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.

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....

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68 Coupe, 350 4-speed
Jim's Camaro Corner (http://www.personal.psu.edu/jxu109/)

You will also notice several rockers out of adjustment. and glitter in the oil.

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67 prostreet BB Camaro The Combat Rat
80 z28 Camaro 355ci
71 BB SS Chevelle (clone)
2002 35th anniv SS Z28 conv.

I'll check into that.
Thanks guys.
vic

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

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.

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).]

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

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.

Would that be the cam button?
I did not use one this time.
vic

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.

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.

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.

sounds to me the distributor is not set correctly and/or the advance is incorrect

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.

Vic,
If at all possible before you go ahead and pull the motor, do the dynamic check and snap throttle check in my earlier post. It'll only take you 40 minutes or so and afterwards there will be no doubt if it's a cam or not. Plus you'll see how each individual cylinder is breathing, you might learn something about the motor in the process that could sway your decision about it.

Dave

1. car was parked for some time...year or so.
2. New cam and lifters, fresh heads, new gaskets, new performer intake and plumbing (hoses), new wires, new distributor w/cap and rotor. New gas tank, fuel lines and fuel pump (had rust). I should have got a new carb for it.
I fired it up for about 10 seconds and was startled by a loud exhaust leak. I shut it off and looked for a header bolt that I may have forgot to tighten. I checked them all and found them all to be OK. I started it up again for another 10 or 15 sec. and noticed I had forgot to plug the small port on the pass. side of the intake. I found the small rectangular cover in the box that the intake came in. I secured the cover on the opening and started it up one more time. It sounded nice and healthy. I did have a couple of backfires through the carb and the exhaust.
After a brief warm up, I try to take a drive in it. NOO WAAYY. Well, it does run OK..as long as you don't try to accelerate. It falls flat on its face. When I try to accelerate, I get the sensation that I am stepping on bothe the gas pedal and the brake pedal at the same time. The car wants to take off, but it feels like something is holding it back. WEiRD. Since I did have a rusted out fuel system when I got it, I did borrow a friends holley and had the same result.
I guess I will play with it a little more before I yank it.
keep em coming.

You could always take it to a dishonest mechanic and when he tells you what he is going to replace you'll know what your problem definately isn't by what he is going to take you for first. Just an idea.
If you have power brakes check that big hairy vacume line for a good seal and possibly check to make sure it isn't full of water. Maybe the trans is freezing up auto or 4spd. I'd hate to think your compression is so high your going to need to dump octane boost in all the time. What heads did you use? We are all lost with ya on this problem.
OH yah. If the fuel pump had rust it might be shot for really making fuel flow.

[This message has been edited by Snatchin'gears (edited 12-29-2002).]

It will slowly get up to speed, but it will not let me get there fast. I have to accelerate slowly. I'll get up to 25 mph and hit the gas and it just makes a big whoosh sound as if it is wanting to go but it is choking or something. After a while it runs like crap and sounds as if a couple of plugs are not firing any more.
stock 194 heads.
Fuel pump is new.
TH 350

did you follow a proper cam break in procedure? All you mention is a "brief warm up." To run in a new cam you need to bring the car up to a good 2500rpm instantly once it starts and keep it at that engine speed for a good 25 minutes. This will ensure good oil propogation and splash oiling to the cam to keep it from going flat. The run in period allows the cam and lifters to mate to one another via a polishing process on the lifter surfaces.

If this is a hydraulic cam, I would try adjusting the valves with the engine running and warmed up before I would start tearing things apart. It sounds to me like the valves aren't adjusted properly. If he had a wiped lobe and hasn't adjusted the valves since break in, the engine should be clacking like Hell. I don't think it's the cam.

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Bob
Garnet Red 69/SS396/TH400/355 Posi ( 454 now)
94 HD Dyna Wideglide

Actually I had this problem myself and one exhaust lobe was wiped out completely. It looked perfectly round. Engine made no noise, idled fine, only when you came up on power did it backfire badly through the intake, because there was no where for the charge to go other than back out the intake.

With a cam lobe worn away the rockers won't make any noise, because it is just like they are never coming off the baseline, same as when they were adjusted new. Unless it continues to wear well below the base circle of the cam, past the point that the lifters were preloaded to, then the rocker will get noisy.

I know this ones reaching... But this Summer I lost a pushrod on # 7 and got simular behaviors... Pull the valve covers and do some initial inspections. If any of the lobes are wiped, you'll find loose rockers and possibly pushrod/pushrods disloged from the rocker are itself. When mine went it forced the pushrod into the back of the head and bent it, however I caught it in time and only had to replace it at a cost of $2.49? I've never had issues with it after the fact and yours could be something this simple.


Best of luck and keep us posted.

