tach setting

ive just installed an autometer tach on my 225 now there are little switches on the inside for 2 3 and 4 pulse , right now im set on the 3 pulse which is for 6 cyl, it just seems that the rpms are a little high at that setting, should I be using the 4 pulse setting, and also what are you guys reading at say 45 mph . Im getting about 2000 rpms at about 45mph at that setting and idle is about 850, when I had it on the 4 pulse setting i was running about 13 to 1500 at 45 mph and idle was about 750 , thanx for the help

 

3 pulses should be right. If you have 4.88 gears the engine will rev that high at 45mph. As far as idle if its smooth you probably do have it idling at 850rpm.

 

yeah thanx im trying to find out what gears I have in it , its a 1960 and i think its a stock axle, doing a search but if anyone knows id appreciate the info

 

You running an overdrive?
My Sixty runs 2800 to 3000 at 45 with the 5.38's T90 tranny and the 215x75x15's.

 

Any tags on either of the axles? Or else you can remove the cover and the tooth count will be stamped into the edge of the ring gear.

 

X2.
Would be a lot less messy than pulling the cover, Unless you want to check the condition of the gears and all.