Looked at a truck the other day , pretty nice buy but .... The original cam in the 454 went flat, And thats how the current owner purchased it. Current Owner had a new cam, lifters and timing chain installed, but that's it. The engine runs but the converter doesn't match the cam. The turbo 400 was rebuilt just before the cam was done. Its a bit noisy and the current owner claims it needs valve adjustment. He knows this because one of the rocker nuts had completely backed off and he tightened it. It diesels on shut down. In my opinion the metal from the original cam lobes did plenty of damage. I think I should look at the current engine as core and price my offer accordingly. He's showed receipts for the work done. Does that sound reasonable to you guys ?
I'd be making an offer figuring that I was going to have to go through the engine at some point in the not too distant future. Flat cams are changed every day and the oil and filter changed and away you go for a lot more miles but there is always that one engine that suffered more damage than just the flat cam in the process. That the guy will even show the truck to a prospective buyer without making sure it's pretty well squared away leaves room to bargain.
I would add that because you understand the consequences of improper cam break-in, the seller may not. He may not be willing to give up a "fresh rebuild" selling point. I would offer only what you are willing to pay for the good parts that are there. That may be the truck with a rebuildable engine.
Not all flat cams make cores out of the engine. Sometimes it is just a good flushing and oil change away from being a good engine. It all depends on how and what was actually damaged (big pieces v little pieces) the only way to know is to pull it down for inspection and hope to be pleasantly surprised. I would guess that one should consider that the engine may not have much life left in it and go from there.
I was in the production engine rebuilding business years ago. If checked after a "premature cam failure" in a factory motor, more than 90% of the time lifter bore angles were found to be off. These blocks if uncorrected would fail the same lifters again prematurly, we tested 4 in "life cycle" tests.... This was testing strictly related to Chevy big blocks.
Its the luck of the draw when it comes to metal from a flat cam eating the rod and main bearings on a BBC or any motor for that matter.The cam in my tow truck went flat (completly wiped the lobe off) last summer.I had only had about a 1000 miles on the motor when it did it.I bought the 468 from a guy i know a month before.It had a lifter ticking in it ,but i figured it was just stuck from sitting.I readjusted the rocker a few times .A month later it was spitting through the carb and i knew what it was at that point.I changed the cam ,lifters and timing chain ( installed and broke this one in myself ,so i know it was done right) ,and its going strong for over 5 months and 2000 miles.I pulled the pan washed it out and flushed the motor with diesol .I poured it through the block to try and wash out the metal particles .I also changed the oil before the new cam ,then changed it again right after the new cam was broke in.I then changed it after a 100 miles again.Driving the truck daily since and the oil pressure had not changed ,and there is no knocking rod bearings .To say that a motor is automatically gunna need a total rebuild due to a flat cam ,is just plan wrong .Check out the camlobe and the cupped lifter that cam out of my 468 .Sorry moderators for showing vid of my off topic truck .Im just trying to show the guy that a flat cam doesnt always mean its over for the motor .Truck is running just the same as it did after the cam swap last June .Just got home from work in it a few minutes ago as a matter of fact .BTW im sorry for my langauge on the vid .I was pretty well lit from drinking beer and working on the motor all day in 100 degree heat ,plus i had just put this motor in the truck when the cam went flat a month later ,so i was a little discusted with it at the time ,lol...
Shocker- If this question is answered in your video I apologize I havent watched it yet, but... What exaclty am I looking for when I look at a used cam to determine its condition? Wear patterns, if so what do good and bad ones look like? I am in a similar situation in that I also acquired a BBC that the previos owner had said started "ticking" so he shut it down...never did personally hear the engine run myself...
Best way to tell is to look at the lifters that came off the cam.If one of them looks dished or cupped on the "face" or the part that rides on the lobe ,its bad .The lifter will usually show wear visually before the cam lobe in my expierence .The cam lobe going flat (if its just starting ) will have a different looking wear pattern than the others.Lots of times the lifter bore being messed up will cause a flat cam ,because the lifter cant rotate freely .Many times this is caused from a previous flat cam and damaged lifter that was mushroomed on the bottom .Someone will force it back through the bore with visegrips and it scratches up the bore ,making the new lifter not spin .If the lifter stops spinning in its bore its finished .If you have a set of calipers you can measure the height of the lobes .If one of them is way shorter than the others its bad.Make sure that when you do this you check intakes to intakes and exhausts to exhausts.Most cams (especially hydraulic flat tappits) have different lift on intake and exhaust valves ...
Ive lost a couple of cams in a BBC. Both were flat tappet cams. Both times we just swapped in a new cam and drained the oil and filter. Didn't see any bearing damage when we tore the engine down the next season but had PLENTY of piston skirt and cylinder wall damage.
I agree on the piston skirt damage .I have heard that metal particles off the cam lobe and lifter will embed into the piston skirts.On another note the starting compression on both banks of my 468 was 155-160 psi before the old cam lost a lobe.I checked it a few weeks ago and it still the same .I was already out $1500 for the new Big block ,and it was only about $300 or so for me to change the cam and lifters (i used a sealed power kit) plus the timing set ,so i took a gamble and opted to fix her without pulling it back out and basically rebuilding it .It was the best option for my situation at the time ...
Oil no longer lubricates like it should. It no longer has zinc in + most new cars have roller lifters. They use synthic oil which has better lubricating propeties than fossil oil You need to use oil additives or there's potential for this to happen to any flat tappet cam especially if you have high pressure valve springs
This doesn't help with op's question but since we're talking flat BBC cam lobes. BBCs are notorious for flattening cam lobes. What some rebuilders do during machining is cut a small groove in the lifter bore to help with oiling. Just something to keep in mind but hopefully the motor won't need a complete rebuild anyways
Im with you Risky on the BBC being known for loosing cam lobes.IMO a Big Block Chevy has one of the worst valve train designs ever.Not only are they great about loosing cam lobes ,but they are also great about bending factory pushrods ,wearing out valve guides ,and eating up valve tips.I have never seen an older BBC (pre Vortec anyway) last more than 150k without having internal problems of some sort.Despite their drawbacks i still love those big tourqey Bastards .I have two of them at the moment and have had several others before these...
Here's a link to the lifter bore groove cutting tool. There's also a universal one that's cheaper but haven't found a linhttp://www.jegs.com/p/Comp-Cams/Comp-Cams-Lifter-Bore-Grooving-Tool/753195/10002/-1k for it yet.
Just offer the guy what you think it's worth. If he thinks it's worth lots more and doesn't want to budge, walk away. He won't want to hear your technical explanation, no matter how true it is. There are plenty of BBC's out there. Of course, if you want it that bad, maybe you should pay a bit more............ Just sayin'
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