Fast Marina Magazine

Hi All,
Got a bit of a misfire. I have ruled out sparks and petrol so decided to do a compression test. Results are
Cyl 1 155
Cyl 2 155
Cyl 3 110
Cyl 4 180

Retested with a little oil in and got mostly the same results apart from cyl 3 which went up to 155. This I believe points towards piston rings. My manual states a cranking pressure of 170. I assume this is the figure to aim for.

What should I be looking for as a result? Why the big difference between 3 and 4? Is it time to take my head off.

Thanks Glen

Could be a valve not seating properly-burnt out / bent etc. but with increase with oil in I'd guess ring.

Whatever I reckon head off to check.

If no. 3 comes up to the same as nos. 1 & 2 with a drop of oil then I would say definitely rings/bore for no. 3.

As for no.4 a reason for being high, I would think that it would point to a past repair. If at some point in the past someone had re-bored and ringed just no.4. It sounds weird but it was a low cost fix in the 70s/80s, rather than reboring all four cylinders. With the head off you can use a mic to check the diameter of all the cylinders. Take several readings at different points if the clock to establish whether any have worn oval.



Chris

Sent from my iPhone

Thanks chaps,off with his head to have look and measure.
Glen

Before you take things apart you could try this to prevent work.
Get engine to temperature,remove air filter,rev car to about 2000rpm & sprinkle droplets of water through the carbie.
If the rings are stuck,this can free them.
I have used this in the past & it works more than it doesn't.
You still can't beat a rebuild.