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muddin4fun
11-20-2001, 02:42 PM
<font color=red>Update-go to last reply</font color=red>
Gawd I hope not. &lt;img src="http://coloradok5.com/forums/images/icons/frown.gif"&gt; But can someone give me some symptoms?
I've got a carb I can throw on it tonight and I'm also going to check the plugs (again) to see if they're fouled out. I've got some major backfiring and it's falling on it's face when you accelerate. Right now, if I keep it under 25, it won't backfire. How tight would the valves have to be to flatten the cam? I've got hydraulic lifters.

Peace and stuff &lt;img src="http://coloradok5.com/forums/images/icons/tongue.gif"&gt;,

Muddin

&lt;a target="_blank" href=http://www.geocities.com/muddin4fun79blazer&gt;www.geocities.com/muddin4fun79blazer&lt;/a&gt;
<P ID="edit"><FONT class="small">Edited by muddin4fun on 11/26/01 07:29 AM.</FONT></P>

Rob 85K5
11-20-2001, 03:14 PM
Listen for a rattling sound inside the valve covers. If the lobe is flat, the rocker arm may be off of the pushrod and be moving around.

Rob

<font color=orange>Bleedin' Chevy Orange</font color=orange>

RedDwarf
11-20-2001, 04:16 PM
My guess is that you have made an accurate diagnosis. Cams are cheap though. Auto Zone has a Melling cam with good torque for 90 bucks. Add 25 for a new double roller chain and you're in business.

jimmyjack
11-20-2001, 04:34 PM
Take of your valve covers and look for a rocker that isnt lifting. Thats a dead giveaway! Is your distributor good and secure? Plug wires burned at all? My blazer ran great at 40 and under but if I stomped on it it was horrible. Turned out I had 3 burnt wires. Couldn't see them til I removed them and really checked them out though! Good Luck, hope its nothing big

That jeep thing? Yah I understand it....... Like my Blazer? <a target="_blank" href=http://community.webshots.com/user/blazerk5>http://community.webshots.com/user/blazerk5</a>
Jim

K5Jimmy
11-20-2001, 06:24 PM
I like the burnt wire theory also, 'specially with headers.....you can sometimes feel "hard" spots on the unblemished wire that's burnt.....I've had a bad coil act weird like that also, although it was non-HEI....I had a burnt wire that would backfire like hell when I romped it, but acted ok if I just rolled smoothly on the gas.....I'm havin' a hard time gettin' to a flat lobe on a motor as new as yours.....isn't it still in warranty?....I'm takin' a hard look at the NAPA motor you got as a replacement for mine this spring.....I'd hope it was way more durable than that.......Joleen deserves the best......JD

Stuck?...Hell no..I still got some gas left..

mike reeh
11-20-2001, 07:33 PM
I lost a lobe (if i remember correctly an exhaust lobe) on a stock 77 cam.. it idled and stuff pretty good but if you stomped on it it fell on its face and if you kept it at full throttle you could hear metal noise in the engine.. if you babied it, it was definately driveable. drove me nuts, i didnt even consider the lobe.. tried different carbs, distributors, fuel pumps, etc..

the easiest way to check though is start the engine with the valve covers removed.. might as well adjust the rocker arms while you're there too...

I got a "rv" cam from a machine shop (generic brand but said it was a bigname in disguise) for cheap... never run used lifters on a new cam.. just get 16 new lifters while you're at it.. and a timing chain would be good too, like was mentioned.. you can have it all fixed in a weekend if you play your cards right. probably for under $150 too..

mike

RedDwarf
11-21-2001, 12:07 AM
You don't even have to start it. You can just turn it over with a ratchet. That's how I discovered a bad cam once. It was completely flat, and the lifter had a big dish in it. It was popping like you described.

84_Chevy_K10
11-21-2001, 12:31 AM
I definitely wouldn't run a $90 cam in a $3,000 motor.

If your cam is a Comp, it's pretty typical from what I hear. It will be covered under warrenty in that case.

If I were you, and I'd payed that much for a crate motor, and it had a flat cam, I'd probably pull the whole motor. God only knows what all those little bits of metal did to that motor when the cam went flat. Sounds like a replacement of the motor is your best bet.

Tim
'84 Chevy K10, lifted, loud, fast, and 3/4 ton axles

chevyracing
11-21-2001, 12:36 AM
could be a collapsed lifter too. If it is an exhaust lobe you can get some popping from the carb. If it is an intake lobe it will run rough and that cylinder will not heat up like the others. Also could be a warped valve. Do a compression check.

