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Discussion Starter #1
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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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.
 

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

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Discussion Starter #4
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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Could be. Might be a loose rocker arm that's fallen off the valve, or a broken valve spring.
 

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Discussion Starter #6
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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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
Larry
 

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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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Discussion Starter #9
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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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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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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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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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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Discussion Starter #14
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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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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Have you checked the Vacuum lines from the carb. You had mentioned the carb rebuild. maybe you should pull vacuum from MANIFOLD instead of PORTED. Might help.
 

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Can you post a video of your vac gauge at idle then various loading scenarios up to it stalling out
 

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Also what's the best way to make sure the distributer is getting proper vacuum advance?
If was running ok before lets assume its the right VA for the job
To check, suck on the tube real hard, till it hurts and u will see the lever move... and it MUST hold that vaccuum.

And if the cap HT leads etc are ok.....then going on everything else I tend to agree with a the wiped cam lobe thought.
And triple check the timing order... go as far as to get the missus....and get her to check the oder and where they go.. by her self....

I assume this is a basic engine with hydrolic lifters ...
I have a couple old tin tappet covers with a strip cut out in the middle, just enough to drop a modded ring spanner and screw driver into....
This stops the oil mess everywhere
park the car on the flat... not uphill or the pooled oil will run down the back of the block
Drop the cut cover on and have it sit straight.. no need to bolt it down.
Fire the engine up and set to a slightly high idle
back off the lock nut, then slowly back off the adjusting screw till starts to "clank" then slowly , so engine doesnt stall tightened up till "clank " goes, then another 1/2 or 3/4 turn.. which ever u prefer..or 1/2 what between.
If a lifter is already clanking do that 1st... a mechanics stethoscope with the good tappet covers still on will get u within 2 possible lifters to check 1st... if these or any one needs excessive adjustment then u have a cam lobe run.
 

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Discussion Starter #19
Ok, I adjusted the left side valves with the cover off and engine running and they all seemed to need at least a little adjustment. Also seems like the headers are leaking a little in the back so that made it a bit harder to hear the tapping but I could also feel it in the socket when it started. I'll look into the leak in the header a little later and adjust the right side tomorrow. It got a little messy but not too bad. I also changed out the fuel pump for good measure since they are so cheap and replaced part of the fuel line. Also changed the filter though the old one did not seem plugged at all. Hoping after all this tomorrow I will know more. Thanks for the help. I'll post tomorrow. Also the Vacuum seems to be pulling when I suck on the line manually. Just feeling the lever with my hand. Can't really see it very well.
 

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Discussion Starter #20
Update today. Stared just fine this morning. I wanted to check the adjustment on one of the lifters so I loosed just the one until it started to tap and then started to tighten 1/2 turn and it died. Typical I probably went to fast. Problem is it will not start again. Sounds like it wants to but never fully turns over. Checked for spark an I'm getting spark though it's not a solid blue. Plugs are wet from fuel so I pulled them all and cleaned them off. Let car sit for about an hour and tried again. Still nothing.
 
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