How can you tell when a camshaft is going flat?. [Archive] - Team Camaro Tech

: How can you tell when a camshaft is going flat?.


bigblockkid
Oct 2nd, 00, 08:13 AM
Does a camshaft make any sounds before the lobes start to wear away?. If a cam is going flat, how does one tell by sound?, I have a hyd. Camshaft in a 396 that sounds like a solid lifter cam. I checked all valvetrain clearences. I had electrical problems when I first fired the car up and turned the car on and off a few times but, It was always at 2500 rpm. The cam sounds like the ramps are gone or somthing. I have correct valve spring pressure and use top dollar stuff. The cam is fairly tame, 280-288 adv. dur. .522"-.527" lift crower cam and lifters, crower springs, crower stainless steel roller rockers, 1.7 ratio. I would like to know what happens when the cam goes flat and is it because of the off-on cam break in. I am also not useing vari-duration lifters, I bought the comp cams high energy lifters. The concern is the car has a ticking sound that sounds like valve train but nothing is hitting and the sound goes away at 1900 rpm but comes back a 3000 rpm and goes away untill 4800 rpm. Any help would be great, thanks-Matt.

mutant 68
Oct 2nd, 00, 08:16 PM
If you keep having to adjust the same one or two valves,this is a good sign.
Also check the action of the rocker with the valve covers off.If all the rockers are mooving up and down the same amount, except for the ones that you keep adjusting,its a dead giveaway.

davidpozzi
Oct 2nd, 00, 10:52 PM
Make shure you are getting oil to the rockers up through the pushrods.
I had a friend who had no oil on the left side rockers. It ground up the rocker balls.

It might also be possible if the pushrod length is wrong that the rockers are at a wierd angle and the rocker oil holes aren't lining up with the pushrod oil holes and the lifters would not be able to purge air out.

I have also heard the base circle of the cam could be wrong and allow the lifters to leak oil, or not line up properly with the oil gallery holes and not recieve oil.

Make shure none of your rocker arm studs are not loose.
David

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Steve R
Oct 2nd, 00, 11:21 PM
Check your oil, if there is a metalic sheen to it you may have a problem. After all if the cam is going flat the metal has to go somewhere.

Steve R.

johnnyr
Oct 3rd, 00, 02:15 AM
Hey I have the same promblen engine sounds like solid lifters,have checked everything & it runs excellent, the engine was professionly built & installed & broken in. I even have taken the car back to the engine builter & he is lost as for the sounds everthing checked out perfect. He said to run the engine & he would back it if it failed. We took a oil sample & he sent it to a lab for analyst came back fine

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johnny

CA420
Oct 3rd, 00, 10:23 AM
I built some 454's using the the comp cams lifters and they rattled some but the engines never had a problem.

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68 RS, Ash Gold,pwr windows,Hounds tooth

RobR
Oct 3rd, 00, 11:14 AM
I had a cam go flat in my 67 El Camino 327 a few years ago. When the lobe starts to go, it goes fast. I barely got it home and it was backfiring and ran like crap. When I took it out, there were 2 lobes that were worn WAY down.

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Rob Rice
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DjD
Oct 3rd, 00, 11:17 AM
Pull the valve covers disconnect the coil and have a friend crank it over for you. Watch the rockers. If you have a flat lobe you should be able to see it by the rocker movement or lack of it. I have seen pushrods ends get flattened or mushroomed and cause what you describe.

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BC
Oct 3rd, 00, 12:42 PM
bigblock,
Make sure your push rods are hardened and are not getting ground off. I just had that happen in a 350 in my Nova because I reused the stock pushrods with Comp Cams roller rockers. It was something I never thought about since the pushrods were in good shape. Luckily, no real damage done to the motor, but I did learn something!! Another possibility could be a leaking exhaust/header gasket. I was chasing what I was sure was lifter noise, tick-tick-ticking, but it turned out my header gasket was not sealed good. That was on my Chevelle w/468 BBC.

Bill C.

DEVIL'S LAKE
Oct 3rd, 00, 06:57 PM
or if you have a good ear you can hear it.

jmar
Oct 5th, 00, 12:42 PM
Hey, this may sound really dumb, but here goes...
Are you using "tall" rocker covers? I had a similar sound coming from my 396BB that has aluminum extrusion, roller tipped, needle-bearing rockers.

I found out that the bigger aluminum roller tipped rockers were slightly hitting the stock "low profile" Chevy valve covers.
The edge of one rocker was actually "self-chamfered" by the action of rubbing against the inside of the valve cover! (It made clearance for itself with no damage to the valve train.) I didn't build my motor, so I didn't know what the cam is or if the lifters were solids nor not. My noise sounded almost like solid lifter noise.

The biggest noise problem I had, however, was that the internal baffle had actually been broken off on the passenger side valve cover. The piece was laying (innocently) inside the valve cover, on the surface of the head, waiting to cause a BIG problem. I of course removed the broken piece of baffle, and the "valvetrain noise" went pretty much away.

This whole thing was discussed in a previous post. Do a search for "valve cover".
Also, some of the guys who responded to my previous post said their 396's always made the kinds of noise that you are hearing.

What kind of heads are you running?

