doubleyellow
Well-Known Member
1970 440, stock, fully rebuilt, couple hundred miles since going in the Challenger.
So been chasing a vibration/roughness issue. Idle is OK, but over 200 RPM, engine get progressively worse in regards vibration/roughness.
Checked timing, dwell, plug wires, tuned carb, multiple times. No real improvements.
Although engine fully rebuilt top to bottom, decided I should do a compression test.
Here are the numbers (in psi):
1 - 210, 3 - 205, 5 - 210, 7 - 212, 2 - 210, 4 - 200, 6 - 198, 8 - 202
Hopefully did the check correctly with all plugs out, and throttle wide open
Now here are pictures of the plugs (not 100% perfect focus)
Looking at 1-3-5-7
Here are 2-4-6-8
Overall the compression range from 198 to 212 should be OK, but you guys tell me if that range is OK for a fully rebuilt engine.
What is concerning is that the lowest compression cylinder #6 (at 198 psi), also has the spark plug that is has carbon and not looking normal (or at least similar looking) to the other plugs
I do have an overkill carb (750 CFM ProForm) and engine still running too rich.
Any expert feedback on the Compression data, and, the spark plug diagnosis would be greatly appreciated. Not sure if I need to start digging deeper into the engine to find something, or, I've still got external thigs to chase (ignition, vacuum leak, fuel, etc)
Thanks
So been chasing a vibration/roughness issue. Idle is OK, but over 200 RPM, engine get progressively worse in regards vibration/roughness.
Checked timing, dwell, plug wires, tuned carb, multiple times. No real improvements.
Although engine fully rebuilt top to bottom, decided I should do a compression test.
Here are the numbers (in psi):
1 - 210, 3 - 205, 5 - 210, 7 - 212, 2 - 210, 4 - 200, 6 - 198, 8 - 202
Hopefully did the check correctly with all plugs out, and throttle wide open
Now here are pictures of the plugs (not 100% perfect focus)
Looking at 1-3-5-7
Here are 2-4-6-8
Overall the compression range from 198 to 212 should be OK, but you guys tell me if that range is OK for a fully rebuilt engine.
What is concerning is that the lowest compression cylinder #6 (at 198 psi), also has the spark plug that is has carbon and not looking normal (or at least similar looking) to the other plugs
I do have an overkill carb (750 CFM ProForm) and engine still running too rich.
Any expert feedback on the Compression data, and, the spark plug diagnosis would be greatly appreciated. Not sure if I need to start digging deeper into the engine to find something, or, I've still got external thigs to chase (ignition, vacuum leak, fuel, etc)
Thanks