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my friends 460 needs help
I have a friend who is having issues with his 460 motor and I wanted to get some help from you guys. The engine was a 460 crate motor and only has about 20K miles on it. Recently it started "missing" and knocking a bit so he took it into a shop. The Shop owner told him that he had developed a "flat" spot on his cam and would need to have the engine pulled and cam replaced with a hydraulic one....major work and expense.
I know I may be using some wrong terms but does this sound possible? Has anyone had this before???? If you have questions let me know as my friend is not computer friendly and I just want to help out a really good Cobra Friend. Thanks guys (and maybe gals). Kramer |
not sure about the "replaced with hydraulic". but a flat spot is probably easy to find. pull the valve covers are rotate the engine over with a breaker bar. look at each rocker arm. if there is really a flat spot, there should be one rocker that is noticeably not moving as much.
i had a 1973 malibu in college that i bought for $50. it had a flat spot, no lobe on one of the exhaust values. it sputtered and knocked and did all kinds of goofy stuff. a new cam fixed it. pulling the valve covers made it easy to see that one rocker arm was not moving |
On the suspect rocker (if visible to the naked eye) use a dial gauge to measure lift of the lobe. If they all sorta move measure each one individually.
If it is a worn exhaust lobe you may hear a chuffing (like air compressor noise) through the air cleaner as the gasses cant all get out the exhaust port and try and backfeed. I have seen a lobe on a Mack truck completely gone, nothing but round. It can occur when the hard facing on the cam fails, the rest of the softer metal then goes rather rapidly. An oil sample analysis would show this also. |
Yes, it is possible. He can verify it himself by using the process that Outwest described.
It shouldn't be a big expense, a cam and lifter set is around $200. Of course their labor rate may be expensive. If your friend (or you) are mechanically inclined, you can verify their findings and also do the cam swap. |
Thank you. I am guessing most of the cost is just the labor to pull the engine. Does anyone have any suggestions on what kind of CAM / Lifter set to buy?
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No need to pull the engine.....but will probably need to remove the radiator and fan. You just need enough room to stab a new cam in.
I can certainly give a recommendation for a cam if you have all the specs on the engine and car. |
Happens a lot.....usually does it within the first couple hundred miles during break in.
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Thanks all. I will go visit my buddy today and talk to him about your thoughts and get some engine specs.
Blykins. regarding your comment "I can certainly give a recommendation for a cam if you have all the specs on the engine and car." it certainly would be appreciated. Kramer |
No problem, I'll do what I can to help out.
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I had a cam go flat on me back in the 70's. If his is going bad, he will hear lots of valve clatter. As the cam wears away, the valve lash increases, along with the valve noise. The way I identified mine was to adjust the valves, then drive it till I heard lifter noise. Didn't take long. There was no noticeable change in performance, only noise. Then I measured the valve lash. Found several lobes were indeed disintegrating and needed tightening. Then I had the cam and lifters replaced.
If you're not hearing any valve clatter, probably not a cam problem. Check it out before you start pulling stuff off. The symptoms you describe could be just an old fashioned tune up needed. I would investigate further. |
Well, one indicator of grinding your lobes down is your oil will become real black, real quick.
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i'm skeptical with 20 thou on the motor its the cam at all......crate motor? what type?
a complete factory drop in for a particular year? a performance engine? does this motor have an EGR plate on the intake? the 70's 460's suffered symptoms like you describe when the EGR went bad.....it acted like a huge vacuum leak, and yes it could knock too. a little more info on the application of the motor and some build info may get you some more definitive answers fred |
If the camshaft has lost a lobe it could do it again if the right process is followed on the new camshaft break-in. You would want to check the valve spring pressures as well. You will want to use special break in oil for the new camshaft with a high level zink, like the Jo Gibbs break in oil and there are a few more. You will need to run the engine at about 2000 to 3000 rpms for about 30 minutes to break the camshaft in.
All canted valve engines like the BBC, 351C and BBC engines are harder on camshaft break in and longivity. You will know more when you take it apart. Good luck, Keith Craft |
I use 1 pint of Lucas Engine Breakin additive with 5 qts of oil when I start new engine. This is approx 35,000 Zinc PPM. When I change oil in all my cars
its 4 to 6 ozs with up to 5 qts of oil, this is approx 1700 Zinc PPM. Jay |
May be (and most likly is) a flat cam lobe. BUT, it could be a bent/or bad pushrod, a bad rocker, or other valve drive train issues such as a broken spring, in addition to the other stuff listed above. Hard to call from far away, so find s good mechanic. All of this stuff is fairly easy to fix when you find the right problem. Don't forget to think about what might have caused the problem in the first place. It could set off a chain of other fixit problems. Good luck, cobrashock
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