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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Layne on August 02, 2009, 06:23:21 pm
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I just got my sb 400 put in and running. I took my truck to the shop to get an exhaust. I have duals with an H-pipe from hooker headers. I got a cheap-o carb at a swap meet which as far as I know it's a 750 Holley (too big?) Any way it was tuned and runs reasonable until I get my foot into it. It's like it cuts the power in half and it has a nasty popping sound from i think the carb. Also the temp on the engine is about 200-210, but I've heard 400's like to run warmer. Thing is, my 700r4 is at 220-240 when it warms up. Isn't it supposed to be around the same as the motor? Or do I need to get a trans cooler? Lastly, I set the tv cable, as it used to be on a straight six, and it seems to shift softer. I had the shop check that and they said my tv adjustment was ok? It's a 77 c-10 with a 86 700 r4 with a shift kit. Any input would be really appriciated. Thanks
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The back firing and over heating both seem to point towards a lean fuel mixture scenario. Pull your plugs and check them. They should have a tannish color on the porcelin, black would be rich, but from what you are describing, the electrode would look like the metal got real hot and have a bluish tint to it if its lean.
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Readjust your valves and set your timing. Tighten the TV cable one click at a time til it feels right. Trans cooler is a smart move and run a 180° thermostat
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The shop set the valves and I'm at 4 dergrees btdc per the book. Pulled the plugs and It's a light brown color and the electrode is silver. The porcelean is blackish brown. When I'm sitting there idleing and hit the gas, it smokes black at a high rpm while popping. Motor ran fine when i pulled it out of a 77 K-30.
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Black is unburned fuel. Address your carb. Advance your timing more too.
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probably around 8 for the timing? it seem to liven up a tad at 4, it was at 9, but maybe the power increase is in my head. Lol. Thanks Vile