Engine Knocking

[melfan]

I have a 1972 Thunderbird with a 460ci engine.

The car origionally ran on regular gas, I now use the 94 grade of gas but still have an engine knock. I have put octane boost but still have some knocking. It also has the "run on" problem after turning off the key.

I am going to have the timing adjusted but do not want to adjust it back to much becuse it will cause a power loss.

Can anyone suggest another fix?

[overl0rd]

How many miles are on it? It's not a bearing going south is it? If not, then timing is about the only way you'll get rid of it, if I'm not mistaken it should be 8 degrees BTDC at hot idle with vacuum advance plugged.

[97Bird]

You may have a carbon build up problem. We used to pour a small stream of water slowly into the carb with the engine at a fast idle to break it up. Pour too much at once and you will hydrolock the engine! As for timing, the specs I have show 6B for 3.00 axles and 10B for all others.

[melfan]

Originally Posted by overl0rd

How many miles are on it? It's not a bearing going south is it? If not, then timing is about the only way you'll get rid of it, if I'm not mistaken it should be 8 degrees BTDC at hot idle with vacuum advance plugged.

It has about 147,000. It has been maintained well and some parts (water pump) and others were replaced before I purchased it.

It does need a lot of TLC but overall in good shape. It does not knock at idle just when driving it.

It was purchased from Arizona and I figured the elevation diff. may be causing the knockiong so I figured the timing my be a good start.

I am a novice so I am still learning.

Thanks

[MagicRat]

Your 460 was a 'low compression' design. If it is running-on, you have severe carbon build up.

At this point, retarding the ignition may make no difference to the engine knock.

Try pulling the plugs. Do they look brown or ate they black? Are they oily or sooty?

The water trick as shown above can help, but only works with a hot engine.

Try spraying a full can of carb cleaner down the carburetor when the engine is at a hot idle. This will help remove some of the carbon off.

At worst, you may have to remove the heads and clean up the piston tops, combusion chambers and valves with a wire wheel.

[melfan]

Originally Posted by MagicRat

Your 460 was a 'low compression' design. If it is running-on, you have severe carbon build up.

At this point, retarding the ignition may make no difference to the engine knock.

Try pulling the plugs. Do they look brown or ate they black? Are they oily or sooty?

The water trick as shown above can help, but only works with a hot engine.

Try spraying a full can of carb cleaner down the carburetor when the engine is at a hot idle. This will help remove some of the carbon off.

At worst, you may have to remove the heads and clean up the piston tops, combusion chambers and valves with a wire wheel.

Plugs, points, wires, cap, rotor are all new. New fuel filter. Definately runs better after the tune up. Sprayed the crap out of the carb as well. Some of my problems may be due to many unconnected vacuum lines. I have been unable to locate a vacuum diagram and the factory one on the valve cover is gone.

I think my problems started when I put 89 octane in it for the first half tank, when I realized what I did and topped it off with 94 and octane boost.

I did find someone in my area who can work on this old of a car, but I will have to wait till the first week of January to get it in.

I never heard of the water trick but will ask him about it.

Thanks for all the great advice.

BTW here it is: