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Discussion Starter · #1 ·
I recently rebuilt a 350 for my dads 85 suburban .Everything is stock exept the cam witch is a crane energizer 260H i believe. I cant get the darn thing to run right Im at my wits end :mad: . It has 150 psi compression on all 8 cylinders. and about 17 in of vacuum. So i took the spark plugs out to check them and the front two plugs on each side (1,3,2,4 Cylinders) were in perfect condition and the back two plugs on each side (5,7,6,8 Cylinders) were covered in soot (lots of it) What would cause this to happen. thanks in advance
 

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On some cams the Chevy fireing order is a little different...... Give the cam manufacturer a call and check on the fireing order.
 

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Discussion Starter · #4 ·
I double then triple checked the plug wiring (checked out ok). as for the cam i have the exact same one in my blazer and it runs good. i just can fiqure out why on the front half of the engine the plugs are good and the back half fouls them out
 

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One main thing that you dont want to overlook either is the condition of the trans vac modulator valve if equiped. When they go bad they allow trans fluid to be drawn into the intake usually affecting the rear cylinders.

Also insure intake is properly sealed also.
 

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Discussion Starter · #9 ·
there isn't a vac module on this one and i think the intake gasket is good i used a vacuum tester and sprayed carb cleaner were the intake bolts to the heads although i don't know if that is the right way to check just something my dad taught
 

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I guess one of the first questions to ask did it run right to start with at all or did it run poorly right from the start?

Other questions would be what plug gap are you running, ignition system, advance ect.

If this has not run right from the start I would start with the ignition system look inside the cap for condition. While the engine is running look down inthe carb primary and secondary and see if it is flooding at any point, also check this right after shutting off engine.
 

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You definetly have something somewhere that isnt right. It will run worse as time goes on as the plugs become more fouled. I would definetly start with the basics, recheck ignition, ohm spark plug wires, new plugs ( but ohm them first to eliminate adding a problem, should all be fairly even), may have to recheck valve lash settings. Make sure fluids arent mixing, coolant in oil or oil in coolant.
 
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