Gain extra benefits by becoming a Supporting Member Click here find out how!
Classic Performance Products Classic Parts
American Auto Wire Classic Industries
Chevs of the 40sDanchuk Catalog
Hellwig Products IncPerformance Rod & CustomEcklers AutoMotive
Nu-Relics Power WindowsRain Gear Wiper Systems
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy





 Page 1 of 2 12
Username Post: Flat cam        (Topic#354130)
J C 
Senior Member
Posts: 519
J C
Loc: Orange Co. Calif
Reg: 04-17-04
11-29-18 12:13 PM - Post#2752804    

I have a 86 chevy g30 1 ton van. GM crate 350 with approx 175K. When i got it back 4 yrs ago after smogging, it idled horrible. I did not have a tool to adj. the idle mixture so I just lived with it. Within the last 4-6 mo I have had choke prob making it run fast each start up. Also diesels. Some times it backfired. Goes down the road fine. Took it to a smog shop to hopefully get things adjusted & smog ready. He said I had a flat cam. Timing is now set now at approx 14-16 degrees. Idles a little fast & still diesels and a little hard to start. Raining here so I haven't messed with it to get it back. He did not pull anything off so how can he or I tell if the cam is indeed flat? Like I said once off idle it runs fine. This is a work van bone stock. My hearing is poor so I can't hear slight ticking (lifter, rocker arm) or the like.

69RSZ28 71 Chevelle 79 Silverado 24K mi.


 




Shepherd 
Frequent Contributor
Posts: 1554

Loc: Lake George, NY
Reg: 11-11-15
11-29-18 04:02 PM - Post#2752827    
    In response to J C

To properly diagnose worn cam lobes, the rocker covers should come off and comparative valve lift measurements should be taken, otherwise a lot of guesswork is forthcoming.



 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17234
grumpyvette
Age: 70
Loc: FLORIDA USA
Reg: 03-16-01
11-29-18 04:48 PM - Post#2752831    
    In response to Shepherd



http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
65_Impala 
Very Senior Member
Posts: 4139

Reg: 12-29-02
11-30-18 07:03 AM - Post#2752885    
    In response to J C

It a cam lobe has gone flat then the rocker clearance would have opened way up and it would be tapping quite loudly.



 
J C 
Senior Member
Posts: 519
J C
Loc: Orange Co. Calif
Reg: 04-17-04
11-30-18 09:20 AM - Post#2752898    
    In response to 65_Impala

Thanks for the info. I kinda though that there would be a more positive way to determine it or a audio noise. Plus the van runs very good once it gets off idle. I'll have someone listen to it due to my hearing problem. Taking the valve covers off the van is not real simple with a clearance prob and numerous hoses that would have to be removed.

69RSZ28 71 Chevelle 79 Silverado 24K mi.


 
Shepherd 
Frequent Contributor
Posts: 1554

Loc: Lake George, NY
Reg: 11-11-15
11-30-18 10:33 AM - Post#2752906    
    In response to J C

65_Impala is right, a totally flat lobe will cause rocker clearance, but partially worn the lifter can pump up enough to close up the rocker clearance.



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
11-30-18 01:35 PM - Post#2752922    
    In response to Shepherd

I don't ever remembering any significant rocker tap when hydraulic cams have lost lobes, only intake, and/or exhaust note changes.



 
65_Impala 
Very Senior Member
Posts: 4139

Reg: 12-29-02
11-30-18 04:45 PM - Post#2752939    
    In response to Shepherd

The wear that a lifter could compensate for is maybe 0.040". I'm doubting that less than 0.040" of wear would cause idling issues but it would likely lead to the cam wearing further rather quickly.

Now, if a 0.28" lobe wears half off then you've got around 0.24" of rocker to valve clearance. Anyone could hear that clicking.

Besides, I helped replace a cam in an engine not to long ago after diagnosing a badly worn lobe. It was VERY obvious there was an issue just listening to it.



 
Shepherd 
Frequent Contributor
Posts: 1554

Loc: Lake George, NY
Reg: 11-11-15
11-30-18 06:11 PM - Post#2752947    
    In response to 65_Impala

Interesting point, pretty sure the hydraulic lifter has more than .040 travel, gonna try and find out what it is, fun. Ok did some online research, Ford is about .120 travel, non ls lifters are about.090. I am sure there are different designs based on performance aftermarket stuff. So, a lobe that was really worn down would certainly result in excess valve lash.



Edited by Shepherd on 11-30-18 06:32 PM. Reason for edit: No reason given.

 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-01-18 12:21 AM - Post#2752962    
    In response to Shepherd

There's where we all mostly differ, I don't let them get bad enough to make a bunch of noise, I just fix 'em first.

Also, the button usually sits close to the top of the plunger travel, so, not a lot of clearance is there to begin with when lobes go flat.



