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Old 08-04-2021, 04:30 PM   #1
intothelabyrinth
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Default B30 rod knock?

I'm in the process of reviving a 80k mile 1969 164. I got the B30 running but it's making some weird noises. I pulled the timing gears and they did have some damage. New gears are getting installed this week, but in the meantime who wants to make bets on if the sound was the gears or a rod knock?! One way or another I'll get it back on the road. It has an aftermarket oil pressure gauge and it's reading about 20psi at idle warm, and about 40psi when revved.

https://youtu.be/qSGrGSizlpQ

https://imgur.com/gallery/kdKuaaS
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Old 08-04-2021, 04:34 PM   #2
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Recorded sound is always bad for diagnosing noises like that. But it doesn't really quite sound like rod knock to me. The one time I had a spun rod bearing on my PV's B20 is sounded a bit deeper and 'thunkier', and would pretty much go completely quiet at times, much louder at others.

I've heard far worse noises that were bad timing gears (you'd have seen that though), and worn cam thrust plates (the cam will 'rattle' back and forth at lower speeds). Also, perhaps valve noises?
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Old 08-04-2021, 04:34 PM   #3
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Take a look at the valve adjustment. Sticky lifter maybe? Might as well eliminate the easier stuff before going right to rod knock.

After that I would start looking at the bottom end. Almost sounds like my grandfather's chevy 216 when it spun a bearing (it was converted to inserts from cast babbit), but John is right, I would expect a deeper noise from rod knock.
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Old 08-04-2021, 04:37 PM   #4
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I'm going to put the new gears on, adjust the valves, and give it a try. Hearing it in real life it didn't sound like rod knock to me. The rod knock I heard in a b230 that had dropped a valve and I put another head on was much more deep and not as frequent. Like a 3lb sledge hitting the block. This sounds tinny to me, and I can see those worn gears making the sound. fingers crossed!
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Old 08-04-2021, 04:44 PM   #5
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The timing gears can make a noise just like a rod knock but only when the fiber gear breaks loose from the metal hub which allows the gear to wobble and make contact with the cover.

The noise I heard in the video sounds more like top end/valve train noise than a rod knock to me. The engine isn't hitting on all of the cylinders which could indicate a flat cam. Check the cam before installing the gears as the cam gear will have to come back off to change the cam (not to mention the cylinder head). Chance are the head will need a valve job unless someone already did one and installed hardened exhaust seats.
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Old 08-04-2021, 04:44 PM   #6
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Quote:
Originally Posted by intothelabyrinth View Post
I'm going to put the new gears on, adjust the valves, and give it a try. Hearing it in real life it didn't sound like rod knock to me. The rod knock I heard in a b230 that had dropped a valve and I put another head on was much more deep and not as frequent. Like a 3lb sledge hitting the block. This sounds tinny to me, and I can see those worn gears making the sound. fingers crossed!
Put some new oil in it if you haven't already. I've had it help knock things loose when they are gummed up. It really sounds like a valvetrain part.

Last edited by spock345; 08-04-2021 at 04:50 PM..
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Old 08-04-2021, 04:51 PM   #7
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I should just pull the cam and visually inspect to see if any of the lobes are obviously flat? This car was the previous owner's long time project, it only has 80k miles on it. He said it had good compression on all the cylinders, I'll have to see if the numbers are written down in his notes anywhere. I personally haven't checked compression yet.
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Old 08-04-2021, 04:53 PM   #8
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Originally Posted by intothelabyrinth View Post
I should just pull the cam and visually inspect to see if any of the lobes are obviously flat? This car was the previous owner's long time project, it only has 80k miles on it. He said it had good compression on all the cylinders, I'll have to see if the numbers are written down in his notes anywhere. I personally haven't checked compression yet.
I would think a flat cam lobe probably won't cause a low compression number because the valves are not being opened by a flat lobe, therefore no way to lose compression.

You can just remove the valve cover and turn the motor by hand. Watch to see how far each rocker moves. They should all move the same distance. Also a good time to do the valve adjustment.
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Old 08-04-2021, 04:54 PM   #9
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Pull the valve cover and crank the engine over while watching the rockers/valves. A flat cam is easy to spot as the offending cam lobe(s) will be opening the valve(s) less than the others.
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Old 08-04-2021, 04:56 PM   #10
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I'll need to put those gears back on first. Then I will turn it over and adjust the valves before buttoning it up. See if anything jumps out as being amiss there.
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Old 08-04-2021, 05:03 PM   #11
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Obviously I am in need of guidance. lol I just wanna get the thing back on the road. It is not a perfect car. It was hit in the back with a deer... I wanna just get it going and keep it original. Here's the car.

