B

boggie

New Member

• Feb 19, 2011

• #1

Hi All,

I performed a Comp Test today and came up with the following results:

1: 138 psi
2: 145 psi
3: 145 psi
4: 138 psi

Do these sound ok?

After consulting the Haynes book of lies, I found the following info:

7:1 Motor
145 psi

8:1 Motor
160 - 170 psi

How do I know if I have a 7:1 or 8:1 compression ratio engine please?

Cheers,
B

 

jamesmartin

Well-Known Member

• Feb 19, 2011

• #2

its stamped on passenger side of head nr rocker box in the middle ,i would have thought that your readings were not too bad as near each other in less than 10% depends on starter speed etc ,you can add oil if it improves compression shows ring wear but i wouldnt worry unless you have excess smoke especially blue

 

B

boggie

New Member

• Feb 21, 2011

• #3

Great! Thanks James. I should also point out that these readings were taken cold, I assume they will be lower when hot? I had a quick look at the head with a totch in the dark but it has been painted so it is difficult to see. I don't suppose you (or anyone else) has a picture of the compression markings so I know where to start scraping off the paint?

Cheers,
B

 

jamesmartin

Well-Known Member

• Feb 21, 2011

• #4

piston will fit bore better when hot

 

B

boggie

New Member

• Feb 21, 2011

• #5

Interesting, so compression may actually be higher warm!
Thanks again James, much appreciated.
B