Wiped cam or what? How can I tell. - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 39 (permalink) Old Dec 26th, 02, 07:44 PM Thread Starter
 
Join Date: Dec 2002
Location: salinas, ca. us
Posts: 10
I recently put a new top end (cam,lifters,heads,intake) back on my car and started it up for a few minutes. The car revs nicely at a stop while parked. It craps out on me and backfires when I put a load on it. It seems to not have any power at all. We did a compression check and all cylinders registered 165 to 170. I am a novice at this tuning stuff, so be nice. What are the symptoms of a flattened cam. I know the first seconds on a new cam are critical.
v8zone is offline  
Sponsored Links
Advertisement
 
post #2 of 39 (permalink) Old Dec 27th, 02, 01:29 AM
Senior Tech
 
Join Date: Sep 2001
Location: Elizabethtown, PA
Posts: 980
Send a message via AIM to Spames
Those symptoms sound like a wiped cam to me. Can you remove the valve covers, and look at your rocker arms, and see if one or more don't seem to be moving as much as the others? I had the same thing happen to me once. It was the first time I tried to replace a cam, and I had it advanced so far that my headers glowed red. Whoops....

------------------
68 Coupe, 350 4-speed
Jim's Camaro Corner
Spames is offline  
post #3 of 39 (permalink) Old Dec 27th, 02, 02:05 AM
Senior Tech
 
Join Date: May 2000
Location: Westlake, OH 44145
Posts: 707
You will also notice several rockers out of adjustment. and glitter in the oil.

------------------
67 prostreet BB Camaro The Combat Rat
80 z28 Camaro 355ci
71 BB SS Chevelle (clone)
2002 35th anniv SS Z28 conv.
Milan is offline  
 
post #4 of 39 (permalink) Old Dec 27th, 02, 06:28 AM Thread Starter
 
Join Date: Dec 2002
Location: salinas, ca. us
Posts: 10
I'll check into that.
Thanks guys.
vic
v8zone is offline  
post #5 of 39 (permalink) Old Dec 27th, 02, 06:50 PM
SY1
Senior Tech
Dave
 
Join Date: May 2001
Location: Michigan
Posts: 2,920
Vic,
Your compression check (static compression) will only tell you the sealing ability of your rings and valves. To determine if you have obstructions in the intake or exhaust systems, such as wiped out cam lobes, plugged converters, etc., you need to d a dynamic compression check. This will tell you how well each individual cylinder breathes. It's simple to do and it works, I've found bad lobes on cams this way. Even when the oil looked fine. But since your failure happened pretty rapidly if it is a cam wiped out you should see it in the oil as was suggested.

Dynamic compression check:
-warm engine up
-remove one plug and insert your compression gage in that sylinder.
-ground out that plug wire to protect the ignition module
-remove the shraeder valve core from you tester, or you can leave it in and bump the bleed button several times while testing if you choose to leave the schraeder in.
-start the engine and take a reading.
-now take the throttle and snap it wide open and release it as quickly as possible. You don't want the engine to accelerate, you're trying to make it take in a large "gulp" of air, but releasing it before it has time to accelerate, so you must do this with the linkage by hand, not with the gas pedal, to do it quick enough.
-write down the reading at idle. repeat this for every cylinder.

Now compare your readings for every cylinder, dynamic, static and snap throttle test readings. The dynamic reading should be about half of what the static readin you had taken originally. The snap throttle test should be around 80% of the static compression. If the snap throttle test is much lower than 80% of static reading you have a problem on the intake side of that cylinder. If it is much higher than 80% if static reading you have an exhaust side problem.

This test works better than checking the vacum at the base of the carb, that looks at the breathing of the entire engine, not individual cylinders.

Dave

SY1 is offline  
post #6 of 39 (permalink) Old Dec 27th, 02, 06:54 PM
SY1
Senior Tech
Dave
 
Join Date: May 2001
Location: Michigan
Posts: 2,920
Vic,
Forgot to mention, I suspect you have a wiped cam as well, or other valvetrain restriction. If it is backfiring through the intake look for a bad exhaust lobe. I recently had 180 psi static comp, car ran fine with no load. With a load it would fire through the exhaust above 2500 rpm and made no power. Problem was a completely wiped out #5 exhaust lobe. The dynamic test along with the snap throttle test let me know exactly which valve was the problem before I tore it down.
SY1 is offline  
post #7 of 39 (permalink) Old Dec 27th, 02, 09:29 PM Thread Starter
 
Join Date: Dec 2002
Location: salinas, ca. us
Posts: 10
This is my first 69 camaro and am having a blast messing with it. I almost have the engine out of the car now.
I did not want to mess with it any longer.

