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nkaminar · 03-19-2024, 05:26 AM

The best course of action when putting a new head on an engine is to put it on without a gasket and without nuts and turn the engine over by hand to see if the head rises when the pistons reach top dead center. If it does then you will need to re machine the pockets in the head for piston clearance. Best clearance is 1/16 inch. The gaskets compress so you have to figure that into your calculations.

A deep knocking is a main bearing. It will knock more when the engine is under load or being accelerated. A rod knock will happen when the engine is not under load, like at a fast idle or slowly being slowed down.

A high compression head needs far less ignition advance. If you are advancing the ignition to a point on the sector that you used with the old head you are advancing it too much. You have to search for the knee. Start with the ignition retarded and the hand throttle set to a fast idle. Advance the ignition one notch at a time until an additional notch does not increase the rpm. Retard one notch. That is where you should run the engine most of the time. You can retard one notch when the engine is lugging under heavy load and advance it one notch when cruising down a level highway. If you have a distributor with an automatic advance you will still have to search for the knee but do so by experimenting with different cam settings in the distributor. In this case a degree wheel and timing light helps.

To test whether the knock is coming from some place other than the engine, take the fan belt off and run the engine for a few minutes.

03-19-2024, 05:26 AM	#9
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 4,002	Re: Deep knocking sound The best course of action when putting a new head on an engine is to put it on without a gasket and without nuts and turn the engine over by hand to see if the head rises when the pistons reach top dead center. If it does then you will need to re machine the pockets in the head for piston clearance. Best clearance is 1/16 inch. The gaskets compress so you have to figure that into your calculations. A deep knocking is a main bearing. It will knock more when the engine is under load or being accelerated. A rod knock will happen when the engine is not under load, like at a fast idle or slowly being slowed down. A high compression head needs far less ignition advance. If you are advancing the ignition to a point on the sector that you used with the old head you are advancing it too much. You have to search for the knee. Start with the ignition retarded and the hand throttle set to a fast idle. Advance the ignition one notch at a time until an additional notch does not increase the rpm. Retard one notch. That is where you should run the engine most of the time. You can retard one notch when the engine is lugging under heavy load and advance it one notch when cruising down a level highway. If you have a distributor with an automatic advance you will still have to search for the knee but do so by experimenting with different cam settings in the distributor. In this case a degree wheel and timing light helps. To test whether the knock is coming from some place other than the engine, take the fan belt off and run the engine for a few minutes. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 03-19-2024 at 05:33 AM.