As to cams
I'll say it again, if you are not gonna bring the compression up, then the 340 cam will have a very disappointing off-idle performance, with the 3.23s and the factory TC. Me personally,I wouldn't ever do it again.
Especially since I have already done it the other way, and have experienced a 340 with a teener cam! Now, a 360 with a teener cam has got to be even wilder, within the parameters of a DD and streeter. The torque boost should be exceptionally nice. Worth the $200,oh yeah!
But I tell you what, it's not the cam alone that makes it a winner, but the early closing intake valve, that keeps the cylinder pressure up. If it was me, this time around, I would be calling a cam grinder, and getting a cam with a similar ICA, but with as much lift and duration as the grinder will be able or willing to put on it.If he tells you to put certain springs on it and a rev limiter,do it! There is really no reason to limit your engine to a teener cam, when it is the
Intake
Closing
Angle that you are after to keep the pressure up.
By doing this, you may be able to extend the operating rpm just a few hundred rpm,and thus pick up more power, and the added lift will punch up the midrange. A cam like this would have to have very fast lobes, and typically would need a ton of spring pressure to keep it all together.A flat tappet might not survive that for long. So, my theory is, with the very short period teener type ICA cam, the rpm is gonna be limited to an early redline. Therefore the spring pressure can be reduced some, and the cam will live longer.
So that's what I would do.And the cost difference is very small. I would order the cam dead-last, after the exact Compression Ratio has been determined.
Actually, having already installed a teener top-end and cam into a 340 in the early 70s,I would be very tempted to slam some small-chamber teener heads onto a 360 and with a stock teener cam. So, the heads will run out very early, but so what,it's a DD.And the torque increase will be phenomenal! And it would only cost me time, cuz, I already have all the parts.
Ok are you ready? I did some math....
In order for a stock 360 to make a 8.5 CR, with 72cc heads, the pistons need to be about 17.3cc or .084 down in the hole.
Now if you took some closed chamber heads of about 60cc and bolted them on instead, then your Scr would come up to about 9.5.
This is the magic number for that 340 cam, that you already own! The Dcr comes up to 7.62 and the pressure to 150psi.The Dcr is still not optimum, but it will support the cheapest gas around.And the 150psi, will make the off-idle performance just as snappy as the teener cam.The 340 cam will extend the operating range several hundred rpm.
The only downside might be if those 60cc heads came with small valves; that would kindof defeat the purpose of the 340 cam,again.
So now we are looking for 60cc heads with big valves, and bigger ports would also be a bonus.But hold on a second. How often are you looking to run 4800 to 5500rpm? It's a streeter with street-gears right? Well, 5500 is about 50mph with 3.23s.
And I'll bet you a donut that you are only gonna get there once in a while, versus all the hundreds of trips where you are gonna be shifting at sub-3000rpm.
So now if the choke of 5500 bothers you, you still have choices; With the newfound compression, you can go back to say 2.94s. The 10% torque-multiplication loss will be a 10% gain in speed at 5500, which now is 55mph. With a 2200 TC, and 150psi, never having driven the car with 3.23s, you will not notice a loss of torque down low, as compared to the stock 360 cam. So now things are coming together. But if you need a bit more off-the-line, the next bigger TC will probably get it.
Another choice you have is headers and a free-flowing exhaust; Which should really be the very first thing on your list. If the hot exhaust can get out of the chambers in a hurry, the choke of the small valves will be a little more tolerable, on the street.
And I can attest to my totally-stock-long-block winter-teener pulling really hard thru TTIs and full-length 3inch duals, to well past 5000, and with springing, to 6000;allbeit with less authority.I even ran it with 2.76s and a 2.74low gear,and a 2800TC and was not unhappy with it.
So, I know I just thru a monkey-wrench into the mix, but I remember that combo so fondly, I just had to mention it.
For you,the added cost of the 60cc heads, would supplant the cost of the 340 cam which you are so eager to install.
Now you can machine your 360 heads down to near 60 cc, but the cost is hardly worth it, when better small chamber heads are out there, and don't forget that with so much cut off the 360 heads, the intake will no longer fit,so that will have to be remedied as well. And if anything gets cut crooked, well that is just incredibly aggravating to find out after the engine is assembled.......or installed.
So just in case I have really confused you, here is a recap;
-Stock 360 short block, with
-closed-chamber heads around 60cc
-340 cam kit
-2.94 gears,
or less.
-headers and freeflowing duals
-Stock-type 2200TC; up to 2800 optional
In a DD, I know that I could be happy with that combo, especially in a lightweight chassis.
Sorry,man
But this is what has to be done in order to work with those sorry-azz pistons;compromises.
Personally, I think the best solution ,bar-none, is proper pistons and leave everything else alone. .084 down-in-the-hole is 17.3cc. This handicap is incredibly hard to work around in most cases.Plus with the proper sized chamber, and tight-Q, you are all set up for any future changes in camming.Yes, if you get the proper pistons in there, then the 340 cam that you already have, will be perfect. And so will be the stone-stock 360 heads.
I'd say "trust me on this", but that just sounds so impudent when I hear that it totally turns me off; so I wont..
My pistons of choice would be the KB 191/192s, custom fit into your unmachined heads to achieve a reasonably tight squish. The bonus of doing this is that you will be able to run a higher compression on crappier gas. The
bonuses of the higher compression are; Better drive-away, more torque,more power, and better fuel economy. You can run less gear and less stall. You can put 3 other hefty boys in that car, and still be able to take off briskly; or in my case with a 10.97 starter gear,take off with fire,smoke,brimstone, and screaming tires! Well maybe not the fire and brimstone.....
