318 build advise
What should be the next "bolt on" upgrade (1000$ budget) to wake up more the engine? If you have any references do not hesitate.
to wake up the bottom end; you will need more cylinder pressure.
You could do this with either a solid-lifter shorter advertised period cam, or with more Compression ratio.
Failing that; you may have to install a higher-stall Convertor ... like a 2800 . This will allow your engine not to have to work in that low-power, mushy zone.
But if it's Performance you want, then you need some Torque-Multiplication, which points straight to performance rear gears, like 4.10s with that K6901 cam. A cam with less advertised duration would be OK with both less stall and less rear gear.
See, here's how this works; I suppose it would be possible to obtain 10 or more cams, all of
the same/similar, .050 numbers like your 218/228. That means, most of those cams are gonna make about the same power.
But the advertised durations could range from a huge 276/288 like your 6901, to a minimum of around 258/266.
And the LSA or
Lobe Separation Angles could be as wide as 114* like that Summit, or as narrow as 106*
These latter numbers, are gonna affect; the idle quality, idle-speed, low rpm power/torque, and sub 3000 driveability; which with 2.76s goes out to 3000~28mph.
Your 6901 cam was designed to sound big, have a broad powerband, be easy on the valve-train, and last a long time. But that same cam wants to be in a much higher compression ratio engine. And the reason is that at low rpm, the long advertised intake duration delays the trapping of cylinder pressure, so it comes in at a weak number, and the 114LSA only aggravates the situation. IMO, looking at the specs, it is a terrible cam to put into an already low-pressure 8/1 Scr street-318.. But if the idle-sound is what you're after, then it will be a good cam (54* overlap); so long as you stall and gear it to minimize it's weaknesses.
The good news is that the early Swingers were pretty light to start with. My 1970 was 3310 with skinny 17year old me in it. The car was 3200 on the track-scales. So they are not that hard to get moving.
As for me, I would pull that cam out, before it's broke in.
In an 8/1- 318 I would run a fast rate of lift, short advertised period, tight-lash, hi-lift , solid-lifter cam; and I would NOT care what it sounds like. I would still run the 2800 TC cuz I love that thing in a 318. And I would gear it to run outta revs in second gear at about 50/55 mph, which will probably be 3.73s to 3.91s; depends on tire size and where the power-peak comes in. I would get that cam on a 108 for a couple of hundred rpm on the top, to stretch my chosen gears out to 60mph.
For a Street-Performance 318, that's what I would do. Well, actually, I would pump up the pressure first, lol. But I get that not everybody chooses that path. Which is really too bad because that low static compression ratio is the 318s biggest handicap to making low-rpm power.
Here is something to think about; your 318 with a composition headgasket is gonna come in at about 7.8Scr. and in France I'm gonna do all calculations at 200ft elevation. With that 6901 cam, the specs are 276/288/114+4 and the Ica comes to 68*. Loading those into the Wallace calculator, I get;
Dcr of 6.07 @112 cranking cylinder pressure, and a
VP of a mere 80, like a stock 225 slanty; so at low rpm, your 318 is gonna feel like a stock slanty. Yes at 4800/5000 the
[email protected] will make some power, but not a whole bunch.
Ok lets take that cam outta there and install a solid-lifter cam of the same 218, but with an after lash Ica of 56*. this will make the same power at 4800/5000. The new numbers are; Dcr of 6.6, pressure of 126, and
VP of 100. That is a 100/80=25% increase of low-rpm performance.
Next, let's pump up the Scr to 9.5 with this solid-lifter cam, and the numbers are Dcr of 8.0, pressure of 163, and
VP of 129. Now 129/80=plus 61% ! That's what pressure can do for you.
Now you can go bigger on the cam, say 1 size , and pump up the pressure to 9.8Scr, and the new numbers are Dcr of 8.0, pressure of 164, and VP drops to only
126. But the bigger cam will make another 15 or more hp.
Read about VP here;
V/P Index Calculation
I know your engine is already assembled, and it might sound callous of me to print these numbers, but your thread has a good title, and new members will be finding it with the Search feature, for decades to come; so this post is more for future readers.