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| | | | Joined: Jan 2011 Posts: 138 Wrench Fetcher | | Wrench Fetcher Joined: Jan 2011 Posts: 138 | When I go to pull out of my parking spot and up the very slight hill in my driveway, sometimes my 283 spits back through the carb. It does not sound like a gunshot, its more like a sneeze or cough. the inside of the carb is covered in carbon because of it. Would the vacuum advance help this? It is not hooked up. Thanks
Alex
57' 3100 (The Bondo Bandit)
Bad rust and worse wiring, but so much fun.
| | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Yes the vacuum advance not working can cause this. Also check the initial timing. It might be slow. You might bump it up a little & see what happens. Check the accererator pump shot. It could be a low float level causing it.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Jan 2011 Posts: 138 Wrench Fetcher | | Wrench Fetcher Joined: Jan 2011 Posts: 138 | The timing was set at 12 degrees before tdc at 650 rpm or so (idle). With that initial timing it fell right on 30 at 4000 rpm. It acts a little better than it did before we did the timing, so your comment leads me to further believe that the vacuum advance is the culprit.
Alex
57' 3100 (The Bondo Bandit)
Bad rust and worse wiring, but so much fun.
| | | | | Joined: Nov 2006 Posts: 2,544 Shop Shark | | Shop Shark Joined: Nov 2006 Posts: 2,544 | Try pulling the choke out just a little. See if your sneeze goes away th.en | | | | | Joined: Apr 2005 Posts: 1,971 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,971 | Try pulling the choke out just a little. See if your sneeze goes away th.en YES! I usually see a carb sneeze as a lean condition. WHat do your spark plugs look like? | | | | | Joined: Nov 2002 Posts: 2,763 Carburetion specialist | | Carburetion specialist Joined: Nov 2002 Posts: 2,763 | A backfire through the carburetor can occur:
(A) When an intake valve does not seal (sticky, burned, etc.)
(B) When a cylinder fires out of time (ignition, valve timing, etc.)
Think about it. If the intake valve is not open when the cylinder fires, there can be no backfire through the carburetor.
Jon.
Good carburetion is fuelish hot airThe most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes!The Carburetor Shop | | | | | Joined: Feb 2011 Posts: 583 'Bolter | | 'Bolter Joined: Feb 2011 Posts: 583 | I had a 283 that didn't backfire through the carb, but (coughed). It ran fine at idle, but past idle it would (cough). It was caused by a bad exhaust lobe on the camshaft. The exhaust valve wasn't opening, so it would send the exhaust gas up the carb when the intake valve opened. Found the problem by taking the valve covers off and watching the rocker arms as the engine ran.
1939 Chevrolet Stake Truck
| | | | | Joined: Jan 2011 Posts: 138 Wrench Fetcher | | Wrench Fetcher Joined: Jan 2011 Posts: 138 | I hooked up the vacuum advace last night and drove it. It didn't backfire, but it normally did it only once about every 5 drives. So we will see. I did notice that it was MUCH easier to get moving. I kinda doubt it is running running lean because it smells like a gas station at idle and low speed driving from the tailgate lol. Oh and I have an electric choke so how could I leave it choked a little?
Alex
57' 3100 (The Bondo Bandit)
Bad rust and worse wiring, but so much fun.
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