John

Like to go sloppin' 'round in da mud in a rapid fashion....=)

<a target="_blank" href=http://coloradok5.com/gallery/albun31?&page=1>See my pics here</a>

muddin4fun
11-21-2001, 08:30 AM
I was gonna work on it last night, but decided not to so it's parked. I can get a cam for free. I bought the long block only a few months ago. This weekend I'll look at it. It sure does sound like a bad lifter or flat lobe. http://coloradok5.com/forums/images/icons/frown.gif.
I'll update ya'll this weekend (prolly friday is when I'll look at it-no work! http://coloradok5.com/forums/images/icons/laugh.gif). Thanks guys! I'll keep ya'll posted.

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

<a target="_blank" href=http://www.geocities.com/muddin4fun79blazer>www.geocities.com/muddin4fun79blazer</a>

muddin4fun
11-21-2001, 08:32 AM
Oh...I'm also gonna take a good look at the wires...possibly replace them. When I changed the spark plugs a week ago, they looked a little on the crispy side. Is there a good way to do an at home test on them?

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

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Butch
11-21-2001, 08:41 AM
If your cam went flat that quickly on a new motor your oil will be shiny. Pull your dipstick and hold it up to a strong light and see if it shines. When I build my motor the cam I got had not been hardened properly and I lost three lobes plus the fuel pump eccentric in about 50 miles after breaking the motor in. If it is the cam make whoever you bought it from stand good for new bearings and turning the crank because they will be toast. Any change in oil pressure?

I thought I was wrong once,
but I was mistaken

chevyracing
11-21-2001, 08:49 AM
You need an ohm meter and just check the resistance in the wires. If you bend them and it sounds like someone stepped on a box of frosted flakes or feel crunching they are shot. Too many people take the wires for granted. They are one of the most important external components of an engine.
Oh, the resistance should not be over 8000 ohm per foot of suspression wire. On point systems check the wire with the ohm meter connected to each end of the wire, on electronic systems check one end of the wire (spark plug side) and remove the dist cap with wires still attached and check it through the cap at the wire contact where the rotor picks up.
One more thing to is to make sure you have not routed your wires wrong. (ie:parallel and touching)

John

Like to go sloppin' 'round in da mud in a rapid fashion....=)

<a target="_blank" href=http://coloradok5.com/gallery/albun31?&page=1>See my pics here</a>

Mudzer
11-21-2001, 09:29 AM
Lara,

A flattened camshaft is at times difficult to detect. You almost cant detect it just by removing a valve cover. Camshafts almost never completely flatten a lobe (unless it has like 2 million miles on it), it may loose some of the profile, but usually never wear down to completely flat. So, trying to turn over the engine and watching the rockers is difficult unless you have a trained eye! Didn't you just rebuild that engine a while back? Has it always driven this way? I would say either you have a timing issue or carb problem. Your Hydraulic lifters were probably set to zero lash. I woudnt think unless you had an oiling problem or really cheap camshaft, that the lobe was worn flat in that short of time. Give me your info on the type of carb. You say this only happens on acceleration? Is this Hard acceleration or just normal driving? What RPM does this happen at? Does it smooth out after acceleration? How many miles on the rebuild? Did you use a nylon gear on your timing chain?

Mudzer 1978/91 K5
<font color=blue><a target="_blank" href=http://www.mudzer.rockcrawler.com>www.mudzer.rockcrawler.com</a></font color=blue>

muddin4fun
11-21-2001, 09:49 AM
It's a crate motor. It's got about 5000 miles on it. Last week is when it all of the sudden went to the crapper, but yesterday is when it really hit bottom. At first, it was ideling real rough. I changed the plugs and it fixed it for a day, then went back to ideling a little rough, but not as bad. The old plugs were fuel fouled. Then, yesterday driving home for lunch (it made it to work that morning just fine) it would just fall on it's face when you accelerate normal to fast. If you barely touch the pedal, then it wouldn't stumble. Then, when the rpms got to a normal range or high range, it would back fire constanly. You can only hear it out of the pipes. A few times it backfired thru the carb. Not a real loud bang, but that "Pooofst" sound? If I'm on flat land and stay under 25 (TH350 with 33's and 3.73's-I don't have a tach, but with that combo whatever the rpm's would be at that speed) it won't backfire or I'm not hearing it backfire. If I go up a hill and am trying to keep it at least at 25, then it backfires, stumbles, spits, cusses...you name it. The timing is set at 6 degrees and the disty isn't loose or anything. I'm running a 600cfm performer edelbrock. I have a new one in the garage that I am going to put on to rule out the carb. Seemed a little fishy that the plugs were fuel fouled. If I cruise at any speed above 25, it will backfire constantly. The motor was a crate motor BTW. A long block.

