I got original 2F in my truck and for a while it developed some knock...When driving with gas pedal light it is ok but when I push it more it knocks..I looked for exhaust leak but don't see it...Is there any way to find out if it is exhaust leak ?Like vacuum test for example?Thanks for opinions....
Exhaust leak?
- Thread starter drnekFJ40
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Oil level ok? A knock usually is top end, valves.
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Oil is good..It does have a plenty of power otherwise....If I go on the higway and take gas pedal of it runs good but if I push it more it knocks ....What to check?Valves are knocking some,but I think is normal...
Valves tick, rods knock...
Are you sure it is a knock and not just pinging? Low octane fuel with too much carbon buildup (increased compression) or too advanced timing will cause pinging. Try running higher octane fuel and see if the knock or ping subsides or lessens. If it does try running some cleaner through the system that will break down the carbon buildup and lesson the compression and you should be able to go back to lower octane fuel. Or, you may need to retard the timing some.
If you want to test for an exhaust leak, an old trick I've used in the past is to use a clean shop vac. Situate the hose so that the vac is pushing air, not sucking. Hook the hose up to the tail pipe, and use duct tape to seal it. Get a mixture of soapy water in a spray bottle, turn on the vac, and start spraying the soapy water around the manifold, and any junctions. It'll blow bubbles anywhere there's a leak. Might be a little ghetto, but it works! 
- Josh
- Josh
If you want to test for an exhaust leak, an old trick I've used in the past is to use a clean shop vac. Situate the hose so that the vac is pushing air, not sucking. Hook the hose up to the tail pipe, and use duct tape to seal it. Get a mixture of soapy water in a spray bottle, turn on the vac, and start spraying the soapy water around the manifold, and any junctions. It'll blow bubbles anywhere there's a leak. Might be a little ghetto, but it works!
- Josh
Great idea Josh - thanks for sharing!!
I think a lean condition might add to that problem more than an exhaust leak. I would check for intake leaks around the base of the carb, as well as the intake manifold where it mounts to the head. Make sure the exhaust/intake manifold nuts are tight. Also check for aged and cracked vacuum lines...