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Fresh B20 engine tapping mystery

blackbird939

blackbird939

New member
Joined
Sep 8, 2015
Location
Orlando
Hello once again,

Recently rebuilt B20. Head, Stage 1 redone by John Parker. Dual springs, new guides, opened combustion chamber, ports. New bearings, resurfaced flywheel, 123 distributor, mikuni HSR carbs. New crane cam, coil, plugs, plugs wires, lifters, pushrods, milled head and block, etc. The pistons had been replaced 3k miles ago with new and were within spec. No sign of piston slap, cyls were lightly honed at the machine shop. the works.
Well, it ticks loudly. I used the rule of nines to set the valve clearance to .41mm no fewer than thrice, before and after the break-in and final torque of the head. Plug gap at .7mm dead on. I sprayed starter fluid around intake gasket (which worked last time ) and it's not leaking- at least not badly. The rocker assembly is old, untouched, the alternator is an older Bosch. When I walk around the head with a stethoscope I hear a loud tapping/clacking near #1 or #2. The valve lash is dead on according to the 9s. The sound increases with rpm and temperature does not affect it. I get a vibrating needle on the vacuum gauge at 15hg. Vibration dances 0.5hg, not wild. The cam might be causing the vibrating needle. Timing at 12?BTDC at idle.

It used to diesel terribly, now that is all gone, thank goodness. But this ticking stinks.
My guesses are- ?? Sticking valves, bad rockers? exhaust manifold leak?

Here's a video I just took. Volvo B20
 
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ZVOLV said:
Stethoscope.
Click to expand...

Yes, I used one, mentioned above. It sounds like valve train close to #1, but the valve lash is spot on. Other than lash, what could cause a clacking. Quiet below the head. (With stethoscope). New cam, lifters abs rods. Less than 50 miles on them- probably 10.
 
cwdodson88 said:
How do the rocker arm faces look? When they groove out, you have to use those tipped feelers or take them off and face them.
Click to expand...
You know, to be honest, I thought they looked worn and I had the idea of getting a used set and having them restored. It could very well be that. But, rocking them, one by one after I set the lash, they all 'feel' about right. You know what I mean, it's obvious when it's too loose or too tight. But I think you're right. I mean, what else is there? All new components besides the rocker assembly. Maybe I'll invest in one of those fancy billet rocker bridges.
 
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cwdodson88 said:
How do the rocker arm faces look? When they groove out, you have to use those tipped feelers or take them off and face them.
Click to expand...

^This. If the faces of the rockers are grooved, you need to use a wire type feeler gauge to set the valve lash.

I usually have rebuilt rocker shafts in stock. I also sell a spring eliminator kit for the rocker shaft. It replaces the springs with aluminum spacers and shims so you can precisely adjust the location of the rockers over the valves.
 
hiperfauto said:
^This. If the faces of the rockers are grooved, you need to use a wire type feeler gauge to set the valve lash.

I usually have rebuilt rocker shafts in stock. I also sell a spring eliminator kit for the rocker shaft. It replaces the springs with aluminum spacers and shims so you can precisely adjust the location of the rockers over the valves.
Click to expand...

Question about that:
I always thought that the springs were there to allow some slight lateral movement and allow he valves to maybe rotate? I can imagine precise placement of the rocker arm being desirable however...

Are the rocker arm faces hardened? Any adverse effects from running s notched arm? Potential uneven wear spot?
 
Kjets On a Plane said:
Question about that:
I always thought that the springs were there to allow some slight lateral movement and allow he valves to maybe rotate? I can imagine precise placement of the rocker arm being desirable however...

Are the rocker arm faces hardened? Any adverse effects from running s notched arm? Potential uneven wear spot?
Click to expand...

The factory alignment of the rockers is poor at best. I've seen rockers that were only making contact with ? of the valve. Having them centered over the valve reduces side loading of the valve and therefore guide wear. I don't think it was done to promote valve rotation because they're not all off center. The spacers and shims still allow a little lateral movement if set up correctly.

The rocker arm faces aren't put thorough a hardening process after they're re-faced AFAIK. They're made from forged metal that's close to the hardness of the valve stems.

A notched arm won't have the proper arc. Obviously, they'll run forever that way, but it's not ideal and the end of the valve will wear more.
 
Any possibility it's related to a seat coming loose slightly? The vacuum flutter seems a touch odd given the lash spec. Even mine with one of the VPD cams is pretty stable.

Ian...might have to hit you up for those spring eliminators...got a link with details?
 
Cool deal, might have to toss those on the list for the B20 build, unless I spring for some rollers since it's getting built to the hilt. :)

Thanks for the link!
 
gsellstr said:
Any possibility it's related to a seat coming loose slightly? The vacuum flutter seems a touch odd given the lash spec. Even mine with one of the VPD cams is pretty stable
Click to expand...