 
Shepherd 
Frequent Contributor
Posts: 1554

Loc: Lake George, NY
Reg: 11-11-15
12-01-18 05:20 AM - Post#2752967    
    In response to IgnitionMan

Yeh, seems we would all get plenty of notice before you had no lobe! Lol



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-01-18 06:30 AM - Post#2752975    
    In response to Shepherd

Fully agreed, sir. Worked just that way for at least a century, so far.



 
65_Impala 
Very Senior Member
Posts: 4139

Reg: 12-29-02
12-01-18 10:07 AM - Post#2752994    
    In response to Shepherd

LOL, the one I fixed was driving down the road not making a sound and the tick came on really quickly. It was banging away very loudly by the time it went 3-4 miles to get the car home. The cam and lifter feet are only hardened to a certain depth and once you wear through that hardened layer the rest wears away rather quickly.



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-01-18 10:24 AM - Post#2752996    
    In response to 65_Impala

Sounds like the oil mist lubrication was insufficient to support the few thousandths of hardening on the lobe, and lifter face.

Probably some sort of full synthetic, or partial synthetic snake oil "lubricant" that did its job, fail.

Seen that so often, and, it has never been funny.

Who knows, who cares, cam needed replacing anyway, just another engine fix it job, tick or not.



 
Shepherd 
Frequent Contributor
Posts: 1554

Loc: Lake George, NY
Reg: 11-11-15
12-01-18 12:34 PM - Post#2753008    
    In response to IgnitionMan

A couple of bad cam sbc engines I ran into, wiped the bearings out also that metal get all over the engine.



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-01-18 04:04 PM - Post#2753025    
    In response to Shepherd

Yup, seen that as well.

Only cams I have seen that aren't as succepable to lobe/lifter wear away in a mist oiling system, are roller cams. They don't require a lot of oil mist to be happily lubricated.



 
J C 
Senior Member
Posts: 519
J C
Loc: Orange Co. Calif
Reg: 04-17-04
12-01-18 06:16 PM - Post#2753035    
    In response to J C

Based on comments I suspect that the smog guy who worked on my van was just guessing. The idle problem has gone on for about 3 yrs now and not gotten worse & no loud ticking. I just haven't had the time to work on it. The only thing that has changed is the timing. Seems to run better at approx 14degrees. Doesn't seem to have as much power but is ok. No dieseling or backfire now. Don't know if the balancer has slipped. Bought a tool to adj the fuel mixture. Package says it's correct for my year but it doesn't seem to turn the screws.

69RSZ28 71 Chevelle 79 Silverado 24K mi.


 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-02-18 12:24 PM - Post#2753111    
    In response to J C

It just sounded like your smog guy didn't pull the valve covers and fire it up to take a look at the rocker action. Hard to make an "edumacated" guess if that isn't done when a flat cam, or other valve issue is suspected.

That engine is well within the bounds of emissions tuning specs, and although "throwing more ignition timing at it" might help one running parameter, changes can make the rest a giant adverse running issue.



 
65_Impala 
Very Senior Member
Posts: 4139

Reg: 12-29-02
12-03-18 10:42 AM - Post#2753196    
    In response to J C

  • J C Said:
The idle problem has gone on for about 3 yrs now and not gotten worse & no loud ticking. I just haven't had the time to work on it.



It's not too likely to be a lobe if it's been about the same for 3 years.




  • IgnitionMan Said:
Sounds like the oil mist lubrication was insufficient to support the few thousandths of hardening on the lobe, and lifter face.

Probably some sort of full synthetic, or partial synthetic snake oil "lubricant" that did its job, fail.

Seen that so often, and, it has never been funny.

Who knows, who cares, cam needed replacing anyway, just another engine fix it job, tick or not.




Are you attempting to describe a new spec oil that doesn't have enough extreme pressure additive in the supplemental additive package, ie zinc as it's commonly called? Because that's what I suspect, an oil blended for a roller cam engine which is unsuitable for use with a flat tappet cam. Doesn't matter what kind of oil, the wrong blend of synthetic or conventional would both do the same thing.




 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-03-18 05:13 PM - Post#2753252    
    In response to 65_Impala

Pull the valve covers, check things out, fix what's broke.

Simple as that, stop trying to fault my every word.




 
65_Impala 
Very Senior Member
Posts: 4139

Reg: 12-29-02
12-04-18 11:32 AM - Post#2753348    
    In response to IgnitionMan

  • IgnitionMan Said:

Simple as that, stop trying to fault my every word.





What's your problem exactly? You were posting comments diagnosing why I was replacing a cam.....



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-04-18 04:07 PM - Post#2753379    
    In response to 65_Impala

No, I only added info to help people, you did what you always do, began to cut what I posted apart, as you always do.

Can't you just help, and not pull whatever personal problem you have with me out for everyone else to be forced to endure.

