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Need Experienced Engine Builders Advise

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Old 09-04-2002, 04:57 PM
  #1
Ranman
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Question Need Experienced Engine Builders Advise

My brother is having some work done to his 68 Corvette by another family member who is pretty proficient with Chevy 350's. He's having a new cam, intake, carb and headers with sidepipes installed. The engine is a basic crate 350 that was in the car when he bought it over 10 years ago. I would estimate HP prior to modifications at 225 - 250 having driven the car. My brother has not driven the car 3000mi since he's owned it. The builder told him that the engine looked brand new inside upon teardown. Here's the issue:

The builder told him that the new Edelbrock cam that was installed was "soft" and consequently every other set of lobes were wiped out upon initial startup. (I don't know what this means) The engine was not run for long and was promptly shut down upon discovery of the problem.

A new Edelbrock cam has since been installed, but now there may be oil pressure problems. The car is now running 15psi oil pressure at idle (not sure what it was before).

QUESTIONS:

1) Has anyone ever heard of a brand new cam being "soft" and consequently wiping out the lobes? Is this possible or is this hogwash? What would typ[ically cause you to wipe out the cam? (I know it's not a roller cam, but I don't know anything from there)

2) What are the repercussions of wiping out lobes in a running motor? Is this a big deal? No big deal? Opinions?

Thanks for any advise anyone can provide. Randy
 
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Old 09-04-2002, 05:50 PM
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bobby daniels
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Thumbs down SOFT LOBES ;HOGWASH

ALL CAMS COMPANYS I'VE EVER HEARD OF TEST EACH CAM AND I'VE NEVER HEARD OF A SOFT CAM ,THIS IS JUST A GOOD EXCUSE FOR NOT BREAKING IT IN RIGHT ! THIS IS COMMON PROBLEM WITH FLAT TAPPET CAMS AND NOT WITH ROLLERS ,
YOU CANNOT LET THE FLAT TAPPET IDLE FOR THE FIRST 20 OR SO MINS. AND HAVE TO COAT IT WITH THE PROPER CAM LUBE ! MOST OF THE TIME PEOPLE LET IT IDLE OR HAVE TROUBLE WITH THE TIMING AND LET IT IDLE A SHORT TIME WHICH WILL WIPE THE LOBES OFF.
ALSO THE METAL OFF THE CAM AND LIFTERS FALLS ON THE PISTON SKIRTS AND CRANK ECT.AND UNTOL DAMAGE CAN BE DONE ,IT DEPENDS ON HOW MUCH METAL WAS WIPED FROM THE CAM ECT,HOPE THIS HELPS SOME
THIS MAY HELP ,HAVE A GOOD DAY
 
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Old 09-04-2002, 06:35 PM
  #3
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Ranman,

The typical break in for a non roller cam is as bobby says.. You have to coat the cam and each lifter with a special lube. Then when the motor fires it has to come up to 2500 rpm right now.. If the cam is radical and high spring psi's you need to either put in weak springs or run it during break in with just the outer springs. This helps break in the cam. The lifters need to start turning right away so the two surfaces get used to rubbing each other. After 20 or so mins at high rpm you then shut down and put the big springs on.. then run it again for a short period.. and change the oil filter between runs. The poly cam lube will plug up the filter.

Now if this wasn't done properly at start up it can and will take out the cam lobes. I have had trouble getting a motor to fire and have not hurt cam lobes, but I ususally run it with just the outer springs. If you lose one lobe.. there is enough metal to make a mess out of the cylinder walls. If will fall on to the skirts and embeds in the piston, then you have a grinding wheel type of piston in the hole and it keeps eating at the walls...

So yes it is a big deal and the motor should come all apart to make sure of what damage has been done. First I would check to see if the lobes are in fact hurt.. Use a dial indicator to see how much lift each lifter has.. You can take off the rockers so you are not doing any more damage with the psi of the valve springs. If you see one with .010" less lobe lift.. take the intake off and pull the lifters.. look at the lobes you should see a wear pattern on the lobe but it should be smooth.. no ground off metal..


The flat tappet cams are soft to begin with that is why the break in is so critical. A roller cam is made from different material and does have the wheel thing going for it.. untill that breaks and then you have the same mess..

Sorry to hear about the new motor problems.. any other questions.. you can email me and I will try to help..

Dick
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Old 09-04-2002, 06:49 PM
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Default Toast

All that metal from the cam lobes is like sandpaper and that engine is toast. Full rebuild is necesary.

Was the low engine oil pressure part of the original problem that caused the cam to self destruct is my question, or a by product of the metal damage?

Wannabe in motor city
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Old 09-04-2002, 07:36 PM
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MoneyShot
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This one is a no brainer- take it to a the professional! Do what ever it is that you do best, and let a qualified motor builder do what he does best. What a concept-
 
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Old 09-04-2002, 07:56 PM
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What everybody said, I use Edelbrock cams and they are fine but must be broken in correctly. I even use a dial indicator to check them after the 30 minute run in.
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