Did you do a compression test?
A Leakdown test?
A blowby test?
In your case;
First let me say; here is a wild card;
if the oil has been washed off the cylinder wall in the low-reading cylinder, for whatever reason, well; ALL BETS ARE OFF. Assuming this has not occurred, then;
If you only have 80psi cranking cylinder pressure in one hole;
Or, if you have over 4% leakdown, then
Notta chance would I install that engine.
I would go to the side with the low CCP, and remove the rocker gear. Then I would check the LD on the bad cylinder again, with the piston at the bottom of the bore, which, if the engine has not been rebored, is the part of the cylinder with the least wear, and compare it to the LD with the piston at the top/the most worn part.
When checking, use no more than 30psi.
1) If the two LD measurements are not the same, but are very close, then measure a few more and compare them. If you get more than 4%, again I say, not a chance would I install this engine.
If any hole is over 4%, in my book that hole is no good, unless you installed chrome rings which on the street is a bad idea.
2) but if the numbers are not close to the same, then I would check the LD at several points between top and bottom, looking for a scratch in the cylinder-wall. For this test, you better not use more than about 30psi for this, cuz on a 4" bore this will make 376pounds of force, and you will need a 2ft or longer bar to hold the piston in any one place accurately.
3) but if the cylinders WERE bored and honed, then there should be NO DIFFERENCE in the LD numbers from top to bottom.
4) if all the cylinders measure the same CCP within a very few pounds, but all are low, check your gauge calibration, then if the gauge is OK, check the cam-timing.
Depending on your Ica, the pressure can range something like 20 psi over 20 degrees, so I cannot tell you what your pressure should be without more information;
but if my stone stock iron-headed 318LA didn't make at least 135 in every hole, I'd be tearing it apart. and whatever iron-headed SBM I build for personal use, it will never be built with less than 155psi; course it will never be built with open chamber heads either, lol..
5) I reiterate;
if the oil has been washed off the cylinder wall in the low-reading cylinder, for whatever reason; ALL BETS ARE OFF.
Just for reference;
On one freshening (not a rebuild) my 367, with Plasma-Moly rings,
on the engine-stand; (NOT a run-stand)
and with no break-in (cuz the cam was the previously installed one);
The Compression test was 187psi on every hole, and
the Leakdown was too low to even measure on my 2.5" gauge.
After start-up, the blow-by gauge was very difficult to stimulate.
I love those Plasma rings!