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

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muddin4fun
11-21-2001, 09:53 AM
I'll get the dig cam out and get some video so ya'll can hear

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

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tRustyK5
11-21-2001, 10:00 AM
Weak crispy wires will do that too...bad miss under load. I used a small inductive lead tester to confirm my then 6 month old Accel wires were crap. My Accels were routed properly and were not burnt...just junk right out of the box.

Rene

<font color=green>Dyslexics of the world...UNTIE!</font color=green>
<a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>

Mudzer
11-21-2001, 10:08 AM
Ok, sounds like a fuel problem for sure. I had a street car I used to dragrace. I installed an 850 Holley Double Pumper and had the same problems. At high RPMs the carb would cut out and backfire through the exhaust so bad, I could see orange sparks coming from the exhaust in my rearview mirror. My problem was being too rich. You can get similar reuslts from being lean. Belive me, your 600 may sound a little small for a 383 at first, but it really depends on several factors. I calculated your Optimum Carb Size using a Volumetric Efficiency of 85%, max RPM of 5500, and 383 Cubic inches. This result was 518 CFM. You also probably require about 20 Gallons Per Hour fuel requirement. I think I would try a known working carb, then go from there. Don't throw away that Edelbrock, just buy some new metering rods for the secondaries. Sounds like thats where the problem is. Perhaps the primaries need some fine tuning as well. Secondly, there is a possiblity the accelerator pump is not delivering the proper shot of fuel, whether it be too much or to little, I am not sure.

Mudzer 1978/91 K5
<font color=blue><a target="_blank" href=http://www.mudzer.rockcrawler.com>www.mudzer.rockcrawler.com</a></font color=blue>

muddin4fun
11-21-2001, 10:30 AM
I've got a brand new edelbrock performer sitting in the box in the garage. That's the one I was talking about putting on there.
My plan of action is as follows http://coloradok5.com/forums/images/icons/smile.gif:

1. Test the wires
2. Pull plugs and look at them-check compression while I'm pulling them
3. If all that checks out, replace 'defective' carb http://coloradok5.com/forums/images/icons/laugh.gif
4. If that doesn't work...kick the tire, rant and cuss, have an alcoholic beverage and come back to CK5 for help http://coloradok5.com/forums/images/icons/smile.gif

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

<a target="_blank" href=http://www.geocities.com/muddin4fun79blazer>www.geocities.com/muddin4fun79blazer</a>

tRustyK5
11-21-2001, 10:32 AM
<blockquote><font class="small">In reply to:</font><hr>

1. Test the wires
2. Pull plugs and look at them-check compression while I'm pulling them
3. If all that checks out, replace 'defective' carb
4. If that doesn't work...kick the tire, rant and cuss, have an alcoholic beverage and come back to CK5 for help

<hr></blockquote>

Sounds like you got it under control...http://coloradok5.com/forums/images/icons/smile.gif

Rene

<font color=green>Dyslexics of the world...UNTIE!</font color=green>
<a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>

muddin4fun
11-21-2001, 10:45 AM
LOL! I'm fooling you then!

It sucks...the truck knows she's boss http://coloradok5.com/forums/images/icons/tongue.gif

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

<a target="_blank" href=http://www.geocities.com/muddin4fun79blazer>www.geocities.com/muddin4fun79blazer</a>

ftn96
11-21-2001, 11:22 AM
See you got your order all messed up. You need to move the alcoholic beverage up to #1 then proceed with the rest of them. Just dont throw your back out lifting that heavy carb.http://coloradok5.com/forums/images/icons/laugh.gif Then you'll be whining like ****ter (aka Rene)http://coloradok5.com/forums/images/icons/laugh.gif

Surgeon General's Warning:
Viagra and steroids may be harmful to your spouse!http://coloradok5.com/forums/images/icons/laugh.gif
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tRustyK5
11-21-2001, 11:31 AM
**** you sparkyhttp://coloradok5.com/forums/images/icons/smile.gif...my back is already feeling better and I haven't missed any work.http://coloradok5.com/forums/images/icons/cool.gif

I will agree the alcohol needs to move up on that list though.

