1966 C10 250ci ring/pinion swap?

[The1960APE]

I'm just full of questions this week! I've been driving the 66 around town a bit, the truck is a 3 speed on the column with 4:10 gears, right now in turning around 2800-2900 rpm at 55 mph with a 27" tire, I am getting ready to swap to a 29" tire which should change the rpm to around 2600, being that I would like to commute to work and some truck shows 100 miles away I would like a more highway friendly ratio... I am not interested in swapping to a 5 speed as I may do a LS swap down the road!
I was looking at ratio charts and it looks like with a 3:42 and a 29" tire I would be at 2179 rpm at 55 mph which seems a lot better, my question is does the 250 6 cyl have enough power for me to swap to a 3:42? Has anyone done this?

[Lugnutz65]

Originally Posted by The1960APE

I'm just full of questions this week! I've been driving the 66 around town a bit, the truck is a 3 speed on the column with 4:10 gears, right now in turning around 2800-2900 rpm at 55 mph with a 27" tire, I am getting ready to swap to a 29" tire which should change the rpm to around 2600, being that I would like to commute to work and some truck shows 100 miles away I would like a more highway friendly ratio... I am not interested in swapping to a 5 speed as I may do a LS swap down the road!
I was looking at ratio charts and it looks like with a 3:42 and a 29" tire I would be at 2179 rpm at 55 mph which seems a lot better, my question is does the 250 6 cyl have enough power for me to swap to a 3:42? Has anyone done this?

I have a 230ci in my 1965 short bed stepper. My 230ci has enough power to pull my 0.72 OD gear and a 29" tire. You should be fine unless your 250ci lacks power because of low compression, etc.

[The1960APE]

Originally Posted by Lugnutz65

I have a 230ci in my 1965 short bed stepper. My 230ci has enough power to pull my 0.72 OD gear and a 29" tire. You should be fine unless your 250ci lacks power because of low compression, etc.

The 250 runs really well, I am also going to do a little work to it, HEI, tune up etc but unless I am taking off up a hill I don't even use 1st gear!

[TJ's Chevy]

250 has plenty of pull for a 3.42 ratio. HEI will help some, more in mileage and easier cold starts.