inqbus383

So my engine has been running great except with a little roughness starting a month ago. In the last couple weeks I went drag racing, best of 13.3 or so but the timing glitched. I know I can get into the 12s just with a little practice and a well prepared track. So last weekend I went to an autocross and had electrical problems on the track, doh. On the way back the engine started running rather strange, and later that day it started clicking in the valvecovers and running very poorly, not idling, very rough at low rpms. I pulled it apart and found 6 of 8 of the rockers on the right side very loose. I tighten them up and run it for a few seconds and they become loose again. The rockers on the left side are all fine by the way. So I changed the oil, which had lots of metalic sparkle, and eventually tightened down the right rockers enough that they mostly stopped clicking. Some of them required me to tighten them down nearly 3 turns, at least a mm or two. It finally starts running well enough that it will idle without my foot, and I check the right bank. Several of the rockers are moving very little compared to the other ones.

So I believe that my hydrolic flat tappet cam (comp XE274-h10)has flattened at least one lobe completely in only 8 months and 8 thousand miles. I had the engine rebuilt and assembled by a reputable shop, which I will be speaking to soon. I guess I'll probably upgrade to a hydrolic roller cam, maybe a little longer duration since I'm planning on going to afr 195s and a holley stealth ram fuel injection system. Any comments or ideas on what could have caused the cam failure, or suggestions about the new cam would be appreciated. Thanks guys

metal tech

I had the same problem years ago on a 427BBC. The bottom of several lifters were worn to a bowl shape. The best I can determine is that with a cam that requires dual springs is to break-in the cam using just the outers and then swap in the inner springs afterwards. I've been told that several "engine builders" use special 1.2 ratio rockers to break-in hyd & solid lifter cams that run heavy spring pressures. These parts need to develop a wear pattern and the lesser pressures of either less spring or less rocker ratio helps this happen. Rollers don't have this issue. And yes we did pre-lube that 427 before we fired it up. Hope this helps.

Al

biggjimm

I am assuming that this was a brand new cam installed with new lifters. When an engine with a new cam and lifters is fired up for the first time you need to run the engine at 2000 RPM's for at least 20 minutes. If this is not done the lifters will eat the cam. If this procedure was not followed on your motor then this is probable the problem. Answer--- new cam and lifters (broke in the proper way) as your old ones are trashed. Good luck Biggjimm

bigvette1

Something that gets overlooked when you modify the valve train is the pushrod length. Changing valves, springs, cam, lifters and rockers changes the geometry and the tolerances and in turn the length of the pushrod. The stock may not be the correct length. Since you have to change the cam and the lifters out again, invest in a pushrod length checker for about $15 bucks. You may find that you needs a +/- .100 or so rod. Good luck on this change and remember - break it in right.


[Modified by bigvette1, 9:16 AM 3/15/2003]

shotgun_000

FWIW, when I had my engine built, I had a professional to build it. For the most part, they allowed me to buy the parts that I wanted for them to install. The one thing they refused to install, and still have a warranty, was a competition cam. I had wanted to install the XE series, but settled on a Crane Powermax after discussing cams with the engine builder.

He told me that he had seen several customers with comp cams that flattened in less time than yours, despite following the break-in procedure exactly.

I always look for opinions from more than one source, so I visited several forums, and after talking with other people, confirmed what the engine builder had warned me about.

I have used comp cams in the past with no problem. So, it may be a quality control issue that comp cams has had lately. Also, the XE series has rather aggresive lobe profiles, that places extra stress on the valvetrain. That coupled with the quality control issue is not a good thing.

Others may disagree with me on the Comp. Cams issue, but I'm just passing along what I have heard from others. Hope you get it all worked out soon :cheers:

Ironcross

A camshaft is just a camshaft, whether racing or stock by any manufacturer. The difference is that installing a modified cam several things should be checked first. Most modified cams are not drop ins. Trying to modify a stock engine requires checking clearances. Most important is coil bind and guide to retainers. Both of these measurements are critical. Heads have to be checked for these problems or the cam will wear right from engine startup. Breaking in new or rebuilt engines and camshafts is really a JOKE. They must run perfectly from the start at any RPM. Any racer would laugh at braking in an expensive fuel engine for 20 minutes. Thats 10 engines lifetimes plus Nitro is expensive. They are built to run 4`s at 300+ immediately, no waiting around for so called brake in`s` It must be done right, stock or racing. Cams and bearings are not our problems, we burn pistons these engines are inspected every round. Except for bearing clearances, racing and modified street engines are really no different on assembly. Clearances are the critical factor or it will not stand a chance. To wear out a cam, some clearances were not correctly checked. Just remember they are not all drop ins. Good luck, :cheers: :thumbs:

ken markusa

This is not all that uncommon on Chevy engines with a hot cam it's part of the design fault with the .875 dia. Chevy lifter it has a small wear area compared to a Mopar .904 dia and if the cam is a little soft it doesn't take long to wear out. You won't regret going to a roller it'll make more power and and add driveablity.
Ken who's worn out a camshaft or two :cheers:

Bob Jenkins

I had an Comp Cams XE274 in my big block Camaro and the #8 exhaust lobe went flat after about 500 miles. All the other lobes and lifters looked perfect. I replaced it with a Crane Cams 396/375 hp blueprint cam....so far so good :smash:

inqbus383

Thanks for the replies guys. The engine was rebuilt by a reputable shop, they picked the parts and did the assembily. I broke it in properly in the manner described above. They used new rockers, pushrods, and the lifter and cam kit.

