Help Diagnose Cam/Lifter Problem UPDATE

[ARAMP1]

BACKGROUND: I'm having a bit of a problem with my GTO. The motor has about 9K miles on it and when I rebuilt it, it got a new cam and lifters. It has the stock rocker arms and pushrods.

SYMPTOMS: It just recently developed a tick pretty much all the time. Sometimes it's more noticeable than others. And, it now backfires under hard acceleration. I thought they might be unrelated problems. For the backfiring, I thought it might have a vacuum leak in the carb (vacuum secondaries) so I rebuilt the carb. It runs and idles a whole lot smoother now, but did not correct the backfiring.

Tonight, after it dropped below 100 degrees, I decided to pull the valve cover and see if any of the rockers were loose. The were all torqued down tight, but my last lifter was loose and couldn't be tightened any more. The pushrod isn't bent.

DIAGNOSIS: The lighting sucks, but you can see the rear rocker not really moving as much. I'm thinking it's either a worn cam lobe or a bad lifter. Here's a video of it running. What say CK5?

 

[4xcrazy]

well, when you go to pull the intake to possibly replace a lifter/s, you'll see alittle of the cam and should be able to determine. I'd say right off a bad lifter. I just had my motor rebuilt last year and am already having problems with lifters ticking, with several attempts at adjusting, I have them at a happy medium where only one is really noticable at start-up.

 

[cybrfire]

I heard recently that alot of lifters currently on the market are not being ground correctly. The lifter itself is supposed to spin in the bore and the way these lifters were ground they don't spin. Causes them to wear improperly and basically wipes out a cam lobe.

No clue if this is what you got going on, just came to mind when I read your post.

 

[ktmoutfront]

Check the lifter stud. Is it the same level as the others? I had one back out and was doing the same thing.

 

[79rustyk10]

Id guess its a flat cam lobe. I hate to be the bearer of bad news, by my understanding its a very common problem in the last few years for a few reasons.
-cheap china cam cores
-cheap lifters as was already mentioned
-lack of zinc in the regualr oils because they say it pollutes and modern cars dont need it.
-and improper break in, which I wouldnt suspect here.

I was told on sunday actually by a Comp Cams rep that they recomend their break in oil for the first two oil changes then regualr oils should be ok. I dont know about that as I wiped a flat tappet cam a few years ago in an engine that was already well broke in.

 

[diesel4me]

I had to replace the lifters in my 69 GTO ,at 110K,it had one valve that refused to close all the way,and it would cause ahigh RPM misfire and backfire thru the carb,or act like bad valves springs ,sounded just like the valves were floating above 4000 rpms...

When I pulled the intake off,first thing I noticed was the pushrod on that cylinder with the vavle that was not closing fully,was sitting right on the little plunger in the lifter body--the little "cup" thing it was supposed to seat on was missing! --the snap ring had flew out,and allowed the lifter to pump up too high ,and evidently the "cup" was able to jump out,yet not let the pushrod fall out of the lifter!...
I found the "cup" thing in the oil pan,along with 2 more,and the wire clips that was supposed to hold them in the lifter...funny thing was,ALL the other 15 lifters were intact!-I also found a peice of broken push rod in the sludge at the bottom of the pan,and none were missing on all the valves,so evidently the car had cam or lifter problems before I ever got it!...

I looked the cam lobes over the best I could,saw they all had good "lift" so I decided to risk just replacing the lifters,as I wasn't up to the task of installing a new cam with the engine IN the car....I bought cheap "Amgauge" lifters from the parts store I was working at for about 40 bucks,in case the cam was wiped,or the lobes didn't want to wear in properly..I put it all together and the car ran great again--no more misfire at high rpms and it gained a lot of power with that "missing" cylinder now putting out 100%...

I have seen a lot of brand new cams flatten lobes in very low miles in recent years..my friend put 2 Edelbrock cams in a stock '68 Chevelle with a 327,the car didn't go 1400 miles before it started backfiring and the second one he installed only lasted ablut 2000 miles--he knows how to break them in right,used the proper break in lube,good oil with zinc for the lobes,etc..he also installed new Edelbrock valve springs and retainers and valve stem seals,the cam was a "kit" that he installed all at once..


I think the cam lobes were just never heat treated properly...the owner of the car is super anal about changing the oil and all other maintenence too..so far,camshaft #3 is hanging tough with 10K on it--he's been using Lucas oil treatment with the oil,and it took a lot of convincing to get him to use it--he acted like it was engine poison,and didn't want that "gook" in MY engine!--but I think thats what is keeping the cam alive..

Pontiac engines always had top end troubles--timing chains,push rods,and lifters were common parts failures..but they didn't seem to eat cam lobes as bad as small or big block Chevies did for some reason..I cant recall ever selling a cam for a Buick or Olds V8 either,unless someone wanted a "hotter" cam,the OEM ones seemed to never have lobe failures for some reason...

 

[ARAMP1]

Well, for all those who guessed the lobe, you win.

Here's a poor picture of the ground down lobe. It's the last one on the left in the rear. That should be the lift side of the cam and it's almost as flat as the back side of the lobe.

Here's a picture of the lifter too. It's ground down like a mo-fo.

Last time I changed the oil, I wasn't missing a drop and I didn't notice anything in particular that was bad about it. Well, I guess I'm about to order a new cam and try this again.

 

[tRustyK5]

Not cheap, but I say go full roller and never worry about that again.

I have a 454 here and have been looking at various cams and stuff for it's build. Although it'll be a budget killer I plan on full roller for it.

Rene

 

[63chevyll]

The biggest problem with that bad lobe (and prob worn others) is the amount of material which got ran through the rest of the engine. Possible oil pump.and bearing problems.if the filter didn't catch most of it. And even if the filter was good those particles are so.dangerous.

This won't be cheap

Improper break in, incorrect oil, heavy vAlve springs, adjustment or combinations of all.could have caused it.

 

[ARAMP1]

The biggest problem with that bad lobe (and prob worn others) is the amount of material which got ran through the rest of the engine. Possible oil pump.and bearing problems.if the filter didn't catch most of it. And even if the filter was good those particles are so.dangerous.

No doubt. That's the worry. I've had good oil pressure at idle and at cruise, so I'm hoping the filter got most of it. Either way, stuff would have made it through anyway. There's got to be some wear. Either way, cam and lifter kit is $150. I'm going to try that and if I end up with more problems, I'm going pull it and to go the LS route.