Putting a 268* cam in it will raise the horsepower all right, but it will do this by raising the rpm of that peak power. It will trade away low-rpm power to get that hi-rpm power.
So lets talk about what is happening. in terms of road speed. Your slanty car probably has 2.76s in it. And your new teener probably will make peak power with a 4bbl and headers NO CAM,and NO compression boost, of about 260crank hp, or a bit more. And it will do it at about under 4000 rpm. With2.76s, this will be about 42mph@4000. The stock cam starts making torque right off idle and by 2400rpm is peaking. This is 26 mph. So what you have with the stock cam is a very strong blast off to 26 mph, then as power is building, the teener "rockets" ahead to build peak acceleration at 42 mph, then as the power falls off, she will be done by maybe 4800 with the 4bbl and headers, which will be 48mph@4800.
This is almost ideal power delivery for a streeter.
>Now lets put that 268* in her.
This will move the power peak up to 5000 or so, and the torque peak up to 3800. The road speeds associated with these numbers are 41 and 54. Furthermore, the low speed torque will be traded away to get those few horsepower at the top. So now your car will be slower up to 26 mph, then build acceleration to equal what you had before at maybe 35mph, and then begin to rocket in acceleration, to peak at 54 and run down the backside of the curve to be running out of steam at 62mph.
There is no getting around this.
>To recover the bottom end you have two or three options; waay more rear gear, and/or way more TC. I would guess that the fix would be at least 3.23s and a 2800TC.And a healthy dose of compression.
Were you aware of this, and are you prepared for it?
>Knowing that the car is gonna need gears and a TC no matter what, here's an idea; Put them in NOW! It will save you going thru the too-big-cam syndrome with the lazy low rpm performance. I would also suggest, at this time, to skip a cam altogether, until you see what 260 crank hp feels like in your new barnstormer.
The cam increase works best with a compression boost, which calls for a complete engine overhaul. If you skip the boost, you are heading down a trail of disappointment. The overhaul may escalate to 4Gs or more. Are you prepared for that?
>So, in the interest of saving you this aggravation and disappointment, why not go ahead and do TC and the gears first.
>Lets look at that 260hp engine again with 3.55s and a 2800 tc
This Tc will let your engine spool up to where the torque is, and the power starts. And the 3.55s will put it to the ground earlier and faster.Whatever power that engine has,these new gears will multiply it by the difference in the gear ratios, so; 3.55/2.76 more times than before. This is a 29% boost. This is about 3 times what a camchange will do for you. But unlike a cam,which trades away low-rpm for hi-rpm, this is an across the board increase. More TM (torque-multiplication) from idle to whenever it blows up. Next is the TC. By letting the engine spool up to a new higher rpm, lowspeed performance is also increased, just what the teener needs. This boost is fleeting, tho. It starts as soon as you hit the gas, with a healthy dose of Giddy-up, but this kindof slips away as the roadspeed increases , also perfect for a teener.
So lets throw out some numbers;
>With these changes, you will be able to smoke your skinny rollers back there, so the next thing will be getting bigger tires and a traction aider and of course an LSD. Once that is sorted, And you can actually floor it; this is what I see.
>I see the teener blasting out of the gate to its rpm of peak torque, which with the new TC is at less than zero miles per hour, so no more waiting til 26mph. Then,I see the mighty teener "rocketing to it's power peak,still at 4000 or less, but now at 35 mph instead of 42.Then I see acceleration slowing a bit as the engine approaches shift-rpm of 4800@42mph, instead of 48. So all your engines power will be used up by 42 mph instead of 48. This is about 13% earlier, and the blast-off is vastly superior, with the bigger TC.
The result of all this is that your ET from zero to top-of-first-gear is going to be waaay quicker; because of the more average power put down per unit of time.
> I suggest adequate spring pressure to allow up to 5500 rpm shifts. Then you can extend the run from 42mph, back up to 48mph, when you need to. Power will be dropping off rapidly after 42, but sometimes a few extra hundred rpms comes in handy.
Long story short; I would leave the long-block alone. I would get some more gear under there with an LSD, and a 2800TC and some valve-springs and of course,bigger tires. The biggest tires you can fit . I would have fun with this, until such time as you have become accustomed to the performance, and it becomes not-enough for you. At that time I would drop in a stock long-block 5.9 This will be able to use all your bolt-ons and will be a 360/318= a 13.2% increase; or from 260ish to 290ish And you do not suffer the gas mileage hit. Camming up the 5.9 is no different than camming up the teener. Low-rpm power is traded away for hi-rpm power, and every cam change should be accompanied with a compression change;and very often a new rear gear to release the power in a timely fashion.
