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10-27-2003, 11:12 PM
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#1 |
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Top of the foodchain
Join Date: Oct 2003
Location: 3.5 miles from Mile Hi Stadium
Posts: 127
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engine to gear ratio
New member here, Ilike this site. even more if someone could give me some pointers on my engine to gear ratio. I built this engine 10 months ago and am somewhat pleased. I pulled out a 1970 K-10 4x4 4-speed maual tranny with 3.07 gears and a tired 350, smokin, burning, leaking felt sorry for engine and
i replaced with a blueprinted engine from Popular hotrodding performance trends. As built it is a 350 sbc .030 over =355 4 bolt main All ARB,Clevite 77 KB pistons, 9.5-1 CR Melling H/V opump, Sportsman II heads 2.02i/1.60e 200cc intake runners Compcam xtreme energy 12-246-3 adv dur.274i 286e @50 230i 236e lift .487i .490e 110'ls ( I installed a different cam as comp tech line encouraged) This one here: 12-239-3 adv dur.262i 270e @50 218i 226e lift .462i .480e 111'ls edlebrock rpm performer intake, 750 cfm holley 4160 1 5/8 primary w/ 3" collector into 2 1/2" pipes with flowmasters As advertised in the blueprint dyno - 415.6 hp @5800 and 396.1 ft. lb.@ 4300 . I thought nice sbc engine I'll build it. I changed the cam becuase Comp cam tech line said i need to salvage tourqe cuz the truck is over 5000lb. So i did. In back of the mouse is a Manual 4 speed 4x4 with a tiny 3.07 rear end. With this combo i can smoke rubber starting in second gear And chirp shifting to third with 31" tall general mudder tires!( only about 50% tread left ) So without a dyno done to this engine i know it must have some desent #'s But I want more!! Bigger cams = bigger gears right? I'm about to buy 4.56 gears with a detriot locker. mini-spool up front. So from 3.07 to 4.56 gears. imagine 4.56 gears. I wonder if I should "water down" my cam, look for the highest tourqe #'s with 3.07 gears. Or find a hotter cam and enjoy the 4.56 gears.maybe a compcam xtreme energy 12-250-3 adv dur. 284i 296e@50 240i 246e lift .507i .510 e 110'ls Or if that cam with 4.56 gears would wake the heavey ass truck up some? I can twist wrench with the best of them. but deciding and figuring out the best combos, I think is the hardest part of building the baddest truck in the nieborhood. Any help will be nice. __________________ 1970 K-10 4x4 Smell the Magic! Report this post to a moderator | IP: Logged
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1970 K-10 4x4 1975 Jeep CJ-5 4x4 1990 Jeep XJ 4x4 Smell the Magic! |
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10-27-2003, 11:22 PM
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#2 |
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Collector of rusty Items
Join Date: Dec 2001
Location: Sisters,Oregon USA
Posts: 731
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Welcome to the site. Sounds like a heck of a motor.
I had 456's in my tired old 70 and I had to take them out because the damn thing wouldn't go much over 55 mph. Personal opionion: Unless you are running really big tires, you won't gain anything. Sure, you might burn more rubber in 3rd, but you will be going 20 mph slower. 456 ratio is for big tires or heavy trucks with no power, like my 6.2 diesel in a 7500 pound truck. 62 mph max.
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Scrub Sisters, Oregon - Home of the Sisters Rodeo. 70 GMC 1,000,000 + miles 72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends. |
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10-28-2003, 12:03 AM
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#3 |
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Top of the foodchain
Join Date: Oct 2003
Location: 3.5 miles from Mile Hi Stadium
Posts: 127
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What I'm looking for I guess is a huge cam making all the power the 355 can. And pick up and go as fast as the truck can. I think bigger gears to keep me in the right power band. I should get a labtop dyno. 65 mph is all I need. but i want to climb a mountain in granny gear with 400+ ft.lbs of tourqe backing me up!!
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1970 K-10 4x4 1975 Jeep CJ-5 4x4 1990 Jeep XJ 4x4 Smell the Magic! |
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10-28-2003, 06:36 AM
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#4 |
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user # 2756
 
Join Date: Jun 2001
Location: Chesapeake, Virginia
Posts: 4,612
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I'm no engine expert but I'd say what's limiting you is the tranny. The SM465 is by no means a sporty transmission. Have you thought about a TH350 built to go with the 355? Then If you keep the 31" tires you could go with 3.73 gears.
Welcome to the board! I have 33s w/ 4.10 gearing and turn about 2800 RPM @ 65 MPH my 350 is stock w/ 2.5" dual exhaust.
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1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm 
Last edited by JIMs70GMC; 10-28-2003 at 06:38 AM. |
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10-29-2003, 08:11 AM
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#5 |
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Registered User
Join Date: Dec 2001
Location: New Richmond, WI
Posts: 547
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4.56 is a lot of reduction, I would condider 4.10 or 3.73 with 31" tires. Remember you have 4 lo for pulling stumps.
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Eric 1969 K20, 465/205 package |
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