If a low compression stock short-block, and in a chassis under 3500pounds, and a streeter; then any performance cam will want one of;
A) more compression, or
B) a higher stall and
C) if a 318, probably a lot more gear,but
D) if a 360, probably 3.23s to 3.55s depending on the trans , but
E) if a heavy beast, or for towing a trailer,forget the teener go straight to a 360, but
F) If a stick, you can just rev it past the doughy part on take off, and live with the slug it will be when stuck in the doughy part,in traffic.
G) if going racing, I can't say.
H) at 105,000 MILES, the timing chain on anything but a 340 s about to let go
If you don't know, performance cams don't make power. Cams move the Operating Rpm up higher, and the new operating rpm makes the power. But in the moving of the operating rpm, the cam always trades away low rpm to get the higher rpm....... so the bottom end performance of a low-compression engine , gets even lower performance. This is not real exciting to your 1975 Swinger 318 with it's non-LSD 2.76 hiway gears, and it's 1850rpm stall torque convertor. So now you have the added expense of those handicaps to deal with.
The 360 was born with 13% more cubes, so the low-rpm performance doesn't fall away quite as fast, but it's still the same story.And the 360 starts off with a 252 cam versus the 240 in the teener.
So long story short, the best cam for a low-compression318/360, IMO, is already in it. If you up-cam your streeter,and you don't bring the compression along with it.......it's gonna cost you a lot more than the price of the cam-kit. It's gonna cost you low-rpm/low-speed performance, up to say 3000rpm or up to 35 mph with 2.76 gears, and it will suck gas.
Now heads, on the other hand.......
BTW
Headers are never a bad idea.......................but on a stock combo won't count for much, unless what you're taking off is really really really,restrictive.
Now why do I say that? Well firstly, and engine is an air pump. If it only can process 200 cfm, then any old exhaust is sufficient. And secondly, if it doesn't process that 200 cfm until 3500 rpm, a reasonable number for a 318, This may not occur until 35/40 mph with the 2.76 gears that 318 cars typically have.. And after 3500 rpm the efficiency of that engine is falling anyway, so now again, the stock exhaust, if not too restrictive, is still able to pass the gas. If anything convert to dual exhaust and call it done.
But say you put a 4bbl on that otherwise stock engine. Guess what, it still may not pull more than 200 cfm thru it until 3500 rpm, so there you are in the same pickle.
There's only one way to make more power, and that is to burn more fuel, and to burn more fuel, you have to process more oxygen. and to do that you have four choices; 1) more cubes, and 2) more efficiency, and 3) more rpm, and 4) supercharging.
So with a given engine size, if the exhaust will only process 200 cfm, then you can put the biggest carb ever, on the intake, and it will still only process 200 cfm. Or if the carb will only process 200 cfm , headers will not make it flow any more. And if the cam in there says here your proud airflow stops,at 200, then there is nothing that you can bolt onto that engine,(save for a supercharger) to make it flow any more.
So as you can see, it's all in the combo. And yes a 4bbl and dual exhaust might free up a couple of hp..... but at what rpm?, and more importantly, at what roadspeed?
The absolute quickest and most noticeable increase in performance, is with a higher stall TC, and the second is lotsa more gear.
Some of the most fun I have had with my Barracuda, and a1973 stock low-compression 318, was with a 2800TC and a 9.73 starter gear. This was 3.55s and a 2.74 low gear-set in the A998. The equivalent rear for a regular A904 is 3.91s. The 4bbl and headers/dual exhaust was just icing.
Happy HotRodding
