Healey Gear Ratios

MPH 1st 2nd 3rd 3rd/OD 4th 4th/OD  
20 3405 2120 1475 1150 1105 860  
30 5110 3175 2215 1720 1660 1290  
40   4220 2940 2290 2205 1715  
50 5260 3665 2850 2750 2140  
60 4380 3405 3285 2555  
70 5090 3960 3820 2970  
80 4510 4350 3380  
90 5055 4875 3790  
100 4200  
110 4600  
120 5000  

The chart at left is the factory chart from the handbook of a 100 Six (BN6).

That car would have been equipped:

Tire size mm inches
Cross section 165 6.50
Wheel diameter n/a 15
Tire diameter n/a 25.39

 

 

 


Speeds with 165/SR tires and common gear sets on Big Healeys

diff. O/D 3000 3250 3500 3750 4000 4250 4500 4750 5000  
3.55 28% 82 89 96 103 110 116 123 130 137  
3.91 75 81 87 93 99 106 112 118 124  
4.10 71 77 83 89 95 101 107 112 118  
3.55 22% 78 84 91 97 104 110 117 123 130  
3.91 71 77 82 88 94 100 106 112 118  
4.10 67 73 79 84 90 95 101 107 112  
3.55 4th
no
O/D 		64 69 75 80 85 91 96 101 107  
3.91 58 63 68 72 77 82 87 92 97  
4.10 55 60 64 69 74 78 83 88 92  

This chart shows the engine speed/road speed for most combinations of gears with the standard radius radial tire.

Bold type shows my 100-Six with the 3.54:1 rear end gears.

Most Big Healeys have the 3.91:1 gears with a 22% overdrive

 

Engine Speed in RPM/ 195/60

diff. O/D 2500 2750 3000 3250 3500 3750 4000 4250 4500  
3.55 28% 65 72 78 85 91 98 104 111 118  
3.91 59 65 71 77 83 89 95 101 107  
4.10 56 62 68 73 79 85 90 96 102  
3.55 22% 62 68 74 81 87 93 99 105 111  
3.91 56 62 67 73 79 84 90 96 101  
4.10 54 59 64 70 75 80 86 91 96  
3.55 4th
no
O/D 		51 56 61 66 71 76 81 86 91  
3.91 46 51 55 60 64 69 74 78 83  
4.10 44 48 53 57 61 66 70 75 79  

This chart shows the engine speed/road speed for most combinations of gears with the 195/60 tires that I use on my car most of the time. Notice that the road speed is lower for the same engine speeds.