273, or 318?
I plan on running 3.73 gears and putting in an A500 overdrive. Try to stay with like the Isky E4 cam. I want to make an all around good driver, not just a drag car! All opinions welcome.
If you're really gonna cut up the tunnel to fit the A500, then numbers matching originality is gone . and
If you are installing that A500 in a bid for fuel-economy, then a short-period cam, high-pressure 273, is a natural.
But;
if you're idea with the A500 is to reduce the engine rpm that comes with hi-performance gears, then the hi-pressure-318, with a modest solid-lifter cam is a natural.
But if yur going that route, a cheaper alternative is the 360 or a Magnum with a regular automatic and compromise rear-gears.
There are so many ways to skin this cat, that it can takes months to finalize your decision.
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>IMO, for this Combo, you need to make your transmission decision the very first one, cuz it can/will make or break the rest of the combo.
>As for originality, the only guy that cares, is the one-in-a bazillion guy; and if you can supply the "numbers matching" parts, at the time of sale, it's all good, regardless of what's under the hood .
>Besides all that, we seem to be living on the Eve of Destruction, so ....... build whatever you want while you can, and drive it while you can, cuz there's a really good chance that, you'll never be able to sell it anyway....
>If it was me;
and overdrive not available; then
I'd go with more than a 273, cuz bigger will have more pulling power as the Torque-Multiplication wanes in each successive gear. Bigger will allow you to run less hiway gear. But
>If it was me:
and the A500 is for sure; then
your rear gears are unlimited, up to about 4.30s. This makes the lo-torque273 a natural...... in a streeter, and let the track results be whatever.
>No matter what;
the smaller the engine, the more important the flash-stall will be.
The TC in the A500 may not be available, in the stall that you may need, for a small engine. Or, if it is, it may be very expensive.
However, as the installed engine puts out more low-rpm torque, the flash-stall will be higher, increasing take off performance, and so, requiring less torque-Multiplication out the back-door.
>As for me, the smallest cid I would run in your dual/triple-purpose combo would be a very small-cammed, tight LSA, 340 with headers.
If fuel economy is somewhat important, than a high pressure 318.
If fuel economy is very important, than a high-pressure 273.
If fuel economy AND performance is desired, then you need a longer stroke with a cam that has a longer power-extraction cycle and less overlap.
>With log manifolds, forget any long period cam.The overlap provided by long period cams is totally stifled, and with it goes the power........ so the long-period does nothing but kill cylinder pressure, reducing low-rpm torque. All-in-all a disappointing situation.
> but here's the thing, with 3.73s and .69overdrive, the Final-drive becomes 2.57 and 65=2080 with 27" tires. This is too low for the stock-type distributor to meet the engine's cruise-timing requirement with even the stock cam, never mind any performance cam. So you kindof shot yourself in the foot. But, you can get a stand-alone timing computer to fix that, but fuel-economy will depend on the chosen cam.
The minimum rpm that the modified stock-type distributor can provide adequate timing, for fuel-economy purposes is ~2400, and that would require 4.30s@6500. and a cam to support that cruise-rpm.
Or you could cruise the 3.73s up to 2400, which would get you 75mph.