I have owned a few camaro's and the wife is finally taking a liking to these car's.
I do certainly appreciate your input and am jealous of your knowledge of these motors.
Thanks very much.
vic



[This message has been edited by v8zone (edited 12-28-2002).]
v8zone is offline  
post #8 of 39 (permalink) Old Dec 27th, 02, 09:44 PM Thread Starter
 
Join Date: Dec 2002
Location: salinas, ca. us
Posts: 10
Wow!
This is one hell of a website. Excellent tech guys!!
I will do my best with your suggestion.
I'm more of the Just-pull-the-motor-and-put-in-a new-one kinda guy.
I love this 69 camaro of mine and am probably gonna end up putting together a 383 for it.
The boss (wife) gave me the OK.
vic
v8zone is offline  
post #9 of 39 (permalink) Old Dec 27th, 02, 09:55 PM
Senior Tech
 
Join Date: Nov 2002
Location: Aiea, Hawaii
Posts: 571
There's an old error of the cam being able to slide without a spacer to hold it solid. I'm not sure but I've heard of it with ford engines. I think it's a deal where the spacer is left out at the end of the cam and the cam sliding on it's bearing caues a change to timing since the distribitor gear is fundemental to timing and lateral movement changes your timing. Maybe maybe not. Also mechanical versus hydrolic cams being able to be accidently installed would be a fun one but getting way out there.
Snatchin'gears is offline  
post #10 of 39 (permalink) Old Dec 27th, 02, 10:01 PM Thread Starter
 
Join Date: Dec 2002
Location: salinas, ca. us
Posts: 10
Would that be the cam button?
I did not use one this time.
vic
v8zone is offline  
post #11 of 39 (permalink) Old Dec 27th, 02, 11:32 PM
Senior Tech
 
Join Date: Nov 2002
Location: Aiea, Hawaii
Posts: 571
If it goes at the end of the cam I'd think so. The story I heard was the guy wondered where that thing came from that fell on the floor disassembling his cam to put a new one in which new cams don't include the part. Hehehe. Life sucks when you don't know whats going on. Don't ask me how I know. It's allot of long stories. Anyway I was just reading on MSD Ignitions website about certain timing chain covers like the stock ones and chrome that if they have a buldge the cam walks forward which can run you like 20 negative in timing from their writing. That's probably a real cool in temp running engine right. Good luck.
Snatchin'gears is offline  
post #12 of 39 (permalink) Old Dec 28th, 02, 01:13 AM
Senior Tech
Eric
 
Join Date: Dec 2000
Location: Kentwood, MI
Posts: 8,097
Cam buttons are only needed with roller cams. They will not affect your timing either, the prevent a roller cam from walking back and forth in the block. The lobes on a flat tappet cam are ground with a slight angle that allows the lifters to rotate in their bore and keeps the cam pushed toward the back of the block.

Here are some symptoms of a bad cam lobe:

1) glitter in the oil

2) a rocker arm(s) that don't move up and down as much as the rest. To check, pull your valve covers, start the engine, and watch the rockers.

3) valve train noise, sounds like a rocker out of adjustment that you just can't seem to get set right.

4) engine pops back through the carb or exhaust when under load. "Breaks up" at high RPM.
Eric68 is offline  
post #13 of 39 (permalink) Old Dec 28th, 02, 09:01 AM
Senior Tech
 
Join Date: Nov 2002
Location: Aiea, Hawaii
Posts: 571
Well I guess you can make a rear view mirror ornament out of the factory cam button for the 383 rides and smile allot cruising. It kinda seems the parts installed were used since you say new back on my car and started it for a while and nothing seems to say what the exact parts were and the comments kinda seem like you might not of run the car for a season or so. I'm running too small of a set of heads for the 513 lift and 306 duration cam in the 350 I just bought. The engine likes to border on the mentioned problems at lower rpms. I'd think it might even be a good idea to check the distributor to carb vacume advance line. 60 cents for 2 feet of line to trim in isn't a bad price. There is always the age and quality of the fuel being burned from the tank. I'm not sure if you had the car sitting around but I'd drop some water disolving fuel additive to help get rid of any water that might be in there or just drain the tank if there is water in there. A clear inline filter might give a view of water pooled not blasting in at lower rpms. Mostly do the little things till you get that 383 in. Lifes no fun if the 383 shows the same problem. I also get a funny feeling every time I see somebody say their car backfires with out the mention of out the carb or out the exhaust. It makes a difference. Have fun.
Snatchin'gears is offline  
post #14 of 39 (permalink) Old Dec 28th, 02, 01:09 PM
Senior Tech
robert
 
rolling-robert's Avatar
 
Join Date: May 2002
Location: netherlands/waddinxveen
Posts: 1,114
sounds to me the distributor is not set correctly and/or the advance is incorrect
rolling-robert is offline  
post #15 of 39 (permalink) Old Dec 28th, 02, 04:37 PM
Senior Tech
John
 
Join Date: Feb 2001
Location: Maine
Posts: 3,099
I agree that you should ensure proper timing and carb adjustment before pulling the engine apart. It could be something much more easily fixed than a wiped cam.
boodlefoof is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome