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Gear Change-What difference? #1496401 09/04/13 11:16 PM 09/04/13 11:16 PM
Joined: Feb 2009 Posts: 1,532 off the grid 340B5 OP pro stock
340B5 OP pro stock Joined: Feb 2009 Posts: 1,532 off the grid	Sooner or later, I'm gonna put my 4.56's back in. The 4.88's served the 340 well, but now it's a 374 in.(3.58 stroke)with light internals. The bobweight is 1807 and it revs pretty quick; enough that I'm on the rev limiter for the last 300'. Present 60' is 1.49 and best ET is 10.95@ 119.7mph in 73 deg air. I can't remember DA for sure. Anyway I'm guessing 1.51-1.52 60' and definitely some more mph. Car is 3085 w/me in it. Anyone care to guess? It couldn't possibly stay the same or improve 60', could it? Yeah, it's got a smallblock.

Re: Gear Change-What difference? [Re: 340B5] #1496402 09/04/13 11:26 PM 09/04/13 11:26 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	I'll ask... what rpm are you at now... a small block loves the revs IF it has the carb, intake, heads and exhaust to let it rev... remember this is nothing but a air pump

Re: Gear Change-What difference? [Re: MR_P_BODY] #1496403 09/04/13 11:43 PM 09/04/13 11:43 PM
Joined: Feb 2009 Posts: 1,532 off the grid 340B5 OP pro stock
340B5 OP pro stock Joined: Feb 2009 Posts: 1,532 off the grid	I've been shifting @6050 and 6450. Trans has 2.74 low and tires are 30.25 true dia. The engine is limited to 7000 and that's pushing it as far as I want to go. Yeah, it's got a smallblock.

Re: Gear Change-What difference? [Re: 340B5] #1496404 09/04/13 11:52 PM 09/04/13 11:52 PM
Joined: Aug 2003 Posts: 43,173 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,173 Bend,OR USA	If it is at 7000 RPM in high gear why wouldn't you want to rev it to 7000 RPM in 1st and 2nd gear so there is less strain and high RPM time on the motor in high gear at 7000 RPM Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Gear Change-What difference? [Re: Cab_Burge] #1496405 09/05/13 12:23 AM 09/05/13 12:23 AM
Joined: Feb 2009 Posts: 1,532 off the grid 340B5 OP pro stock
340B5 OP pro stock Joined: Feb 2009 Posts: 1,532 off the grid	ET has been better w/ the lower shift points. The engine has iron J heads. Yeah, it's got a smallblock.

Re: Gear Change-What difference? [Re: 340B5] #1496406 09/05/13 02:11 AM 09/05/13 02:11 AM
Joined: May 2011 Posts: 101 NC 1 1967Valiant member
1967Valiant member 1 Joined: May 2011 Posts: 101 NC	Put a 4:10 in it I think you will be amazed!

Re: Gear Change-What difference? [Re: 340B5] #1496407 09/05/13 02:35 AM 09/05/13 02:35 AM
Joined: Aug 2003 Posts: 43,173 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,173 Bend,OR USA	Quote: ET has been better w/ the lower shift points. The engine has iron J heads. The motor is talking to you, it saying don't rev me past the 1st and 2nd gear shift RPM All kidding aside, all the SB Mopars I've dyno tested with stock type heads ( 6 to 8 motors, CRS )iron heads with 2.02 intakes valves made peak power between 5900 and 6400 RPM Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Gear Change-What difference? [Re: Cab_Burge] #1496408 09/05/13 09:02 AM 09/05/13 09:02 AM
Joined: Jan 2003 Posts: 9,997 Frostbitefalls MN (Rocky&Bullw... gregsdart master
gregsdart master Joined: Jan 2003 Posts: 9,997 Frostbitefalls MN (Rocky&Bullw...	Quote: Quote: ET has been better w/ the lower shift points. The engine has iron J heads. The motor is talking to you, it saying don't rev me past the 1st and 2nd gear shift RPM All kidding aside, all the SB Mopars I've dyno tested with stock type heads ( 6 to 8 motors, CRS )iron heads with 2.02 intakes valves made peak power between 5900 and 6400 RPM I don't think the 4.56 gear is enough of a reduction to put you in the sweet spot. The 2.74 gear is going to help a lot in the 60 ft, and you may stay the same(or pick up some) plus pick up in the last 400 feet considerably with a gear that is lower still(4.30?). If it were mine, I would add about 3 to 5 mph to your best top speed so far, and gear it for 6400 to 6600 at that speed, based off Cabs experience with those heads. If your converter puts you over the torque peak, the loss of time in the 60 ft won't be much, and may actually improve. Last edited by gregsdart; 09/05/13 09:09 AM.

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