Wiped Cam Lobe Theory - Imput Wanted:

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Inertia

Inertia

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For a long while I've been reading about wiped cam lobes, and have been wondering if we can establish a trend in the number of wiped lobes compared to whether the connecting rod had a functioning squirt hole.

The new roller small blocks don't come with the Oil squirt hole in the connecting rod, and when ordering new bearings for older motors, I had noticed that some sets of new bearing shells didn't come with the notch nec to supply oil to the hole, and machined the nec hole myself.

It was my belief that the "squirt" of oil was to lube the cyl wall, but I can't help wonder if residual/partial spray lubed the cam lobes, specially since the squirt hole seemed to disappeared with the advent of the roller lifters, and cam lobe failure seems to have increased.

Theory or ?

If you wiped a lobe, do you know if the rod bearing had a functioning squirt hole.?

Thanks for your time.
 
How can you tell if a lobe is wiped?
I have my intake off now and can see the cam and lifters
What should i be looking for?
 
d100clubcab said:
How can you tell if a lobe is wiped?
I have my intake off now and can see the cam and lifters
What should i be looking for?
Click to expand...

Odd shaped lobes, metal in the oil, and ticking sound when ending is running. The lobe will basically look rounded on the edges and different than the others.

Causes I know of:

1. Excessive fuel on break in diluting oil.
2. Cam change and retainer to guide clearance not checked and hitting.
3. Pre-loaded lifters over loaded.
4. Improper break-in.
5. Mismatched lifter to lobe if cam and liftere's are removed and not put back on the same lobe.

I'm sure there are other ways as well.
 
I agree with your theory as stated in the other thread.
 
inertia said:
Thnx Rusty, It'd be kinda cool if we could find 15 outta 20 guys that know their squirt holes were non functional, and experienced wiped lobes.

I think I asked the question the wrong way..
Click to expand...

Well.......maybe if somebody ain't smart enough to figure out what you meant, they ought not to be in the conversation. lol
 
In my case I believe the cam lobe wiped due to the lifter not spinning,and building up a hot spot . Only one lobe went bad the others looked beautiful with a nice swirl pattern. The bottom of the lifter was carved out from the cam lobe. In subsequent builds I have always made sure the lifters rotate . That was nearly ten years ago have done three builds since with no issues.Hope this info helps someone.
 
DARTH V8R said:
Ok.. I must be stupid. Take away the crank splash, drain backs, & lifter gallery oil and just leave the rods to lube the cam. how long do you think the cam will last?
Click to expand...

Stupid?, certainly not. You have an opinion as do other very knowledgeable members.

I now realize my mistake was asking for opinions, instead of asking only those that had experienced a lobe failure,

"Do you know if the bearing shell installed, had the squirt hole notch, Yes or No.??"

Hopefully that may narrow it down, hopefully not too far, cuz I find this very curious.

Thnx All again.. cheers

thnx jomoper
 
Wiped a lobe once putting a new hydraulic lifter on an old cam. Totally stock 383 4bbl.
Put lots of STP in the 20w50 oil, but didn't matter.
Lifter wouldn't stop ticking even after removal and solvent flushing as recommended, so I chanced it.
Took about a week before I could tell one cylinder was off power.
 
Cam lobes are usually wiped during the initial start up of the engine because they weren't lubed and broken in properly. On A engines the lobe that gets destroyed the most is the one at the very back of the engine because there is no oil drain hole directly over it so it relies almost entirely on oil splash from the crank to lubricate it. If you don't get the engine started and revved up immediately the cam is doomed.
 
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DARTH V8R said:
Ok.. I must be stupid. Take away the crank splash, drain backs, & lifter gallery oil and just leave the rods to lube the cam. how long do you think the cam will last?
Click to expand...

Naw, you missed my point. I didn't mean it like that. lol
 
Crank splash absolutely contributes to the amount of lubrication the cam lobes gets, and how much is whatever RPM X the amount of oil 1 RPM throws. :D
Just don't know how much it matters because some of the cam sections are blocked from getting slung oil.

