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#1 |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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350 for torque/mileage
This spring I'm planning on tearing down the 350 I have in my 72 K-2500 and building it to be more of what I want. I'm looking to get the best low end torque/mpg combination out of my motor since I may be driving the truck as far as six hours to college in a year and a half. I'm looking for suggestions and what you guys have done with your trucks.
The truck is currently set up with: 350 short block from Oreillys with 600 cfm edelbrock, eddy performer intake, oversized air filter and cast iron 62cc heads (casting #468642) 2" dual exhaust with glasspacks coming out of factory manifolds 4 speed with granny 1st and np205 transfer case D44 front and D60 rear geared in 4:56 with 245/75/r16 Bf goodrich T/As The truck will be getting: 650 eddy thunder series (maybe) Roller rocker arms and the things needed for that conversion Different cam Long-tube Headers going into 2 1/4" exhaust with flowmasters 3.73 gears with a gear vendors overdrive/splitter (eventually) All terrain tires sized in 265/75/r16 Right now my motor has a 9:1 or 10:1 compression ration, depending on the pistons Oreillys installed. My question out of this is a good cam to go with the combination I'm going with. I've been told a thumper is not always a good option but I have seen in some cases they produce really good low end torque and good mpgs. I don't have much experience with cams so that a big problem right now. |
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#2 |
Registered User
![]() Join Date: May 2013
Location: WEST PALM FLORIDA
Posts: 1,174
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Re: 350 for torque/mileage
Thumper cams are made for one purpose , to have a rough idle , I had one in my 454 and hated it ,The engine was built with secs where it should have run great ,but it ran like crap ,I went with a diferant cam and it turned into the space shuttle . for what you want , Id suggest a 268 or smaller , most people over cam their engines and they run like crap .
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68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs 67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive 58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white 69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive |
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#3 |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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Re: 350 for torque/mileage
When you say 268 are you referring to the lift or duration?
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#4 |
Registered User
![]() Join Date: Dec 2012
Location: Chandler AZ
Posts: 1,149
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Re: 350 for torque/mileage
268H is a cam grind profile. Good choice for truck or RV types.
I prefer the XE250H from Comp Cams for a bit lower RPM torque. It seems to work especially well if you have lower compression, stock heads, headers and want to cruise in the 1800-2500 RPM range. Below are links to dyno sheets for SBC (with DART heads). XE250H profile 268H profile
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1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11. 1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9 Last edited by Longhorn 70; 01-01-2014 at 11:00 PM. |
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#5 |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: 350 for torque/mileage
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#6 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,149
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Re: 350 for torque/mileage
Forget about carburetors and go fuel injection. In my '83 K20 I went from 14.5 to 17+ mpg when I changed to Tuned Port injection. The torque is unreal better. Used to be that pulling trailers at interstate speeds I was on the gas hard at every hill, now it just goes on up. It always starts at the touch of the key. I also have a 700R4 overdrive transmission which would be nice, but a lot more trouble for you to add. I have 3.42 gears. You cannot beat TPI fuel injection for a combination of economy and power-with reliability and simplicity. Uses virtually all stock parts that can be found at any auto parts store in the country.
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'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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#7 | |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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Re: 350 for torque/mileage
Quote:
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#8 |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: 350 for torque/mileage
No that's just the power band for the cam. Where it makes it's most power. If your short block is from O'reilly's it's probably got a cam pretty close to this.
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#9 |
Registered User
![]() Join Date: May 2013
Location: WEST PALM FLORIDA
Posts: 1,174
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Re: 350 for torque/mileage
x2 your redline will be around 5500 or 6000 , depending on the rest of your components , it should pull well up to around 5000
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68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs 67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive 58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white 69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive |
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#10 |
Registered User
Join Date: Sep 2007
Location: Katy TX
Posts: 1,268
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Re: 350 for torque/mileage
The single biggest thing you can do for mileage will have very little to do with your motor. If you want to fix mileage a gear swap is the highest impact thing you can do. If you still want to take the engine out put a torque cam in it. I have a 383 small block with an Edelbrock torque cam and a 3.08 gear in the truck. That combo works great with the turbo 400 trans.
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![]() Slammed 53 5 window Blown/Bagged 54 Pickup Patinaed 67 LS stepside Supercharged 67 Nova Bagged 69 Suburban Turbo'ed 5.3 LS |
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#11 | |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: 350 for torque/mileage
Quote:
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#12 |
Registered User
![]() Join Date: Sep 2010
Location: Formerly MD and San Diego, now loving life in Arizona
Posts: 1,636
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Re: 350 for torque/mileage
Don't discount the Lunati offerings. They have many cams that sound good at idle, and have great pulling power as well.
