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Gearing change ? #231285
02/21/09 01:31 PM
02/21/09 01:31 PM
Joined: Feb 2006
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Alberta Canada
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Current setup

4.56 gears with 727 with 9 inch converter 5300 stall
31.8 tall MT radial slick (constant height)
last season car was trapping around 7000 RPM at 134 MPH this spring power should be up 70 hp and car should lose around 50 lbs

question is should I be gearing the car down ? I am concerned about spinning the stock block (just a girdle) much above 7100 rpm (milodon external oil system with an Olson pan) was considering gearing down to 4.30 ?

What do you folks think ?


76 Duster work in progress
Re: Gearing change ? [Re: Edge] #231286
02/21/09 02:13 PM
02/21/09 02:13 PM
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Romeo MI
MR_P_BODY Offline
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Do your gear change as a percentage and I would guess
that you will run about .120 quicker and about 2 mph
so you can base it on those

Re: Gearing change ? [Re: Edge] #231287
02/22/09 12:04 AM
02/22/09 12:04 AM
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Bend,OR USA
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put a 4:10 ratio in it and let it eat Unless it is a small cubic inch small block with no torque


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Gearing change ? [Re: Cab_Burge] #231288
02/22/09 12:12 AM
02/22/09 12:12 AM
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Alberta Canada
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I was concerned dropping to 4.10 would soften the launch too much car would 60 foot 1.35 on a good track. It is a 493. Any experience getting a 3000 lb ride to 60 acceptable with 4.10 's

thanks


76 Duster work in progress
Re: Gearing change ? [Re: Edge] #231289
02/22/09 12:36 AM
02/22/09 12:36 AM
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Bend,OR USA
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My Duster weighs 3400 lbs with me in it, it has gone a best of 1:43 sixty foot with 3:91 and 4:10 with a 94 inch circumference M/T street radial rear tire(10:34 ET, 128.6 MPH) This is a street and strip car on pump gas corked up, not real powerful(518 C.I. Eddy heads and a six pak). I do use a 2:77 Mopar low gear set in the trans and a custom built 10 inch street and strip conventer, the car will push the front tires thru the staging lights at 2300 RPM foot braking It flashes to around 4300 rpm according to the playback tach. The car ran almost the same ET and MPH with a set of 3:73 in it also


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Gearing change ? [Re: Cab_Burge] #231290
02/22/09 12:38 AM
02/22/09 12:38 AM
Joined: Oct 2004
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back in Georgia
dthemi Offline
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If you picked up 70 HP did the peak power RPM not go up too?

Re: Gearing change ? [Re: dthemi] #231291
02/22/09 12:49 AM
02/22/09 12:49 AM
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Alberta Canada
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Not sure on the hp peak I expect it will move up but old peak was quite low 6100 -6200. Picked up 50 cfm head flow with porting so the 70 hp is an estimate. Planning to dyno next weekend and will see then.


76 Duster work in progress
Re: Gearing change ? [Re: Edge] #231292
02/22/09 01:26 AM
02/22/09 01:26 AM
Joined: Oct 2004
Posts: 3,097
back in Georgia
dthemi Offline
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I bet you pick up 400 RPM on peak too.

Re: Gearing change ? [Re: dthemi] #231293
02/22/09 01:40 PM
02/22/09 01:40 PM
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Alberta Canada
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So if my hp peak moves to 6600 RPM what should I target as a finish line RPM, 6900 RPM ?


76 Duster work in progress
Re: Gearing change ? [Re: Edge] #231294
02/22/09 01:49 PM
02/22/09 01:49 PM
Joined: Oct 2004
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back in Georgia
dthemi Offline
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I'd just try it like it is first, if it starts to buzz then change the gearing. More often than not if you're changing heads, and cam and making more power everything moves up in the rpm range, peak tq and peak power. So changing to a higher gear could hurt you off the line. If you're adding cubes then yeah, the added TQ down low would take longer legs.

Re: Gearing change ? [Re: dthemi] #231295
02/22/09 02:24 PM
02/22/09 02:24 PM
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Alberta Canada
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Sounds like a good plan, I will try the car with the existing gearing. I can always lift if it really starts to buzz

thanks


76 Duster work in progress






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