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Old 05-06-2019, 09:31 PM   #1
vwbusman66
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Default B20B bad cam, popping out of carb

Currently discussing the symptoms caused by a ruined camshaft in my 71 142S (B20B, dual SU HIF's). Czech out the video below to see the issue. I am fairly certain the popping out of the carbs is caused by an exhaust valve that isn't opening.

Any other reasons why it's popping, besides a lean mixture?

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It's all just lifter noise til it comes out the side.
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Old 05-06-2019, 09:40 PM   #2
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It's the exhaust coming back out the carb because the valve isn't opening.
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Old 05-06-2019, 09:45 PM   #3
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It's the exhaust coming back out the carb because the valve isn't opening.
That was my logic- I just wanted to make sure that was sound and realistic.
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Old 05-06-2019, 09:58 PM   #4
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That's an exhaust valve with a flat lobe. When the lobes wipe out, the base circle isn't affected (much) so the valve adjustment can still be on point. But yeah, it's managing to gargle a little fresh fuel-air in the intake, then it fires, then it ends up blowing the exhaust back into the carb, where it pops the rest of the air/fuel waiting around there.

Head comes off, radiator and grille comes out, fish the lifters out from the top (and that flat lobe will have mushroomed the lifter some and it will NOT be easy - just clamp some small vice grips on it, pull up, and twist. Let the raw cast iron end of the lifter bore wear down the mushroomed metal. Pull and twist back and forth. It will probably come out at some point.

Then pull the distributor drive, timing cover, pull the gear, and the cam slides out the front through the grille opening.
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Old 05-06-2019, 10:07 PM   #5
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Fuel pump needs to come off also.

If the damaged lifter doesn't want to come out hold it up while you pull the cam and let it drop into the pan rather than risk damaging the lifter bore.
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Old 05-06-2019, 10:30 PM   #6
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Fuel pump needs to come off also.

If the damaged lifter doesn't want to come out hold it up while you pull the cam and let it drop into the pan rather than risk damaging the lifter bore.
Do I have to drop the cross member to remove the oil pan like a 240?
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Old 05-06-2019, 10:40 PM   #7
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Yes, but you can just leave the lifter in there. It'll end up in the sump and won't hurt anything.

If you don't want to drop it in the pan you can cut a piece of PCV tubing in half lengthwise and stick it the the cam bore to try and catch the lifter and pull it out the front of the engine.
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Old 05-06-2019, 10:43 PM   #8
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You might be able to fish the lifter out with the pan off and everything else still in place.

But the bottom side of the block under the lifter bore is rough cast iron, if you rotate the lifter that will grind off the mushrooming. Or hopefully it won't be an issue and they'll all come out.

Even if they aren't mushroomed, sometimes they can resist coming out the top because they have some oil crud built up on the bottom part of the lifter.
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Old 05-07-2019, 10:48 AM   #9
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And just from experience, be careful when removing the timing gear from the cam. The gear is what holds the cam in place - at least from it sliding back into the engine.

So if you were to... say... brace the cam gear and tap on the cam nose (since you are replacing the gear and cam anyhow)... and then the cam finally pops free... and slides back into the engine with a modest amount of force... it can knock out the metal plug on the back side of the engine. Inside the bellhousing, behind the flywheel. And suddenly you have added a transmission remove and replace task to your cam swap.
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Old 05-07-2019, 12:20 PM   #10
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Like the other mentioned : lobe of cylinder 2 exhaust isn't existing anymore.
If you remove the head to swap cam and lifters swap the exhaust manifold too. Your version is crap. It's with a butterfly inside. If new condition it should be better in sight of pollution. In reality it makes it worse when aged.

Nice car and way better than my 142.
Good luck, Kay
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Old 05-07-2019, 12:31 PM   #11
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Like the other mentioned : lobe of cylinder 2 exhaust isn't existing anymore.
If you remove the head to swap cam and lifters swap the exhaust manifold too. Your version is crap. It's with a butterfly inside. If new condition it should be better in sight of pollution. In reality it makes it worse when aged.