Regards,
Tom

I honestly did not do the proper break-in procedure. I did fire it up the first couple of times. Each time it could not have been on for more than 10 seconds each time. I think that may have been when this happened.
On the third start, things sounded good and as foolish and anxious as sometimes I can be, I just wanted to get in it and go.....not cool!
I do know proper break-in procedures, but I did not follow them. Stupid stupid stupid!
I'll keep ya posted.
vic

What about your ignition timing? Is it set right? Sounds more like timing than a cam lobe. When I toasted an exhaust lobe it would run fine until you got on it.

Vaccume behavior will tell you if you fried one or more lodes on your camshaft!

An erratic vaccume that pulses is an indication of improper valve opening (or not)in the case of lobe failure.
take a vaccume reding and describe the behavior of the needle at idle. Someone will surely point you in the right direction once the idle vacuume behavior is knowm,

thx
joe c

The distributor has been removed a couple of times and has had the timing adjusted a few times.
I also had a friend of mine re-adjust the valves again.
I have not touched it in a couple day's.
It's been raining here on the central coast.
I'll get on it maybe tomorrow.
vic

This isn't very nice of me but maybe you have a valve spring or two that is stacking or too close of a tolerance. A real whammer jammer treatment for the cam and valve train. Isky's site has info on finding this problem if present. Just in case you have double spring and somebody local did the heads. It would answer why right away there was a problem.
THE CHECK FOR RETAINER-TO-GUIDE INTERFERENCE http://www.iskycams.com/camshaft.html
Have you watched the timing while reving with and without the vacume advance tube to the distributor?

Does this car have dual exhaust all the way to the back? Sounds to me like a very restrictive exhaust? Try running open headers just for a test. Good chance it's something else but this is a cheap fix if is the problem. Good luck, Barry.

Someone already mentioned this, but I honestly think that the cam break in procedure (or lack thereof) has caused your problem. Im more than willing to bet that the cam is wiped out. I know thats not what you wanted to hear, but thats probably what happened.

Sorry guy : (

Ouch. Anything but that doctor. I'm sure we are all hoping it's something simple. I sure hope it is. The only solution is going bigger cam. I think maybe if it is the cam and it was a big one our pal V8 needs some history on what's going to be going on after start up. My cam is a little rough hehehe just a little like 2K it smooths out. When advertised rpm range is listed sometimes they aren't lying one bit. It might be a case of untill a certain rpm the engine is going to running pretty rough. Possibly next time go for broke with the break in no matter how rough things are getting up to the rpm.

are they solid or hydraulic lifters? did you lash them properly before you fired it up for the first time? if you tightened them too tightly, then i would say for sure that the flat edge of the lifter dug into the lobe and shaved it off. this brings up another question; did the cam you replaced have a roller profile? on these profiles, there is a slight indentation right before the opening and closing ramps of the lobe. with a flat tappet lifter, the edge of the lifter will go into this indentation and shave the lobe away. like some of these other posts said though, dont overlook the obvious. could be something simple. i would do the Dynamic comp. tese like SY1 said earlier. this will either rule the cam out or will find out if the cam is at fault.

he said it runs worse when warmed up, so i think it may be timing. when we said " I'll get up to 25 mph and hit the gas and it just makes a big whoosh sound as if it is wanting to go but it is choking or something" that sounds like the timing is way off to me.

Vacuume, vacuume, vacuume!

I have national guard this weekend and might miss the big conclusion of this mystry even though a wiped cam wouldn't be to mysterious. Anyway we need to get budweiser to sponsor a team of mechanics to travel the globe chasing trouble shooting posts here in an effort to get big advertising and keep the races going. Anyway the suspence is killing me. I hope the firing order was double checked. My 71 with an transplanted hei distributor has me going since number one just doesn't seem to be right being the one plug 2nd from the two on the point. You've got me but that's how the book looks and it was wired when purchased a few weeks ago. Hehehe hopefully the fuel pump isn't sucking on the fuel tank return line. That would be something I'd do.

[This message has been edited by Snatchin'gears (edited 01-10-2003).]

Start with the basics before you tear down your engine.If it were me the first thing i would do would be to install a fuel pressure guage to make sure you are getting enough fuel since you said that your fuel system was rusty?You might have debris in the line.Then i would check the ignition system and then do the dynamic test as stated in the earlier post.If you rule out fuel and fire then it has to be a mechanical problem.

v8zone,
new to the site,if you are still having the problem and could use a fresh set of eyes
let me know.
these guys are pretty sharp here.lots of good ideas on checking.
i've built a fair amount of engines for own
cars and some local roundy-roundy racers

I have not touched the car or checked out my post in a couple days.
Been very busy out of town and have not had time for the beast.
Next week I will have time to lift the hood.
Hey, R/S Bill, maybe I'll take you up on your offer. Next week I'll be working on a job closer to home off highway 68. I don't live far from there.
The cam was lubed and installed like any other cam with new hydraulic lifters.

v8zone,
just e-mail me and let me know
be happy to give it a shot
bill