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Old Feb 29, 2008 | 08:47 PM
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Default Cam issue!

I know this may not be in the right section but i need everyones opinion. I wanted to see what yall guys think could make this happen and maybe why. My car was running like crap so i took it back to the shop and we find out that one of the lobes on the cam is rounded off. We found out because one of the valves was only lifting about .100 Just wanted to know what causes this and why. Its a hydraulic flat tappet cam just incase that helps. Could it just be a bad part or could something be wrong with any of the valvetrain? We already replaced the cam and is getting put back together as we speak. Thanks!
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Old Mar 1, 2008 | 03:21 AM
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Originally Posted by a-mean-89-iroc
I know this may not be in the right section but i need everyones opinion. I wanted to see what yall guys think could make this happen and maybe why. My car was running like crap so i took it back to the shop and we find out that one of the lobes on the cam is rounded off. We found out because one of the valves was only lifting about .100 Just wanted to know what causes this and why. Its a hydraulic flat tappet cam just incase that helps. Could it just be a bad part or could something be wrong with any of the valvetrain? We already replaced the cam and is getting put back together as we speak. Thanks!
you ever run it low on oil? could be that or just a bad cam from the factory. i had that happen way back when i ran flat tappet comp cams .however i can gaurantee one thing. that bottom end will start knocking soon. be ready.
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Old Mar 1, 2008 | 03:42 AM
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Originally Posted by a-mean-89-iroc
I know this may not be in the right section but i need everyones opinion. I wanted to see what yall guys think could make this happen and maybe why. My car was running like crap so i took it back to the shop and we find out that one of the lobes on the cam is rounded off. We found out because one of the valves was only lifting about .100 Just wanted to know what causes this and why. Its a hydraulic flat tappet cam just incase that helps. Could it just be a bad part or could something be wrong with any of the valvetrain? We already replaced the cam and is getting put back together as we speak. Thanks!
It is because flat tappet sucks...that is why the world went to roller. Especially if you are running new iols, they dont have zinc and sulpher that oil manufacturers had to cut out due to emmissions. That is a must for flat tappets, there are additives and even companies that still make oil for flat tappets but it is easier to use roller, cost more but worth it. Maybe you didnt break it in right.
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Old Mar 1, 2008 | 07:29 AM
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Originally Posted by a-mean-89-iroc
I know this may not be in the right section but i need everyones opinion. I wanted to see what yall guys think could make this happen and maybe why. My car was running like crap so i took it back to the shop and we find out that one of the lobes on the cam is rounded off. We found out because one of the valves was only lifting about .100 Just wanted to know what causes this and why. Its a hydraulic flat tappet cam just incase that helps. Could it just be a bad part or could something be wrong with any of the valvetrain? We already replaced the cam and is getting put back together as we speak. Thanks!
Did you ever replace the lifters? Lifters can get stuck doing what you describe.
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Old Mar 1, 2008 | 10:37 AM
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Originally Posted by ex-SS-ve
you ever run it low on oil? could be that or just a bad cam from the factory. i had that happen way back when i ran flat tappet comp cams .however i can gaurantee one thing. that bottom end will start knocking soon. be ready.
No never ran it low on oil. And why do you say that about the bottom end? They said the oil filter caught most of the metal shavings.
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Old Mar 1, 2008 | 10:39 AM
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Originally Posted by ZONES89RS
It is because flat tappet sucks...that is why the world went to roller. Especially if you are running new iols, they dont have zinc and sulpher that oil manufacturers had to cut out due to emmissions. That is a must for flat tappets, there are additives and even companies that still make oil for flat tappets but it is easier to use roller, cost more but worth it. Maybe you didnt break it in right.
The shop that built me the engine said they had broken it in. and i would go roller but seriously i just aint got the money to go roller right now.
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Old Mar 1, 2008 | 10:40 AM
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Originally Posted by Howie Felterbush
Did you ever replace the lifters? Lifters can get stuck doing what you describe.
Yeah well they replaced the lifters and cam now that this happened.
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Old Mar 1, 2008 | 02:34 PM
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Originally Posted by a-mean-89-iroc
No never ran it low on oil. And why do you say that about the bottom end? They said the oil filter caught most of the metal shavings.
the reason i say that is cause the metal shaving have been cycled thru the motor befor they went to the filter. the rod bearings definately catch some of the material. every old school sbc that ive seen a flattened rounded off cam in started having rod knock issues after 1k miles. not trying to hurt your feelings just letting you know what to be ready for.
