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350 Vortec Fouling Plugs

1057 Views 11 Replies 5 Participants Last post by  Aaron
Guys need some help. Recently acquired a sbc 088 Vortec engine with unknown cam. It had been sitting for about a year and the carb was in need of a rebuild but ran decent. Long story short I’ve replaced everything that bolts to the long block. It ran decent for a few miles and then the plugs turned black and sooty. I’ve verified timing with a tdc tool as the balancer mark was off. Now when I blip the throttle it want to sputter back thru the carb and shoot the occasional flame. I verified timing again and then pulled the plugs and noticed how black they are. Need some advice. Specs below.

350 Vortec with 1.54 pistons (so I assume they are .045 in the hole and horrible quench unless previous owner milled the block more.

unknown cam but it’s mild as the Vortec springs appear stock.

Quickfuel 650-q carb (stock and the accelerator pump shoots good as soon as I give it throttle)
Accel HEI distributor
Summit wires
Ran TR55 plugs gapped at .045 but just purchased some 3926 to try a hotter plug.
edelbrock rpm intake
Hv oil pump (60 at idle)
6.5 psi fuel and floats are in the center of sight glass.

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1 - 3 of 12 Posts
The QF carb is the problem, they have a very rich idle circuit.
What would be a good easy tunable great outa the box carb under $500? . Aside from ls swapping it I’m hoping a carb swap would do it. Worst case changing the jets.
A Holley 4777 650 dp would work good out of the box. You can fix the QF carb but it takes some time to get it right. The jetting on a Holley 650 should be pretty close out of the box, also the FST 650 works very well also that's what I have on my 350 Vortec engine right now. Floats were set right and the idle mixture and speed settings is all I tweaked. A very good carburetor.
Just switched to an avs2 and it does much better and no fuel smell. I switched to autolite 3926 plugs. Any issues running these in Vortec heads?
Other than cracks they are great heads, best production head GM ever made for a SBC.
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