Rene

<font color=green>Dyslexics of the world...UNTIE!</font color=green>
<a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>

ftn96
11-21-2001, 11:40 AM
Martha ****er!!! http://coloradok5.com/forums/images/icons/laugh.gif

Surgeon General's Warning:
Viagra and steroids may be harmful to your spouse!http://coloradok5.com/forums/images/icons/laugh.gif
<a target="_blank" href=http://www.nashvillek5.freeservers.com>www.nashvillek5.freeservers.com</a>

muddin4fun
11-21-2001, 11:46 AM
Oh no...one drink and I'm acting goofy! http://coloradok5.com/forums/images/icons/laugh.gif I don't have a high tolerance for that stuff at all!
I'd either be laughing at a 'kanooter valve' or passed out on the motor which nick would get a pic of and use it to blackmail me http://coloradok5.com/forums/images/icons/laugh.gif

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

<a target="_blank" href=http://www.geocities.com/muddin4fun79blazer>www.geocities.com/muddin4fun79blazer</a>

sosamantx
11-21-2001, 12:16 PM
when my cam went flat on my chevelle (3 times), i could hear it backfiring under the intake when I was on the highway. it turned out that I had stock springs for a more than stock cam, and I was floating the lifters at 5,000+ rpm's.

<font color=blue>Steve Sosa a.k.a. "sosaman"</font color=blue>
<a target="_blank" href=http://sosaman.home.texas.net/carpics.html>http://sosaman.home.texas.net/carpics.html</a>

dyeager535
11-21-2001, 12:41 PM
You know, if you think you have a flat cam lobe on one cylinder, you should be able to pull one plug wire at a time while its running (if it will even idle on its own) and determine which cylinder, if any, doesn't change the idle when that plug wire is pulled. THAT will tell you at LEAST where to focus on for troubleshooting.

Better clarify. At least if you can narrow it down to one cylinder, you know WHICH wires/plugs and cylinder compression to check. Don't rule out the cap, if a terminal comes just a bit loose, the rotor will bend it out of the way, producing no spark at the end of whichever wire it is. I'm not sure a compression test will let you know if you have flat lobes though, since either way, the valves are closed when compression is measured/produced, so if one or both valves is not OPENING, what difference would a compression test show? Perhaps low if intake wasn't opening?

Dorian
My tech/links page: &lt;a target="_blank" href=http://www.dorianyeager.com/index2.html&gt;www.dorianyeager.com/index2.html&lt;/a&gt;
Why insist on counting when the ring gear has the tooth counts stamped in?<P ID="edit"><FONT class="small">Edited by dyeager535 on 11/21/01 02:16 PM.</FONT></P>

Ryan B.
11-21-2001, 01:46 PM
I agree with dyeager535... do a cylinder drop test, and that can narrow it down to which cylinder or two the problems are coming from...

When I had 3 flat cam lobes in my K/5's first engine (not completly flat, but pretty bad), it ran really good for 6 months, then I started to notice a ticking noise. I tried to locate the problem while the engine was running and it sounded like a blown header gasket for sure. I changed it and of course the ticking was still there.
I drove normally maybe another 10 miles, and by the end of that, the tick became serious, it was popping through the carb and out the exhaust at times... Pretty much a lot of what you are describing. Started sounding more like a rod knock the worse it got.
We took off the valve covers and put your hand across the rockers, you should be able to tell if one or two of them are not lifting as much as all the normal rockers.
Drink an alcoholic beverage, &amp; twist one up, if all else fails!

Twiz
11-21-2001, 09:58 PM
Back-fireing thru the carb.
- Lean A/F mixture. The fire is looking for more fuel to burn, the fuel is not going to be down the exhaust sys, so it "looks" for it in the intake sys. (this happens during valve over-lap on the exhaust stroke)
- Ignition problem. Fireing a plug when the intake valve is still open (cross fire, induced spark, timeing is advanced, plug-wire routing, cap/roter problem)
- Cam shaft is advanced. Opens the intake too soon. (not likely here)
Back fire thru the exhaust sys.
- Rich A/F mixture. A rich mix will burn slower and when the exhaust valve opens, it's still burning. Plus, there is un-burned fuel still in the exhaust sys (-high H.C. content- raw fuel has a high H.C. reading- for those who may be batteling emissions)
- Timeing is retarted. Spark is going off too late, the fuel is still burning when the ex. valve is opened. Also, poor excelleration from a stop.
- Cam is retarted. Ex. valve opens too soon.
Flat intake lobe. (take this with a grain)
- Valve does not open fully. Poor high RPM performance but idles O.K., possible engine miss or valve tick. The cyl is not getting enuff A/F mix at Wide Open Throttle. Possibie casuses due to poor oiling, lifter not rotateing properly (possibly due to an obstruction inthe oiling sys.), excessive valve spring pressure.
Flat exhaust lobe.
- Exhaust valve does not reach full lift. Poor high RPM performance, idles O.K., possible detination problems if lobe wear is exsesive. (same possible causes as Intake)
I'm not sure if it would back-fire if the lobes were worn..