Nice car and way better than my 142.
Good luck, Kay
You want the exhaust manifold from a B20E/F and the intake for a '65ish 122 single piece intake, not the intake/exhaust abomination.
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Old 05-07-2019, 08:00 PM   #12
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Oh my, that's too bad.... As a consolation prize [???], your video is great. Start at 2:55 if you're just gawking....
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Old 05-07-2019, 11:08 PM   #13
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Old 05-09-2019, 01:22 PM   #14
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I spy a VW bus
You would be correct.
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Old 05-09-2019, 01:44 PM   #15
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Oil pan needs to come off to clean out debris from failed cam.

Debris = Metal Mud
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Old 05-09-2019, 01:59 PM   #16
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It's nice to take off the pan, but not entirely necessary. Change the oil now, change it after the cam swap after 100 miles, change it again in 1000 miles, consider that a done deal.

Wiped cam lobes is an unfortunately common issue on these old motors. They just aren't oiled well. As far as I can tell, they maybe get a little trickle down oil from the lifter gallery (which is itself only getting a little hand-me-down oil from the pressure fed rocker shaft - the lifter bores have no oil feed). I think it's mostly splattered with windage from the crank spinning around.

High RPM's and taller cams and stiffer (and/or double) valve springs - all make them more likely to fail. Break them in according to all the old myths, and then use some zinc additive in the oil. Zinc is great for sliding contacts like that, but it's been greatly reduced in modern gasoline engine oils, because it's not good for catalytic converters. But since you dno't have a catalytic converter, no need to skimp on the zince.

https://lucasoil.com/products/engine...e-tb-zinc-plus

I'd use a full bottle on the first oil change, then maybe a quarter bottle added in with the regular oil from there on. Or use diesel oil? I think it still has a higher zinc level since diesel engines don't have cats (or at least, not the kind that is damaged by zinc).
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Old 05-12-2019, 04:59 AM   #17
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B20 from '74-> had much better cam material. Similar to OHC engines.
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Old 05-12-2019, 11:51 AM   #18
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I'd use a full bottle on the first oil change, then maybe a quarter bottle added in with the regular oil from there on. Or use diesel oil? I think it still has a higher zinc level since diesel engines don't have cats (or at least, not the kind that is damaged by zinc).
Be careful how much ZDDP you use, Too much ZDDP can damage bearings.

https://forums.swedespeed.com/showth...gle-Weber-carb)
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Old 05-12-2019, 12:49 PM   #19
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Volvo did have some soft camshafts and IIRC, there was a recall back in the day.

However, new cams shouldn't have this problem.

The cause of excessive wear nowadays is usually due to the low levels of ZDDP(Zinc and Phosphorous) in over the counter multi-weight oils. We suggest using 30w engine oil as the levels of ZDDP are allowed to be higher. We use Napa Premium 30w as it made by the same company that makes Valvoline and it's cheaper than Valvoline.

We recently replaced the cam in 544 whose owner is a loyal Rotella oil user and we found a significant amount of wear and pitting on most of the lifters. We used 30w VR1, a high ZDDP oil made by Valvoline, in his motor along with a high ZDDP lube on the camshaft lobes and lifters. Normally we switch back to 30w after that, but the owner wants to use 10w-40, so I suggested a ZDDP additive or to use VR1 10w-40.

For a longer life, it is extremely critical to break in a new camshaft and lifters by running the engine at 2000-3000 rpm for at least 15 minutes during the initial start up.

Lately, we've been suggesting to customers engine removal when replacing a camshaft for pushrod Volvo engines.

With the engine removed, you don't have to remove the head to change the camshaft.

Since the oil pan gasket almost always tears when removing the front timing cover, with the engine removed the oil pan gasket has to be changed. A gasket patch can be used and glued in place, but it can still leak.

While the oil pan is off, the main and rod bearings can be inspected or changed if necessary as well as the oil pump and oil pump seals.

