Value of the compression?

[R/T]

Hi!
I have a Dodge Challenger 1971 with an original 383 engine! I am planing to do a Compression test on it! And I wondering what is the proper value of the compression?

Regards Eric

 

[challenger6pak]

100-140 pounds cranking compression pressure.

 

[moparleo]

To get accurate numbers, do the following:
Make sure that the battery is fully charged.
Disconnect coil wire if possible from both cap and coil.
A few squirts of Marvel Mystery oil or equivalent in each cylinder.
Wedge the choke plate open with a screwdriver or whatever will work for you.
Crank the engine 3-4 rotations only. You should get your top reading by then.
Make sure to crank each cylinder the same amount of rotations.
Ideally your compression should be within 10lbs or 10% of each other or you have an internal problem.

 

[R/T]

Okey Thanks! I have just done the test and I get from 116-123 psi on all cylinders! That's ok then!

 

[R/T]

I did the test with cold engine.. I know that it would be on hot engine but just now I can't do that! And I did the test without the oil!

 

[moparleo]

It should be fine.

 

[challenger6pak]

I agree. It sounds good to go.

 

[R/T]

Thx! The reason I did the test is that I have problem with oil on my sparks plugs! I just take off the cylinder heads! And I find that the intake manifold didn't have any gaskets and the bolts we're lose... And the heads have a hole/cavity in the center that's connects with the intake! And in the hole it's was a lot of oil? And the valve seals seems just sitting on the top ov the valve? Wouldn't they be fixed... Any ideas where the oil comes from? I hope you understand my writing... My English isn't so good!

 

[challenger6pak]

Looks like a lot of carbon on the valves. Oil gets splashed on the back of the intake when the motor is running. Without a gasket, oil may have been sucked up into the ports by the intake valves. The valve seals may be bad also. Are the valves seals hard or soft?

 

[R/T]

Looks like a lot of carbon on the valves. Oil gets splashed on the back of the intake when the motor is running. Without a gasket, oil may have been sucked up into the ports by the intake valves. The valve seals may be bad also. Are the valves seals hard or soft?

Thanks again! It seems like that was what happened! I can't see any other explanation! And I notis that the cylinder heads is milled! I guess that the angel were to join the intake with the heads do not match or align!

 

[moparleo]

You know, it does help to tell us what you are really looking for than to say you are checking one thing but you are really looking for the answer to something else. It can save time on both sides. The hole in the center of the heads is for heat crossover to warm the fuel in the manifold when cold for better cold weather performance. Does nothing for you after the engine warms up. Intake gaskets are made with and without the port opening. Unless the car is used in cold weather a lot it is best to use the gasket that blocks the port. The compression test will not show the problems that you have, so was a waste of time. Since you did find that things on this engine were not done correctly, it would be safe to assume there are more problems waiting for you. Tear it down or cross your fingers.,

 

[R/T]

okay sorry! :crybaby2: Everything depends on that I'm not so good at English! :dontknow: would be fun to see you try to explain something in Swedish! :toothy10: I just wanted to do a test on the engine before I took it apart! I do not know much about it since I bought it from California in 2012! Maybe I should have started a new thread then! Thanks for the tips anyway! Here it is really cold and snowy! But of course I'm not driving my car other than the nice summer days, so I'll try to get hold of a gasket without hole!

 

[moparleo]

Ok really. Does oil on the spark plugs and compression test sound the same in any language ? Anyway, Some common tips. Photograph every thing before disassembly and during. Bag up and label all parts as they are removed. Try to stay on one problem at a time. A common mistake is to get too excited and take everything apart and now just have a pile of parts. Focus. Sounds like the previous owner probably had another intake manifold on the engine and put the old one back in a hurry. Missing gaskets and loose bolt are a clue. He might have hurried other work too, so it is good to recheck everything.

 

[R/T]

Ok really. Does oil on the spark plugs and compression test sound the same in any language ? Anyway, Some common tips. Photograph every thing before disassembly and during. Bag up and label all parts as they are removed. Try to stay on one problem at a time. A common mistake is to get too excited and take everything apart and now just have a pile of parts. Focus. Sounds like the previous owner probably had another intake manifold on the engine and put the old one back in a hurry. Missing gaskets and loose bolt are a clue. He might have hurried other work too, so it is good to recheck everything.

Okay, I forgot to mention that I also made a leak down test because of the oil leak! Then I thought that a compression test would also be good to do to check the head gasket! Thats was maybe not so smart! Thanks for the tips! I'll check how everything else seems to be, and take pictures on my way!

 

[moparleo]

Best of luck on your journey with this car.

 

[R/T]

Best of luck on your journey with this car.

Okej! Thx!