This topic has run its course.



 
beagrizzly 
"10th Year" Gold Supporting Member
Posts: 1932
beagrizzly
Age: 68
Loc: south texas
Reg: 08-04-12
12-05-18 07:26 AM - Post#2753458    
    In response to J C

Maybe I am missing something here.

Why do you think you have a flat cam? Because some high school auto tech that runs a smog computer said so?

Forget that. If it is hard starting, like binding when you are turning it over, and dieseling, just retard the timing about 5 degrees.

If you have a flat cam, check for a miss my pulling plug wires one at a time. If you do, indeed have a miss, there is a problem somewhere. I just refuse to accept that you have a flat cam based on the smog "adjustment". Doesn't make any sense.

If you don't have the skill set to check for a miss, take it to a good mechanic. Let him find the problem. If you DO actually have a flat cam, by the time you pay for that to be replaced, you can buy a good WTO 350.

I would not recommend replacing your engine if it was something that you built, and wanted to keep, but, by your post, there is nothing special about your engine. 350 engines are a dime a dozen. Internal engine work is very expensive.
With 175K on that engine, when you replace the cam, you are looking at lifters, cam gears, chain, gaskets, oil and filter, labor. You are talking about over $1500 just to replace a cam on a worn out engine. The next thing to go are the rings, then the mains and rod bearings. It goes on, and on, and on.

At my age, I look for the simplest solution to a problem. I see a lot of fretting, and fighting here over a non-issue.

Griff



if you're gonna be a bear..................

1960 Biscayne (the 6T)
2005 Yukon XL
2007 GMC Sierra Classic 8.1
2009 Silverado
2011 Escalade ESV


 
Rick_L 
Honored Member
Posts: 27510
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
12-05-18 08:28 AM - Post#2753465    
    In response to beagrizzly

Well stated.



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-05-18 08:50 AM - Post#2753469    
    In response to beagrizzly

Fully agreed.



 
65_Impala 
Very Senior Member
Posts: 4139

Reg: 12-29-02
12-05-18 09:44 AM - Post#2753477    
    In response to IgnitionMan

  • IgnitionMan Said:
No, I only added info to help people, you did what you always do, began to cut what I posted apart, as you always do.

Can't you just help, and not pull whatever personal problem you have with me out for everyone else to be forced to endure.

This topic has run its course.




It's OK, it's not like you were purposely being an ignorant SOB bringing up synthetic oil only because I've previously posted how synthetic oil is superior to conventional or anything other nonsense like that. Obviously, you are completely innocent, LOL.

As I posted - the additive package in most oils sold for use in new engines don't support performance flat tappet cams any longer. At best, they might support a low lift, weak valve spring setup. The extreme pressure additives have been reduced since new engines don't have flat tappets any longer. It has nothing to do with the oil type.



 
IgnitionMan 
Valued Contributor
Posts: 3509

Reg: 04-15-05
12-05-18 02:04 PM - Post#2753511    
    In response to 65_Impala

Can't you just help others, they don't deserve to hear all your hate towards me, nor anyone else.



 
J C 
Senior Member
Posts: 519
J C
Loc: Orange Co. Calif
Reg: 04-17-04
12-05-18 09:14 PM - Post#2753567    
    In response to J C

I can't argue with anything that is suggested. I don't think I have a flat cam. The Van runs good when it is off idle. No miss or anything. I know the smog guy did not pull the valve covers because they are a pain in the butt. My thought at this time but first some history. Van started dieseling bad for a few weeks. Had to shut it off in gear to try to stop it. Nothing was changed to cause this. The choke started to stick on after every stop, even if only for a few minutes. Now the van will not idle at 6 degrees advance. It will not idle or run until approx 14-16 degrees. Could the dieseling have caused the timing mark on the dampner to have shifted. My understanding is the dampner is a two part assembly held together by rubber. If it could be the dampner I will have to pull the pully and see where the timing mark is in relation to the keyway on the dampner unless there is a better way or suggestion. Thanks again for everyones ideas

69RSZ28 71 Chevelle 79 Silverado 24K mi.


 
aghaga 
"4th Year" Silver Supporting Member
Posts: 2172
aghaga
Age: 64
Loc: Altavista, Va.
Reg: 07-05-08
12-06-18 07:12 AM - Post#2753616    
    In response to J C

Sounds to me like you may have a vacuum leak



 
YOUNG57 
Frequent Contributor
Posts: 1076

Loc: Tennessee
Reg: 12-06-10
12-07-18 09:44 PM - Post#2753817    
    In response to aghaga

  • aghaga Said:
Sounds to me like you may have a vacuum leak



Bingo, I agree with a vacuum leak. probably a cracked vacuum hose or the carb mounting gasket.



 




 Page 1 of 2 12
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

807 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.078 seconds.   Total Queries: 16   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 08:38 AM
Top