Wiped Cam Lobe ?

[scrobbyd]

Not quite sure of how to tell if a cam lobe is wiped, but the third push rod standing in front of the car on drivers isn't moving. This is on my dads GN which has a 218/218 cam. Is this what normally happens when a cam lobe is wiped or should we be looking for something else?

Thanks in advance

 

[sabersaw30]

You could also have a broke pushrod.but sounds like a wiped cam lobe.
Pull your rockers and see what the pushrod looks like.

 

[moose]

If you have a lobe wiped on the exhaust side you can tell by letting the car idle with a vaccum guage. The guage will tick tock back and forth under vaccum.:wink:

 

[BlackBandit]

Pop that lifter out. If you're cam is wiped the bottom of the lifter will be dished. You'll know what I mean when you see it. Good luck. james

 

[jpwalt1987]

Robby, If it is a flat tappet cam consider it wiped! #3 exhaust is the lobe that have wiped everytime in every motor. Get a 206/206 roller and call it a day. Your wallet will thank you. Jeremy

 

[Jerryl]

Robby, If it is a flat tappet cam consider it wiped! #3 exhaust is the lobe that have wiped everytime in every motor. .....

I know you did not mean that ........

 

[dr_frankenstein]

Robby, If it is a flat tappet cam consider it wiped! #3 exhaust is the lobe that have wiped everytime in every motor. Get a 206/206 roller and call it a day. Your wallet will thank you. Jeremy

lots of guys do fine on flat tappets. i think you need to check yourself.

A.j.

 

[Scott231]

If you have no gauge, the symptom will be that the car runs fine at low boost and below. Once you bring it up on boost > 10 psi (your actual level may vary) it will backfire through the intake - because the exhaust lobe is opening the valve enough to 'empty' the cylinder of burning gases.

BTDT

 

[jpwalt1987]

flat tappet= flat cam

lots of guys do fine on flat tappets. i think you need to check yourself.

A.j.

I have "checked myself" plenty of times. I wiped the stock cam out with only about 55-60k miles on it back in 1996. Then there was the "club cam"200/200 lunati. The engine was taken apart and all the oil galleys cleaned/flushed blah ,blah, blah. That cam didnt last past the start up. And yes break in procedure couldnt have been done any more correct. Next ATR whatever cam(dont remember the spec) lasted about 10k in a different block than the first 2 cams. Next up.....210/205 reed cam from modern muscle and one from RSC engineering out of GA. Both of those went flat after about 10k mile also. SO....five different cams in 3 different blocks. (i didnt mention one of the blocks) That is basically 5 rebuilds with everything being spotless clean, break in procedure followed exactly, new lifters, Valv 10/30 VR1 oil used during break in. #3 exhaust was always the worst but the others were not too much better. Guess I am not one of those guys who have luck with flat tappets. I'll stick to the roller setups....my wallet does thank me. When my other GN is ready for the road(it is in bad shape) I will pull the motor and take the stock cam out and use a 206/206 or something like that. Thats my story and I'm sticking to it..:biggrin:

 

[dr_frankenstein]

I have "checked myself" plenty of times. I wiped the stock cam out with only about 55-60k miles on it back in 1996. Then there was the "club cam"200/200 lunati. The engine was taken apart and all the oil galleys cleaned/flushed blah ,blah, blah. That cam didnt last past the start up. And yes break in procedure couldnt have been done any more correct. Next ATR whatever cam(dont remember the spec) lasted about 10k in a different block than the first 2 cams. Next up.....210/205 reed cam from modern muscle and one from RSC engineering out of GA. Both of those went flat after about 10k mile also. SO....five different cams in 3 different blocks. (i didnt mention one of the blocks) That is basically 5 rebuilds with everything being spotless clean, break in procedure followed exactly, new lifters, Valv 10/30 VR1 oil used during break in. #3 exhaust was always the worst but the others were not too much better. Guess I am not one of those guys who have luck with flat tappets. I'll stick to the roller setups....my wallet does thank me. When my other GN is ready for the road(it is in bad shape) I will pull the motor and take the stock cam out and use a 206/206 or something like that. Thats my story and I'm sticking to it..:biggrin:

its true, just giving ya hell, I have a 4.1 block like that, doesent matter whats done to it... still craps the cam. I really do believe the core shift problem occurs with about 60% of all blocks. I forgot my smiley face, so i guess that comment did make me sound like a dick. just foolin though....

:biggrin: A.j.

 

[turbobob924]

my powerlogger should record the vacuum at idle to show that there is too much tick tick?

The blow out back into the intake is exactly the miss I have been chasing for months!