With the engine removed, you have access to the back of the motor so you can get to the rear main seal and the cam plug. And if your cam bearings are bad, it's way easier to have them changed with the engine removed.
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Old 05-12-2019, 07:37 PM   #20
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Quote:
Originally Posted by planetman View Post
Volvo did have some soft camshafts and IIRC, there was a recall back in the day.

However, new cams shouldn't have this problem.

The cause of excessive wear nowadays is usually due to the low levels of ZDDP(Zinc and Phosphorous) in over the counter multi-weight oils. We suggest using 30w engine oil as the levels of ZDDP are allowed to be higher. We use Napa Premium 30w as it made by the same company that makes Valvoline and it's cheaper than Valvoline.

We recently replaced the cam in 544 whose owner is a loyal Rotella oil user and we found a significant amount of wear and pitting on most of the lifters. We used 30w VR1, a high ZDDP oil made by Valvoline, in his motor along with a high ZDDP lube on the camshaft lobes and lifters. Normally we switch back to 30w after that, but the owner wants to use 10w-40, so I suggested a ZDDP additive or to use VR1 10w-40.

For a longer life, it is extremely critical to break in a new camshaft and lifters by running the engine at 2000-3000 rpm for at least 15 minutes during the initial start up.

Lately, we've been suggesting to customers engine removal when replacing a camshaft for pushrod Volvo engines.

With the engine removed, you don't have to remove the head to change the camshaft.

Since the oil pan gasket almost always tears when removing the front timing cover, with the engine removed the oil pan gasket has to be changed. A gasket patch can be used and glued in place, but it can still leak.

While the oil pan is off, the main and rod bearings can be inspected or changed if necessary as well as the oil pump and oil pump seals.

With the engine removed, you have access to the back of the motor so you can get to the rear main seal and the cam plug. And if your cam bearings are bad, it's way easier to have them changed with the engine removed.
Interesting about the straight-grade oils having higher zinc levels.

I'm debating yanking the engine and really don't want to without driving it first. If I pull it, I may be too tempted to plop something newer into it.

I'm not too concerned about bearings as the car has a true 131k on it, and all the owners seemed to have kept up on maintenance based on some records included in the glovebox.
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Old 05-12-2019, 08:32 PM   #21
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Exhaust emissions changed in 74. Engineering submitted cam specs to quality control for approval. Bean counters said you don’t need metal the good for the cam and lifters. We all know where this went. I built a piramid out of flat cams that was over a foot tall from 74 to 76
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Old 05-14-2019, 03:53 AM   #22
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Originally Posted by JohnMc View Post
And just from experience, be careful when removing the timing gear from the cam. The gear is what holds the cam in place - at least from it sliding back into the engine.

So if you were to... say... brace the cam gear and tap on the cam nose (since you are replacing the gear and cam anyhow)... and then the cam finally pops free... and slides back into the engine with a modest amount of force... it can knock out the metal plug on the back side of the engine. Inside the bellhousing, behind the flywheel. And suddenly you have added a transmission remove and replace task to your cam swap.
Listen to this man. I did just this earlier this year. Also had a flat cam with almost no lobes that ran just like yours. Dont forget your break in paste!
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Old 05-14-2019, 09:35 PM   #23
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Listen to this man. I did just this earlier this year. Also had a flat cam with almost no lobes that ran just like yours. Dont forget your break in paste!
What is the recommended flavor of that stuff nowadays?
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Old 05-14-2019, 11:50 PM   #24
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What is the recommended flavor of that stuff nowadays?
CV grease with a tea spoon of 90W140 is a easy and perfect cam break in lube.
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Old 05-15-2019, 08:23 AM   #25
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Listen to this man. I did just this earlier this year. Also had a flat cam with almost no lobes that ran just like yours. Dont forget your break in paste!
Just loosen the big nut that holds the cam on, but leave it threaded on the cam snout. So the gear has like 1/8" of room to move. A puller is obviously a good thing to use here, but you can't always get a generic puller to fit onto a timing gear properly. But if that nut is on there, whatever you do to pop the gear loose, it can only go back that 1/8".
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