Installing a 4bbl on a 273 advice
Can I install the manifold and 500 cfm Edelbrock AVS2 carb in the mean time and expect the car to run reasonably or should I just wait.
Yes.
But, the engine will only pull as many cfms as it is physically capable of pulling. So if it can only pull 206cfm , it doesn't matter how big the carb is, 206 is all it will pull.
What I mean is this;
suppose you have 2.76 gears in the back, and a 904, and 25.5" tires (80"roll-out). At 3000 rpm this will be ~29mph, and by the math your 273 should pull
237cfm at 100% efficiency. But your stock 273 cannot hit 100%, with the small stock cam and heads. One might expect 60% so that would be
142cfm/29mph
By 4000rpm, the number at 65% now, might be
206cfm, now 39mph,
By 5000, your engine is way down the efficiency curve so maybe the number is
180cfm, now at 48 mph..... still in first gear.
No wonder it breaths thru that small single exhaust pipe (stock).
but go ahead and install a 500 . The 500 will pass the maximum required amount of air, without a hiccup.
Suppose your peak efficiency with the next bigger cam jumps to 70% at 5000rpm. Your new cfm requirement is
277cfm.
If you install a tunnel ram with a pair of 500s up there, and headers of course with a free-flowing exhaust, suppose your efficiency goes up 5% with those tiny heads, at a new higher rpm. Your new maximum cfm at 5000 is predicted to be, at 75%, is
297cfm . So I mean you got the potential up there to pass 1000cfm, but the engine will only pull what it can physically pull.
But suppose you spent a wheelbarrow of money on that 273 and got her up to 100% at 5000rpm, that would be
396cfm. So yeah, the 500 has lots of room to grow.
But I mean the stock 2bbl was rated at IIRC 180 cfm, in the 2bbl way, which I think, is 268 in the 4bbl way.