Man, I hope you're wrong. I have a sinking feeling that you're right. I spent big money on this head. I then pestered John relentlessly to get it back and it still took 3 months. Would a dropped or cracked seat cause this clacking/tapping? I mean, if it was loose, wouldn't it mean certain destruction of the top end? If the whole ring is THAT loose where every rev is tapping, it would not come back to its correct location after a couple of cycles. Or maybe I am wrong. I thought a dropped seat was as bad as a dropped valve. The top end components would be doomed in short order?

Maybe I just need to pull it inspect the valves myself. Is it safe to drive?
 
Some spitball idears:
- as a diagnostic only - try setting the valves by feel. Sure, there a specific gap they're supposed to have, but try just tightening/loosening them until they have just a faint and similar 'click' across all 8 valves. Then start it up and see if you've altered the tapping noise at all. If you haven't, then the tapping isn't likely due to valve clearances.
- I'm not entirely sure what the 'rule of 9's' is in terms of setting valves, but if you ever look at a Volvo cam out of the engine you'll see that starting in the middle and moving out toward the ends, each lobe is 180 degrees away from its mirror twin on the other side. So what I do when setting valves is rotate the motor until a rocker is fully depressed, and then set its mirror twin on the other side. I.e. #1 is down, set #8. #2 is down, set #7. #3 is down, set #6. And so on. To keep it simple I got right down the line, which takes a few extra rotations of the motor. Doing it this way ensures that you are setting the valve clearance at the mid point of the base circle.
-Another thing that can make nasty tapping noises that are vaguely valvetrain related is too much gap at the cam thrust plate. There's a spacer between the cam snout and the cam gear, when the gear is tightened down it's supposed to leave a few thou's worth of clearance on the cam thrust bearing. If the thrust plate is too thin, or the spacer is too thick, or the cam gear isn't snugged down onto it, then the cam can slop back and forth in the block, making a somewhat deeper clacking noise. This generally quiets down at higher RPM's when the cam gear gets into a most steady pull torque (oil pump drag?) and isn't pushed forward by the lifters passing TDC on the lobes. You can most easily check this by taking the fuel pump cover plate (or fuel pump) off and seeing if the cam has any side to side movement when you briefly run the motor.
- Might also want to just eyeball the valve stems while you are setting the valves. Is any one of them noticeably higher or lower than the others?
 
JohnMc said:
Some spitball idears:
I'm not entirely sure what the 'rule of 9's' is in terms of setting valves
Click to expand...

It's what you described here. When one valve is fully open or depressed, say #8, #1 is 180 degrees out, so adjust #1. Each valve pair add up to '9'. 1,8 4,5 2,7 etc.

When I pulled the old cam out (no idea what the previous builders had in there) the spacer was not there! They left it out, which IPD says could pop the end of the cam off. I bought a new one and dropped it in. One thing I noticed. They had upgraded to steel timing gears. The cam gear did not require pressing. It slid right on, into the key. I torqued it to 105ftlbs I think, per the spec in my 71 manual. I can check for that side to side movement. But I think I am having valve issues because my vacuum gauge is not steady. And, perhaps more importantly, it runs rough, with the carbs perfectly balanced. Also, when I hook up the gauge to the #1/#2 advance port, I get much more dancing on that carb than I do on the #3/#4. And the noise is up near #1. If I had to make a guess, I'd say that it's #1 intake (#2 valve). I'll do a compression test today as well. John did the leak down. I just feel like it's those rockers, because I can hear a tink tink tink through the stethoscope. Not a knock knock. No sound at all from the bottom end. It's eerily quiet down there. Will report back. Thanks much for the help. Without this forum, it's all swags.
 
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Try putting your steth on the intake and exhaust runners. I actually just went thru finding a collapsed lifter on the dodge when I started hearing a tapping. Found it was only in the left part of the Y. Teardown showed #3 lifter was failing, cam was hammered.

Do any of the rockers have play on the shaft in any direction? Got another rocker assy you could toss on for testing?
 
gsellstr said:
Try putting your steth on the intake and exhaust runners. I actually just went thru finding a collapsed lifter on the dodge when I started hearing a tapping. Found it was only in the left part of the Y. Teardown showed #3 lifter was failing, cam was hammered.

Do any of the rockers have play on the shaft in any direction? Got another rocker assy you could toss on for testing?
Click to expand...

No spare set. I think I will pick up a set from hiperfauto. These are shyte anyways. I had always intended to hunt down a rebuild assembly, but I thought this would do for now to get it on the road. This is the dark cloud that's been following me around for 45 years. Always something, nothing just goes smoothly. The C303 B30 rebuild was actually much easier and tuned right up. Purrs like a kitten.
 
Hey, it's not just you. Things seldom go smoothly for me as well. Simple head swap on mine required outside help and specialty tools just to get the damn crank bolt out for a timing belt swap. Idle isn't quite as stable now, with some runtime, and the oil pressure dropped over what the old head had. Awesome.

Don't feel bad, definitely don't think you're special, in terms of things only going haywire for you. lol
 
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