Your saying a 48* vs 51* is gonna murder the bottom end ?
What about if you carve the xe250h cam on a 107 lsa for the same 48*, shouldn't be all gain since it will have the same V/P ?
No, My comparison was to the 48* stocker.
Well that's the thing, the V/P at 116 is already at lawnmower status.
51* "only" drops it to 112.
Now pump the 8/1 engine up to 10/1 and run the stock cam at 48*Ica, and the pressure goes to 186psi and V/P to 155, now you got a chitload of bottom end with nothing but a change in compression.
Of course you can't run that much pressure with iron heads, without detonation.
But, you can run 9/1 @ 163 psi, 136V/P, about as good as it gets with iron heads. Personally, I wouldn't even run that low with my 367.
Now, I have run 197psi @ VP of 173 in my alloy headed 367 and can, without reservation say, that 173 is ludicrous on the street. So I took the motor out and apart and reduced it to 184psi, V/P of 158, and what do you know, I really missed that 173V/P. I tried all summer to get at least some of the missing bottom end back. In the End I installed a Commando transmission with 16% more First-Gear multiplication, and by the time I hit shift rpm in First, the rpm drops to just 4000, so V/P is no longer a thing, instead, now I'm riding on the 184psi. 11/1 Scr.
The point is this, a V/P of 112 or even 116 is so darn weak, you gotta get past it ASAP, and the 3500 will do that, But now the engine is trying to go fast on 140 psi@8/1 Scr, and it's all done by 4500 with that 250* cam, so the power band is from 3500 to 4500, and with 318 heads, and log manifolds, going down the backside of the curve, yur only gonna get a couple of hundred more rpm out of her. If you shift at 4800, the Rs will drop in at 2800, back in the crappy V/P zone, unless you get a higher stall convertor. Then, if the car is still running 2.76s, now yur in Second gear at 2800rpm, and pushing about 50 mph. Can you say sluggish?
Been there done that, it was no fun, I'll never do that again
The 2800TC works reasonably well with 3.55s , and the totally stock, but 4bbl engine, pumping thru a Free-flowing exhaust. Mine shocked a lotta riders.
Worked better with a 4-speed.
Even better with the A833od, 4.30s, and GVod as a splitter. This combo actually pleased me, but running a manual trans with snow on the ground, even with 4 studded tires, was not my cup of tea.
Eventually, I ran the A998 low gears, a 2800, with 2.76s, and a big Thermoquad. That combo turned out to be my favorite winter combo. I could hit 50 at the top of first gear, lol. Course at the shift, boom, she dropped to a tic under 3000, and with 2.76s, the rush was over.
But I learned to love that TQ carb. I installed a manual-shift on the trans, then I used to roll the barracuda out, and get her into "drive" as fast as she'd take full throttle, which with a 2800 is like right away. So then, the rpm goes to about 2800, and more or less stays there 'til I lift or like 80 mph, with the TQ howling all the way, what a hoot. Not fast but sure was fun. And the dual 3" cannons sung a sweet song the whole way.
But
I digress,
My 318 is a 1973 model, Still has the 73 cam in it. I gave it new rings in about year 2000. Mine cranks 140CCP at 900 ft, cuz I advanced the cam a lil. and I found some springs that will rev to just around 5200 IIRC; but otherwise, the long-block is 1973. The V/P at a calculated 116, is ridiculously low. I only used this engine for the winter, cuz it's what I had, and I doctored it with the 2800, and the gears.
Before the snow came, I sometimes still had the "meats" on the back, and notta chance could she break them loose, even with the 2800 TC. So, even tho it was, a ton of fun; I comforted myself by knowing that, come May long weekend, the HotRod367 was going back in.
