Aluminum cylinder heads
I just wanted to be able to explore my options for when I freshen up the 318. Magnum heads require a expensive magnum only intake and the 302 heads are usually cracked, so I'm trying to find out what I can / should do, I'll probably wind up rebuilding the factory heads.
IMO
as usual
you will never be sorry if you go alloy.
But
one of the best ways to get the most out of them, is to pump up the cylinder pressure ........ because
you can and should; on account of their excellent resistance to detonation. With a 318, getting in the neighborhood of 11:1 or more, is a bit of a challenge, as the cam's ICA grows ever later. Pistons are the problem.
IMO, to date, this is by far, the best idea you have had. The high cylinder pressure opens the door to so many advantages; Power, Torque, economy, a very low cruise-rpm, excellent throttle response that is almost guaranteed to pucker you pooper, the ability to run the lowest octane gas at least most of the time, and more.
Alloy heads, in the right combo, will help your 318 get to the next level in performance, while simultaneously increasing your fuel-economy, and shedding the "old-retired-guy/tread lightly cuz I'm done" nature, of the lowly 318.
Sure you can achieve similar results with closed-chamber iron heads, but probably not on 87 gas. And at the price of gas today and into the future, this is gonna become a serious concern. The savings in fuel costs alone are pretty significant. And so is a 20 or 30 percent increase in mpgs. IDK the price of your fuel down there but lets say you pay 6.50 a USg for 87 and plus 12% for 89 and plus 24% from 87 to 91. The numbers might be off but the percent difference should be accurate.
Say you drive your low-compression 318, 6000 straight hi-way miles in a year and typically a 318 A-body gets 20mpg. that will cost you 300 gallons of 87 gas equals
$1950.
If you modify that unit with iron heads, and have to run 91gas@WOT, but now she only gets 18mpg due to loss of effective compression,etc, then you are looking at $2690
But if you install alloy heads, and pump up the effective compression, and now she gets 24mpg on 87, your costs drop to 1625.
But wait, now you are primed for an overdrive, and say the mileage jumps to 27; now yer looking at $1440.
So in a year, the theory is to save the difference from 2690 to 1440, and I get $1250.
If you spend $5000 on the alloy heads/valve gear and the A500, and NOTHING on gears or TC, cuz your hi-compression 318 pulls any gear at all, what's the pay-back period?
I get 4 years.
After that, yur still saving 510 per year, until you need a valve job, lol..
And during the which, your power-increase is soooooooo much fun. When you plant your right foot and stuff actually happens at the back tires, it's like;
"yeah baby, shower-time!".
I have run 185psi and more on 87E10. Other FABO members claim 200 on best gas. My current combo is a tic under 180. If I ever get an opportunity to do it again, I will target 190 or better.
Now, recall that the numbers I used are straight from my imagination, but the differences between them are proportional, so, by percent, they could still be meaningful. AND
My Eddies have over 100,000 MILES on them, and are still going strong. In terms of Dollars, those heads payed for themselves many many years ago. In terms of fun, I loved the significant cylinder pressure possible, right from the first time I ever nailed the gas!
So if there is one thing I can tell you, it is this;
with alloy heads; FORGET 9.5Scr, it is meaningless. Forget 10/1, and also forget 11/1.......... The thing that is important is your EFFECTIVE cylinder pressure, which starts with knowing your cranking cylinder pressure. And you cannot know that until the cam is installed. But you can use all those numbers in a Dynamic Compression Calculator, to get pretty close. I use the Wallace Performance one.
Wallace Racing: Dynamic Compression Ratio Calculator
