Did a compression Test today

[kcfirstbuild]

I have a 1968 chevy Lwb With a 307 that has 54,000 miles on it. I ran a compression test on it today and this is what it got.

1. 130 2. 140
3. 135 4. 150
5. 135 6. 140
7. 130 8. 140

They all started at 90 or so on the first rotation then jumped up to the numbers I posted above. One sit is lower then the other not sure if its from the battery running low or not ? Where should i go from here ? Do i need to rebuild everything or will i be ok with just gaskets and seals ?

Another question. There is a hose running from the air cleaner to valve cover is that the Pcv Valve ?

This is my first build so i don't know alot but i'm learning.

And i know I should change it to a 350, but its a numbers matching motor so i would like to keep it.

[Jobe72]

Numbers look good to me , you should have a line to the carb that has a PVC valve in it

[kcfirstbuild]

What is the line running from the Air cleaner to the valve cover with a hole and a grommet. It looks like a big Pcv Valve ? I Know for a fact that I have that A.I.R emissions on my truck.

[kcfirstbuild]

anyone else have any thoughts ?

[jgreene0717]

The PCV valve will go to a full vacuum source on the carb. The Hose from the valve cover to the Air cleaner is the crank case breather.

[fixit-p]

X2

[El Jay]

Originally Posted by kcfirstbuild

I have a 1968 chevy Lwb With a 307 that has 54,000 miles on it. I ran a compression test on it today and this is what it got.

1. 130 2. 140
3. 135 4. 150
5. 135 6. 140
7. 130 8. 140

They all started at 90 or so on the first rotation then jumped up to the numbers I posted above. One sit is lower then the other not sure if its from the battery running low or not ? Where should i go from here ? Do i need to rebuild everything or will i be ok with just gaskets and seals ?

Another question. There is a hose running from the air cleaner to valve cover is that the Pcv Valve ?

This is my first build so i don't know alot but i'm learning.

And i know I should change it to a 350, but its a numbers matching motor so i would like to keep it.

Just a rule of thumb re: compression; the lowest cylinder should be within 80% of the highest.
In your case, 120#; so things look okay.

It looks like everybody else has answered your other questions.

[kcfirstbuild]

ok thanks everyone. So with my numbers looking good do you think i should just pull the motor and put in new gaskets and fresh paint. Or would you rebuild it? Which would cost me 1,500 since i have no idea what im doing when it comes to the inside of a motor. I'm leaning towards new gaskets and fresh paint. I know its what I want out of it but would like to hear other peoples opinion.

Run it and paint it or Complete rebuild ?

[neba]

what are you trying to accomplish. your compression is fine. why would you want to pull the motor. are you having problems? no reason you shouldnt get 100k out of motor

[chevy88]

I would also keep the 307 as its numbers match and the compression is good. Any pics?

[kcfirstbuild]

No pictures just yet, Im going to pull it so i can clean i up and paint it as well as put new gaskets in.

[Arizona oldguy]

When you took the comp. test did you remove all the plugs before you started? the engine will spin over much easier and give you the full reading faster. If you plan on dressing up under the hood like painting the fender wells, fire wall and such pulling the engine for gaskets and paint job would be fine, if it is leaking oil or if you suspect the timing chain and gears are getting on the loose side you may want to pull it and fix them, if you pull the pan do not neglect the oil pump, cheap and easy to replace on the stand. Good luck and have fun.

[msgross]

make sure you don't have any leaks and run it... unless you are building a show truck. If you have oil leaks then fix those seals while it's inthe truck and then run it...

[tim21391]

from my class i took.. 90 is the base anything below 90 its time to rebuild.. guys does that sound right? but like stated here.. your good

[kcfirstbuild]

I only did one plug at a time - when i did my compression test. Thanks for the advice on the oil pump. I plan on taking the oil pan off an putting a new gasket there too.

[kcfirstbuild]

Not sure about the timing chain the truck only has 54,000 on it do you think i would have too?

[Sinister]

If you're going to pull the motor anyway, might as well do the timing chain and oil pump. Get a double roller timing set.