Wanted Advice On 383 Big Block

[Cianmini1]

If I am going to change oil right away I get the motor hot and dump in with the oil and let idle for 20-25 minutes. Bumping it down carb prior will break up carbon on the valves and pistons. A motor is an air pump. When that air is being compressed and it is leaking into the crank case it happens in a few ways. Past the rings, past valve seals, or you have a hole in the piston is most common. A bleed down test will show you which cylinder it is. A bore scope is a good idea as well as maybe you can get an idea of the ring ridge and judge the bore wear. Your motor could just be tired. make sure breather and PVC is working. I picked up an all original 53 Plymouth with the flat six 3 years ago that never saw 48k miles. But the car lived on unpaved roads. Runs like a top but the dust wore the cylinders and compression is lacking. Just make sure the breather is good and clean and it doesn't pressurize the crank case. These cars had road draft tubes that hung down next to block and sucked it out.

Hi thank you for all this info very helpful!

 

[CBODY67]

Compression readings are relative to the elevation altitude of the vehicle when the test is done. Most of the specs usually indicate "At or near sea level". As long as the readings are within about 20psi, all is good.

When I was "worried" about cylinder wear on our '66 Newport 383 2bbl, I got a screw-in hose compression gauge. Readings were slightly lower than spec, but even. Engine ran smooth. Started well and got the same mpg as when it was much younger. I did that check after it was well past 100K miles.

You can use a borescope (attaches to computer or your smartphone) to look inside the cylinder/combustion chamber. IF the oil is coming up past the oil rings, you'll see less carbon around the tops of the pistons. If it is coming in "from the top", with the piston crown consistently covered, that is valve guides and valve seals. If changing seals, seek out the ones made of orange silicone rubber.

Have you checked the hot base idle ignition timing to see if it has moved? In ANY event, a new timing chain can not hurt AND can be "insurance" against any issues from that area in the future.

Berryman's B12, used in the gas or in the motor oil, when used as directed, is a great tool to use. It's been around for over 60 years.

Get things cleaned up and THEN check for oil leaks. Might not be nearly as bad as suspected. Then look at the tune-up specs and make sure they are near-right. I have had best results in starting our Chryslers by using 1/3 throttle after an initial movement to set the automatic choke. Pre-filling the carb through the carb bowl vent, if the engine has set fora while, is much better than cranking and pumping the accel pedal.

Might need to consider replacing the fuel pump push rod, too. If you smell "gas in the oil", look about a new fuel pump. A stronger smell than normal, though.

Enjoy!
CBODY67

 

[Cianmini1]

Compression readings are relative to the elevation altitude of the vehicle when the test is done. Most of the specs usually indicate "At or near sea level". As long as the readings are within about 20psi, all is good.

When I was "worried" about cylinder wear on our '66 Newport 383 2bbl, I got a screw-in hose compression gauge. Readings were slightly lower than spec, but even. Engine ran smooth. Started well and got the same mpg as when it was much younger. I did that check after it was well past 100K miles.

You can use a borescope (attaches to computer or your smartphone) to look inside the cylinder/combustion chamber. IF the oil is coming up past the oil rings, you'll see less carbon around the tops of the pistons. If it is coming in "from the top", with the piston crown consistently covered, that is valve guides and valve seals. If changing seals, seek out the ones made of orange silicone rubber.

Have you checked the hot base idle ignition timing to see if it has moved? In ANY event, a new timing chain can not hurt AND can be "insurance" against any issues from that area in the future.

Berryman's B12, used in the gas or in the motor oil, when used as directed, is a great tool to use. It's been around for over 60 years.

Get things cleaned up and THEN check for oil leaks. Might not be nearly as bad as suspected. Then look at the tune-up specs and make sure they are near-right. I have had best results in starting our Chryslers by using 1/3 throttle after an initial movement to set the automatic choke. Pre-filling the carb through the carb bowl vent, if the engine has set fora while, is much better than cranking and pumping the accel pedal.

Might need to consider replacing the fuel pump push rod, too. If you smell "gas in the oil", look about a new fuel pump. A stronger smell than normal, though.

Enjoy!
CBODY67

Hi thanks for all your help!
Will defo consider all this thanks!
Fuel pump and pushrod are both new yes!
Thanks