Tiwiz's check;
- Same as Dyeager535, this guy knows his stuff! (as a matter of fact, when the custom cut Q-jet project gets rolling, *soon*, Dorians is my go-to-guy)- just giveing credit where credit is due.

I'd like to add to the power balance test.
If you have a Timeing-gunn that has tach reading, use it, if not, go by ear. Take note of the RPM at idle. Than pull a plug wire off and ground it, restart and check idle speed. Write it down. Recannect the wire and complete the same with the next, than the next, ext. The cyl. or cyls. that have the least drop -might- be where the problem is located ( A plug, wire, dis., comp.,) Further testing will indicate which one is the cause.
Also,
- Mist the wires with water from a squirt gun, or something. Start and check for arcing. Load the engine if needed (power brake it if it's auto.)
- Carb problems will genneraly effect all the cyls. A carb swap -may- change or corrct the problem, all though it may not. It might help if you complete only one change (rods, jets, timeing) and redrive to compare. Change and redrive. It's a long processes, but helpfull in the process of elimination.
- Fuel saturated plugs can be miss-leading on a poorly running engine.



<font color=blue>Twiz &lt; My longest reply ever, damn my finger furtshttp://coloradok5.com/forums/images/icons/smile.gif

muddin4fun
11-26-2001, 08:31 AM
It was the carb! It was just dumping fuel everywhere. Since I bought it in march of this year, it can be defected and I don't have to pay for a new one. So, with the new carb on she's running great!

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

<a target="_blank" href=http://www.geocities.com/muddin4fun79blazer>www.geocities.com/muddin4fun79blazer</a>

ftn96
11-26-2001, 08:53 AM
Did you put one of those go fast chrome ones in? http://coloradok5.com/forums/images/icons/laugh.gif

Surgeon General's Warning:
Viagra and steroids may be harmful to your spouse!http://coloradok5.com/forums/images/icons/laugh.gif
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muddin4fun
11-26-2001, 09:29 AM
It's the edelbrock performer....I guess that's sorta chromed?

My truck is sooo much faster than yours! http://coloradok5.com/forums/images/icons/laugh.gif. Cause I've got a chrome thermostat housing! Ya! I do! http://coloradok5.com/forums/images/icons/laugh.gif

Peace and stuff http://coloradok5.com/forums/images/icons/tongue.gif,

Muddin

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ftn96
11-26-2001, 12:21 PM
Oh yeah, well I painted mine gloss silver! So Ha!!!! http://coloradok5.com/forums/images/icons/laugh.gif

Surgeon General's Warning:
Viagra and steroids may be harmful to your spouse!http://coloradok5.com/forums/images/icons/laugh.gif
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muddin4fun
11-26-2001, 02:03 PM
With sparkles?

Don't hit me, Mr. Moderator... I'll go back on topic... I swear!http://coloradok5.com/forums/images/icons/laugh.gif

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78Suburban
04-25-2006, 10:15 PM
I was just reading through this thread, its absoulutely rediculous how much this sounds like all the problems i was having. Now that I've adjusted the vavles the problem's seem to have gone away for the most part, but I think I need to do some tuning on my edeljunk :laugh:
sorry for gravedigging :crazy:

74BBPowerHouse
04-29-2006, 09:54 PM
You don't even have to start it. You can just turn it over with a ratchet. That's how I discovered a bad cam once. It was completely flat, and the lifter had a big dish in it. It was popping like you described.

I had the same exact problem on my Big Block. Cam looked like an egg on an exhaust lobe. And the lifter looked dandy as well.

roadnotca
05-01-2006, 06:27 PM
Thats such a relief when you find that D**n bug.
But there really is a cam problem. Everybody get yourself a copy of the June HOT ROD. :mad:
Oh, and BTW, diesel is getting reformulated (1/1/07?) for less sulphur. New trucks will be ready, supposed to be OK for 100 years worth of Diesels out on the road. :haha: :haha: :haha: :haha: :haha: :haha: :haha:
Oh, and price of fuel? Read Ann Coulter's write-up "Its' Hard Out Here for a Pump" 5/1/2006 :haha: :haha: :haha: :haha: :haha:
Sorry, I should be in the Lounge.