The only thing I know for sure is that I replaced a cam and lifters in the Wife's 72 318 that were fairly new and had a wiped lobe on the number 8 exhaust and it's been fine now for months with the new stuff in it.
So if it was because of a non existent or plugged oil slinger hole you would think it would have done it again.
Maybe?
 
in the case of the lifter not spinning , it would diga curl out of the bottom of the lifter and start rounding down the cam lobe the long waysbeing stuck in 1 position goin tellm RR up ,down up , down , until blue in the face I mean the metal causing heat and fatigue and start eating away at 1 and other until POOF knock knock rattle rattle boom boom boom . and ends up looking like my 360 did
 
Not to blow the research but I've personally built about 30 flat tappet engines since the bearings lost the squirt hole. Some used stock rods but the oil holes had "no soruce". I've never lost a cam that wasn't due to my own inexperience. The last one was '87 when I lost a roller cam because I didn't use anything to anchor the dog bones...lol.

While "any" oil flinging off the rotating assembly will probably have some chance of hitting a cam lobe, I am positive this is not "the cause" for the vast majority of cam related failures.
 
yah is there possibly a burr dug into the lifter wall from pre existing metal , is the block brand new to you or was it used when you got it ?
it got hung not to spin for a reason like peticular matter or prevois damage .894 lifters make a ton of oil pressure but way less friction than the .904
 
d100clubcab said:
How can you tell if a lobe is wiped?
I have my intake off now and can see the cam and lifters
What should i be looking for?
Click to expand...
Put the rockers on that puppy and spin it over, if a lobe is wiped youll notice the valve doesnt lift as much as the others...

Inertia, my rod bearings did have the holes to lube the "squirters" the only thing i can think of as to why i lost a cam lobe is maybe the lobe itself was soft. My block was freshly machined and i even honed the lifter bores to ensure all lifters moved free and smooth, once installed i turned it over by hand to make sure the lifters all spun.
Maybe some of these cams arent made of the metals they once were?
 
k and that's what my builder will tell you , evry 1 and his mama are passing cams you gotto go back 40years and find the MAN that was cutting them for the big 3 or the big race guys all this new steal was my 10 speed in 1980 its all junk until you find the connected guys
 
pull the lifter feel it see the swirls, any blue, , feel the bottom isit100% flat, shine a light in the hole , turn the cam to see the lobe
is it blue ? still oblongated I wrapped1 1/2 way backaround the shaft
lifter got hungin the cam bent the pushrod and thru it into the distributor bent the dizzy shaft then went to the oil pump gear took that out and got metal down in the crank and KIPOW = shoulda just walked over to the shreader and thru $3000 in$100 bills and had less mess to pick up
 
Larry shepard-Chrysler engineer- "this hole only occurs in production such as H.D. trucks to lubricate the cylinder walls. Do not add one." long before roller cams passenger car rods did not have them, and most bearings did not have a hole. mopar lifters get a bunch off oil from the big holes in the lifter oil gallery. I have never used said oil hole, and in 40 years never wiped out a cam lobe
 
I agree that oil holes in rod bearings don't do anything special to the cam compared to the oil bleeding out the sides of the bearings. The cam is already well oiled. It's a bad break-in that really hurts people's ego. Ive been there too. That's why it's so Important to pay attention to detail, follow a checklist, and have a helper during break in. It doesn't take much for lobe - tappet friction to runaway and to the point where you've lost hydraulic preload and that tappet is getting hammered more to death.

After break in, it's important to remove that damn valve cover at idle and physically watch your lifters and pushrods spin. Break in May have been successful but if they don't spin or spin poorly, it won't last very long.
 
I agree. I have an old set of covers with the tops cut off. Paint a white dot on each lifter and push rod so you can watch each one rotate. Inspect each lobe for burrs before you install cam.
 
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