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Old 06-22-2005, 06:47 PM
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Cam failures - sbc

I've had several posts lately questioning Summit cams & other reasons for cam failures but I've now flattened several lobes on my 3rd camshaft in a row & am getting REALLY frustrated as well as POOR! They are flattening after only approx. 30 minutes run time! The 1st was Summit, #2 was Crane & #3 was a Comp 284..all in the same newly rebuilt sbc short block with hyp. pistons 9 1/2-1 Eagle crank, double roller chain, Edelbrock Perf. RPM heads-64c.c. Crane roller tip rockers (long slot), etc. And YES, I do know how to break in a cam properly & with the right oil & cam lube & GM EOS supplement & zinc content etc. & proper run in time. My builder replaces the cams but can't find the solution!!! He's now saying that I should leave off the valve covers on break in & see if the pushrods are turning & if not give them a spin to also spin the lifters! Ok, Crane has that in their small print to cover their ***** BUT can ANYONE see doing that with oil spraying all over while you break in?? I'm suggesting that the lifter bores are not aligned square to the cam lobes but am not getting the proper head nods from the builder! He's saying I should buy a hydraulic roller cam to solve all problems .... & I'm thinking that this sort of confirms my bore/lobe alignment theory?

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Old 06-22-2005, 07:23 PM
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Athough the lifter bore relationship may have worked fine in the olden days THESE days with the new (basically single source) supplies of lifters the surface of the lifter may not like it. Your gut is CORRECT, the first thing you need to verify is if the lifters are spinning. We do this on mock up with the cam installed and the lifters installed in the bare block. Spin the cam with a drill. I don't think it makes any sense to do it under operating conditions as once you see the lifters are not spinning it's junk already. If the lifters don't spin then we fixture up the block and hone/true the lifter bores. The next thing we do is break in solids with 1.3 break in rockers on the dyno. Both those steps have basically eliminated camshaft failures on solids and standard hydraulics.

This issue is well know in the camshaft industry and should be well know at the shop level as it relates to the core problem.

If you can't locate break in rockers then you need to locate break in springs or remove the inner if they are duals. In the majority of cases you can't cheat this overall process with some combinations, as you have found out.

If you looked at all those cam cores I suspect you would notice as well that they all seem to look the same as well. I suspect they are all Crane cores, just an FYI when your snoopin around the shop. This industry is pretty in breed.
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Old 06-22-2005, 08:08 PM
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Quote:
Originally Posted by Rick WI
Athough the lifter bore relationship may have worked fine in the olden days THESE days with the new (basically single source) supplies of lifters the surface of the lifter may not like it. Your gut is CORRECT, the first thing you need to verify is if the lifters are spinning. We do this on mock up with the cam installed and the lifters installed in the bare block. Spin the cam with a drill. I don't think it makes any sense to do it under operating conditions as once you see the lifters are not spinning it's junk already. If the lifters don't spin then we fixture up the block and hone/true the lifter bores. The next thing we do is break in solids with 1.3 break in rockers on the dyno. Both those steps have basically eliminated camshaft failures on solids and standard hydraulics.

This issue is well know in the camshaft industry and should be well know at the shop level as it relates to the core problem.

If you can't locate break in rockers then you need to locate break in springs or remove the inner if they are duals. In the majority of cases you can't cheat this overall process with some combinations, as you have found out.

If you looked at all those cam cores I suspect you would notice as well that they all seem to look the same as well. I suspect they are all Crane cores, just an FYI when your snoopin around the shop. This industry is pretty in breed.
Great stuff! Thank you ..as an aside, they are not dual springs, they have the flat spiral "dampeners" which come with all Edelbrock , complete heads.
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Old 06-22-2005, 08:52 PM
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Quote:
which come with all Edelbrock , complete heads.
So these are new Edelbrock Performer RPM heads...? If not which ones...? The springs on the Performer RPM heads are for up to .575 lift and are pretty stout... You might consider swapping springs for break in along with the low ratio rockers too...?

Also dont ever assume a single spring is a light weight... If you think so check out Lunati part number 73815 and understand its just a little 1.5 diameter single spring that installs at 1.820 but will handle a .660 lift cam (120lbs seat & over 300lbs open) better than alot of dual springs and works with .600 lift hyd rollers too...
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Old 06-22-2005, 10:00 PM
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After three cams and inspecting for lifter rotation I'd basically be to the point of installing ball point pen springs and the 1.3 rockers. As well as pulling out the rest of my hair.
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Old 06-22-2005, 10:01 PM
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When you install the lifters do they go in easy? Are any of them tough to install/tight fitting? I ask because I've heard of tolerance problems causing the lifter not to spin. I usually polish the lifter face with 1500 grit sandpaper before I use them. Some say this is stupid but I've never lost a cam. A cam button will also guarantee the cam isn't pulling forward and only costs about $5. I know the lifters are supposed to keep the cam from moving forward but hey it doesn't hurt a thing to run a cheapo alluminum solid cam button just to make sure. If the cams are walking you'll surely lose the cam. Use the good grey cam lube, not just regular engine assembly lube. You can also add more oil to the pan for more splash/windage during breakin. Just some things to consider. The last cam I broke in was a solid flat tappet with 130lbs on the seat- no problems. Bob
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Old 06-23-2005, 06:18 AM
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cam

A few more points...

I now check every lifter i install for proper crown..... It should be .002.... there was a problem with the lifter manufacturers and quality for some time. They seam to have it fixed but i will not take any chances....

I personally think Rickwi hit on the problem..... The lifter bores are not square with the cam... It's been my findings that if you go through more then 2 cams you better start looking at the lifter bores as the source for the failures.... The stock cams are so lazy on the ramps that it is not a problem for them, but when you start getting into the performance grinds the lifters just will not spin due to the incorrect lifter bores.....

By any chance are you checking the main and rod bearings after the cam failures???? If not you really should look at them... I would bet the debris from the missing lobes has damaged them......

I would recommend go roller or getting the lifter bores indexed if you want to keep the same block.

I have done a buch of lifter bores with the BHJ fixture and it will really open your eyes when you see how far the factory bores are out....

Keith
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Old 06-23-2005, 07:40 AM
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What's it cost to rebush and correct the lifter bores to .904?
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Old 06-23-2005, 08:33 AM
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cost

In my shop i charge $300,,, the guy i used to work for got $350..

Keith
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Old 06-23-2005, 10:28 AM
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Cheaper than a cam and lifters huh?
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Old 06-23-2005, 11:03 AM
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when a lobe goes down trash goes everywhere, the motor really needs disassembeled and cleaned or you're just asking for another failure, especially with the newer profiles and stiff springs.
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Old 06-23-2005, 11:44 AM
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Quote:
Originally Posted by johnsongrass1
Cheaper than a cam and lifters huh?
Yea but most people will not spring for it.... And the truth is 19 out of 20 blocks are close enough to work, but if you pulled number 20.... well everyone knows the rest of the story......


NSX, Good catch.....that is why i asked in my post if he looked into it,,,,,,The few cams i have lost all trashed the bearings..... I am not sure how he made it through 3 times?????

Keith
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Old 06-23-2005, 01:29 PM
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Yep, I did after the 2nd one & found minor abrasions including on the oil pump rotors so replaced bearings, etc. Now back to square one again I guess!
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Old 06-23-2005, 02:09 PM
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wow, good luck on the next breakin al37ford. sorry to hear you're running into too much trouble.

tbw
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Old 06-23-2005, 03:12 PM
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Just curious, I skimmed through reading all this so sorry if someone asked, are the lobes going bad in the same locations for each cam? Is it all the lobes or just some
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