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Discussion Starter · #1 ·
I need some expert advise. Last year, I had an small oil leak at the rear of the engine. This is a rebuilt 1972 Engine with only 400 miles on the engine. OGTS said when the rear crank bearing is installed, 2 small drops of gasket sealer are needed at the rear of the bearing to prevent this small leak. I removed the subframe and supported the engine. I removed the oil pan and then the rear lower bearing cap and inserted the gasket sealer(not on the bearing surface) into the appropriate location. I retorqued the bearing cap and replaced the pan gasket(4 pieces). I ran the engine and the oil leak was resolved. I put approx 250 miles on the engine. This was last year. In the past month, I installed a weber to replace the worn out Solex and cranked the engine over for the earlier this week for the first time since October of last year. It ran great. Today, I cranked over the engine and let it idle at approx 1000 rpm after it warmed up. It was running for about 20 minutes and I turned the key off very slowly. I think the ignition cut out momenteraly and then the engine continued to run because I put the key back onto the run position. I started to hear a intermittent knock towards the lower rear of the engine. I shut the engine down and then restarted the engine. It was still in intermittent. I shut the engine down again and restarted the engine. The knock is now constant.

Oil pressure and temp is good. What could of happened? Could the bolts on the rear main bearing of come loose? Did I spin a bearing?

I need all of the help I can get. I've had this car for over 20 years with 18 of them restoring the car. I want to take this car to Carlisle under its own power.
 

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Bummer, but if it were mine, I drop the pan and have a look at the tourqe on the main bolts and a look at the bearings themselves to see if they were damaged. jmtcw
 

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Discussion Starter · #3 ·
Here is an update.

I started the engine this morning(cold engine). The knock is back to intermitent. I only ran the engine for approx. one minute and shut it down.

More background info. The head was rebuilt in 1984. It now has 20 K on the head. The lower end of the engine was rebuilt in 1985 or 1986. The engine was cranked and run every so often to keep all of the parts lubricated until 2003 when the body was restored.

The gas in the tank is also from last October.

I stopped at my mechanic of 20 years and told him what happened. He said since the rebuild was 20 years ago, some carbon may of built up on the pistons which can cause this knocking due to the short run times I had the engine going over the past 20 years. When I had the Solex on the car, I also had a major "dieseling" problem every time I shut the engine down after it was completly warmed up.

Here is my mechanics suggestion. Take a quart of water and slowly pour it into the engine, through the carb with the engine running. Pour the water in slowly so the engine doesn't die. This will "steam clean" the engine and remove the carbon build up.

What do you guys think?
 

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steam clean

I have heard this from some experienced (old) mechanics that this is a good way to get carbon buildup off the piston head. I had a GT that would knock loudly (sounded like a nut was dropped into the piston chamber) from the head area everytime a piece of carbon build up would come loose. You could hear it rattle and tink out of the exhaust once it went through the exhaust port and the knocking from the top of the engine would instantly stop. Very scarey considering all the possabilities of what knocks in an engine can be. Hope yours is as simple to fix! Good Luck.
 

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I have heard this also. I know it works cause my Chys car had a water port leak and was sucking in water on the #4. When I yanked the head, it was mighty clean compared to the other three. There's also a trick w/ using diesel fuel in a mix with the oil (2qts oil to 3qts. diesel) to clean out any carbon or sludge in the oiling sytem. Just have to make sure to watch the pressure and temp. When it gets warm or pressure drops, shut it off and do a oil change.
my 2c's
 

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one adition to this, had a 51 packard with so many stuck valves, it was unbelievable, was only running on 3 of 8 cylinders due to stuck valves. ran it about 1500-2000, didnt have a tach, hard to tell the engine speed.... anyway, ran a quart of automatic tranny fluid through the engine, smoked horrable, couldnt see nothing but smoke, couldnt see your hand infront of your face because the exhaust was only a few feet long. after a quart of tranny fluid, i was then told to dump a quart of water through the carb, i guess the reason was since automatic tranny fluid is a detergent, it helps to loosen the crud and carbon, and then the water does a better job of steam cleaning the internals. seemed to work somewhat decent, as it was then running on 6 cylinders, 6 out of 8 is alot better than 3 out of 8.....surprised it even ran on 3 cylinders....haha
 

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Discussion Starter · #7 ·
Thanks for all of the replys. Keep them coming!!


I spoke with OGTS this morning and they said since I changed the carb. recently, something may of been sucked into the engine. I am going to remove the spark plugs and see if I see anything or any damage to the pistons first. If I don't see anything, then I will try the water trick. OGTS doesn't think it is carbon since the bottom end of the engine only has 400 miles on it but my mechanic disagrees.

If nothing works, then I will have to pull the head and pan. Not something I am looking forward to. I'm getting too old for this!!
Needless to say, I haven't gotten much work done at work today. At least it is Friday.
 

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Discussion Starter · #8 ·
Sucess:) :) I cleaned the plugs(only 400 miles on them), Inspected the cylinders and found some loose carbon on the piston tops. I poured some fresh premium in the tank and fired it up. As soon as the new gas made it to the engine, the knock lessened and I heard the carbon flakes "tink" out the exhaust. The engine ran smoothly and quietly. As a precaution, I added "seafoam" to the engine. This product is made for just this application. The engine smoked(as per the instructions) and blew out the remainder of the carbon. I checked the plugs again and they were much cleaner. My depression is over and I took it for a short ride around the block.

I was now confident and installed the petronix ignition. Another sucess story.

Hopefully we will make it to Carlisle.
 
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