327 plugs randomly not firing-- help - Team Camaro Tech
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post #1 of 30 (permalink) Old Sep 17th, 06, 02:20 PM Thread Starter
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Terry
 
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327 plugs randomly not firing-- help

My newly built 327 (aluminum heads, hi rise, Holley, HEI ignition) has ran great for the first 800 miles or so. Suddenly began misfiring and popping. Several cylinders are taking turns not firing, first #1, then #4, then #8, #5, randomly. Low power and won't idle, engine shudders a little, classic signs of less than 8 cylinders firing. I've checked the obvious-pulled the plugs, they look dark but not too bad, swapped different spark plug wires. These are Vpower racing spark plugs, installed by my engine builder. I took off distributer cap, no visible cracking. The only change I made this summer was to install a 14 inch air cleaner, which when screwed down made contact with the top of two spark plug wires at the top of the dist. cap for a few weeks. Could this have messed up the ignition somehow? Anyone have any ideas?

Thanks in advance, Terry

Last edited by tmannet; Sep 17th, 06 at 02:50 PM.
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post #2 of 30 (permalink) Old Sep 17th, 06, 02:50 PM Thread Starter
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Re: 327 plugs randomly not firing-- help

Actually the air cleaner wasn't ON the plug wires, but it's real close:

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post #3 of 30 (permalink) Old Sep 17th, 06, 03:42 PM
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Re: 327 plugs randomly not firing-- help

When you installed your air cleaner, could your dist have been loose and moved your timing? May want to throw a light on and check it. Also look for a vac leak. Maybe a hose or plug came off.

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post #4 of 30 (permalink) Old Sep 17th, 06, 03:50 PM Thread Starter
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Re: 327 plugs randomly not firing-- help

I did have alook at it, distributer was marked w/ white paint, marks still line up perfectly although it could have moved very slightly... no vacum leaks visible...I'll keep looking.
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post #5 of 30 (permalink) Old Sep 17th, 06, 06:43 PM
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Re: 327 plugs randomly not firing-- help

Terry , did you try running it with the air cleaner off so its not touching the wires ? just a thought.

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post #6 of 30 (permalink) Old Sep 17th, 06, 06:49 PM Thread Starter
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Re: 327 plugs randomly not firing-- help

Jerry, no but I did put my old 11" air cleaner back on....I'm going to talk with my engine builder this week and see if he has any suggestions...
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post #7 of 30 (permalink) Old Sep 17th, 06, 07:50 PM
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Re: 327 plugs randomly not firing-- help

How did you know which cylinders weren't firing? You've got quite a bit of race components on it. If it's possible,try putting on stock items (module, coil, plugs,?) to see if you can eliminate a few other possibilities. Also, maybe connect a volt gauge directly to the 12v into the distributor to verify your getting full voltage.
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post #8 of 30 (permalink) Old Sep 17th, 06, 09:14 PM
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Re: 327 plugs randomly not firing-- help

I'd say check the power valve if the engine has backfired--Holleys are notorious for blowing them. It would make the engine run rich, idle awful and foul plugs. The erratic plugs misfiring isn't timing--you might have some kind of spark scatter going on if the plugs aren't fouling. This may sound nuts, but check the tip of the rotor to see if it's made contact with the firing lugs inside the cap and bent it out of position. This can cause crossfire. Good luck.
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post #9 of 30 (permalink) Old Sep 18th, 06, 04:03 AM Thread Starter
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Re: 327 plugs randomly not firing-- help

I did in fact check the rotor tip & center contact area....tell me more about checking the carb power valve, I'm an amateur when it comes to carbs-- I am going to pick up a fresh set of plugs & install...and recheck for spark.
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post #10 of 30 (permalink) Old Sep 18th, 06, 06:04 AM
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Re: 327 plugs randomly not firing-- help

Have you done a compression test? Simple and easy to do. This would ensure no blown head gasket.

Did you use a new timing chain and gears? Almost sounds like you skipped a tooth on the timing chain.

Most likely though, is simple ignition or fuel issue. As stated, check power valves. I just take them out and suck on them to make sure diaphragm is still intact, though all later model Holley carbs have blowout protection.

I see you're running HEI distributor. I have had plenty of problems with those. I would suggest swapping out distributor for another one, and just trying it out. I might suggest doing same with carb, just swap out and test. Also, check for vacuum leaks, bad vacuum hoses, intake gaskets, intake loosened up.

Could be you simply need hotter spark plugs. My car was loading them up in short order. I tested 3 or 4 different heat ranges, until I got a nice light color for my style of driving. The plug needs to have proper color to it. If it's black and sooty, then engine is running too rich, or the plug ain't hot enough..........

Here's a good site (with pics) for reading spark plugs:
http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

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post #11 of 30 (permalink) Old Sep 18th, 06, 08:24 AM Thread Starter
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Re: 327 plugs randomly not firing-- help

All good ideas...timing chain & gears are all new, HEI dist. is new, this was a $9,000 engine/transmission/header/component build-up and installation custom built for this camaro, so it wasn't a hack-job... The builder just told me this morning that perhaps that air cleaner up against the plug wires grounded them out, causing fouled plugs and then a no-spark situation...I'm going to look into all the above suggestions & post the results when I get the the bottom of it...

Thanks everyone- T.M.

PS Great spark plug site!
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post #12 of 30 (permalink) Old Sep 18th, 06, 09:52 AM
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Re: 327 plugs randomly not firing-- help

your ignition module might be going bad.
i had new modules go bad out of the box.
thats why i ditched the HEI and got a unilite distributor.
also makes more room .


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post #13 of 30 (permalink) Old Sep 18th, 06, 10:33 AM
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Re: 327 plugs randomly not firing-- help

Terry, after 800 good miles, what parts were new then is not a factor any more. something has failed, plain and simple.

I really hate to even go there, but you might check your valve adjustment.
Might also cut open the oil filter. A flat cam is not out of the question from your description.





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post #14 of 30 (permalink) Old Sep 18th, 06, 10:50 AM
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Re: 327 plugs randomly not firing-- help

I'm gonna guess he's got a roller cam setup in there.........

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post #15 of 30 (permalink) Old Sep 18th, 06, 09:59 PM
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Re: 327 plugs randomly not firing-- help

I agree with JimM--did you break the cam in? If you have any valvetrain noise you could have cam lobe going flat. That would make the engine run erratic, but the scattered misfiring still bugs me. In my humble opinion, the air cleaner shorting out the plug wires is out-and-out b-s, especially since you have new wires. The power valve is a simple thing--take the front bowl and metering block off and try a 65 power valve and a fresh set of plugs. My 2 cents.
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