just rebuild sb350 ,and had cam failure.. - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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  #16 (permalink)  
Old 12-02-2003, 11:56 PM
Grumpy
 
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Sounds like your cam, or lifter bores are starving for oil. This does not sound like rotating pushrods. Never heard of that one before. Are you using 3rd party lifters, or did you forget to scrub out the oil paths in the lifter bores?

EDIT: This is also why I recommend NOT replacing the valve springs with stiffer ones. Can cause too much pressure. But not likely the issue

EDIT again: The cam break-in thing is a bit of BS. You really think it is going to matter if you drive it for 15 mins. or let it sit for 20? I would just let it idle for a few than drive in for about 15 mins. When cars come off the assembly line, they dont break them in at all. Sometimes this break-in stuff is the reason you hear about rebuild failures at 5,000miles. Also the assembly lube is bs as well, a good thick gear oil works best, the assembly lube can clog oil passages in key area before it breaks down and cause the same problem. Best solution is lube everything with a medium oil and turn the engine with a drill or by hand for a few mins or so.

Last edited by 87442lover; 12-03-2003 at 12:10 AM.
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Old 12-03-2003, 05:12 AM
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My thought is that there is something restricting the oil to the area of the cam that is wearing prematurely. Since the original assembly wiped a lobe, that virtually eliminates an improperly installed cam bearing by the machine shop. If I had it apart again, I would remove the crank and insure that the oil passages from the crank bore to the camshaft bearings are completely clear.

Good luck
Vince
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Old 12-03-2003, 09:09 AM
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this is robbie

i didnt soak the lifters, i use to in the past but every sence i got in to drag racing i stoped. this is how i justed my vaules. i turned the engine over until the exhaust vaule starts to move up and i adjust the intake, but before i adjust it ,i will spin the pushrod until i feel a slight drag,or no more up-down movment,then i will push down on the rockerarm to make sure that the lifter plunger goes all the way down and back up, then i will turn it about a 1/4 turn more,and push down on the rocker to make sure the plunger moves still,then i will turn the motor until the intake goes all the way up then back down then i will adjust the exhaust , and set it the same way i did the intake, I have done it that way for years, i use to do it with the engine running. i just looked at my cam bearning,and they looked like they in right, Im going to take it to the machine shop and get it redone again. AINT THERE AWAY THEY CAN CHECK THE OIL PASSAGE TO MAKE SURE OIL IS GETTING TO THE CAM RIGHT.?? cause the cam swiped the lobe in about the same place as the otherone did. 3-4 cyl across from each other. thanks again for all the help guys, im glad i found this sight,its alot of help robbie

but keep in mind guys that im going with a hyd roller this time ,and roller rockerarms and i was told i want have to worrie about the lifters ,cause roller lifters dont spin,and plus i was told even if the lifter bore might be alittle out that i would still be ok, the machine shop said with me running it at high rpm that the lifter bore will change alitte,he said he has took an engine apart and the cam wear would be fine,and the lifters, and after he put it back together that after he cranked it up he would have to rotate acouple of pushrods cause they wouldnt be rotating.,and if they dont rotate,cam failure will happen. thats why im hoping going with a roller cam is a good choice,cause i have read you cant hardly wipe out a roller cam thanks again robbie

Last edited by Robbie; 12-03-2003 at 09:09 AM.
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Old 12-03-2003, 01:50 PM
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not wanting to get in the 20 min. debate or not, other than crane says to do it. also for the rings, running at varying speeds. which is how i do mine too, just after the 20 min break in. and yes, how nec. could it be when GM doesnt do it?
adjusting rockers: straight out of the book i havent had to pull a valve cover back off yet. but... if you have a clogged oil passage i fail to see how changing cams/lifters to rollers is gonna make a dif
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Old 12-03-2003, 02:08 PM
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Yeah, I dont understand chevys, Why would you want to adjust the rockers? Cant you just steal a set of rockers from an olds? That way no worrying about adjusting and spinning rods and lifters nonsense.

Or why cant you just torque them to spec before you put the heads on the block and not worry about it? I really dont get it, but I havent had a chance to work on chevy heads yet, and by the looks of it I dont want to.
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Old 12-03-2003, 03:18 PM
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Car Manufacturers

Hello,

The GM Fairfax Kansas Plant (Kansas City, Kansas) does run their assembly line cars before they leave the assembly line.
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Old 12-03-2003, 04:05 PM
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I see 87442lovers ignorance is rearing its ugly head again. You never ever let an engine idle before the cam is broken in! Push rod engines rely on spash from the crank and rods to lubricate the cam and at idle there isn't nearly sufficant splash. And acually most manufacturers do run their engines prior to installing them. Its not just me saying this its every respected engine builder I have ever heard of feels the same way.
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Old 12-03-2003, 04:20 PM
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My ignorance? Well.. MY ignorance comes from trying it the way the manufacturer says to and having it fail. Lifters and the cam lobes do NOT really rely on splash like you think, they rely on the lube from the lifter bore oil path to drain down on the bottom of the lifter and on to the cam lobe. Maybe you should do your research a little better before calling me ignorant? Splash does contribute aswell, but if it wasnt for the inefficiency of the hyd. lifter-to-bore letting oil drain down all cars would fail at idle. It only takes one good rev to get the cam wet, after that all your doing is wearing in your parts early. Remember everyone has their own way of doing things.

And I really hate ignorant people that say they have 25 years behind them and dont want to open their mind to different ideas. No i dont know everything and I stick with oldsmobile, pontiac, and buick.

EDIT: I do understand the point of break-in which is to get all the surface to "mate" so they are use to that other surface that, that part touches(ie. lobes to lifter) I'm not ignorant, I just do things the way I see them working better and I feel driving conditions is the best way to break-in the parts.
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Old 02-09-2012, 07:12 PM
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Just a thought?

I think we all have to used to either running roller cams in these old hot rods or buying zinc additive. They are now even taking it out of the most of the 10w-40 diesel oil. We either have to buy racing oil like valvoline or add zine, or just run the good roller stuff!
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Old 02-10-2012, 04:08 AM
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This thread is 9 years old.
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Old 02-10-2012, 04:19 PM
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Unbelievable, Double. It is 9 years old. Still makes for good reading the ignorance out there regarding cam break-in. Anybody who hasn't run their flat tappet cam up to 2K RPM and kept it there for twenty minutes and hasn't wiped a lobe is just plain lucky.
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