Thread: engine eats cam lobes

Tweet

Hi I just rebuilt my sbc 350 engine I put the vortec heads on it and went with a mild cam comp cam 212 intake and exhaust and 440 lift on intake and exhaust. The problem is that it took out number 7 intake lobe less than a hundred miles. We put a new cam and lifter in it and broke the cam in and drove for 20 min. and it was acting funny. we took it apart and found out that number 7 exhaust lobe was gone. Does anyone have any ideas what is causing this.

I have to ask, did you load up the the cam lobs with assembly lube? were all the lifters new? did you run it for at least 20 min. at 2000 rpm to break it in? Did you answer no to any of these questions? did you have plenty of oil pressure on startup? Carlg

DID YOU ADJUST THE VALVES THE WAY COMP CAMS SAID TOO

Here is a quote from the Sallee Chevrolet site:

Stock Vortec heads come with pressed-in 3/8-inch rocker studs and do not use guideplates. The rocker arms are guided (also called “rail” rockers) and employ a pair of guides or rails that center the rocker arm over the valve. This eliminates the need for pushrod guideplates. GM Performance Parts, Crane, and Comp offer self-aligning stamped-steel and roller-rocker arms that will bolt right on. Or, you can modify the heads to add screw-in studs and guideplates and then use conventional rocker arms, but be forewarned that this can add over $200 to the cost of the heads. Do not use guided or self-aligning rocker arms with heads that use guideplates, since this will cause pushrod bind and excessive wear. Also be aware that 1.6 rockers move the pushrod very close to the pushrod hole. Elongating the pushrod hole should be considered essential when using 1.6 rockers.............All of this conspires to limit total valve lift to a safe figure between 0.420 and 0.430 inch. The limitation is the clearance between the bottom of the retainer and the top of the valve-guide seal.

Could it be that you have too much lift for the stock springs??? Sounds like it might be so. They sell heads modified for higher lift cams. OR, are you using 1.6 rockers? That would surely bump the lift up to the danger zone.

I have ran into the same problem with almost the same setup. I'm running vortec heads, 1.5 self aglin roller rockers, and have eaten three cams within 100 miles. The last cam I called Comp directly and gave them every spec on the drivetrain and they ground a cam just for application. That cam only lasted 20 miles. I finally got sick of it at took it to a local machine shop. They are in the process of re-building the long block. This time we are going back Roller. The machine shop and Comp both recommended it wtih the setup I'm running.

You're eating lobes because the cam isn't getting sufficient lubrication. The cam is not directly lubricated by the pump. Whatever drains back from the cylinder heads goes through holes in the lifter valley and drips down onto the cam lobes. If these holes were plugged, particullarly the ones around the #7 cylinder, the cam would not get enough oil. The cam is also lubricated by oil slung off of the crankshaft. If you had a windage tray or crank scraper, it may be affecting lubrication of the cam. A plugged pushrod would affect the amount of oil going to the cylinder head which would also affect the amount of oil draining back into the lifter valley and onto the cam. Oil galley plugs set too deep will block oil flow to the entire bank. Lifter bores that are too tight will keep the lifters from rotating properly, causing premature failure. Too stiff a valve spring will also do the same thing.

When you say you installed a new cam and lifter, that means you reused the other 15 lifters? That is a big no no.

Just so you know, I also recently built a 350 with stock Vortec heads, 1.52:1 roller tip rockers, and a Comp XE256H cam. It actually has more lift on the exhaust at .454", but has caused me no problems whatsoever.

I have the mechine shop helping me with it. When we put the new cam in we put all new 16 lifters in also and we put alot of lub on done everything by the book. We broke the cam in at 2000 grand for 20 min. I had the head rocker arm studs pin. I have good oil pressure and good amout of oil coming up the push rods. Would the problem be my block?

What valve springs are you using?

It has the z28 spring on the head.

There are 5 lifter on the driver side that has a weired ware pattern.

There is a possibility that there was a burr under the register when the lifter bores were machined at the factory.

The shop took the engine apart and measure the lifter registers with two other block and they found the specs. The block measured out perfect. So we are going with a different Cam. I hope we are just getting a bad batch of cams. Everything look good.

I had a block that had a very worn lifter guide. The lifter would rock. In this case, it only wore out the lifter. We ended changing the block. The remedy would have been to hone out the lifter guide, and sleeve it. Not really worth it as it was a 350, and blocks, then used to be stacked like cordwood.
Lifter bore alignment is one of the things I check before a rebuild now. I used to just drop new lifters in.

could be a bad batch of cams.....sucks for sure. hope you have this problem sorted out. i have heard of the blocks shifting slightly during the casting process. this alone could misalign the lifter bores in the block. I buy my cams custom ground from a local cam grinder, so far so good. i have read on other forums from guys complaing about compcams about lobes failing prematurely. sure is dissapointing putting time and money in a motor only to have it fail repeatedly....good luck and hope your runnin soon

there was some bad lifter out there i seen some big block and small go right out and they where broke in right they where hyd lifter. the lifter were junk. now they have gone back to the hard face disk type lifters they are much better about three years ago there was a lifter shortages eaton was closed down and they made a lot of the lifters who knows where you lifter come from china ?? you could of had a bad one or the lifter was not turning .the cam in or out to far then the lifter will not turn .bore not in the right spot and low rpm no oil splash. to fix this i use direct lube lifters they make them for soild only but they did make side cut lifters that put more oil on the cam some of this stuff can be off and will work on stock stuff but when spring pressure goes up bad things happen i try to talk customers hyd rollers