With free breathing in and out, my low-C, 1973 stock long-block teener, pulled pretty good to 5000, and with more valve spring pressure to over 5500 with the stock 240/248/112 cam. It didn't pull hard up there, but what did I care; it was my winter engine.
With 3.55s,and a A833od/GVOD, 5500 was 52mph in 1st/over using 2gears.
With 4.88s, and same trans, 5500 was now 54mph in second, using 3 gears (still splitting gears). And cruising (with the 4.88s) was still 65=2180 with double overdrive; That combo was a real hoot.
Eventually I put an A999 in her for winter, that was nice in it's own way.
If I was gonna hop up MY 8.0ish teener, this is the cam I would go shopping for;
First it would be a mechanical flat tappet with ramps of around 38*. Lunati seems to have a handle on this.
Then I would tighten up the LSA to 102, cuz this teener is gonna be a one or two gear deal, so I'll be looking to move the power as far up the rpm band as I can. Next I am gonna slam that intake closed as early as I can to actually make more cylinder pressure than stock, to increase the low-rpm performance, so I can run 3.23s. I don't care so much about the power/exhaust side, as long as it comes along for the ride. And finally I'll be looking to increase steady-state point to point fuel economy.That looks like a winner to me.
To that end; the stock cam is 240/248/112 and has durations of: intake of 240,exhaust of 248, overlap of 20* ooo so scary. Now compression and power total 252*, and if you install it at 110, then you will have an ICA of 50* . At 8.0 Scr,Mr. Wallace says this will bring the Dcr in at 7.0/135psi/111VP. I have no clue what the .050s of this cam might be but I suspect less than 190*. Sooooooo; 111VP is not quite marshmallow soft but almost.
>>So here is the solid flat-tappet cam I worked out: 252/256/102 It has durations of: intake of 252 (plus 12), exhaust of 256 (plus 8), overlap of 52 (so she idles with a bit of a lope), compression and power total up to 264 (plus 12), and if you install it at 100*, then you will have an ICA of 46* . Still at 8.0 Scr, Mr. Wallace says this will increase the Dcr to 7.2 (up .2), pressure of 139 (plus4psi), and VP now 117 (up 5.4%). The .050s of this cam might be 214/218. So I estimate this cam to be (214 less 111)/7= more than 3 sizes bigger than factory. That's a huge jump to not have to sacrifice low rpm performance to get.
Now lets analyze this cuz I know you all think I'm crazy to install a 102 LSA cam in there. Ok so this cam will power peak at what? I'm guessing 4700, and she'll be dropping off rapidly after 5000. But she'll be building power very fast and peak at a higher number than the generics. The sacrifice is the powerband; there ain't enough for an automatic; the 1-2 shift will drop the Rs from 5000 to 2950= 2040rpm, and I'm guessing the engine might struggle a bit with that. But I don't care cuz I'm gonna slam it into Drive and call it done. Why? Cuz with 3.23s this is 50mph,fast enough for my application: I just want to scream thru first gear burning up the tires, and rattling windows thru my dual 3inch cannons.
Now, to help me get off the line, I'm gonna try my 2400TC. 65 mph will be 2500 with 28s so that should work out for me. I like the 2800TC that I already have, so if the 2400 doesn't work out, she's my back-up.
>>Now let's talk about fuel economy.
Firstly the cylinder pressure is low enough that she'll run on 87E10. This is important to me Cuz I'm gonna rack up a lotta miles on this poser. Wait Poser? Well yeah.... It idles quite a bit lopier than A 340, but she's done real early, and when she hits second, she's gonna nose over for a while. I'd call that a poser.
Secondly, with the ICA set to 100, the time allocated to compression is 134*. That's a lot of time. But it doesn't mean that much in this combo, cuz the pressure only hits 139psi. But, on the other side, power extraction time is 130*. This is HUGE. Normally a guy wouldn't run this much on purpose cuz most of the energy in the exhaust is pretty much used up by 110/115 in a hotrod engine, and if it's not,we don't care cuz there's another charge coming right behind it. ....... But this is not a hot rod engine. And the only way to run less is to muck up the other timing events, so 130* it will have to be. However, in this engine, those 130 degrees will help her burn up every last molecule of gas that finds it's way in there.... at cruising speed. Finally this cam will come out of reversion a little below 2200, so that's a minimum economical cruising speed of 54mph.
So that about covers it; I get a fat little power-curve, a little more torque down low, better Hi-way fuel economy,and the lopey idle everybody loves. The sacrifice is occasional valve adjustments........ And with an automatic, it's kindof a one gear deal.
>>But I don't have an automatic.I have a 3.09low 4 speed and am using the GVOD as a splitter. That makes my powerband requirement with a 5000 shift, just 1100rpm ............... purfect for this cam.
So that's what I would be shopping for; a 252/256/102/52 o-lap, fast-rate, solid, flat tappet cam, with as much lift as the grinder will give me or whatever lift I can make the heads accept. and ................ you just know I'm gonna send those little tiny heads out for a little work ........ Or maybe I'll.........
but if a 102LSA cam scares you
>here are some other, a lil less power numbers;252/260/104 now 48* of overlap, still makes extra pressure with an ICA of 48* (vs50* stock)
> or how about 250/256/106,now 41* overlap same 48* ICA as factory
> or how about 248/256/108, now 36* overlap, same 48* ICA as stock, in fact, same 252 total for compression plus power, as stock. This is actually one size bigger than stock but with the LSA closed up to run a few hundred rpm higher.And higher rpm .....is supposed to make more power.
But I myself would go straight to the big dog; 252/256/102/52 overlap
