Screaming Mad - 351W Cams ??

[Idaho Slim]

Just had the 3rd cam go out on my 351 in 20,000 miles. Only 5300 miles since the last total rebuild of this motor. Competition CAMS, the previous were Edelbrock, motor has been fully checked out at the machine shop. Correct install with Joe Gibbs Racing lube etc. by FORD mech.

Is this a common issue with my motor? This is getting ridiculous and now I dont trust the motor to keep it. Where I go in the backcountry, I need reliability, and this aint good. Even thinking of selling the whole outfit once it gets put back together, my Ford dealer is stumped (and they are VERY experienced high performance engine builders. The issue is not the mechanics, but they are standing behind this) Aluminum heads, roller rockers, Edelbrock performer manifold, 10:5-1 compression.

 

[needabronco]

Frankly cam's don't go flat all that often! I'd be looking for a different mechanic or I'd teach myself to swap a camshaft.... Things to look at closely would be lifter springs, rocker ratio and making sure they are compatable with the cam's your using. If they don't add up your only wasting time, and making an incompetent mechanic more money.

 

[wildbill]

;D;D;D I have only lost one cam in a small block ford and it was a comp cam. My cam of choice is Erson the one in my bronco was installed in 86. Its a fact. 351 4V 4 speed (69) and is 10:1. I would suggest finding a new cam co. Good luck Bill %);D

 

[br0nc0xrapt0r]

Is it a roller or flat tappet cam? Is the correct high zinc oil being used to break it in?

 

[bmc69]

It sounds to me like the block could have a fundamental oiling issue or that the springs are wrong and/or set up wrong.

The springs were part of a kit with the cam? Carefully set up and checked for installed height and seat pressure?

How many lobes are involved in the failure each time? Intake?..exhaust?..random? Are the lifters badly cupped/dished out or is the damage more focused on the cam lobe(s)?


I've never lost a cam in any of the engines I've built (a lot of them) but I've seen a few over the years that failed and with the removeal of zinc from motor oil in recent years, it is more common. But what appears to be very unusual in your case is not just the number of failures but also how long after the normal break-in period is over that you are seeing the failures occur. That is why I suspect a setup/design problem in your particular cam and valvetrain configuration.

 

[Timmy390]

Cam failure is more and more common these days due to the removal of all zinc in oils. There's a thread a week on a failed cam over on fordFE.com and all of them are falt tappets.

General thinking is the oil being used and impropper breakin are the most common reason for the failure. Also the aggressive nature of some cam grinds seems to be a factor. It's not just Comp cams, it's all cams manufatures.

Many people are running Diesel oil now as it still has most of the "bad" stuff the EPA has removed from reguler motor oil. Rotella seems to the the oil of choice. Some race oils also have a high zinc content.

What oil/cam/lifter/spring combo are you running? What kind of oil pressure does the block have?

Tim

 

[gearida]

Do check to the "zinc" in your oil. I have heard lots of engine builders who had not considered this component of older oils, which no longer exist in today's engine oil. There are Zinc additives and as mentioned "break in" oils.

got me

 

[bmc69]

Some builders I know are using "break in" valve springs that have lower seat pressures than that specified for high-lift/high-RPM cams. Then after a few thousand miles, those come out and the spec springs go in. I've never gone that route myself..even with the .600+" flat-tappet cams I was running in the race trucks.

 

[Broncobowsher]

Lets back up a step...
What has been going bad on the cams?
Specs on the motor, especially the valvetrain, heads, etc.

 

[73azbronco]

Rotella makes a great zinc additive.

But to go back to basics, what is failing? Pictures tell a thousand stories.

 

[spap]

5000 miles is way to short, like someone said. To me it sounds lik a an oiling issue. Even without zinc additive I can't believe a cam would go out in 5000 miles if it was getting oil.
How is the cam failing all flat lopes one flat lope. The journals. Just curious.

 

[Hozr]

If the mechanics are just swapping cams without looking at WHY they are being eaten...

Have the lifters been swapped with the cams? Springs? Pushrods? Checked for legth? Was the engine preoiled prior to startup? Assembly lube, zinc, break in oil?

