at a DEAD END! (help) - Team Camaro Tech
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post #1 of 24 (permalink) Old Aug 30th, 13, 08:04 AM Thread Starter
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Dan
 
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at a DEAD END! (help)


Ok, a little background first, this is what I am working with:
327 punched .030 over 11:1 .194 heads
750 double pumper holley
accel ignition sysem (box)
cam is .324 duration and .530 lift
headers
**major rebuild on the motor 20 years ago, and was running fine until last late last fall. It is now running rough, it has a miss that I can't pin down. No response...no power. It run's but not very well. It will get from point a to point b but it is running sour. It doesn't overheat either. I am coming to the forum because I have tried the following things without success:
1. new plugs and wires (old plugs looked in good shape)
2. new cap and rotor
3. had the carb checked out
4. compression test on all cylinders. all tested 150-160
5. pulled valve covers and checked to see if the rockers were making a full sweep (no missing lobes on cam) checked out ok.
6. new fuel filter
7. checked all wires and connections

**there seems to be air coming back out through the carb when it's running and you go to give it fuel. Almost like it is expelling air instead of sucking in fuel. any ideas?
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post #2 of 24 (permalink) Old Aug 30th, 13, 08:17 AM
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Re: at a DEAD END! (help)

How many miles on the motor since that 20 year old rebuild?

I'd check for timing chain slop and make sure the timing between crank and cam is still where it's supposed to be or did it possibly jump. If there is no or minimal slop, unlikely it could have jumped. If there is enough slop, that could be the issue?

I'd also make sure the components of the ignition system that you haven't already replaced or checked were working properly.

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post #3 of 24 (permalink) Old Aug 30th, 13, 08:19 AM
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Re: at a DEAD END! (help)

was the carb taken apart?
fuel pressure
vacuum leak
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post #4 of 24 (permalink) Old Aug 30th, 13, 08:28 AM Thread Starter
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Re: at a DEAD END! (help)

carb was taken apart. yes. Carb also had a rebuild less than 4 years ago. I have not replaced the "accel" ignition box yet at this point. Is there a test you can run to check those? Do those normally have issues? Thanks for the input.
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post #5 of 24 (permalink) Old Aug 30th, 13, 08:29 AM Thread Starter
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Re: at a DEAD END! (help)

also, only about 5000-7000 miles since rebuild.
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post #6 of 24 (permalink) Old Aug 30th, 13, 08:47 AM Thread Starter
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Re: at a DEAD END! (help)

also checked all vacuum connections. No leaks that we can tell. Sprayed around the intake manifold to see if there was a leak there. No leak.
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post #7 of 24 (permalink) Old Aug 30th, 13, 09:17 AM
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Re: at a DEAD END! (help)

With only 5k to 7k miles since the rebuild, a worn and/or jumped timing chain is very unlikely unless there was/is a problem with the parts that were used and by that I mean a manufacturing defect that showed itself since engine assembly. Wouldn't hurt to check for slop just to rule it out, it's relatively quick and painless to check for.

I'd definitely investigate that Accel ignition box and coil, don't know of a specific test for it but perhaps someone else will have a suggestion for you.

Do you have any other known good ignition setup(s) you could swap in to see if it makes a difference?

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post #8 of 24 (permalink) Old Aug 30th, 13, 09:41 AM
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Re: at a DEAD END! (help)

For the carb to be blowing air out it sounds like it might be a stuck intake valve. However I think a compression test would have indicated that if you had a stuck valve. A timing chain breaking or having some issue could also cause this. Try running some amsoil power foam or seafoam thru the carb while its running to see if it un sticks a valve that might be sticking. If that doesn't work you may need to look at the timing chain..
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post #9 of 24 (permalink) Old Aug 30th, 13, 09:42 AM Thread Starter
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Re: at a DEAD END! (help)

I don't have another system. But the Accel has been on there for years. I was thinking maybe "bad" or "old" fuel also. This car is not driven a lot. And sits over the winter. I do put Stabil in it but, some of the fuel could still be a year old or so.
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post #10 of 24 (permalink) Old Aug 30th, 13, 09:43 AM Thread Starter
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Re: at a DEAD END! (help)

I will also try the seafoam to see if that is the problem. Thanks Dan
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post #11 of 24 (permalink) Old Aug 30th, 13, 09:50 AM
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Re: at a DEAD END! (help)

Hate to say it but it really sounds like a motor that has "jumped timing". I would be careful about running it too much until I looked at the timing chain, valve adjustment, etc.
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post #12 of 24 (permalink) Old Aug 30th, 13, 10:24 AM
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Re: at a DEAD END! (help)

A quick check on timing chain slack is turn the engine by hand and align the h/bal mark with 0 on the scale.
Now turn in the opposite direction until resistance is felt.
If more than 10, replace timing set.

If ign timing has changed, and a point set is being used for triggering the box, I would wager the rubbing block is worn, reset point gap/dwell.

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post #13 of 24 (permalink) Old Aug 30th, 13, 10:55 AM
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Re: at a DEAD END! (help)

I agree with the stuck intake valve suggestion.
Pull the valve covers and take a look..

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post #14 of 24 (permalink) Old Aug 30th, 13, 12:25 PM
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Re: at a DEAD END! (help)

Put a timing light on it. If the timing is way off, your chain jumped. Like Scott said, you would expect that at 7k miles, but stranger things have happened. I have seen nylon gears let go during the warranty period on GM cars back in the 70's.

It that is OK, then PERHAPS (but not likely) you have a poor fuel issue. Easy enough to drain it out and put fresh fuel in.

Highly unlikely an intake valve (or exhaust for that matter) is stuck. You said all rockers were making a full sweep, so it would have to be stuck OPEN. If it were OPEN, you would have 0 compression on that cyl., not the 150 to 160 reported.

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post #15 of 24 (permalink) Old Aug 30th, 13, 12:38 PM
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Re: at a DEAD END! (help)

Easy way to check if it's bad fuel is to disconnect and plug the car's fuel line that is usually connected to the carburetor. Next get a temporary gasoline container (from a quart to a gallon in size) and run a fuel hose from it to the carburetor. Hang this temporary fuel supply from the front of the hood and let gravity feed the fuel to the carburetor. This should be enough to notice if fresh fuel changes the way it runs without draining the entire system down. Keep a fire extinguisher close by just in case.

I'm still leaning towards a timing chain issue or ignition issue due to the results of your compression test and your visual inspection of the rocker arms and valves.

Do as Everett outlined to check for timing chain slop/stretching.

69 Camaro Z/28 RS, original Azure Turquoise, M21 & 3.73 12-bolt posi. NOM 406ci, AFR 210 heads, Straub hyd. roller cam & Dynatech 1-3/4" > 1-7/8" headers, QuickFuel 750 Annular. Photos at:
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