced, and after shooting this video I threw it into the garage and killed it,

Van

Is your balance shaft belt too tight?

odonnell

Tension is set to 0, doesn't exist on this car

Which is why I'm worried. If I had a balance shaft setup and it made this noise, I wouldn't think anything of it because that's fairly normal.

V2Rocket

Did you turn the timing belt tensioner roller the wrong way, pushing the timing belt teeth into the belt guard?

odonnell

KVDR

... maybe just a noisy new belt?

Sounds exactly like mine did when cold for the first ~1000 miles.

968workaholic

How easily can you spin the water pump pulley? Sounds like it may be slipping and causing the noise imo. What belt did you use?

944Ross

Have you run it with the belt guards on? Is it still audible?

What DIS system are you running?? Mighty strange to see it running with no distributor cap!

odonnell

Maybe - I'll back off the tension a hair and just let it settle in. Everything has been done by the book so far.

The water pump is hard to spin by hand but will spin a little. This leads me to believe I'm a little on the tight side, which was intentional to account for belt break-in. That's probably the issue. Belt is a Contitech, I had the same product on the car for 3.5 years previously and it's still supple and in overall good shape.

I haven't run it with the guards on, although on my last timing belt I ran it with just the inner cover. The fact that I can hear it inside the car leads me to think it's abnormal from just a timing belt.

Re: ignition
They're LS1 coils running in wasted spark, via a MegaSquirt (Microsquirt to be specific). In the video, you can sort of see the crank trigger and the AFM delete setup w/ GM IAT sensor haha.

odonnell

Ok, now I'm second guessing myself on the belt tension. I set it using the Arnnworx tool, and I'm unable to spin the water pump by hand. That seems to be the other "rule of thumb" test passed around in addition to the 90* twist method. I've done belts before and usually I can spin it by hand.

WP is new and is not seized...it spins freely with less tension on the belt. Maybe the belt just has more grip on the water pump due to its material, and I'm worrying about nothing? I'm only concerned because of the whining noises earlier, but every other method of determining a good tension in checked off.

V2Rocket

I've never been able to spin the WP pulley by hand with the belt set at 90* twist.
Never figured how people got that one.

odonnell

Ok, thanks for the sanity check. I'll set it one last time and just run it.

marc abrams

Mike, my car also whined like that also after I replaced the belts and rollers. I used the ArnnWorx 920x also. After a 100 mile drive the whine was about half of what it was. After 500 miles there's almost no whine when hot. I used Continental's belt and roller kit. I hope this makes you feel better.

AZ520

I know this sound, its the t-belt rubbing on the belt guard, the one right above the water pump pulley.

odonnell

Thanks Marc, I'll keep that in mind.

AZ250, I don't believe this to be the case. I painted the belt guard for this reason (to tell me if there was contact under any circumstances) and there is no scuffing. With the engine off, there is at least 1/8" gap, and the idler doesn't push the belt span closer.