Quote:
Originally Posted by FUNFER2
Dave- "Given a 3.31 rear ratio, .82 final drive, and a 27" tire you will turning 2195 RPM at 65, 2027 at 60. 26.5" tire height will yield 2237 at 65.
All things equal, with a 0.64 and a 27" tire you'll see 1714 RPM at 65 and 1582 RPM at 60."
To save gas in 5th gear from 65 mph-75 mph and up, would the .64 be a better choice ?
A potential problem may be with my 331 gears on the highway at 60 mph, will the engine be running too high of rpm's for 4th gear, but too low for 5th and will be lugging ?
Like I said, 331 gearing, 295/50 tires, at 60 mph my rpm's are at 2,000.
These are quote's from another site. I don't understand with his taller gears, how he can have such low rpm's at the speed he's at ?
"I run a TKO-600 w/ 0.64 OD and 3.27 gears out back. RPM id 2100 at 75mph. My engine is a 427 Side Oiler, 10.6:1 CR, Edelbrock Performer RPM heads, single 850cfm carb, and a VERY heathy cam.
but 2100 @ 75mph while good for the hwy means that you rev up 4th gear for those 40-65 mph jaunts down back roads and traffic situations"
Another-
"I running a TKO600 with lots of h.p. With 370 gears in the axel my rpm's are at 2100 at 70 mph. in 5th gear. 125 mph at 4000 rpm. good luck."
Last example-
depending on camshaft you might want to think about a road race version tcet4617 for the 0.82 overdrive
some of the bb guys we sold to in the past had issues with the 0.64 od in that the car was doing 80-90 mph before they could really use 5th gear- either the motor wouldn't work down below 2500 rpm in 5th or they couldnt wind out till that speed to get it into 5th
also what rear end ratio are you going with i have some customers running 3.73 /0.64 od for a fix of above problem
this is a rare occurance but its something to concider before laying out the cake
if you have any ??s give us a call
FORTE'S PARTS CONNECTION
508-875-0016 "
Getting confused on which OD, .64 or .82 ?
|
My gut feeling with your combo, the small mechanical roller, 482", Victor intake that with your 3.31s, 26.5" tires and a 0.64 overdrive your engine's not going to like to cruise under 75+ mph, maybe 80. That's just 2014 rpm at 75 mph with a 0.64 overdrive, 2533 with a 0.82. With the 0.82 you'll be able to sustain a 65 mph cruise at 2200 rpm, very doable with your setup. If your tire height is 27" it's even worse with the 0.64. I also think that you're even going to get some bucking at the 0.64 cruise RPM with what you'll be running. Take my advice and get the 0.82s and never look back. I'm sorry I didn't, but am not willing to spend the $$ and time to switch out my 0.64 TKO 600 to the 0.82 at this time.
As Patrick said, confer with your engine builder (Keith) before you make any decisions. I'd even pose the .64 or .82 question to him.
Dave