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Discussion Starter #1 (Edited)
Just finalized my Vortec head swap and could only get the oil pressure up to 15psi. Decided to go ahead and try and start her up but I get backfire through the carb and no boom.

Pulled a spark plug and I can visibly see it spark. Gas is getting into the carb, hence the fiery backfire. I have my distributor set to what I think is one and I have gone over the spark plug wires numerous times. Everything seems to be okay but I cannot get any sort of actual firing up. All vacuum lines plugged, power booster, all ports on carb, and PCV.

http://youtu.be/CPF2oXuYzB4

71 Malibu, 350, Vortec Heads, Stealth intake, stock cam, Holley 780cfm vacuum secondary, 700r4
 

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Sounds like timing is way off. I'd start from beginning, verify tdc compression on #1, give it 10º-15º advance, and try again.
 

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Discussion Starter #4
Sounds like timing is way off. I'd start from beginning, verify tdc compression on #1, give it 10º-15º advance, and try again.
First thing tomorrow, that'll be the first step I take.

the valves may be to tight causing the backfire
How would I go about adjusting them? Just loosen the rockers a tad?
 

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Sounds like timing is way off. I'd start from beginning, verify tdc compression on #1, give it 10º-15º advance, and try again.
I once installed my distributor "180 degree" out... it would crank and then "boom", big backfire out the carb...

I set it with TDC #1, but wasn't thinking of "on the compression stroke"... Ah, the fun of youth :D

for a quick check, you can just move all the plug wires on the cap 4 positions and try again...

You can pull the drivers-side valve cover off, and bump the starter, watching the intake and exhaust valves for #1 cylinder... AFTER the intake closes, but before the exhaust opens, that's the TDC you want to set to...


Another thing to check; How sure are you of your balancers "TDC" markings being correct?
 

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Discussion Starter #10 (Edited)
I once installed my distributor "180 degree" out... it would crank and then "boom", big backfire out the carb...

I set it with TDC #1, but wasn't thinking of "on the compression stroke"... Ah, the fun of youth :D

for a quick check, you can just move all the plug wires on the cap 4 positions and try again...

You can pull the drivers-side valve cover off, and bump the starter, watching the intake and exhaust valves for #1 cylinder... AFTER the intake closes, but before the exhaust opens, that's the TDC you want to set to...


Another thing to check; How sure are you of your balancers "TDC" markings being correct?
I have been setting TDC at when I am on the compression stroke with valve covers off.

Do you mean to physically move the distributor wires 4 positions clockwise?

I am not completely sure of anything for this vehicle. I've discovered mismatched heads, use of non-self aligning rockers, plenty of metric bolts, and other oddities with my project so I would be putting good faith in that I can trust the harmonic balancer.
 

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I think your valve lash is too tight. There is an excellent technical reference here: http://www.chevelles.com/techref/ftecref17.html. Read this and compare to the procedure you used.

I don't like the "spin the pushrod" method of determining when there is zero lash. Too many times it's easy to compress the lifter causing incorrect lash. I like to grab the pushrod tip of the rocker arm and rock it while adjusting the nut. You can feel how much play there is and actually feel it going to zero lash. Also use a thin wall socket so the tool is not giving you a false feeling.

Also I don't like guessing about things by making changes that I don't understand the outcome. I would confirm that you are on #1 TDC by pulling the plug and checking for the compression stroke. Then confirm your distributor clocking and wire order. I stopped the video and looked at the wires in the cap and they appear correct if your distributor is phased correctly.
 

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Awesome video. That is one of the best feelings in the world. Good for you, Stewey.
 
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