cj5steve
hey all ok im gettin real tired of this.i just ate my third cam in probably less than 200 miles.the first 2 were summit k8601 and the last was a summit k8600.the 8600 was a known good cam as i had ran it in the same motor before the rebuild.i ran it for about a year with no problems.the only thing i can figure is im not getting enough oil up top.when i primed the pump with the drill i had about 60 pounds of pressure,and it was just dribbling out of the rockers.i dont know if that is enough but it looks suspect to me.i have no idea what to do next if anybody has any ideas please let me know.if you need any more info let me know. thanks
tufcj
Describe "ate". Rounded lobes?
How are you breaking them in? Are you using new lifters each time? When you re-installed the 3rd cam, did you install the original lifters on the original lobes? How about seated valve spring pressure? Usually there's a recommendation on the cam card. Springs that are too strong will wipe out lobes. I did that once, cam recommended 90 Lbs seated, mine were 135.
The cam/lifters need to break in together. LOTS of assembly lube, get the engine started with as little cranking as possible, then get it to 2000-2500 RPM ASAP, run for 20 minutes. Shut it down and change oil and filter. Diesel oil like Shell Rotella T or Mobil Delvac are good break in oils because of their high zinc content.
You can get away with new lifters on a used cam (usually), but used lifters (even just 20 minutes) on a new cam will wipe out lobes.
Another issue to investigate is cam walk. Is there any mark in the timing cover where the bolt has made contact?
Things to think about. :-|
Bob
tufcj
Lifted79CJ7
Are your cam bearings lined up correctly?
tarior
Don't lose hope, I've talked to plenty of chevy guys who had cam failures right out of the gate. Everybody here know what I think of Summit cams. :(:
jeepsr4ever
How did you break in the cam?
tarior
Me or him?
jeepsr4ever
Steve :mrgreen:
cj5steve
the lobes on the cam are going round and the bottoms of the lifters are going concave and getting holes in the bottoms.new lifters used every time.break in is as you described 20 minutes at 2000 to 2500 rpm.i have heard about the differnt oil but have done a few cams before and always used castrol gtx with no problems.i am running the edelbrock heads.the first cam was with the edelbrock springs,the second was with a set of crane springs that were only 65 pounds,i sent the edelbrock springs back to them and they measured 120 pounds which i was told is ideal.on the third cam i put the edelbrock springs back in.i am going to pull the motor and do a complete tear down.i guess all i can do is hope to find bad bearings.in between #2 and 3 i took off the 2 rear main caps and the bearings looked good.i tried to look at the cam bearings but you can only see so much.the bearing surfaces of all 3 cams looked good nice and smooth and round.yeah i know about all the problems with the edelbrock cams.this sucks.but boy when it runs it is a monster.i will look for marks in the timing cover any thing else?
fuzz401
are the springs the right ones for that cam
ironman_gq
dont know if this would cause it but could the pushrods be the wrong length causing the geometry to be off and binding something
J4GRAND
i have heard about the differnt oil but have done a few cams before and always used castrol gtx with no problems.
You are never supposed to use an oil with detergents for an engine break-in, only non-detergent oil and a liberal amount of break-in lube on the cam and bottom of the lifters. You may have gotten away with it in the past but it may have bit you this time. The pushrods are 1.6s at least they were in my 360. Valve springs that are too stiff could cause the bottom of the lifters to wear prematurely.
jeepsr4ever
Its basically the Zinc-phosphates that really make the difference. 120lbs seems too steep for breaking in a flat tappet camshaft. Tell Edelbrock to eat the springs or you will ship the heads back in.
tarior
Ya' know, that's funny, I've talked to racers that break-in their cams with 120+ pound springs in place. But they do always use non detergent oil.
jeepsr4ever
Roller cam?
rollen dean montoya
i think you should try either a TRW or CRANE cam. sounds like summit
has mad a bad batch.
tarior
Flat tappet.
Crane or Comp, all that I will ever buy.
cj5steve
about the valve springs being to strong i ran the crane springs on the second cam and they were only 65 pounds.
Mudrat
rollen dean montoya wrotei think you should try either a TRW or CRANE cam. sounds like summit
has mad a bad batch.
I hope not - I stuck one in my 360 :shock:
Goose
I have hesitated to to say anything on this subject.. but after reading this thread several times, here is my 2 cents worth.. If that engine has munched 3 cams and lifters in a row in such a short time. in such a spectacluar fashion there is something Beyond normal causes.. I dont think the 120 pound valve springs or the detergent vs nondetergent oil could be the cause.. If I am reading your posts right this is all happening in under an hour to each cam.. right?
If thats true, and it is "rounding the lobes and concaving the lifters" you have to assume the pressure on those lobes has to be out of the realm of anything normal.. If it were taking a month or two per cam, ok maybe the springs, but I'm guesssing that you have some bind issues is it bending the pushrods?? are any of the lifters sticking in the bores?? is it always the same lobes? or is it random.
Simply put, I dont think you could round the lobes on a lathe, without a fairly sharp tool in that amount of time(certainly not the bottom side of a lifter!)
jeepsr4ever
I believe it may be a hardness issue between the camshaft and lifters. I can only speculate
