NEED HELP CHOOSING GEAR RATIO FOR TURBO SET UP - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 9 Old 04-04-2011, 12:33 PM Thread Starter
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NEED HELP CHOOSING GEAR RATIO FOR TURBO SET UP

ok guys im building 347 with t-76 turbonetics .81 a/r the block is stock so not going for huge hp numbers it is a filled block with a girdle trying to stay in 500 hp range 5800 max rpm the car is a coupe weighed 2700lbs before turbo setup not sure of weight now im running c4 with brake 28 tall tire what do you guys recommend i have a set of 3.08 but was thinking of going with 3.27 car is not quite back together any help would be appreciated

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post #2 of 9 Old 04-04-2011, 01:20 PM
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Originally Posted by mikethomas View Post
ok guys im building 347 with t-76 turbonetics .81 a/r the block is stock so not going for huge hp numbers it is a filled block with a girdle trying to stay in 500 hp range 5800 max rpm the car is a coupe weighed 2700lbs before turbo setup not sure of weight now im running c4 with brake 28 tall tire what do you guys recommend i have a set of 3.08 but was thinking of going with 3.27 car is not quite back together any help would be appreciated

Assuming drag car/cruiser? Or just drag? I would say the 3.27 would be great if you are only ramping it up to 5800. But with the 28" tire I was wondering where you would be at going through the traps rpm-wise...... I would stick with the 3.27s. Good luck. You might even be able to get away with 3.55 with only shifting at 5800. If you plan to raise that rpm ceiling later then by all means keep the 3.27s in and enjoy.

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post #3 of 9 Old 04-04-2011, 02:12 PM Thread Starter
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its a cruiser that i drag race alot im not sure what rpm ill go through the traps at im going from a n/a 331 with 5 spd and 4.30 gears to turbo 347 with a c4 all new to me so trying to see what others are using trying to keep rpms down have all good valve train to run 6500 but want engine to last trying to be conservative for now stock blocks are junk
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post #4 of 9 Old 04-04-2011, 10:55 PM
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Well i was gonna say go with the 3.55's , But i remembered way back in the day when i had a c4 in a Capri with 3.45's 65 mph was 3500 rpm...of course i had the 390 metric rims too ...a 3.27 would have been perfect....But 275 60's on a 3.08 was too high ....YEA GO WITH a 3.55 your 28" tires will make it feel like a 3.27
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post #5 of 9 Old 04-04-2011, 10:58 PM
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my old setup was 3.27 and C4 and it seemed perfect.

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post #6 of 9 Old 04-05-2011, 05:26 PM Thread Starter
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thanks for you help guys
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post #7 of 9 Old 04-05-2011, 09:39 PM
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I would use 3.27 or 3.55's both should work fine for your ride.

Sold Supercharged 98 Cobra, FFR Cobra, turbocharged 408W Dart Iron Eagle block 225 AFR race heads. 83mm T6 turbo. Dyno numbers 924rwhp / 986rwtq In a car that weighs 2,270 lbs.
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post #8 of 9 Old 04-06-2011, 09:08 PM
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If staying with 500 HP you might really consider running 3.55s. makes more sense since your running a taller tire and running a c4 which has a high 2.46 first gear compared to most sticks which are closer to 3:1 in first gear.

Brett
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post #9 of 9 Old 04-06-2011, 09:24 PM
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Why not try it with the 3.08s 1st then see where to go? I have 3.90s, but I don't run on a track and I love them. 1st is short, but I hit 160 pretty quick.

500hp is just the start for most boosted v8s with HCI.


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