318 Build
Which cam spec, intake, head, and carb combo would you recommend for a just a hot rodded small block with a ldb4. Having power around 35-5500 and a lopey idle. I'd put the 4 barrel on the stock but I don't think it can use it.
Well since you asked the guys gave you some good ideas. But if it was me. And pumping the compression up was not on the table;
Wait, hang on,
when it comes to pricing this out, I can tell you that a rebore with hiC pistons and a refresh, is ,in the big picture, the best almost cheapest part of the equation. Once you have decent compression, the rest gets so much easier. For example, with decent Compression comes a strong bottom end.Back in post #14, we saw a vp of 133 with still the stock engine.
If you don't know what 133 feels like,consider this;
The stock low-C 360 2bbl engine.
Static compression ratio of 8.0:1.
Effective stroke is 3.02 inches.
Your dynamic compression ratio is 6.91:1 .
Your dynamic cranking pressure is 131.95 PSI.
V/P (Volume to Pressure Index) is 120..........................................120
and
the stock 1969 low-C 440-2bbl
Static compression ratio of 8.0:1.
Effective stroke is 3.06 inches.
Your dynamic compression ratio is 6.71:1 .
Your dynamic cranking pressure is 126.92 PSI.
V/P (Volume to Pressure Index) is 137...........................................137
You see that 440 with the 137VP? A 440 has no trouble spinning the tires on a 2.76 equipped 1969 New Yorker.
Also going back to #14, notice that 133/111= plus 20% more bottom end.
Plus 20% if you don't know it, is like bolting on a supercharger, at least from idle to maybe 3000rpm,lol
Plus 20% can be thought of as upsizing the TC to an rpm where the engine is making 20% more torque, like slipping out the clutch on a manual trans.
Plus 20% can sort of be compared to upsizing the rear gear 20% as well; say going to 3.23s from 2.69s, or to 3.73s from 3.10s.
So as you can see compression is a really big deal to low-rpm useage. Ask anybody who ever put a 268* into an 8.0 teener. The first thing you gotta do is get a big TC to restore the bottom end performance. Usually followed by some hi-perf rear gears. And what was the purpose of said 268*?, Mostly everybody does it for the lumpy idle.
Ok so where was I?
Oh yeah, if I was forced to not pump up the compression;
In this case I would combine all the ideas presented so far, with the express purpose of keeping the Dcr as high as possible.
This means a small very fast-rate cam. In fact I would order up a custom cam with the fastest lobes ever built, and follow the grinders instructions to the letter.
Suppose you could ditch 8cc on the 308s by milling .040. and suppose you could install the .028 gasket gaining 1.1cc back for a net loss of 6.9cc. This will get your compression up to about 8.5. Then I'm with the guys and about
[email protected]. So if you could get one ground with say 38* ramps, making a 256* advertised cam, this is what you might get;
With a 252/260/108 cam in at 104
Static compression ratio of 8.5:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.54:1 .
Your dynamic cranking pressure is 148.00 PSI.
V/P (Volume to Pressure Index) is 123.....................................123
Now while that is not nearly optimum,it doesn't look that bad. Your Dcr is only down a half a point and the cylinder pressure is nearly 90% of what it could be. I tightened up the LSA to 108 for two reasons, well three actually.
1) it's a streeter so by tightening it up, you get a bit more specific power, at the expense of powerband. Since this is a zero to 65mph car, and this is gonna be a 1-gear run with 2.76s or even 2.94s, or even 3.23s with 28" tires we don't care about powerband, nor rpm drop into second.
2) this makes 40* of overlap so maybe if you idle it slow enough you might get a bit of lope.
3) but mostly the 108 will keep the compression up
4) the 40* of overlap means that with headers you might get a little bit of "supercharging " at around peak torque.
This 256 might make peak power at 4800/5000 in the teener, so the shift rpm into second will want be about 6200, so make sure you get the right springs for that, and follow the grinders instructions religiously as to installed height and what oil to run. 38* ramps are pretty fast for a FTH, but get the most lift he will let you have, and then follow the break-in instructions to the T.
123 is a reasonable amount of VP for a teener, but might still want a bit of a TC to launch hard. You can make that decision after the combo is up and running and you have run it for a few hours and have got to know it.
With a power peak at say 4800, the torque peak will come in at about 3600. So for best results gear the car to be doing a little under 3600 at whatever speed you want to bust the hides loose at. For instance, 3.23s will get you 30mph at 3300 with 80" (25.5s)tires and 5% slip. If you have 245s start with those,lol. And work your way up as you burn them off,lol.
So that's what I would do if compression was out.
But here's what you're missing by not bumping the compression to what the cam wants.
Static compression ratio of 9.3:1.
Effective stroke is 2.82 inches.
Your dynamic compression ratio is 8.06:1 .
Your dynamic cranking pressure is 161.44 PSI.
V/P (Volume to Pressure Index) is 131.........................................131
131/123= plus 6.5% more bottom end. But in this case, the boost also translates to more power everywhere in the powerband, not a whole lot but still, more.
compare the above to this, copied from #14
To that end and interpreting that to mean from a dead stop,mostly, Here is what your combo would look like with the stock cam, and the compression boosted to the max,again;
Static compression ratio of 9.2:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 133..............................................
133VP
Notice the VP is up to 133, which is 133/122=9% more powerful than that 230@050 cam, and a whopping 133/92=
Plus 45% more powerful than the stocker. And the power peak is down at around 4500, or 50 mph with those 2.76s!, which is 8 mph sooner.
So now you are just 2 points of VP down from the best the stock cammed teener has to offer. I'd say hallelujah!
