Engine noisy after chain guide job--opinions sought

[DAEDALUS]

Need some opinions here. I recently did a chain guide replacement on a '91 Q with 122k and now the engine doesn't sound right. Here's a recording (5MB):http://home.socal.rr.com/robverna/enginesound.mpg

I removed all the belts before recording that to isolate the sound as much as possible. No idlers or components, just crankshaft, pistons, valvetrain, and injectors. The sound seems to be coming from the left head. Here's the complete story: While doing the job the cords I had tied to the timing chain gave and the engine jumped time while I was doing the left bank. It was so quick, I wasn't sure what had happened, so I turned the crankshaft by hand to be certain. I felt the piston hit the valves, and I knew I had a problem.I informed Dave, the owner, and he decided to go ahead and have both chains replaced since I had to open up one cover anyway and because both valve covers were leaking. So in the end, I replaced all chains, tensioners and guides.Initially, I thought the noisy engine was because of the new guides needing to wear in, but now it's been a few hundred miles. I've changed the oil 2x since the job, along with mobil1 ATF flush, and I'm running 10W30 Mobil1 right now.I thought maybe I bent a valve when I did the hand check, but my shop instructor at school, who is an ASE Master Tech with 19 years experience, is certain I didn't. He listened to the car too but wasn't sure what the problem could be. He recommended I go to 0W30 oil, but I'm skeptical that'll help enough.The compression is fairly balanced:8: 148psi 7: 158psi6: 155psi 5: 158psi4: 155psi 3: 155psi2: 162psi 1: 155psi

I think I dripped a bit of Mobil1 into the #2 plug hole, which might explain the higher value there. I've ordered an oil pressure gauge, but haven't got it yet. In the meantime, no oil warning lights, and I have retorqued the main crankshaft bolt a 2nd time and I'm now pretty sure it is to spec.

I will get an oil pressure reading before doing anything else, but I wanted to throw this out there and get some opinions first. I won't hesitate to pull the cover again, but I would like to have some ideas about what to look for. Collapsed lifters? Bent rockers? I don't think the manual gives any gap measurements between the cam and rockers or did I just miss that?Thanks for any help.

[Q45tech]

When ever you change the guides the HLA and tensioners have to bleed the air that was admitted.......clattter clatter clatter sound like the engine is going to explode for a minute.

You crank and turn it off imediately a few or 10 [sometimes 20] times and it suddenly goes away after a few minutes running.

How many teeth did the bank jump usually just one or two [20 degrees] before you fixed it?

After it turns quiet do [multiple] warm/hot power balances and make sure every cylinder drop is no more than 25 rpm variance.

Based on compression they should be within 12 rpm [if injectors are clean]

[911/Q45]

Could a blob of RTV or some other foreign material have plugged a valve train oil passage?

[DougQ45]

After doing the 91 with 187k I had a clatter problem upon strat up that went away after running for a few seconds. In a week or so, it never came back. As Q45tech stated, maybe it just needs to bleed alittle more air?? Compression is good!!

[DAEDALUS]

Thanks for the replies. I put the belts and fan back on and tried the multiple start/kills but it didn't seem to do the trick. I considered a plugged oil gallery, but none of the oil ports going to the camshafts or lifters were ever exposed. I drained the oil in the pan after closing up all covers. And any debris that might have been in there would have had to go through the filter, which I also changed to a new Nissan filter. Q45tech, I really don't know how many teeth the chain jumped, but it sounded like several. It was too quick to count, and I didn't bother counting the links when I took the cover off. Why do the lifters bleed out? The manual suggest they shouldn't bleed if you keep them upright and, I assume, they shouldn't bleed if you don't touch them at all.I recall that on the old NICO board someone had a similar problem after doing his guides. He was wondering if the pump needed to be primed cause he couldn't seem to get it right. Professor Mike said that a flipped oil pump sprocket might break, but I was careful to put that sprocket on right. Plus the error light isn't on. I don't recall if that person ever figured out the problem.Thanks again.

[Q45tech]

All I can say is the noise continues till the air gets out, if you have started, run for 15 secs, and stopped the engine 10 times and it still clatters, take it apart again and recheck the timing marks.

