Dies under power - Team Camaro Tech
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post #1 of 40 (permalink) Old Nov 25th, 14, 05:23 PM Thread Starter
Rick
 
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Dies under power

I've got a 67 327 275 Hp. Used to run great after a rebuild on the quad jet. A few weeks ago it started to die or drop out for a second before picking up when I would push the gas. I checked timing which was about 8B and vac was around 15 at idle.

After that everything just went to the crapper. Can't even drive it now. Just dies and sometimes backfires. I can't get more than 10 on the vac gauge now at idle and really turning the screws does not make that much difference until I turn them far enough that the car dies. The timing is the same as before but I am hearing a decently loud valve tap from the motor. I can rev the motor while in P or N but once it's under load it's over. Exhaust even sound different now. Wondering if there is a way to tell if I lost a valve by just taking the valve cover off. I'm an OK backyard mechanic but not sure how to check the valves and how much play they should have.

Any help would be great.

Thanks
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post #2 of 40 (permalink) Old Nov 25th, 14, 05:33 PM
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Re: Dies under power

I'd check for a vacuum leak before digging into it too far. Likely culprits are disconnected vacuum hose, gasket inner the carb, distributor vacuum advance canister, intake manifold gaskets, vacuum modulator on transmission (if it has one). Hope it's something simple.

69 RS, Hugger orange/black, Deluxe interior, Sony AM/FM/XM/CD, PS & PB. 355, forged pistons, Eagle rods, balanced, Iron Eagles, 9.4:1 CR, .038 quench, XR270HR Cam, Z28 intake, FAST-EZ EFI 2.0, Thorley Tri-Ys, TCI 700R4, 2400 stall, 3.42 posi
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post #3 of 40 (permalink) Old Nov 25th, 14, 05:59 PM
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Re: Dies under power

Could also be the accelerator pump in the Quadrajet. Look for a rebuild kit that is ethanol resistant.


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post #4 of 40 (permalink) Old Nov 25th, 14, 06:01 PM Thread Starter
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Re: Dies under power

What has me worried is I was getting 15 inhg before at idle and now its dropped to 10 or less. Makes me think it might have something to do with the internals of the engine.
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post #5 of 40 (permalink) Old Nov 25th, 14, 06:07 PM
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Re: Dies under power

Could be. Might be a loose rocker arm that's fallen off the valve, or a broken valve spring.

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post #6 of 40 (permalink) Old Nov 25th, 14, 06:16 PM Thread Starter
Rick
 
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Re: Dies under power

Maybe it's time to take the cover off and take a look. The Rebuild on the carb is only two month old so I'm thinking that's not it.
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post #7 of 40 (permalink) Old Nov 25th, 14, 06:39 PM
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Re: Dies under power

Do you have any rubber fuel line?? Many years ago I had a race car that it would sit and Idle for ever But If you pushed the gas peddle down or tried to leave the starting line it would die. fought it for several months. finely found a torn piece of rubber inside a piece of steel braded hose. with little fuel all was fine but under a hard leave It would die. I now change fuel line every 2 years
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post #8 of 40 (permalink) Old Nov 25th, 14, 07:07 PM
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Re: Dies under power

New set of spark plugs and HT leads, also look at a cracked dizzy cap/ rotor.. usually because the cap has not been aligned and clipped own correctly THEN double checked it is.

And return every thing back to how it was....

And/or clean/ replace the fuel filters and crap in the carb

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post #9 of 40 (permalink) Old Nov 25th, 14, 07:36 PM Thread Starter
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Re: Dies under power

Put some new plugs in a couple month ago but I'll check them. Cap looks good. It's and HEI system. Could be fuel but strange thing is still the drop in vac at idle. You would think if it was fuel that would not show up if the motor was idling ok.
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post #10 of 40 (permalink) Old Nov 25th, 14, 11:50 PM
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Re: Dies under power

Pull the valve covers and take a look. Never heard a vac leak cause a loud tapping sound? Exhaust leak yes but vac leak?? Sounds like a valve train issue.
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post #11 of 40 (permalink) Old Nov 26th, 14, 05:57 AM
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Re: Dies under power

Check the easy stuff first. As stated, check for vacuum leaks around the carburetor base gaskets, vacuum lines, even the PCV valve. Check that your vacuum advance is functioning and not stuck. Verify that you are getting sufficient fuel volume AND pressure when under load. After you rule out those items, then I would start pulling plugs one at a time to see if there are any obvious signs of a problem - fouling, misfiring, oil soaked, etc. If the plugs check out ok, then I would pull the rocker covers and look at the springs, rocker studs and rocker arms. Check for loose or broken rocker arms, pulled rocker arm studs ( put a straight edged across the tops of all of the rocker studs ,they should all be at the same level), broken valve springs, anything that looks unusual. Our cars are simple machines, they need fuel and spark to run properly. Many issue's can be traced back to these points. I can tell you from personal experience, that when a fuel pump is on its way out, the engine will fall on its face when you try to put a load on it. Again, easy stuff first. Check the fuel filter, accelerator pump shot, and fuel lines. Make sure that everything is clear and functioning. After you go through the fuel system, check the plug wires, cap, rotor, and points if you have them. I hope this will at least get you started on the right track. Let us know what you find. Good luck.

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post #12 of 40 (permalink) Old Nov 26th, 14, 07:54 AM
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Re: Dies under power

If you disconnect the coil and take the valve cover off, have a friend crank the car. You will see the rockers going up and down fully. If you notice that one is not opening and closing all the way, you might have broken pushrod or wiped a cam lobe . You might get a little oil mess so be preprared. Just a suggestion to rule out the valve train.
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post #13 of 40 (permalink) Old Nov 26th, 14, 08:51 AM
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Re: Dies under power

The symptoms you list and the fast deterioration of the engine's health are the classic indicators that your cam has lost a lobe, most likely an exhaust lobe. Certainly pull the valve covers and observe rocker movement as you turn the engine over. You are likely to find one very loose rocker with a pushrod showing less travel than the other int or exh pushrods. If so, put a new cam on your Christmas list. I recommend the Crane 272H10 for a torque upgrade without an aggressive idle.

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post #14 of 40 (permalink) Old Nov 26th, 14, 09:47 AM Thread Starter
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Re: Dies under power

Thanks for the suggestions. I pulled the valve cover and a few of the rockers are very loose. I don't see any broken springs or bent rods but that's not saying they are not bend where I can't see them. I'm going to take a look at it while running the motor later today. I'll try adjusting them at the same time. Also what's the best way to make sure the distributer is getting proper vacuum advance?
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post #15 of 40 (permalink) Old Nov 26th, 14, 10:00 AM
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Re: Dies under power

You can manually put a vacuum source on the canister and observe if the rod has full movement. Some canisters were adjustable through the port with a hex or jewelers screwdriver so a PO may have cranked it down or up and you may be able to restore the default without replacing the unit.


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