Wondering if I am going to be bringing my machine shop a blank check and a chewed-up head next week.

Here's the situation. Just did the 90K timing belt job on the GSR, its first. Car's been great until now. While I was in there, I decided to do everything in sight: belt, tensioner, water pump, main seal, cam seals.

I took the cam sprockets off to get the old cam seals out and the new ones in. Then put the sprockets back on, then took them off *again* after I realized that the inner timing belt cover has to go on before the sprockets. D'oh! I also had the cam holders off, plus the right-side cam bearing caps, to let me get at the seals.

Everything new went on and I very carefully torqued to Haynes-book spec with a torque wrench. I walked around the TDC loop in the order 1-3-4-2, checking crank alignment, cam alignment, and valve clearance for all cylinders.

I adjusted three or four valves that were just slightly wide of spec. Used a .203mm on the exhaust side and a .178mm on the intake.

Changed filter, added oil, turned it over with starter only a few times to move the fluids. Put on the spark leads and started for real. Immediate clatter. Shut down. Go look for loose mech bits. Find a few, fix them, try again. Immediate clatter. Shut down. Check oil. A bit low. Top it up. Start again. Immediate clatter. Careful listening says that it's from under the valve cover.

Grrrrrrrr. Taking that thing off is a huge annoyance, all eight primary bolts of it plus the various attachments. But OK, I'll do it, there must be a valve madly loose to make that sound.

Ran the engine through the complete TDC cycle again. All marks line up. All clearances are OK. Cover back on. Start up. Chatter.

Damn, what could be wrong? Racking my brain, here are two possible areas where I might have blown it:

(a) I instinctively use threadlocker-blue on major bolts, not so much to keep them from vibrating free, but to keep them from fusing permanently in place once they're torqued in. I put some TL on the cam holder bolts the first time the cam holders were up. Then when I popped off the cam holders again, and pulled those bolts the second time, I found the threads filled with a mixture of uncured threadlocker, and oil. The bolts seem to go through a wet section. Great. So I cleaned them and chased the threads and retorqued. Possible trouble: bits of cured threadlocker in key oil passages?

(b) I had the belt off by the time the cam sprockets had to be removed, so they were free to spin. In order to lock them in place to pull the sprocket bolt, I used a big 19mm wrench with the open end under one of the sprocket arms, and the closed end wedged down in the motor mount space. Similar procedure when I put the bolts back in. And remember, this cycle got done twice, because of my having forgotten the inner TB cover on the first reassembly. Possible trouble: distortion of cam(s) by the force applied on one end?

If anyone has any bright ideas, I'd be grateful. Thanks!

Chris

 

Right, next-day follow up post.

I checked all valve clearances again last night, A-OK. Cams are in sync with the crank (the TDC mark is some *tiny* fraction of a degree off).

The H-A.net archives show that bearing caps can make awful noises if they're unhealthy. I went in this morning and pulled the cam holder and bearing caps for the exhaust cam.

Everything looked pretty much right. I re-installed exactly the way that I had before: cleaned the bearing caps, put fresh clean motor oil on the bearing surfaces, put RTV/Hondabond on the edges where the caps cross the head edge, torqued all bolts in quarter-turn increments plus in the official sequence, torquing the big bolts to 240 inch-pounds, the small ones to 86 in-lb.

Will do the intake cam next, then close it up and start it.

The only thing which I noticed was that the belt-side exhaust cam bearing cap was slightly reluctant to drop back in place. The cap on the other side went right back on. The beltside cap went on slightly angled. One side sat flat, the other was raised 1mm or so. I lifted it off and straightened it and tapped gently with a mallet and it then sat flat on the mounting surface.

Something similar happened when I put that one cap on the previous time. Hmmmmm. The cap might be distorted, or the dowel pins underneath it may be slightly bent.

Or, there might be a possibility that my low-range torque wrench is somehow wildly out of spec. I store it at zero and don't use it as a breaker bar, so I doubt that.

C

 

More info from the exhaust cam:

On this cam, only the beltside bearing cap had been up. I lifted this one and looked underneath and, alarm bells! There are little black flecks in a section of the bearing surface.

Not major damage yet -- they can't be felt with a fingernail, but I am going to polish them out carefully before the bearing goes back on. But how did they get there? That cap was cleaned and re-oiled before going on. And all of the flecks are on the outer part of the cap, towards where the cam seal should be.

What? Let's check out that new cam seal. Ah. There's some dark material around its edge. I don't have the cam out, so all I can do is to edge the seal around in its bore. There's oil down in the lower half of the seal bore -- could I have missed that when I put in the new seal?

OK, here's my current guess. The lower half of the seal bore apparently had some spillover oil in it when the new cam seal went in. This could allow the seal to squirm and flex and move under rotational load when the cam began to spin.

The edges of the bore would then have shaved off some little bits of seal material and let them get into the bearing. Where they would have made these small marks, and made noise.

What I'm going to do now is to clean the bore, RTV the outer edges of the seal to prevent any further motion, polish the bearing, and reinstall everything. That won't get done until tomorrow. Will update when I am done and tested.

 

Reporting on the follow-up valvetrain check:

I took the beltside exhaust cam bearing, which had the tiny flecks of material on its surface, and gave it a careful light polish with number-800 paper, then inspected the surface under bright sunlight with a ten-power binocular magnifying headset. No trouble visible other than two or three pretty much microscopic pits.

Pulled the matching cam seal, which had some scuffs on the outer edge. They weren't bad enough to impair the seal itself, but I put a light coat of RTV over them. Then cleaned and dried the seal bore before the seal went back in.

Cam holders went back on, and everything got retorqued with extra care, including the 86 in-lb small bolts. It's easy to overrun those a little bit with a click-type torque wrench.

Valve cover back on, spark leads off, cranked with the starter to move the oil. No clatter.

Spark leads on, start for good. Quiet idle at first, then as the computer kicked the cold idle up from 1000 to 2000 rpm, the clattering noise appears.

Shut down. Restart. Same thing. Clatter seems intermittent. Can't hear it much if at all at idle. I carefully back out and drive a quarter-block. Definitely there, but not constant.

In the driveway, I tap the throttle a few times until I get the rattle steadily, then get out and go around. As near as I can localize the sound, it's coming from the back of the valve cover, near the injectors. Normal injector clatter? I don't think so. They didn't make this sound before the belt job.

Bent exhaust cam or exhaust cam pulley? Why intermittent noise? I would think it would be constant if something were out of alignment in the valvetrain.

Could I have decked a heat shield against something when jacking the engine up and down during the belt change? Can't think of anything that it would have run into.

Weird...

C