need tuning help on 340

j.d.duggan said

AJ/forms,I don't understand your above statement about a 2.66 low?what is this?The compression # were cold engine,throttle slightly open,all plugs out and 4-5 revs.on each cyl.what would the total advance of a dist be.I don't have vac advance at this time.:BangHead:

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2.66low is the low gear ratio in the A833manual trans. The ratios are 2.66-1.92-1.40-1.00. The starter gear in your combo is 2.66x3.23=8.59 which is fine for a stock 340, but perhaps a little tall for a cammed up one..... unless it has plenty of cylinder pressure, like yours seems to have.
The starter gear ratio, together with the tire roll-out(circumference or TC) can be plugged into a formula and with either the mph or the rpm plugged in, the other can be determined. The formula reeds;
mph= (rpmxTC)/ (1056x R1xR2)
where; the Rs are the ratios; 1056 is a constant; TC is Tire Circumference;

Example; mph= 6800x85(a 27"tire)/1056 1.40x3.23=121mph

or mph= 600x85/1056x2.66x3.23= 5.6mph

the constant 1056 is a conversion factor that converts all the math to the correct mph.