Further to post #7
Putting alloy heads onto a stock lo-compression 318, seems to be a sort of a losing battle.
Here is what I have learned;
Sure the chambers are some 7cc smaller, jumping the compression from 8 to ~8.5 .
For a streeter;
However, in Part Throttle Operation, almost a full point of that is sent into the cooling system, as the alloy does what it does, namely, it pulls heat from the chambers. Heat is torque is power. At WOT, they say, this may be reduced to a half a point.
Therefore, to overcome this heat loss, the Scr has to be increased even more.
Furthermore, with the pistons down in the hole, getting a tight Quench is impossible.
And then, to get the pressure up high enough to make the alloy heads worth it, takes a bit of doing.
Whereas in drag-racing, you can still have fun at 8.5 Scr , on the street, tight quench and high cylinder pressure, make first and second gears, insanely much fun. The problem is getting a 318 up to pressures like 195psi. Everything has to be machined and fitted just right, and the right cam installed., It's gonna cost a lot of money.
and Finally, choosing a cam is gonna be real tricky to make BOTH top-end power, with adequate midrange, and the bottom-end will likely have to be sacrificed.
If you're only gonna run 160 or so psi, I see no advantage for a streeter to run alloy heads. Never mind 2.02 heads in a 3.91 bore.
The one advantage that might help a streeter in a situation as described above, is that my 11.3Scr, 195psi ,367, runs WOT on 87E10 with full timing. Thus, for you, it would take the fear of detonation out of the equation; which at 165psi is always a concern.
Considering the additional machining costs of getting a 318 up to pressure, as compared to the 360 getting to 10.7 with just a piston swap (in addition to the 60779s), that 360 might not be so insane. and once the Scr of a 360 is up to 10.7 with a tight-Quench, and with an overdrive; she will except just about any old street cam, any induction, and any rear gears.. so, there's that.
BTW
you can get very similar results with a 340 bottom end, just a lil less bottom-end torque. AND, they say, the early 318s can occasionally be bored to 4.00 .. A local fella here, about 20 years ago, took a chance on 4.04 and won, lol.. This allowed him to run some used 340 pistons, that he already had, which instantly got the pistons up to the deck. Car runs pretty stout on the street.
Personally, on the street;
I see no point in that; boring ain't cheap anymore. and
if you have to buy pistons anyway, well, there's no real monetary gain.
If I had a 318 to hop up, Yes I might run alloy heads, but I go with small-chamber, slightly smaller intake-valves, Magnums, and again with zero decks, or pistons slightly up but not down, and 039 FelPros. I'm having a lotta fun with 032 Quench.
