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Worn cam lobe... what would you do?
Hey All,
I have a relatively nondescript 350 with 882 heads. The idle seems smooth enough, oil pressure is very good and so is compression at 160-165 PSI. Yet while I was setting the lash running, I noticed that #8 intake was not rocking as high as the rest. It also had the lowest compression reading at 155 PSI. At higher RPM there seems to be a vibration, but it is hard to tell... What would you guys do with this while waiting to drop in another motivator? Drive it as is? (It might take 10 months to 2 years before I replace it with a fresh engine) Swap in a new cam + oil change? (EDIT + new lifters of course...) Going through the short block seems like investing too much into something I will eventually replace... |
First verify it is a worn cam and not a bent pushrod. If cam is wiped, do not operate further. Pull cam and lifters and drain oil. Thoroughly flush engine. You may save engine. Get a new cam and lifters and get rid of those 882 heads. When finished you may like it well enough that you'll forget about changing engine.
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Originally Posted by dochorsepower
(Post 1596400958)
First verify it is a worn cam and not a bent pushrod. If cam is wiped, do not operate further. Pull cam and lifters and drain oil. Thoroughly flush engine. You may save engine. Get a new cam and lifters and get rid of those 882 heads. When finished you may like it well enough that you'll forget about changing engine.
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Any backfiring through the carb upon acceleration? Also another sign of a worn lobe.
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Originally Posted by steveweimer
(Post 1596401093)
Any backfiring through the carb upon acceleration? Also another sign of a worn lobe.
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If you do in fact have a lobe going away, the damage has already been done. All that metal has gone through the entire engine and is embedded in the bearings. It may last a little while but it depends on how many miles and how hard it's driven. I saw your other post about performance launches.
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Originally Posted by bashcraft
(Post 1596401960)
If you do in fact have a lobe going away, the damage has already been done. All that metal has gone through the entire engine and is embedded in the bearings. It may last a little while but it depends on how many miles and how hard it's driven. I saw your other post about performance launches.
Yes. That was rather more theoretical. Mostly exploring how the hell one gets off the line gingerly with such a short box. ;p Under my watch, this car has never seen 4000 rpm and rarely even sees 3000. Not until I know more about its health. That and 95% of the time I drive like a grandma. When bringing it up in rpm at 60 mph is when I became suspicious. At 2500-3000 rpm it didn’t feel as smooth as I was expecting. I’d agree with you on the trashed innards if a lobe went... but now I’m suspecting a bent rod. If this was a cam lobe, it should have been completely deteriorated by the time I took ownership. I doubt the seller could have gotten away with that. Tho not perfect, the operation feels too smooth |
If it is the lobe and it sounds like it is, you can roll the dice with a new cam and lifters but as stated before, that worn metal went somewhere. Hopefully in the oil filter.
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:willy:
stay tuned !!!! |
Originally Posted by DorianC3
(Post 1596402322)
:willy:
stay tuned !!!! One last thing about a wiped lobe, I blame Mobil 1 with not enough ZDDP. This was however ten years ago. |
Interesting. These heads look like they have been rebuilt very recently. They look very clean. No wear pattern on the valve tips. The rocker studs are the screw-in type; that’s not what is supposed to be on 882 heads.
I put a vacuum gauge on the running engine and got a very stable 17 inches. With the engine running, I could see the pushrods spinning. Though #8 exhaust was spinning slightly slower. Pushrod #8 exhaust is bent, but slightly. Spinning it in a drill one can see a slight wobble that the pushrod right next to it does not have. Nonetheless (and bear with me) I do not think this is enough to explain the lack of lift. Hmmm. I’ll have to see if I can find a dial gauge somewhere this weekend. That or I may pull the intake and eyeball the bottom of the lifter directly. |
Originally Posted by ignatz
(Post 1596402979)
My experience - I lost the fuel pump lobe, completely rounded off. That is a lot of metal. Put in a new cam and ran it for years hard. I would think that metal gets into the sump where it first goes through the oil filter. Not knowing what was going on, I never opened up the oil filter, but I did change my oil quite regularly. If it's not a bent pushrod, I would suggest you drain your oil to have a look and have it analyzed. Look at the filter too. I wouldn't be afraid to change out the cam at that point and keep running, especially as how you've described your driving habits.
One last thing about a wiped lobe, I blame Mobil 1 with not enough ZDDP. This was however ten years ago. Ignatz, I may well go that direction. Hmmm |
I’d say there is 1/32 to 1/16 deflection |
I don't know if this will help but keep in mind that if the pushrod is bent that it will flex when the engine is running and the lift will be affected. I would follow the excellent advice given here and investigate further. My advice is if the cam is going flat: replace the cam and drive the car. Even if you are going to replace the engine in the future having a car that you can't/don't want to drive will eventually turn it into a piece of garage art that you resent having to work around. I would also just put a stock cam back into it if you really intend to replace the engine. If you start to upgrade the cam you will have to upgrade other components and that is a slippery slope that we have all been down. P.S. I am a hardcore hot rodder so you should take that into consideration when I say to stay stock in this instance. LOL
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A bent pushrod would be clacking up a storm.
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Originally Posted by zmanabba
(Post 1596404106)
I don't know if this will help but keep in mind that if the pushrod is bent that it will flex when the engine is running and the lift will be affected. I would follow the excellent advice given here and investigate further. My advice is if the cam is going flat: replace the cam and drive the car. Even if you are going to replace the engine in the future having a car that you can't/don't want to drive will eventually turn it into a piece of garage art that you resent having to work around. I would also just put a stock cam back into it if you really intend to replace the engine. If you start to upgrade the cam you will have to upgrade other components and that is a slippery slope that we have all been down. P.S. I am a hardcore hot rodder so you should take that into consideration when I say to stay stock in this instance. LOL
Thanks. It does help. And I agree. I’d MUUUUICH rather this be a running project. This weekend I’ll investigate further. (It’s nearly 10 pm here). If it is a wiped cam lobe, I’ll replace the cam and lifters and be done with it. This only needs to last 12-24 months... and be comfortable during that time. In the meantime I need to save up for a good crate or similar On a 1969 ‘vette, can the cam be replaced in the car or should one pull the engine ? How does one flush the engine as mentioned above? |
Originally Posted by derekderek
(Post 1596404121)
A bent pushrod would be clacking up a storm.
It certainly wasn’t doing that |
I would bet on a bad cam-get it out of there asap. However, many years ago right after I got married all I could afford was beater cars. I would pay $75 to $150 for a car with an inspection sticker and run it till it died. I bought a big 72 Pontiac 4 door , V-8 car. Cam went bad on one cylinder. Pulled the push rods and drove it for 2 more years, then off to the junkyard. It ran rough but it ran !
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Can be done in car , and just change the oil and filter.
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Originally Posted by pop chevy
(Post 1596404261)
i would bet on a bad cam-get it out of there asap. However, many years ago right after i got married all i could afford was beater cars. I would pay $75 to $150 for a car with an inspection sticker and run it till it died. I bought a big 72 pontiac 4 door , v-8 car. Cam went bad on one cylinder. Pulled the push rods and drove it for 2 more years, then off to the junkyard. It ran rough but it ran !
lolololol. |
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