[DAEDALUS]

If the timing were off, wouldn't it show up as poor compression?

[Q45tech]

Not necessarily as you could be off 3 upper teeth [30 degrees] and since the motor is cold the valves wouldn't bend because things have not expanded with heat......just touching.But then again you said it has been driven several hundred miles since the job?

The compression looks a little low anyway [for sealevel] are you using a digital peak storage compression reader.....what was the 1st pulse [half the peak of the 4-6 cycle reading]?

The oil light comes on when the pressure drops below 3 psi vs the 14 psi idle minimum.

Still haven't told me the power balance variance?

[DAEDALUS]

I checked the 6 sets of timing chain marks multiple times until the tensioners and front cover were installed. I am quite certain the timing is good from the chains and sprockets' point of view. The engine doesn't seem to be underpowered. The 1st compression pulse was about 1/2 max, maybe 75psi (hard to read it accurately that quick). I don't have a way to do a power balance check, but it might not tell much. The harness is bad on 2 of the right-bank injectors (~20 ohms to each connector). I'll check the oil pressure first and then go from there. Thanks.

[landtodd]

It took several tries (a heat/cool cycle?) before mine sounded right after chain guides and tensioners. It ran lousy at first, wouldn't idle. That was almost two years ago.

Not sure how much that helps . . . let us know what happens.

[szh]

Daedalus, have you figured out this one yet? What, if any, was the cure?

Z

[DAEDALUS]

Wanted to wait till I was certain before posting, but I found some gunk in the tensioner oil ports. I had already checked the galleries, and I had ignored the tensioner itself because it was new. Working to put everything back together, and then I'll know for sure. It's in line with the noises coming from the front of the engine when I put a stethscope on it.

[landtodd]

And the verdict is ????

[LAQ]

hey daehave you solved this situation? i think i might be needing my guides done before the summer if you can squeeze me in.

[DAEDALUS]

Yes, problem solved. It looks like it was the tensioner...there was gunk in the oil port, clogging it up. The port is a round hole with what looks like metal dowel in it, and I'm guessing there's a pressure compensation system in there, similar to the fuel pressure regulator. There's a small hole on the opposite side of the oil port as well.

I had already investigated the oil galleries for blockage, measured cams, clearances, bearings, and rockers. Broke a brand new bit getting those cam bearings off, then I went and bought a Craftsman bit, which feels like it's *barely* strong enough. I called Joe up and he got Scottsdale's shop foreman's opinion on the symptoms. His first guess was that there was a clogged tensioner oil passage. Pretty damn close. Since I knew the oil gallery was fine, I began to look at the tensioner itself and found the problem. Way to go Scottsdale!

[PalmerWMD]

Good job Robert!

Also real cool, of Joe, to hook you up with the tip, the Scottsdale shop foreman hmmm.

Fred...

[911/Q45]

That kind of persistance would be hard to find anywhere, you are the man!

[LAQ]

hey daeso new member 'hh' wrote this when we talked about noise coming from my 92q.

"I think if they bleed down every time you start the car or after it sits overnight or even just a couple days, then yes, I would replace all four valve chain guide/tensioners including oil chain guide."

my question is, there is oil chain guide that's ususally replaced to besides valve chian guides? how many are there?"

[DAEDALUS]

There are 2 oil chain guides, but 1 wears faster than the other. Unlike the timing chain guides, the slack-side oil pump guide doesn't have a tensioner. It's just set in place and has to be manually adjusted (replaced). There 2 guides and one tensioner for each of the 2 timing chains. There's a really good diagram in the manual. In my print, it's on page EM-14.

[Q45tech]

Remember I spoke of BG Quick Clean for Engines: How in the past it took 3-4 applications to get the varnish out [which was clogging some HLA passages]. Also it was the only thing strong enough to clean the varnish off of valve stems which then let the Viton stem seals return to round and stopped much of the leakage under vacuum and start up blue smoke.

Wonder if the old tensioners were functioning well [clogged up passages] allowing the chain to flop helping to crack the guides?

If you ever try to clean the inside of a valve or front cover you will see varnish that very few chemicals will clean when diluted in oil..........hand rubbing acid or extreme cleaners barely work