Jim

bigblockkid
Oct 5th, 00, 01:16 PM
I am running open chamber #049 oval port heads. I have hardened intake and exhaust seats. I run a 2.07 intake, 1.88 exhaust valve. I run the 396-375 horsepower 11.1 to 1
piston, trw# L2242F 0.30 oversize. My total CR is 10.5 to 1. I have a full msd ignition system. 35 degrees total timing. I use a 2" primary,3.5" collector headers and 3" torque tech exhaust system. The problem is not detonation and I have no header leaks. The engine runs really well, I have an old set of edelbrock finned alum. valve covers and clearance is not a problem. I do know this, The noise was worse with the Alum roller rockers and the body of the rocker might have been touching the rocker stud. I put comp cams steel rollers and replaced the pushrods and guideplates just to be safe. I have a ton of clearance everywere but still have the sound that comes and goes. This engine has 700 miles on it, I have changed the oil 5 times and have not seen and problems except the high pitched ticking sound that comes and goes. I relashed after changing the rockers,Half past zero, at 200 miles and wonder if the cheep alum. rollers caused the cam to go? I have no oiling problems, I had correct Valve spring pressure, all I know is the sound has gotten louder and really is heard at high rpm. I also have a tight timing chain, Cloyes true roller. I really think It's the hyd. cam and will pull the old cam out soon, I dont drive it, and put a solid lifter cam in. Any one have any input?.

LongRod406
Oct 12th, 00, 08:46 PM
Hi,

You can use a dial indicator to measure for full lift.Good luck

LongRod406

RobR
Oct 13th, 00, 09:34 AM
If your cam was really gone, Your car would run like crap and not be driveable.

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Rob Rice
robr54@hotmail.com
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al anthony
Mar 17th, 01, 06:59 AM
I have experienced the same problem on my 427. On the last teardown,I removed the two 1/4 n.p.t. plugs in the block behind the cam drive gear and drilled .0625 holes in each one. This allows air trapped in the oil galleries to bleed off insuring that the oil supply to the lifters on start-up is suffiecient.Lifters will fail bcause of a lack of oil supply, even if it is sporatic.These plugs are aviable at most jobber supliers.

ilbl8
Mar 17th, 01, 10:28 AM
might be a stupid thing but, are you useing a mechanical fuel pump?

on chevy motor's, more comon on the BB, the pump push rod make's a taping noise and it can be confused with valve train or a bearing knock.

in my experiance this happen's mostly in BB but i have seen it in SB too.

it is most noticable at idle but tend's to go away at around ohhhh 2000 RPM. just a thought for ya.

take a pice of ruber hose about 2 feet long, put on end next to the fuel pump and listen through the hose. if the taping is very loud i bet that is the problem.

also, all valve push rod's are hardened. there is no such a thing as non-hardended push rod's. when you up the rocker ratieo you change the valve train gemotry and can get a rubbing problem with the push rod's. you need to clearance the motor for this allway's! some time's you need to change the guied's and or make the rod hole's in the head larger. all push rod's come in contact with the guide's at some time. this what the guide's are for. to guid the push rod and keep the rocker's on the valve stem head.

[This message has been edited by ilbl8 (edited 03-17-2001).]

JOHNNY6
Mar 17th, 01, 06:05 PM
Here is one for u i had a similar problem on a big block recently and it drove me nuts cuz i have built a bunch of em i had this rattle that would come and go and i couldnt figure it out. Well it wasnt even from my Valve train it was the damn flywheel bolts came lose and they flexplate would rattle just enough to sound just like the old vavletrain noise. I have also a similar problem on a vette only at idle or cruise u would here this tapping noise similar to that it also wasnt even motor was the damn trani bolts to motor were loose, so possible checks there. FLywheel is easy crawl underneath car and grab it and jerk it back and fourth if it moves it could be your problem. Oh another time i had a similar situation with a cracked flexplate man the make a ugly noise when broke. So check it out...

travis
Mar 18th, 01, 01:37 AM
Definately check for a cracked flexplate or loose bolts...I've been thru the same thing...chasing a "valvetrain" noise that turned out to be cracked flexplate. Also check for a broken valve spring...then engine may still run fine but if a coil is broke it will tap. You might also look at the distributor...I have seen a sloppy shaft cause the same noise also. And of course the fuel pump and exhaust gaskets. A quick way to check for a cam going flat is to pull the valve covers and look at the pushrods with the engine running...all of them should be rotating fairly rapidly...when a cam lobe starts going flat the 1st thing it loses is its taper that makes the lifters rotate in their bores...the lobe doesnt last long after that. That also reminded me of another thing to check...make sure all your pushrods are straight...I worked on a guys 305 on time that had the same problem...constant tapping...turned out to be a slightly bent pushrod. One last thing to tell if an exhaust lobe has gone flat...you will start getting big fireballs out of the carb...mixture goes in, its gotta get out somehow. Really embarrasing if your driving around town with no hood or aircleaner (dont ask).
Of course, there is one other thing...piston slap or a cracked piston http://www.camaros.net/forum/eek.gif however, thats usually a persistant tapping sound.

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375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova

[This message has been edited by travis (edited 03-18-2001).]