This gives me more comfort. If you get that 360 to run with a 220-230 cam with 11.4:1 and not detonate like crazy I feel better. I'm looking at a 230-240 cam with 10.5:1 mostly to keep the dish size on the piston under control.
It's NOT about the Scr.
It's about the cylinder pressure.
What I'm about to preach, is for if you drive like me; and it's a preach, so, it's my opinion.
My short-block set-up is like Rumbles. With Alloy heads she has run between 177psi, and up to 195psi depending on the ICA of the three cams I have tried. ALL of these have run on nothing but 87E10.
I did not
actively choose a particular Scr, except as was necessary to get to a particular pressure, because;
Pressure makes heat, and heat makes torque, which calculates to power.
The three cams that I have run are;
the DC 292/292/108 that I measured at ~248/249@050
A Hughes 270/276/110 that was advertised at 223/230
Another Hughes, 276/286/110 which is 230/237@050
My favorite was the smaller Hughes.
IF for no other reason, alloy heads are the beesknees for running big pressure, on low-octane gas. and I highly recommend 195psi.
See note-1
The 223 cam sacrificed some high-rpm power compared to the 292DC, but everywhere else was more powerful, good trade for me, and it returned phenomenal fuel-economy, near double of the 292, excellent trade as this was in a hiway DD.
What I learned on that trade was that a long power-stroke duration, coupled with a high pressure, and less overlap, is what makes fuel-economy possible. Obviously, driven to the extreme, this would result in a factory stock early hi-compression 318. I'm not going there.
Going from the 223, to the 230, I lost just a bit of pressure, and I lost a lot Power-stroke Duration. As a result, I lost bottom-end torque, and even the few degrees of lost powerstroke, coupled with the increased overlap; killed fuel economy.
It took me a lot of work to get the torque back, starting with a lower first gear ratio, and ending with a higher Scr to get the pressure back. The fuel-economy, however, was forever gone. But it was all good, the car was soon retired from DD status to weekend bomber, when I bought a old Sunfire to be my new DD.
Point is this, that 223 cam, geared for 65=1600rpm, pulled 32mpg on a certain steady-state day-trip. of Course your results may vary. also of course, around town, it was closer to 22, but that was no fault of the cam, lol. At 195psi, slamming the gas-pedal was always a fun trip.
When I switched to the 230cam, I was not expecting the bottom end to go away, the way it did. But the top-end was similar to what the 292 had been. Since by this time, I had double overdrive, the solution was 4.30 gears.. But as I learned to tune the beast, I eventually was able to go back to 3.55s.
IMO,
with a manual trans, for me anyway, the 230cam (276/286/110) is too big. and here's why; your impressions may be different;
1)
I can't drive slow. 550 rpm with a 2.66 low and 4.10s is ~4mph. Trynta get the engine to pull itself at 550 is a friggen stretch, and most guys with standard volume oil-pumps are not going there. I got down to 3.6mph, with a deep low gear, and retarded timing, but the transfers have to dead nuts working correctly.
2)
This cam requires a lot of Scr, to pull the bottom-end torque up. With iron heads, about the most you can run on 91 gas is 165psiCCP, which is NOT ever gonna make me happy, having experienced 195psi. IDK you may be willing to suffer that. but not me.
3)
Forget fuel economy with iron heads at 165psi. Even at 187, steady-state is nothing to brag on. here's why.
First, see note-1, then;
I ran the 223 straight up. the cam durations were;
270 intake/
116comp/111power/276exhaust/53overlap
and the 230 cam in at plus 4
276intake/
116comp/103power/286exhaust/61overlap
Notice that both have 116 compression, so they both make the same CCP-pressure.
Notice that the Powerstroke has gone from 111 down to 103. That's where the fuel economy went.
Notice that overlap has gone from a modest 53 to a not-so-modest 61. This cam will not suffer cruising at 1600. It likes to cruise at 2200 minimum. and so, I took out the double overdrive, and re-installed the 3.55s for 65=2240. But that killed my bottom-end torque multiplication by 18%, which is HUGE. To get it back, I had to go back inside the engine and increase the pressure. Plus, I had to run the Ignition Timing advance up higher, which then made parading impossible. So then, that mandated a dash-mounted, dial-back, timing module.
So,
in the end, I got most of the torque back, but there was nothing more I could do for fuel economy, except optimize the cruise-timing.
So, look what that 230cam cost me, over the previous perfectly running 223combo:
a different trans,
a different rear gear,
a higher Scr (which went to a higher deck height thru milling)
a new engine gasket set,
and the timing module.
For what? yes, for the next size bigger cam.............
I got greedy, and it cost me dearly.
My conclusion was,
that for me, the 223cam had been perfect. I was very sad when it began dropping lobes. Of course there might be some room for tweeking, lol.
My next cam may be a 272/276/108, if I can get one. the numbers are
272 intake/116comp/114power/276exhaust/58overlap
Again the compression is 116*, With which I can easily make 185psi CCP and
the powerstroke is now back up, 114* this time, and
overlap is 3* less than the 230 cam but 5* more than the 223, so I'm hoping for similar top end power(to the 230) but with better fuel-economy@2240 rpm.
Now,
having said that, those numbers of the 228cam are in at straight up. IF your engine is down on CCP, you can easily trade away 4 or more degrees of powerstroke, and give them to compression. At this level, those 4 degrees are gonna be worth close to 8psi. So your engine can go from say 157psi and a lil doggy, to 165psi, about as high as you dare run with iron heads and best gas. This will hardly affect the fuel economy, which at 114* of Powerstroke, is already borderline excessive.
Thus, I feel like a cam in the range of 223>228 is about right for a streeter that values fuel economy...... which I think is gonna make a real impact in the future, as the price of gas keeps going up.
Note-1
I also think it's worth mentioning, that if your throttle is rarely WOT, then on the street, high cylinder pressure is relatively meaningless. The reason is this;
at part throttle, with the Secondaries closed, your engine can NEVER achieve it's CCP anyway, and you could be operating down at an EFFECTIVE pressure of say 120psi. and I mean, a factory stock 318 can produce 140 at sealevel at WOT. so how often do you run even her at WOT?
That hi CCP, only comes into play, at WOT.
Oh, and every time you slap the throttle with a HolleyDP lol, which is why there is one on my 367. It makes her feel like a much bigger engine, and
I like instant tirespin that I can control with the gas-pedal, lol.
If you don't drive like me,
then just about everything I have said, is relatively, meaningless.
If I couldn't have my 367@195psi, then I would absolutely have a bigger engine to make up for the WOT powerloss. I'ma thinking a low-deck 444 would be about right, and then I could run iron heads @160psi.
Course,
I could also run a 318 at 225psi EFFECTIVE,.......... with a supercharger. You know, to keep Rumble, who has an incomprehensible love of the 318, happy.
But-um, that's not for me. If I'm gonna supercharge something, it ain't gonna be a 318, I want my money's worth..
These are my opinions.
