Which head/combustion chamber is better for performance? Speed master aluminum LA or aftermarket magnum iron head?
My impression of an AJ response!:
I like you. already.
Too bad yur 2000 miles away.
The
short answer is;
IDK the answer to this question.
But I can tell you that running over 190psi cylinder pressure, on 87E10, makes me a very happy streeter. I saved a lotta lotta money on running that cheap gas.
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The
intermediate version is;
My combo is pretty much limited here in Manitoba to 65mph, 75 on certain parts of the TransCanada hwy, and when I come stateside, a lot of interstate traffic is doing 85, unless the occasional Corvette comes by@ 110plus.
Therefore, I set my car up tp be revved right out at ~60>65 in Second gear. Theoretically then, I just cammed it to hit the marks and until I do something with the Suspension, the car is traction limited, and I really can't ET any significantly better.
However, I really don't care how quick the car isn't.
The problem for me was cruizing.
To hit that 60@6000 mark with a 4-speed in Second gear, requires a rear gear of 4.10........ Even with a GVod, that is still 65= 2600, and there is no good mpg to come out at that rpm.
But the thing is, with my suspension, the tires are still spinning at 60mph, so I reasoned that the car won't be any slower if the tires are spinning at 6000 or at 7000
And that opened up a new world for me.
I installed a Commando 4-speed and 3.55s, and I bypassed the GVod ECU for split shifting.
Now I hit 60 @6400 in First-over, and for cruizing I get 65=2240 in GVod. So now, I just recammed it for that. See with an HO 360, you can do stuff like that. IDK how it wouldda turned out with a 318.
Caveat*1
>>One thing with a manual trans, that a guy has to be aware of is driving slow.
With the 4.30s that I was running with the 2.66 low, my slowest speed was 3.8@550
With my new 3.09 low and 3.55s, 550 rpm is 4mph. The only ways to drive slower are; to ride the brake, ride the clutch, or retard the timing. I chose timing and at 5*, now she runs 500@ 3.45mph.
Some of you guys might ask "why is this important?"
Well my answer is this, until you have the capability, you won't get it.
But once you hear your modest street-cam rumpity-rumping across the parking lot at 500rpm, then you'll get it. And following pretty women in a parade is just icing on the cake.
The
long version.
As to fuel-economy;
IMO, cruizing at 2240, really has potential.
For one long distance trip, I set the car up, geared for 65=1600, which was 85@2100. I installed a specially prepped Holley 600, and I had my Cruize timing dialed in. The car went 32mpg on that trip, point to point, with a 223/230/110 cam pumping 195 psi.. Now, I know that some of you are gonna doubt that, that's your problem, yur not thinking outside the box. If your car only needs 35 hp to go 65mph, then just tune your car to make that, and the only difference between a 2.5 liter engine, and a 6 liter engine, making 35 hp, is internal friction. But while the 4-banger has to spin about 2200 to do it, obviously, the 6 literV8 has enough power at 1600. and in my case, even lower.
So before you start slinging mud, go ahead, build the combo and prove me wrong. Then you can get the facts. and BTW, the 600 Holley is a gashog, compared to some spreadbores.
The reason I talk about fuel economy
is because in the very near future, I believe the cost of gasoline is gonna skyrocket, as greed envelopes this old world of ours. Therefore, if we wish to continue to drive our 400 hp behemoths of yester year, it behooves us to modernize them, to get similar to 4-cylinder fuel economy.
I have over the last 20 years, developed a winning combo.
For those of you still running small-displacement, 8/1 iron-headed slugs with open chambers, with near 292 cams, and 3500+ stalls, and 4.30 gears ..... Your days are numbered.
IDK the answer for you.
But IMO; the one thing I believe, is that, the days of 3-speed autos and 4-speed manuals is rapidly drawing to an end.
As are long-period cams and,
and lo-pressure, open-chamber, iron heads are only days behind.
If you are presently building an old-school combo like that, it won't be very long until the car will be a Saturday afternoon only car, and not long afterward, she will be up on blocks; I believe that. This is especially true as most of us are pushing retirement years, and will be on fixed incomes soon.
So here is my recipe, for the coming age.
NUMBER ONE thing is to get an overdrive, and a decently low starter gear . You need to get the hiway rpm down. And I very highly recommend a manual trans, so that you can get rid of the highstall convertor. They say that convertor is costing a DD at least 2mpg. IDK if that is true, as I have never tried it.
Then, after the chassis has been determined, only now should you begin to discuss the engine.
To that end;
I have had good success with a small block with very hi-pressure closed-chamber alloy heads, and Very tight quench flat top pistons. with adequate ring-gaps and notta chance would I run lo-tension rings on the street. and My next cam will be a modest solid lifter flat-tappet cam and I will send some oil directly to the lobes, so that I can continue to rev the beotch with hi-pressure springs, to not lose control, and the lobes yet live. I will need a custom cam, no doubt.
I run a hi-volume oil-pump so I can leak some oil to various important places that will otherwise die at idle of 500 rpm. and of course, I run a hi-capacity oilpan if for no other reason than oil-cooling.
That's the basic plan. After that, the bolt-ons are same as usual.
The last page
What cam?
Well, that's tough; I haven't seen an off-the-shelf grind that interests me.
But two things I already know; Since I will be targeting ~195psi, and I know the Scr will come in at around 11.3 with a 6liter, this already sets the Ica at 60 to 64 degrees. And Ima thinking I want an LSA of 107 or less., and I want a longer than might be considered normal, power stroke, for fuel-economy. The rest is up for grabs, but with direct lobe oiling, I'm thinking a high energy design (not a Comp. Hi-Energy), is what I'll be asking for.
and BTW, knowing what I now know, 430 hp is NOT on my horizon. Ima thinking 300 will be more than adequate. I'm even considering a 318LA, yes it's tru, considering.
Here's a hypothetical cam I'm considering.
226/232/107 hi-lift this is 050 net after lashing.
At zero-lash this might be 272/280/110 and if it was, then
Ica would be ~62*, the Powerstroke would be ~112, and overlap might be ~62*
I could get some serious MPGS out of that 112*Powerstroke, if I can just make that 62 overlap behave at 2200.; that's gonna be the trick. But I got some ideas.
Meh, I might have to downsize a lil. The problem with downsizing is now the cylinder pressure goes up, and I'll have to reduce the Scr to less than 11.3. No biggie, we have the technology.
I have time this winter to play the numbers game.
I even have a couple of 340s I could choose from. Yeah 22 cubes would flesh out the bottom end just about right.