You said; engine was a 71. WIKI says elevation Cedar Lake In, is ~713ft
I said/say; Forget about the cam until AFTER the heads are done and installed, and you have done another compression test.
Your pressure, in a 71 engine, at a true 9.0 Scr, @713ft elevation; should be about 155psi,
Based on your compression test results, and based on 155psi being fresh, and
to the right of the dry results;
in red, I have calculated; the %pressure loss,
Also, to the right of that, in violet, is the %pressure loss based on 140psi being fresh.
Also, to the right of that, is a number in blue, that represents the %pressure difference between the wet and dry.
Here we go;
1-125dry/19.4/(10.7) (5.3) 132wet ..... 2-123dry/20.6/(12.1) (8.9) 134wet
3-114dry/26.5/(18.6) (3.5) 118wet ..... 4-138dry/11.0/(2.1) (10.9)153wet
5-134dry/13.5/ (4.3) (4.5) 140wet ...... 6-125dry/19.4/(10.7) (8.0) 135wet
7-137dry/11.6/ (2.1) (0.7) 138wet ...... 8-136dry/12.3/(2.9) (8.8) 148wet
>The smaller this blue number is, the more it tends to indicate a ring problem ( or no problem at all).
>The greater the blue number is, the more likely that the problem is valves. So your rightside head, at least, is toast, or it has really big chambers.
>#7 is a unique case, in that the wet/ dry results are much the same so would seem to indicate no problems at all; yet the 11.6% points to the engine NOT being a 9/1 engine, or the test was done at a much higher elevation than 700ft, or the gauge was Not accurate. Therefore, I added another column of numbers in violet, based on a normal of say 140psi@713ft; that is to say sorta normal for a low-compression engine. So now if you have a low-compression engine, the pressure loss is only 2.1%
Now, say after the valve job, the pressure by some miracle, in ALL the holes jumps up to 140. Every one. I mean I am talking a miracle. 140/155=10% pressure loss, so rings are still wore out. Except;
140psi is about what a low-compression Smoggerteen makes with the same 318 cam, when it is fresh.... at sealevel. I'll say it again;
With a stock sub-2000 stall convertor and typical street gears of 3.23s or less, forget installing a 340 type cam in that low-pressure (not low compression ratio) engine. If you do it anyway, your pressure is predicted to fall to less than 120psi,(in the 9/1 engine) and, so then, you will come back to FABO, moaning about what a totally lazy dog, your 318 has become, at typical stock stall and gears.
You shouldda at least have done the rings (assuming the holes are still round and straight with no taper,lol). But; if you do the rings only;
the pressure in a 9/1 engine with the 340 cam might rise to around 140; still doggy at stock stall.
If you replace the pistons and readjust the Scr to about 10.0, the pressure is predicted to rise to about 160 with that factory-spec 340 type cam. Now you got something to get excited about. (but I wouldn't run that or any other 114LSA cam in a 318)
Pressure makes heat, which makes power,especially low-rpm power.
Loss of pressure always equates to loss of low-rpm power.
Listen; I'm not telling you these things to make myself look smart.
I'm telling you these things so you don't make the same expensive mistakes I have made in my life since 1968, which in the beginning, mostly ended in disappointment.
Happy Hotrodding