 

[Desert Dweller]

Hmmm--- gotta put my .02 in also. My friend has raced W engines for years and his comment was "SBF's are not as prone as chebbys for cam failure" Now, after thinking on this, I would look at valve spring pressure very closely,as this is the cause of most cam failures. And as others have said, could be an oiling problem also. (remember tho, cam lobes are only oiled by the splash back from the oil falling on the crank)

So, more info is needed and pictures.......

 

[pcf_mark]

As many people noted pictures can help. Also someone noted the cam survived break in - that is when it goes flat not 5,000 miles later. I would look at the valve train. I have seen some cams and/or lifters get killed because the valve train was not set up properly. If you lost one or two versus a bank could also be telling.

Examples:
Not enough clearance between the spring coils - at least .060 static
Rocker slot not long enough - at full lift the rocker runs out of slot and bottoms overloading the cam. You should be able to put a paper clip between the stud and the rocker at full lift
Not enough clearance between the bottom of the retainer and the top of the valve guide - at least .060
Pushrods too short - rocker is pushing across the valve tip not up/down

Each of these usually leave some worn parts behind and with some careful observation you can find it.

Do you have a windage tray and/or crank scraper that may be limiting the oil splash? Those are generally for higher rpm and roller cam motors not flat tappets. You could always give up and put a roller in it and forget about it.

 

[76Broncofromhell]

My guess is putting a mechanical lifter cam in with hydraulic lifters. The extra pressure of the lifters constantly digging into the non-surface hardened cam means it would go flat very quickly. It's important to note that the lobes of the camshaft in a Ford are splashed lubed by oil slinging off the crank and by oil draining down the valley.

Lack of zinc shortens the life of the camshaft, but not to 5,000 miles. I would be very suspect of a mechanic that has replaced 3 cams in anything with so few of miles.

 

[Rustytruck]

check your valve springs at full lift and make sure they are not coil bound. should be able to get at least .050 guage between the coils.

 

[Hozr]

Another question, pedestal or stud mount rockers?

 

[Idaho Slim]

Wow, thanx for all the responses, where to start .......
These problems seem to all originate from the machine shop.
Found out today, my service manager buddy is tearing it down again.

#1. My current mechanics are stellar, the Ford dealer exceptional, (3) re-tear downs at no charge.

#2. I installed the original edelbrock camshaft in 14 years ago, have done 4 others myself Then about 7 years ago, wanted more power & did a complete top end, at a race shop in Washington state, he put in another Edelbrock camshaft & it went out 2 years later, (wore out the front lobe). Needed a quick fix and used a shadetree shop since I was traveling, he Replaced it again and put the front bearing in backwards which was discovered by my dealer when I bent a rod a year ago. FAWK!

#3. Decided to have the whole motor done by my dealer, new Comp Cams camshaft (.268/.280 dur & .510/.512 lift), bored .060 over, balanced, aluminum heads, roller rockers, edelbrock performer manifold, Holley truck Avenger 670 cfm carb, MSD distributor, MSD wires & Blaster coil, all good parts, done right. Joe Gibbs Zinc camshaft lube installed.


#4. Started running like crap, pulled the motor found the machine shop had his KID install the wrong seals/guides/springs in the heads. Replaced and Re-installed and drove it home and it went down, found (2) stuck valves. Heads redone by the owner of the machine shop himself and re-installed, drove it home went down again and found another worn lobe at the same piston location as the stuck valves.

WHAT A NIGHTMARE

Motor is being completely redone from scratch now .............. To be continued in about a week. ugg %)

 

[Desert Dweller]

Aha--- the plot thickens... stuck valves=wiped lobes in my mind. I would certainly check the clearances of all the valve guides, gonna require pulling the heads, tho.

edit: whoops went back reread... I see that the heads/valve guides were supposedly redone...... But betcha the cam lobe was already worn when the heads were "redone" and it just finally gave up.

 

[pcf_mark]

Stuck valves will kill the camshaft but the heads were switched and the cam got clobbered again. If the heads were the same then I would guess valve stem to guide clearance or incorrect valve seals starving the guide for lubrication.

Please take photos of the cam lobes, lifter bottoms, pushrods, rocker arms, valve guide and bottom of the retainer from the dead lobe cylinder.