 

[jpwalt1987]

its true, just giving ya hell, I have a 4.1 block like that, doesent matter whats done to it... still craps the cam. I really do believe the core shift problem occurs with about 60% of all blocks. I forgot my smiley face, so i guess that comment did make me sound like a dick. just foolin though....

:biggrin: A.j.

:biggrin: :biggrin:

 

[Scott231]

The blow out back into the intake is exactly the miss I have been chasing for months!

Told ya! FatGNat should be taking pictures of the cam we just took out of his engine. It is hard to tell the difference between #3 exhaust and the base circle of the lobe next to it.

 

[MikeL.]

here it is...

http://www.turbobuick.com/forums/engine-tech/285543-carnage-du-jour.html

The #3 lobe 'should' be in the foreground on the first pic. You should've seen what my oil pick up screen looked like

 

[Jerryl]

I don't think there is ANY argument from anyone that a roller cam is a better set-up and option for both power and longevity.
Throuhg the years, the consensus for premature flat tappet cam failure has been on the placement of the #3E lobe hole location, reverse taper on the lobe, break-in procedures, spring pressures, etc.

I am no expert, but some of the experts call the hole location thing "folklore".
Every production line machining process is build around repeatability (and accuracy) so, with that in mind it would be a repeat failure in the field, each and every time.
“If” the lifter bore location was truly an issue, it would be at a 90% failure rate in the field and we all know that was/is not the case.

Besides, the cars were picked “randomly” of the assembly line for TR upgrade which makes the lifter bore issue even less plausible (Although the location could have been better :wink: )
Keep in mind that the stock set-up (Cam lifters springs) is still running very strong in a LOT of GM assembled motors.

It is more plausible that aftermarket cams were the problem ……… Don’t know and have no data on this, but think about it.

Here is one of the 1000's of threads on this cam thing ......
Happy reading.
http://www.turbobuick.com/forums/ge...h/128304-what-cams-will-live-our-engines.html

 

[BlackBandit]

I don't think there is ANY argument from anyone that a roller cam is a better set-up and option for both power and longevity.

Flat tappets tend to work bettter than rollers in turbo aps due to there faster initial lift. Depending on turbo size, rpm operating range, and intended use this can result in better performance.

Sorry, I couldn't resist. FWIW I won't ever put a flat tappet cam in one of these cars again.

 

[Jerryl]

Flat tappets tend to work bettter than rollers in turbo aps due to there faster initial lift. Depending on turbo size, rpm operating range, and intended use this can result in better performance.

Sorry, I couldn't resist. FWIW I won't ever put a flat tappet cam in one of these cars again.

Good point kimosabe. :tongue:
And neither will I .......... Although, I never had an issue with the FT cam ........

 

[87GN_70GS]

I am no expert, but some of the experts call the hole location thing "folklore".

Have you seen for yourself? Have these "experts" seen for themselves? Do yourself a favor and go look at one. Once you've actually seen this firsthand, you will be convinced. It's obvious, not maybe or kinda, but visually apparent.

 

[Jerryl]

Have you seen for yourself? Have these "experts" seen for themselves? Do yourself a favor and go look at one. Once you've actually seen this firsthand, you will be convinced. It's obvious, not maybe or kinda, but visually apparent.

Did you take a look at a picture I posted in the link?
Like I said .......... I am no expert but there some good info in the thread.
Take a minute to read it and post back to tell me what you think, seriously.

 

[A2000RICH]

Did you take a look at a picture I posted in the link?
Like I said .......... I am no expert but there some good info in the thread.
Take a minute to read it and post back to tell me what you think, seriously.

in the last year i have done an awful lot of research on this subject----lots of tests and lots of cams and lifters destroyed on purpose--------yes even measured dozens of blocks and compared them to original blueprints for range of variation (yes i even have original GM prints)------measure a dozen blocks and lifter location does vary but not as much as you might think-------variation from the prints is very very little-------and if you check the prints the separation of lifters is greatest on cyl #3 (1.620) and least on #2 (1.515)------the rest of the cylinders are the same (1.520)------the extra 0.10 of lifter seperation on # 3 (compared to # 1-5-4 & 6) is corrected by reverse rotation------and yes it was intentional NOT a mistake------i will explain why-------- fact is, hard as it seems to accept lifter location is not an issue till the cam and lifter wear------with original lifter crown and lobe taper intact, contact point is fixed independent of relative offset-------when wear reaches a certain point then lifter location vs lobe location really becomes critical but by then things are already seriously worn------i'm writing a rather technical and through article for the GS extra that will be in one of the upcoming issues..............RC