Bob Jenkins: Cylinder 8's exhaust valve lobe is one of the worst, I wonder if that is just a coincidence.

Any suggestion on roller cams? The XE274-H idled perfectly, and I wouldn't mind something a little larger since I am going to get afr 195s in 6 months. What would be a comperable roller cam? Comp and Cranes hydrolic rollers are nearly 700 $, and lunatis are much less expensive. Anyone have experience as to the quality of these or any other roller cam brands? Thanks guys. :cheers:

Ironcross

I just read your reply. I presume it`s a small block. You did mention that it was a reputable shop. Make sure that they allowed the necessary head clearances for the modified camshaft or the new one will have the same result. I will not use a roller anything in a street engine. Too many parts to brake. The required maintanence is not suitable for fender equiped cars. Replace it with a good solid lifter camshaft. A whole lot of less required maintance and nearly equally as good. :thumbs:

The Money Pit

I had the Comp XE-274 go flat in 2000 miles when I dropped the 406 in.I ran 1.60 rockers right off the bat,and the break in didn't go well.Boiled over three times during cam break in.
The next cam was a Comp XE-284,which I broke in with the 1.50 rockers,then switched to 1.60's after about 2000 miles.So far so good.I,m playing with a distributor recurve now,and once that's dialed in the Holley 3310 will be going on.Pulls 6500 rpms just the way it is right now,but the Q-Jet can't keep the 406 in gas for very long.
I've built plenty of engines before,and this was the first cam I ever flattened.

Vetterodder

Assuming that the initial breakin was properly done, damaged lobes are almost always the result of a problem elsewhere in the valvetrain and not due to a defect in the cam. As others have mentioned, coil bind, pushrod alignment or failure, rocker slot - stud interference, pulled studs, or improper valve adjustment are likely causes. Also as already mentioned, changing cams (or other valvetrain components) can cause another component to act differently.

A few years ago my neighbor had been chasign his tail over the same problem. He wiped out two cams, on both the damage was to lobes on the same bank. Turned out that he wasn't getting any oil to one head. The cam itself was getting oil just fine but it didn't survive the beating it got from lifters without any oil pressure to keep them expanded. Between his Flowmasters and a killer stereo system, he never heard the valve train beating itself to death.

bigvette1

Am I missing something here. Have read one too many posts that have had trouble with lobes and were all Comp Cams. Changed over to Crane Cams and then ok. Really sounds to me the hardening of the Comp Cams is suspect. Comments?

Vetterodder

I find it hard to believe that any of the major cam grinders are cutting corners on the quality of their cams. The reason that you see Comp Cams in so many posts about cam problems is that so many people are using their cams. As I posted, very few cam failures are the result of the cam itself but, instead, are the result of the failure of another component. As with any product, the more units of a certain make that are in use is likely to result in more failures of that product due to it's greater exposure to the possibility of failure.

I have used, or have been involved with, through friends, the cams of numerous grinders and I've seen a few "bad" cams. NONE of those were from a name brand grinder. The few bad cams that I have seen have been were cheapo, no name "bargains". I'm currently running a Comp XE 274 with no problems. I've had equally good reliability with Crane, Erson, Isky, Herbert, and others. Again, the failure of a cam is rarely the fault of the cam itself.


[Modified by Vetterodder, 8:59 PM 3/15/2003]

Budman68

I don't think I am going to mess with anymore flat tappet cams. My next swap will be a roller. I've experienced this to many times in the past.

dman535

Comp Cams XE series really runs the ragged edge of flat tappet cams. The ramp angles of the lober almost rival those of a mild roller cam. They accelerate the valve really fast. With such a steep cut in it very important that the rest of the valvetrain be perfect and that the break in process go 100% smooth. My XE 274 went flat after a year, my HR 284 roller broke in 8,000 miles. Not a huge fan of comp cams products. Am running a solid lifter LT-1 cam, no problems so far.

clem zahrobsky

a lot of flat cam lobes are caused by the lifter not rotating. always hone the lifter bores before installing a new cam and lifters and check the lifter fit for easy rotation. also when installing higher lift cams and heavier springs in a BBC i would always install roller rockers to cut down on the friction at the pivot points of the rocker arms which put a bigger load in the camlobe lifter interface:chevy


[Modified by clem zahrobsky, 10:31 AM 3/16/2003]

Never Finished

Count me in with the Comp Cams that didn't last. Mine was a XE262 (5,000 miles). I went to a Crane 272 and had no problems (20,000 miles so far). I really wondered if it was the red break in oil they used. I always used cam break in paste before and had no problems.