Bank Balance

[Kegsti66]

Hi all, hoping for some pointers here.
Over the winter I wanted to do a few bits on the car, one of which is to get her running a bit smoother.
I have a carb service kit to fit so that should make that work as well as it can. However, I did a compression test and have uneven readings.
Looking from the front, the left bank (cylinders 1 & 3), both read exactly 170 . The right bank (cylinders 2 & 4 ) both read exactly 155.
I was wondering if perhaps one side has had a head gasket replaced at some point and may have been a different make, and a bit thicker / thinner. Or is that just me being thick? I ask as it seems strange both sets of cylinders are exactly the same.
Water and oil are as they should be and show no signs of cross contamination , and she has never overheated in the last 2,000 plus miles I have done since finishing her.
I don't really want to pull the engine out, but if it may be a matter of odd head gaskets, I could just change them both with the engine still in couldn't I ?
What do you think ? Do the compressions sound any good or does it sound a bit more involved ?
Cheers,
Keith.

[KevJTD]

maybe a head has been off and the head skimmed?

or maybe the cambelt is a tooth out on one side?

[dralf1965]

Kev could be on to something with the cambelt timing theory. I once did some belts on my 1351, and managed to get one cam one tooth out, it ran, but didn't seem quite right, and had an odd exhaust beat too.

[Spacenut]

170 psi sounds about right for a good engine, so unless the low side has a thicker gasket, I would agree with Kev that your cam timing might be one tooth out on the suspect cylinder bank. Got to be worth a check, before you do anything else - quite often the cam timing marks will be slightly offset from the registration mark anyway, but if you are one tooth out it should be pretty obvious.

If your flywheel alignment marks are indistinct, try using some stiff wire down the #1 cylinder bore to be absolutely certain where the #1 TDC point is.

Lauren

[Kegsti66]

Cheers guys, I will start with a check that the belts line up the markers in the cam buckets when she is timed up (T marker on the flywheel).
Dralf1965, hopefully like yours, that will be the case as she runs but has always seemed a bit lumpy.