Used flat tappet cam break-in???? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-09-2008, 07:52 AM
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Used flat tappet cam break-in????

I just installed a slightly used cam in my 454. And I'm about to start it up on my engine stand. This is the first time that I installed a used cam.

The cam was run long enough just for a broken-in proceedure. It was broken-in on a different engine then was pulled out of the engine because of other problems. The cam lobes look great. I remember the old lifters looked good also but were throw away long ago.

So, I put the used cam in with a new set of GM lifters and I'm wondering how much break-in is required since the cam has already been run.

The cam is mild (208/218 with 0.475/0.500 lift), single springs have 90lbs on the seat and 270lbs at 0.500", there is Rotella T 30w (old formulation) in the engine along with a bottle of compcam break-in oil additive.

Thanks for any input.

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Old 07-09-2008, 08:06 AM
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You will want to follow the same procedure as a new cam since you are using new lifters. The lifters wearing to the pattern of each lobe is the reason for the break in whether the cam is new or used.
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Old 07-09-2008, 10:43 AM
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Quote:
I put the used cam in with a new set of GM lifters and I'm wondering how much break-in is required since the cam has already been run
That's a scary deal if you ask me. The cam has been wear mated once(broken in), and now your new lifters are going to wear mate to the cam's previous break in. I'm sure this has been done successfully, as well as not so successfully. The bigger question though, for the price of a new cam, why take the chance? I'd have never done it, not even just to see. This is not the way to do it. Good luck.
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Old 07-09-2008, 11:25 AM
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You'll be fine with new lifter in used cam, just be sure use oil with lot of zinc or add EOS oil supplement in with you oil.
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Old 07-09-2008, 05:29 PM
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FWIW, I spoke to a local (and well-respected) engine builder over here about using new lifters on an old cam and he recounted a 1st-hand experience he'd had just weeks before where he wrecked a freshly-built 454 in an attempt to cure a ticking from the valvetrain. He tried dropping new lifters in (the cam had seen about an hour's runtime on a dyno at this point). This was against his better judgment, but the customer was eager to get his hands on his new engine. Within minutes, he'd wiped the cam lobes and wrecked the bottom-end due to all the fine metal powder from the cam lobes getting into all the bearings.

Flat tappet cam break-in is scary enough as it is, even when you're playing by all the rules. Personally, I wouldn't risk new lifters on an old cam.
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Old 07-09-2008, 06:00 PM
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Don't do it, especially in a Big Block Chevy, once they have been run in another block that is where they have to stay. There is enough variance in the lifter bore machining that the wear pattern on the cam will not be the same. Big Blocks eat lifters even when everything seems perfect, I've seen your scenario fail twice.
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Old 07-09-2008, 09:56 PM
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Is it getting brighter?
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Old 07-09-2008, 11:34 PM
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False economy. You're just askin' for trouble.
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Old 07-10-2008, 02:08 AM
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Call a machine shop. They can get you an RV cam from Melling or Blue Racer with very similar specs for $30-40.

Or ebay. I bought an RV cam for a 396 that was 204/214 for $32 shipped, new in box.
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Old 07-10-2008, 05:25 AM
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I agree with not useing new lifters on an already broken in cam,my buddy tried that with his big block,he had so much trouble he had to pull the motor out.For the price,just get a new cam.
Guy
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Old 07-10-2008, 06:24 AM
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wow! doesn't sound very good.

All these years, I was under the impression that a used cam could be used as long as new lifters were used.
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Old 07-10-2008, 07:54 AM
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Quote:
Originally Posted by 454C10
I just installed a slightly used cam in my 454. And I'm about to start it up on my engine stand. This is the first time that I installed a used cam.

The cam was run long enough just for a broken-in proceedure. It was broken-in on a different engine then was pulled out of the engine because of other problems. The cam lobes look great. I remember the old lifters looked good also but were throw away long ago.

So, I put the used cam in with a new set of GM lifters and I'm wondering how much break-in is required since the cam has already been run.

The cam is mild (208/218 with 0.475/0.500 lift), single springs have 90lbs on the seat and 270lbs at 0.500", there is Rotella T 30w (old formulation) in the engine along with a bottle of compcam break-in oil additive.

Thanks for any input.
I used to use the comp cam oil additive, however since have changed. It had been tested and was low on zinc and high on detergents. Crane's additive is still good and also the new eos is fine.
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Old 07-10-2008, 08:01 PM
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we did used cams & new lifters a few times.

we have done it prob 6 or 8 times in a 5yr period. used cams with new lifters in several 350s and in 2 400 SBCs in demo cars, no problems. we used big Chryslers at 1st and then big Olds and big Buicks, we stuck SBCs and power glide trannys in the chryslers, buicks, olds. we started with good used engines that we would hone & rering and rebearing with new timing chains and gaskets. ever lost a cam & lifters.

we also used the GM 31 spline 12 bolt rears with big wheel bolt patterns. we took a 31 spline ford 9" rearend and pulled the axle tubes, and put the GM axle tubes in the ford 9" rearend centers and bolted the GM axles in. cause the GM tubes were built to bolt in the Buicks and Olds cars. then we used the Big GM steel wheels.

there was 6 of us Big in to the demo derbys, we sold all of the demo stuff, cars, rearends, tires, 456 gears, engines, header sets we made that went up, radiators, ect. and theres still several used cam and lifter combos left and 2 used cams a 1 new set of lifters, after we sold a 400 short block and a 350 long & short block (lifters keep in order). most of the engines we used were honed rerung and new bearings with a set of camel hump heads to up compression, (the old camel humps were a old set that had non harden seats and no acc holes).
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Old 07-10-2008, 11:09 PM
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Quote:
Originally Posted by 454C10
wow! doesn't sound very good.

All these years, I was under the impression that a used cam could be used as long as new lifters were used.

The only really safe way to put a used cam in is if you carefully marked all the old lifters and re-installed them on their original lobes, but its just not a worthwhile risk in most situations. I'm sure if you had a rare vintage grind that wasn't used much and you wanted it for a show car, maybe, but with good cheap new Melling cams costing $40 and a new set of lifters under $50, it just doesn't make sense to me.

Picture a cam lobe like a hard boiled egg - not because of its shape, but because its hard on the outside and soft in the middle. Flat tappet cams are made of relatively soft cast iron, then the surfaces are hardened. When you put a new cam in with new lifters, they wear together, much like if you had two pieces of sand paper rubbing together. After a while, the sand rubs off and you're left with paper on paper. With the cam, the surface of the lobe wears into a pattern with the lifter and (if you're lucky) doesn't break through the hardened shell. Putting new lifters on an old cam is like replacing one of the pieces of sandpaper and it has a very good chance of tearing through the other piece.

Breaking in cam lobes involves friction and abrasion. Asking a cam lobe to survive a second lifter pattern is just asking for trouble.
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Old 07-11-2008, 12:12 AM
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Twice this year I stopped by different shop and watched them install used cams and used lifters by slapping wheel bearing grease all over them.
Cars still seem to be running great after 5-10 thousand miles. yikes.
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