Visit The Dirt Forum for More Information

Author Topic:   burned up cam lobes
f-man2155
Dirt Roller

Total posts: 5
posted April 28, 2005 07:01 PM  
I HAVE BEEN EXPERIENCING A PROBLEM FOR THREE SEASONS NOW I AM TRYING TO PUT IN A NEW CAM AND LIFFTERS AND EVERY TIME I SEEM TO BE BURNING OFF ONE OR MORE OF THE LOBES ON THE CAM. I AM BREAKING THEM IN THE WAY MY MACHINIST HAS TOLD ME TO , EVERYTHING IS NEW AND IT KEEPS HAPPENING. I'M THINKING MAYBE TOO MUCH LASH BUT THE CAM CARD IS CALLING FOR .026 SO THAT IS WHAT I AM SETTING IT AT
I HAVE AN OLD CAM THAT HAS ABOUT EIGHT SEASONS ON IT THAT I KEEP PUTTING IN AFTER THIS HAPPENS AND IT RUNS ME THE REST OF THE YEAR. ALSO CAN SOMEONE TELL ME WHAT A REV KIT DOES AND IF THAT MIGHT HELP.
THANKS

jpotter94
Dirt Forum Racer

Total posts: 94
posted April 28, 2005 08:56 PM  
ARE YOU SETTING THE VALVE LASH WHEN THE MOTOR IS HOT OR COLD,YOU SHOULD BE SETTING IT WHEN IT IS HOT.TOO TIGHT OF LASH WILL WEAR OUT A CAM QUICK.ALSO WHAT VALVSPRINGS DO YOU HAVE IN YOUR HEADS,TOO HEAVY OF SPRINGS WILL WEAR THE LOBES OUT QUICK ALSO..

dre383
Dirt Roller

Total posts: 12
posted April 28, 2005 10:15 PM  
are you using 1.5 or 1.6 rocker arms when you are breaking in the motor in if so try to use 1.3 rocker arms you can get these from speedway motorsports it makes it easier on the valve train and eiseir on the cam i hope this helped

leapinlizard
Dirt Freak

Total posts: 402
posted April 29, 2005 08:29 AM  
Comp cams web site list the reasons for cam failure. Any one by itself probably won't cause problems but group any two together and watch out.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 29, 2005 08:50 AM  
What kind of cam, solid, hyd, roller?

What are you using for cam lube?

What are you using for oil?


With radical flat tappet cams and heavy pressure you will sometimes need either breakin rockers or remove the inner springs on breakin to prevent ruining the cam.

rickbraley
Dirt Full Roller

Total posts: 58
posted April 29, 2005 11:00 AM  
I had a similar problem a couple seasons ago and I found that removing the oil restrictors I had installed resolved the problem. I followed the manufacturer's break-in directions exactly and was getting lobe failures. Removed the restrictors and using the same process never had another failure...

What's everyone's opinions on oil restrictors? I know what they are supposed to do and it makes some sense but at the same time oil is what cools the camshaft and it seems that keeping the cam cooler would be a good thing also.

With a SBC stock block what is the optimum setup for a wet sump oiling system? What pump, how much pressure, oil restrictors, etc.

jpotter94
Dirt Forum Racer

Total posts: 94
posted April 29, 2005 11:17 AM  
on our wet sump motors we do everything in our power to make them work like a dry sump(keeping oil in pan)..we do about 40hrs of grinding on the block,mostly in the lifter valley as oil like to hang around in there,hole point to a good wetsump is to get the oil back to the bottom as quickly as possible.we open up all the oil return holes,grind the lifter valley out so the oil excapes quicker,then we paint the valley to make it smoother.we use vent tubes and also oil restrictors.anything that hot oil hits robs horsepower and adss to the rotating mass.

[This message has been edited by jpotter94 (edited April 29, 2005).]

f-man2155
Dirt Roller

Total posts: 5
posted April 29, 2005 09:12 PM  
it is a solid lift cam
i use 1.5 rockers with both springs
i use 10w30 for break in and race with 20w50
not sure on the springs my machinist sets them up for me
i don't think it is springs or anything like that because i just change the cam and lifters and everything is fine for the rest of the year
any opinions on the lash? my cam that i change to is .018 lash maybe i should tighten up the lash on the new cam
just a thought
thanks for the help

noknowledge
Dirt Newbie

Total posts: 4
posted April 29, 2005 09:31 PM  
if you have oil restrictors in the rear of the block I would take them out, if you have plugs or tubes in the valley to keep oil from returning through the center of the valley I would remove them also...

is this a 355 or a 406 or what......give us a bore-stroke and what rods are being used. could you maybe have a rod nicking a lobe?? And the reason the old cam keeps working is that cam is a small base circle????

