good troublershooters needed

Old 11-29-2007, 07:07 PM
  #1  
chevysteve2
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Default good troublershooters needed

ready to pull my hair out.

I have a crate zz 502. everything is new on this motor. I changed the stock (224/236 @ .50)cam to a 236/242 @.50, put in roller rockers. The problem I have is when it hits 5000rpm it misfires. I have a mighty demon 825 cfm. I have a 6al box. I have changed the carb with a 850 DP and it still misfires. I sent the msd box back to the factory and they tested it and said it is good. MSD said that the box will work the same at all rpm, along with the magnetic pick up in the HEI distruberter. I changed out the coil with a another blaster 2. A friend said he thought I had weak valve springs. the stock springs have 135 at the seat. the comp cam springs that the camshaft calls for, have less seat pressure. the new cam has .20 less lift. I spent 700 bucks on a chassis dyno and tuner today and parts. My tuner could not figure it out. A visual check was peformed on the springs. The car runs excellent, good idle, but when it hits 5000 it falls on its face. Hp peaks at 3500 and slowly tapers off until 5000 it steeply falls off. The jettting was almost dead on, he fattened up the primaries to get it perfect. The A/F ratio stayed at 12 the whole time. He put in new plugs and wires and a new msd billet distruter. timing was at 34 total. nothing changed. The next thing I will do is put new springs in. Is ths a waste of money? Does any one have a suggestion?


thanx,
steve :arrow: :evil: :evil: :evil: :evil: :evil:
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Old 11-29-2007, 07:42 PM
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lanham
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Default switch

You should check what switches you have to your ignition.I had a similar problem with a high end miss and it ended up being the toggle switch to my ignition box.May not be your problem but a $5.00 toggle switch can be a nightmare too.
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Old 11-29-2007, 08:32 PM
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topsportsman1
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Whats the spark plugs gapped at?
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Old 11-29-2007, 10:05 PM
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gs97s10chevy
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what are you running for a stall?
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Old 11-30-2007, 01:13 AM
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cepx111
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First a question.
Did the motor misfire above 5000 before this cam change?

If it DID the problem is not in the cam change or springs pressure etc more than likely something else I.E. electrical bug somewhere in ignition.

If it did NOT misfire before then its definetly pointing to something in the cam change.
I. E. incorrect cam to crank alignment or inadequet spring pressure, improper valve installed height etc.
Sounds like not enough spring pressure for the cam to me, and just because the springs are new as you say in the motor doesn't mean they have the right spring pressure required for the cam you installed.
Its always a good idea to install new springs ANYTIME you install a new cam, saves headaches and give peace of mind when you do run into roadblocks such as this by simply eliminating major things like springs right off the bat.
However it could be something as simple as a cam being out of degree, I'd double check that then springs next.
Goodluck, Charles
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Old 11-30-2007, 06:18 AM
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gimmemud
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Almost deffinatley spring pressure.
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Old 12-01-2007, 12:19 PM
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SST4530
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If you have an eltronic tach,(most do) it could be shorting out at around the 5000 rpm range. I had this happen with a Mallory tach once. Almost never figured it out.
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Old 12-02-2007, 10:41 AM
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chevysteve2
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I checked all the easy stuff first, the ignition switch, the converter flashes out before 5000, I experminted with different plug gaps, and I disconnected the tach. Today I Ordered a set of springs and I will let you guys know what happens when they are installed. Thank you all for taking the time out to help.

steve :P :P :P
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Old 12-02-2007, 01:51 PM
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SST4530
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Hope the springs do it for ya!
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Old 12-07-2007, 10:45 AM
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john858
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could be your high side chip .
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