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7_Zero · 07-24-2020, 01:32 AM

I realize it is difficult to diagnose through text, but I am hoping to get some ideas of things to check before digging deeper into it.

I recently purchased the car and the engine was supposedly rebuilt maybe 10 or 15 years ago. Based on some pitting in the valves I am wondering if it was more of a refresher than a complete rebuild. The previous two owners did not drive the car much and there are only 550 miles on the odometer, so I am assuming it only has that many miles since the ‘rebuild’ but we know what assuming does.

We drove the car around town for a couple weeks before taking it on a long trip and had no problems. On the trip however it started blowing radiator hoses (it has a pressurized radiator). After installing the third hose we watched for bubbles in the radiator and determined it to be a head gasket allowing combustion gasses to pressurize the cooling system. When we had the head off we decided to go with a 5.5:1 head, but unfortunately after the install the engine now has a knock.

The knock is audible at idle and when the engine is revved. You can hear it with the spark advanced or retarded. With or without the fan belt, clutch engaged or disengaged, and has no difference when disconnecting each of the spark plugs. Reversing the timing pin and putting pressure on the timing gear also yields no change.

Using a stethoscope, the sound is loudest at the front of the engine especially around the timing cover, timing pin and cam plunger area. Not sure if the knock has to do with the timing gear and cam, or if it is in the front main and only echoing through the timing cover? The engine had a two piece pulley that we originally thought was the cause so we replaced the pulley and also replaced the cam plunger and spring, but unfortunately it made no change.

Any suggestions on additional things to check, or is it just time to dig in to the bottom end?

Thank you for your help!

07-24-2020, 01:32 AM	#1
7_Zero Senior Member Join Date: Feb 2014 Location: Northern Utah Posts: 103	Help diagnosing engine knock I realize it is difficult to diagnose through text, but I am hoping to get some ideas of things to check before digging deeper into it. I recently purchased the car and the engine was supposedly rebuilt maybe 10 or 15 years ago. Based on some pitting in the valves I am wondering if it was more of a refresher than a complete rebuild. The previous two owners did not drive the car much and there are only 550 miles on the odometer, so I am assuming it only has that many miles since the ‘rebuild’ but we know what assuming does. We drove the car around town for a couple weeks before taking it on a long trip and had no problems. On the trip however it started blowing radiator hoses (it has a pressurized radiator). After installing the third hose we watched for bubbles in the radiator and determined it to be a head gasket allowing combustion gasses to pressurize the cooling system. When we had the head off we decided to go with a 5.5:1 head, but unfortunately after the install the engine now has a knock. The knock is audible at idle and when the engine is revved. You can hear it with the spark advanced or retarded. With or without the fan belt, clutch engaged or disengaged, and has no difference when disconnecting each of the spark plugs. Reversing the timing pin and putting pressure on the timing gear also yields no change. Using a stethoscope, the sound is loudest at the front of the engine especially around the timing cover, timing pin and cam plunger area. Not sure if the knock has to do with the timing gear and cam, or if it is in the front main and only echoing through the timing cover? The engine had a two piece pulley that we originally thought was the cause so we replaced the pulley and also replaced the cam plunger and spring, but unfortunately it made no change. Any suggestions on additional things to check, or is it just time to dig in to the bottom end? Thank you for your help!