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Old Mar 1, 2008 | 03:09 PM
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Well, the oil must have not been good enough.
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Old Mar 1, 2008 | 03:44 PM
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Everyone says oil, I say bull ****. If this is a sbc then it could be a number of things. I would lean towards too tight of a lash or to high of a valve spring pressure. What are the specifics of this motor? Cam, heads, etc. Oil is a lame excuse. If the motor had 30, 40, or 50,000 miles on it then maybe oil could be to blame but I dont think this is the case. Josh
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Old Mar 1, 2008 | 04:06 PM
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Well, it is a fact, you have to use the oil with the high content if you want it to live, it has been going on for a while now, it doesnt have what it needs anymore for the flat tappets, but hell, the valve spring pressure and poor ajustment are possibilitys too.
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Old Mar 1, 2008 | 04:25 PM
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Originally Posted by ex-SS-ve
the reason i say that is cause the metal shaving have been cycled thru the motor befor they went to the filter. the rod bearings definately catch some of the material. every old school sbc that ive seen a flattened rounded off cam in started having rod knock issues after 1k miles. not trying to hurt your feelings just letting you know what to be ready for.
Yeah i mean that can happen and if it does it is going back to the shop.
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Old Mar 1, 2008 | 04:26 PM
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Originally Posted by a-mean-89-iroc
Yeah i mean that can happen and if it does it is going back to the shop.
What are the specs on the motor? What parts were used in the build?
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Old Mar 1, 2008 | 04:26 PM
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Originally Posted by ZONES89RS
Well, the oil must have not been good enough.
Well they used the right oil to break in the cam which is rotella diesel oil. and they break it in right on their dyno as well. So i dont know what can be the excuse. What oil do yall guys suggest i use from now on every oil change? Synthetic?
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Old Mar 1, 2008 | 04:36 PM
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Originally Posted by a-mean-89-iroc
Well they used the right oil to break in the cam which is rotella diesel oil. and they break it in right on their dyno as well. So i dont know what can be the excuse. What oil do yall guys suggest i use from now on every oil change? Synthetic?
Here we ago with the oil debate. I just suggest an oil with the current rating. I think it up to sk or even higher, I dont use oil bottles. A good 10w30 would be fine if the bearing clearances arent alot. I used to run 20w50 in my race motors. In my ls1 I run 10w60 castrol tws3. Motor has some miles and I spray it hard.
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Old Mar 1, 2008 | 05:08 PM
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Originally Posted by Cam72aro
What are the specs on the motor? What parts were used in the build?
355 4 bolt main, 10.5:1 comp, GM performance crank, forged pistons, now since that other cam fd up its got a 240 246 hydraulic flat tappet comp cam, Ported aluminum heads, edelbrock victor jr. intake with a 750 hp series holley.
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Old Mar 1, 2008 | 05:58 PM
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Originally Posted by a-mean-89-iroc
355 4 bolt main, 10.5:1 comp, GM performance crank, forged pistons, now since that other cam fd up its got a 240 246 hydraulic flat tappet comp cam, Ported aluminum heads, edelbrock victor jr. intake with a 750 hp series holley.
What brand cam, what is the lift? Also what is the seat pressure on the springs. I am gonna have to say that it might just have been a lifter with too much preload on it. Cant say without looking at it.
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Old Mar 1, 2008 | 06:10 PM
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Originally Posted by Cam72aro
What brand cam, what is the lift? Also what is the seat pressure on the springs. I am gonna have to say that it might just have been a lifter with too much preload on it. Cant say without looking at it.
Comp cam and it is .507 int. and .510 exh on 1.5 rocker ratio and mine is 1.6 rocker ratio. Dont know what the seat pressure is and what do you mean with too much preload?
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Old Mar 1, 2008 | 09:23 PM
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Originally Posted by a-mean-89-iroc
Comp cam and it is .507 int. and .510 exh on 1.5 rocker ratio and mine is 1.6 rocker ratio. Dont know what the seat pressure is and what do you mean with too much preload?
Preload as in lifter preload, ie valve lash. Could have had a rocker too tight. Seen it do it before.
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Old Mar 2, 2008 | 01:07 PM
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Make sure that your valves springs are installed correctly and still good. They broke it in properly with that oil. Did they run a lifter bore through the hole? I've seen trash get in there before and not allow the lifter to spin correctly.

Other than that, everyone here seems to have the same answers.
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