1966 Compression Test + Exhaust Manifold Vs Headers Conundrum

[cwink5]

Compression Test done with Engine Cold. what am i looking at here? Numbers below. Cars the 390 and Next step i’m Pulling off the Heads to change the Exhaust manifold which i ordered a exhaust manifold RH but before even receiving had decided it wasn’t gonna work so this afternoon i just went ahead and ordered the Sanderson Headers + the Powermaster Starter that was said to be needed but once i got home the exhaust Manifold was waiting for me and it looks to be the exact same as what’s on it. it does fit a 390FE but i believe it was for a truck F100 or something. any input on that would be appreciated.
1. 185. 5. 180
2. 185. 6. 150
3. 180. 7. 155
4. 190. 8. 175

 

[sre]

Before I would pull the heads I do a wet compression test at least on the side that where 6-7 are located. With an oilcan squirt oil in 5-6-7-8 one at a time see if the compression comes up. There could be the start of a head gasket leak between 6-7 or the start of a valve issue. If compression would come up 15-20 points could be a ring problem.

 

[cwink5]

Compression Test done with Engine Cold. what am i looking at here? Numbers below. Cars the 390 and Next step i’m Pulling off the Heads to change the Exhaust manifold which i ordered a exhaust manifold RH but before even receiving had decided it wasn’t gonna work so this afternoon i just went ahead and ordered the Sanderson Headers + the Powermaster Starter that was said to be needed but once i got home the exhaust Manifold was waiting for me and it looks to be the exact same as what’s on it. it does fit a 390FE but i believe it was for a truck F100 or something. any input on that would be appreciated.
1. 185. 5. 180
2. 185. 6. 150
3. 180. 7. 155
4. 190. 8. 175

forgot to mention on #7 it was making a whooshing sound like air release sound

 

[Oly Bob R]

Is 1-4 the left bank and 5-8 the right bank. I ask because it as always been my understanding that odd numbers are on one side of the engine and even numbers are on the other. Therefore six and seven would not be side-by-side. I’m open to being corrected.

 

[doug7740]

Compression Test done with Engine Cold. what am i looking at here? Numbers below. Cars the 390 and Next step i’m Pulling off the Heads to change the Exhaust manifold which i ordered a exhaust manifold RH but before even receiving had decided it wasn’t gonna work so this afternoon i just went ahead and ordered the Sanderson Headers + the Powermaster Starter that was said to be needed but once i got home the exhaust Manifold was waiting for me and it looks to be the exact same as what’s on it. it does fit a 390FE but i believe it was for a truck F100 or something. any input on that would be appreciated.
1. 185. 5. 180
2. 185. 6. 150
3. 180. 7. 155
4. 190. 8. 175

There are a lot of factors, in doing a compression test. Make sure that you take all spark plugs out and make sure the throttle plates are wide open. With a fully charged battery, each cylinder of the engine should go through a compression cycle at least three times to insure that you build up to the maximum compression. The rule of thumb is that that the cylinders should be within 10% of the cylinder with the highest reading.

Put a couple of squirts of motor oil into each cylinder and perform the compression test again. If the compression readings increase, that would indicate that worn piston rings are the cause of the low compression. Performing a cylinder leak down test will tell you a lot without opening a thing.

Another important tool to use for troubleshooting is a vacuum gauge on a operating engine. It is an invaluable tool for quickly finding some issues that are sometimes difficult to diagnose.

doug7740
1955 Thunderbird Blue

 

[daytonthunderbird]

Is 1-4 the left bank and 5-8 the right bank. I ask because it as always been my understanding that odd numbers are on one side of the engine and even numbers are on the other. Therefore six and seven would not be side-by-side. I’m open to being corrected.

Is 1-4 the left bank and 5-8 the right bank. I ask because it as always been my understanding that odd numbers are on one side of the engine and even numbers are on the other. Therefore six and seven would not be side-by-side. I’m open to being corrected.

As you are looking at the engine from in front of the car, passenger side goes 1-4 and driver side goes 5-8, so 6 & 7 are next to each other.

 

[cwink5]

Before I would pull the heads I do a wet compression test at least on the side that where 6-7 are located. With an oilcan squirt oil in 5-6-7-8 one at a time see if the compression comes up. There could be the start of a head gasket leak between 6-7 or the start of a valve issue. If compression would come up 15-20 points could be a ring problem.

okay i’ll do that and does it have to be a oil can or can i just use anything? what kind of oil?

Is 1-4 the left bank and 5-8 the right bank. I ask because it as always been my understanding that odd numbers are on one side of the engine and even numbers are on the other. Therefore six and seven would not be side-by-side. I’m open to being corrected.

i was just going front to back 4 on left and the 6789 on right thats not how the book labels them but i didn’t figure it really mattered all that much

 

[sre]

Sorry I was out till now. Any oil should work. I use a plastic squeeze bottle w/ a short hose to get inside cylinder.

 

[dmsfrr]

Is 1-4 the left bank and 5-8 the right bank. I ask because it as always been my understanding that odd numbers are on one side of the engine and even numbers are on the other. Therefore six and seven would not be side-by-side. I’m open to being corrected.

...
i was just going front to back 4 on left and the 6789 on right thats not how the book labels them but i didn’t figure it really mattered all that much

.
Yes it matters. So the firing order and potential problems & solutions can be communicated to other folks with much less confusion.