FIRES INTO HEADERS - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 9 (permalink) Old Mar 12th, 00, 12:21 PM Thread Starter
 
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thanx in advance for any help. I have a 69 Z28 with a zz4 350. problem is that it fires into the headers from cylinder #8. if I pull #8 plug wire it stops the misfire so I know it's #8. I have new rotor and cap and plug wires since problem srarted. Have adjusted the hydraulic lifters. compression is oK, timing is OK. had heads ported/polished etc. last summer and it ran fine after that. how do I diagnose a bad hydraulic lifter or a valve that is hanging up on me?
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post #2 of 9 (permalink) Old Mar 12th, 00, 12:31 PM
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How do you know it is misfiring into the header? Is the header glowing?

It could be that your mixture is too rich...
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post #3 of 9 (permalink) Old Mar 12th, 00, 01:01 PM Thread Starter
 
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I can feel the blast of exhaust when it misfires coming out of the headers. when the engine warms up the misfire substantially deceases it's frequency
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post #4 of 9 (permalink) Old Mar 12th, 00, 01:50 PM
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It could be a sticking lifter or valve. When the engine is cold, the lifter piston should move when pushing down the pushrod. It should move 3/16" to a 1/4" freely. If it checks out good, then try pushing down on the exhaust valve stem and feel for sticking/binding on the return. Take a piece of flat bar, measure the distance from the valve tip to the rocker stud. Drill a 7/16" hole in the flat bar where the rocker stud measurement is. Now use the flat bar as a lever setup to depress the valve stem. Be careful to press on just the stem tip and not the spring retainer or you'll end up removing the head to retrieve a valve.

Just my .05 worth

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67 Camaro LS6 454/TH400/12bolt 3.73

[This message has been edited by cardude (edited 03-12-2000).]
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post #5 of 9 (permalink) Old Mar 13th, 00, 06:10 AM
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Put a vacuam guage on it. If it's a bad lifter, you may see the guage fall when it misfires.



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post #6 of 9 (permalink) Old Mar 13th, 00, 03:19 PM
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I thought ZZ4 motors came with roller cams??

I would make sure the timing is correct.

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68SS ZZ4, 4sp T-10, 12 bolt, getting painted

78Z28, 330hp vortec, TH350, 10 bolt (just finished)
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post #7 of 9 (permalink) Old Mar 13th, 00, 06:10 PM
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Check the compression on that cylinder. That will be a good indicator as well.

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post #8 of 9 (permalink) Old Mar 15th, 00, 12:55 PM
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ZZ4 crate motors do come with hydraulic roller lifters. It's NOT a worn cam lobe because GM uses billet steel roller camshafts.
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post #9 of 9 (permalink) Old Mar 16th, 00, 04:29 AM
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Good point, could it be something as silly as a misadjusted lifter (rocker arm) on the exhaust valve not allowing the valve to close?



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