For hours and hours of Part Throttle cruising; you can't beat cylinder pressure. You can get it in several ways.
If you want a strong low-rpm take off, you will need a combination of ; cylinder pressure, stall, and gears.
If you want a strong top end you ill need some rpm, and that spells cam. Or a set of worked heads and then a matching cam.
If you want to keep the factory stall, hiway gears, and a take-off at least as strong as the factory; you only have two choices;1) leave it factory stock, or 2) keep the cylinder pressure the same as it currently is.
But since you are changing the pistons, anyway;
1) you can increase the pressure, keep the cam stock, and reap the torque benefits, while maintaining the shape of the current power curve.
2) you can maintain the pressure with a bigger cam and matching increase in compression ratio, or
3) you can maintain the current pressure with a different type of cam, or one that makes more power at the same pressure., or
4) you can sacrifice some low-rpm torque, to get some higher rpm power, and then bandaid the situation with a higher stall TC.
To that end; it is almost hard, with a 318, to make too much pressure for a small performance cam; the swept volume is just 652 cc on a stockbore engine.
The KB 167s are advertised at 1.810 Cd so that totals 9.59 from crank cl to top of piston. If your deck was 9.600, this would get you a deck clearance of .0095 or 1.9cc. Adding 6.2 for an .028 gasket, and estimating 5cc for eyebrows and 60cc for the closed chamber heads, gets you a total chamber volume (with .038Q), of 73.1cc, and therefore a compression ratio of 10.0
This will nicely support a 268 cam with a 63*or greater Ica.
But that is waaay more cam than you need. So what do you do? The Q is .038 under a closed chamber head,which is real nice. Going to the .039FelPro will jack that up to .049 which some guys have trouble with detonation. You shouldn't, but some do.
So the .039 adds 2.4cc and the Scr becomes 9.7, which works with a 60* or later Ica, and you can install a 262 at that . A 262 could be a [email protected], which IMO, is a real nice 318 street cam, when matched to a decent compression ratio; not 7.8!
But what I would do, is try to run the .028 gasket at 10.0Scr with the .038Q. But, if it does detonate; I'm not averse to taking it all back apart, and custom machining the pistons, leaving the Q-pads alone.
Why?
Because at PartThrottle it will pay handsome dividends. And cruising for 6 to 8 hours is PT. Driving around town is mostly PT. Normal acceleration is PT. Ima guessing 98% of your driving hours are gonna be PT.
When will you be at WOT, with the secondaries open?
I'm guessing at KD when passing.
With 2.94s, 60 would be 3400 in second. This is a good number if you have delayed your all-in timing to it.
With 3.23s it would be 3740. This is a better number, and it is hardly likely to detonate, this late in the rpm band.
What about taking off from zero mph?
Well firstly; it is hardly likely that your secondaries are gonna open below about 2800rpm. And they may not be fully open until a lil later; YOU get to set that.
And secondly; contrary to popular opinion, you don't have to run your timing on the ragged edge of detonation. At WOT you are only ever gonna be below 3000 rpm but one time, in first gear, below 28 mph with 3.23s. So give the engine only as much timing as it asks for.
And thirdly; if the tires spin, the load goes away, the rpm flashes past 3000, and you are in the clear.
And fourthly; you can put a smaller carb on it, or just not floor the one you got.
And fifthly; you can reduce the load with gearing.
Detonation is caused by too much heat in the chamber for the octane (detonation-suppressant) in the gas you are using. So the solution is simple, keep the heat in check. Your solutions are; fresh cold air, proper AFRs,a properly sized exhaust system, proper ignition advance, engine loading, and finally coolant temperature. And I use some oil cooling under the valve covers.
The most likely time for detonation to occur is from stall to about 3600 rpm. And that is the reason for the sub .040 quench, which is actually squish. That tight space squishes whatever is in there, out across the chamber like a shotgun blast, stirring everything up; so every molecule of gas gets blasted to smithereens,and they have the best chance at finding oxygen to react with. This is not a detonation suppressant, but the complete mixing promotes an even chamber temperature, which prevents or reduces the primary source of detonation, namely hot-spots.
So yeah, I'd try 10/1 with a 262; even a fast-ramp 262. Check out Wrmriders posts. But like I said; I'm willing to take it all back apart; I'm 66,semi-retired, and got lots of time.
Besides; if you don't try it, you'll never know what coulddabin. And if you have to redo it, you got stories to tell your grandkids.
Oh yeah, be careful, each bigger cam (7*), with no other changes, raises your rpm of peak power about 200 rpm..... but reduces your bottom-end torque. Which usually calls for more stall rpm, also about 200 rpm. Before you know it, your stall rpm is higher than your cruse rpm, and the TC is slipping all the time, and your gas-money ends up heating the atmosphere.... instead of propelling your vehicle.
