My Grandson thinks I know everything, but I'm stumped here. He and buddy changed distributor and carb on a 7o's era SBC along with wires etc, now he tells me it will only run at a 1000 rpm idle for 1-2 minutes before the exhaust manifolds and exhaust pipes turn cherry red and it's not running very smooth either. I thought wiring order but he say's it's checked and rechecked so ???? Help gramp's keep his reputation, any thoughts or help greatly appreciated, Thanks Ralphie
Timing. It’s opening the exhaust valve while the mixture is burning, allowing it to burn in the exhaust pipe. Sent from my iPad using The H.A.M.B. mobile app
Good evening, I would need a little more information. Did they go from a points ignition to an HEI? What is the vehicle? Is this the original motor to the vehicle? Older vehicles with points and coils had their ignition voltage cut down to 9 volts thru either a ballast resistor, or a resistance wire. He will need to verify he is getting 12 volts to the coil. To start, The 1000rpm, seems like the idle screw may be set too high. This could be the cause for the exhaust turning cherry red as it needs to have the carb adjusted and the idle turned down. Stock SBC like around 500-700rpm idle at 8 to 10 degrees advanced on timing. If it is a Holley carb, I like to turn the idle air mixture screws all the way in then back them out 1 1/2 turns. You can use a vacuum gauge to check everything and make sure when they set initial timing the vacuum advance on the distributor is plugged. The rough running can be multiple things from plugs, wires, air/fuel mix, a vacuum leak around base of carb or timing. Best thing to do is make a troubleshooting list and check off each one as it is verified. I hope this helps and can get you somewhere. Sent from my XP8800 using The H.A.M.B. mobile app
too retarded, it is firing with the exhaust valve open. that is why the manifold is red hot. verify firing order, then put a timing light on it....
Bad gasket under the carb, or a vacuum hose off causing a bad vacuum leak making it to run lean and hot.
Mark is right,,,,,timing extremely low will make manifolds glow . Hotrodmyk ,,,is correct as well . At least that is the first thing I thought of . Get the timing correct ,,then go from there. Tommy
Verify "0" or TDC on the balancer and pointer for accuracy, using a piston stop tool. When the #1 piston is at TDC on the compression stroke the distributor rotor should also point or be aligned with the #1 terminal on the distributor cap. There's a few different ways of getting the ignition timing turned around, but if you check it this way, it will be correct every time and should fire right up, maybe need a little advance - 10 deg. or so. If the timing is retarded or late the manifolds will start glowing real quick and may warp valves.
Just the opposite, retarded timing starts the fire late and it ends up burning in the exhaust. I had the mag slip (retard) on my race car and the headers were glowing cherry red.
Retarded timing. Advance the timing .When you get the timing correct, turn the idle screw out and slow the idle down. When you get the timing correct it will be idling even faster. JMO Lippy
Uncross #5 and #7 plug wires and check the firing order again. Advance the timing. Check for a vacuum leak, and/or proper float setting. Gene
If it is points ignition, now would be a good time to teach him the "magic black art" of timing a distributor with a test light.
Just heard from Eric, he and friend are landscapers and can't get to car till next Sunday, Thanks once again, Ralphie
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