Also, the person asking about what springs, I think we was thinking the springs are getting into coil bind and knocking the lobe off the cam...... maybe the old cam has less lift allowing the springs to work without coil bind?????

as for LASH.....if the card states .026 that is what they want....that isn't the problem, in my opinion.... if you tighten up the lash you change duration of the cam....also if you are in coil bind on the springs it will get worse...... have you turned the motor over until you are at max lift and checked for coil bind???

outlawstock17
Dirt Forum Champ
Total posts: 1363
posted April 30, 2005 06:22 AM  
maybe you have a bad block with mis-aligned lifer bores. this is not all that uncommon on a small block chevrolet. it doesn't become a problem until you get into more aggressive camshaft profiles.

Ego Racing
Dirt Forum Champ
Total posts: 724
posted April 30, 2005 10:18 AM  
quote:
Originally posted by noknowledge:
if you have oil restrictors in the rear of the block I would take them out, if you have plugs or tubes in the valley to keep oil from returning through the center of the valley I would remove them also...

is this a 355 or a 406 or what......give us a bore-stroke and what rods are being used. could you maybe have a rod nicking a lobe?? And the reason the old cam keeps working is that cam is a small base circle????

Also, the person asking about what springs, I think we was thinking the springs are getting into coil bind and knocking the lobe off the cam...... maybe the old cam has less lift allowing the springs to work without coil bind?????

as for LASH.....if the card states .026 that is what they want....that isn't the problem, in my opinion.... if you tighten up the lash you change duration of the cam....also if you are in coil bind on the springs it will get worse...... have you turned the motor over until you are at max lift and checked for coil bind???


We have never run a solid lift cam without restrictors and never had a problem. We also run the valley tubes and smooth the intake vaalley and open the front and rear drainback holes.
What assy lube are you running and how are you breaking it in? Get the motor ready to run and pre lubed with a oil pump primer, don,t let it turn over alot before it fires as this wipes the lube off of the surfaces, Fire it up and get it up to around 2500rpm for about 20 minutes then shut it down and allow it to cool off. Check all of your bolts and stuff and then do a oil filter change.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 01, 2005 08:21 PM  
To add to what Ego posted, I would add a bottle of GM EOS and use good 20w50 oil to breakin.

Dont change the lash that is cam specific. Set it to what the camcard says, unless you talk to your cam grinder first.

If the block were bad then it would prob eat up the other cam as well. I would double check to make sure the new cam lift and springs are ok as far as coil bind goes. Roll the engine over with the new cam installed and at peak lift and measure the clearance between the coils. You shold have no coils touching ea other and also make sure you have .060 total clearance.

[This message has been edited by dirtbuster (edited May 01, 2005).]

smallrock98
Dirt Forum Racer

Total posts: 100
posted May 02, 2005 11:51 AM  
I broke in my new comp cam this year using EOS and 30wt Rotella oil. I was worried because of some of the bad things I had heard about comp cams. After I shut her down and seen that the valve lash was still tight, I celebrated with a few beers

f-man2155
Dirt Roller

Total posts: 5
posted May 02, 2005 03:06 PM  
MY BORE IS 4.060 IT IS A 350 WITH STOCK STROKE CRANK WITH 6" RODS DON'T KNOW ABOUT THE BASE CIRCLE OF THE CAM
THE CAM LIFT WAS FINE FOR THE SPRINGS AND THE COILS HAD AROUND .080" GAP AT MAX LIFT
I DON'T KNOW THE SEAT PREASURE THOUGH
I HAVE RUN TWO FULL NIGHTS AND ONE GOOD TEST SESSION WITH THE OLD FAITHFULL CAM AND LIFFTERS AND IT'S RUNNING LIKE A DREAM SO I THINK THAT THE SEAT PREASURE IS FINE
I APPRECIATE ALL THE HELP JUST HAVE TO DECIDE WHICH TO APPROACH THIS
I WILL LET EVERYONE KNOW HOW THIS UNFOLDS

Back to the Archives