https://imgur.com/gallery/ccJCW7u
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Old 08-04-2021, 05:04 PM   #12
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Quote:
Originally Posted by hiperfauto View Post
Pull the valve cover and crank the engine over while watching the rockers/valves. A flat cam is easy to spot as the offending cam lobe(s) will be opening the valve(s) less than the others.
/\ /\ /\ By the time a lobe is flat enough to cause a noticeable running issue, it's really easy to spot by eye. Just run the motor around and watch the valves go up and down, look for one that barely moves.
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Old 08-04-2021, 05:19 PM   #13
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The po has put all new brakes on it, master cyl, rotors, calipers. He had the BW35 out to do some seals, but he didn't do the selector shaft seals so when I put fluid in it they leaked horribly. I replaced them, as well as the trans mount, and the shifter bushings, and now the trans surprisingly is not leaking. There's a drip of oil at the bellhousing from the rear main I assume. Why he didn't do that while he was in there I do not know. He had the carbs apart, and put on a new water pump, and fuel pump. I have hooked the gas tank up, put new ignition wires, rewired the battery/starter, as well as the neutral safety switch. I also fixed up the headlight wiring and got all the turns, high and low headlights, hazards, brake lights, and running lights operational. The car has moved and stopped, shifted into all 3 gears, had a good kickdown and everything. After the initial test drive that's when the noise was very obviously something wrong.
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Old 08-05-2021, 09:00 PM   #14
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Hmm maybe the #7 valve doesn't depress as much as the others.
https://www.instagram.com/p/CSNqxbUF...dium=copy_link
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Old 08-06-2021, 11:33 AM   #15
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So what do you guys think? I'm thinking I should at least try to start it up and see if it's still making those noises after the timing gear change and valve adjustment. Now that I'm thinking about it, that intake valve has to be opening at least enough to get fuel/air because the spark plug looked the same as the others (rich looking). If the sound is gone, then I'll adjust the carbs, because I haven't even messed with them at all, and go from there.
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Old 08-06-2021, 11:34 AM   #16
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Quote:
Originally Posted by intothelabyrinth View Post
Hmm maybe the #7 valve doesn't depress as much as the others.
https://www.instagram.com/p/CSNqxbUF...dium=copy_link

Start it up. See if there is a difference.

I'd be tempted to pull the cam at that point. It does look like it is low.

How were the valve clearances?
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Old 08-06-2021, 11:37 AM   #17
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Some were def a little loose.
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Old 08-06-2021, 11:43 AM   #18
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Some were def a little loose.
I'd adjust those to spec before pulling a cam. I've noticed the valves can get really chattery when the clearances are loose.
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Old 08-06-2021, 11:54 AM   #19
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I adjusted them all to .020. I'll probably throw that timing cover on later and fire it up, see where I'm at.
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Old 08-06-2021, 12:06 PM   #20
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I'm going to go ahead and agree that it sounds more like a valvetrain issue.
Usually rod knock will have some sort of irregularity around it (either crankshaft accel/decel, load, free rev, certain band, etc). It sounds too high pitched to be a knock IMO.
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Old 08-06-2021, 12:07 PM   #21
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How was the clearance on the cam thrust plate?

It's the plate that bolts to the block between the front bearing and the cam gear itself. The cam gear rides against a spacer, and that spacer is supposed to be barely thicker than the thrust plate.

If there's too much of a gap, then the angled cam gear teeth can rattle it forward and backward at some rpms where the torque on the cam goes back and forth (as the cam lobes pass TDC and get pushed forward by the valve springs).
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Old 08-06-2021, 12:07 PM   #22
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Quote:
Originally Posted by intothelabyrinth View Post
Hmm maybe the #7 valve doesn't depress as much as the others.
https://www.instagram.com/p/CSNqxbUF...dium=copy_link
7 and 8 both don't look very lifty in comparison to the rest, though that may just be parallax error due to the camera angle.
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Old 08-06-2021, 12:25 PM   #23
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thrust plate was worn pretty good on the front. the back was not at all, and I flipped it over. lol
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Old 08-06-2021, 12:28 PM   #24
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The way I understand it is the spacer gets tightened between the cam and the gear so there's no movement there...Then the force of the helical gear is pushing the cam gear toward the back so the back of the cam gear rides on the front of the thrust plate. I read on here you can flip them over and have another go...until next time.
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Old 08-06-2021, 12:30 PM   #25
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The spacer is supposed to be just a touch thicker than the plate, otherwise it would lock up when you tightened the cam on.

And the cam is under torque *most* of the time pushing it backward, but at lower RPM's (and maybe more so on a B20?) it can get pushed forward over each cam lobe. And the back and forth torque on the gears can rattle the cam fore/aft.
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