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Alan 2012 Ram 3500 Dually Crew Cab 6.7 Cummins 2014 Palomino Columbus 340RK 5th wheel '69 Chevy C10 396BB |
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#13 |
Registered User
![]() Join Date: Oct 2013
Location: Stockton, CA
Posts: 475
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Re: 350 for torque/mileage
if gear ratio too low just put some 24" rims/tires on it - Ha!
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#14 |
Registered User
Join Date: Oct 2013
Location: Rt 66 Gallup, NM
Posts: 527
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Re: 350 for torque/mileage
Whatever you do, go with 2 1/2 inch exhaust, or even 3 inch. 2 1/2 inch wont cost any more that 2 1/4, but the sound is great and your engine will thank you for letting it breath at cruising rpm, which means gas mileage if you can keep your foot out of it. 3 inch is better but the cost goes up quickly. At least put a crossover pipe between the two, and X pipe will work and sound better. I use 2 1/2 on my 6 cylinder.
I know you didnt ask, but I prefer Magnaflo over FloMaster for better sound and performance.
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2005 GMC K2500HD D/A 1993 GMC K1500 2011 Subaru Legacy. 2013 Subaru Outback 1970 C-10 2WD, SWB stepside, 292, TH350, PS, more rust than anything. God is my pilot. ![]() |
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#15 |
Registered User
Join Date: Aug 2010
Location: San Diego, CA
Posts: 128
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Re: 350 for torque/mileage
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#16 |
Registered User
Join Date: Oct 2013
Location: Rt 66 Gallup, NM
Posts: 527
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Re: 350 for torque/mileage
Not according to many, many dyno test on many motors, by many, many motor builders. Small exhaust chokes an engine. Larger pipes let it breath. You may achieve max torque and stop gaining more torgue but you definatly will not lose torgue. Header pipe diameter and primary tube lengths will change the torque to different rpm ranges, but will not cause a loss of torque, if that is what you meant. Contact Mr. Edelbrock, he has a very good class on just this subject and will explain it a whole lot better than I can.
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2005 GMC K2500HD D/A 1993 GMC K1500 2011 Subaru Legacy. 2013 Subaru Outback 1970 C-10 2WD, SWB stepside, 292, TH350, PS, more rust than anything. God is my pilot. ![]() |
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#17 |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: 350 for torque/mileage
Here's a set of 3.08 axels out of a 76 K5 in Bonner Springs. Not mine, don't know the guy. They should swap pretty easily.
http://kansascity.craigslist.org/ptd/4251356907.html
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#18 |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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Re: 350 for torque/mileage
I'm also not going to go with 3.08 gears because I want to be able to hook onto a gooseneck and haul hay or cows if I need to
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#19 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: 350 for torque/mileage
If it were me...I'd go 2 1/4" exhaust with that motor. I personally think 3" would be too big. Reason for that is, low volumes of exhaust flow faster through smaller tubes, therefore scavenging the cylinders more completely. The smaller exhaust obviously will not flow the volume needed at high rpm, but it sounds like the OP isn't really ever going to visit the high rpm neighborhood hardly at all.
Just IMHO, but that's always been my understanding of it, but I'm young and dumb too ![]()
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71 K20 64 GMC mud truck |
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#20 | |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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Re: 350 for torque/mileage
Quote:
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#21 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: 350 for torque/mileage
Or, kill two birds with one stone, just run open headers
![]() ![]() Also, what size are the primaries on the headers?
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71 K20 64 GMC mud truck |
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#22 |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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Re: 350 for torque/mileage
Lol on the open headers. Straight pipes with factory manifolds were bad enough!
As for the primaries, I wanna say that they're 1 3/8" or 1 1/2". I can't remember right off the top of my head |
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#23 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: 350 for torque/mileage
I'd say probably 1 1/2", 1 3/8" seems pretty small.
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71 K20 64 GMC mud truck |
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#24 |
Registered User
Join Date: Feb 2013
Location: Winchester Kansas
Posts: 145
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Re: 350 for torque/mileage
How bout this. Has anyone on here ever run the jegs performance cam that Airedale94 suggested? Compcams.com has the dyno results for the XE250H, which is what I'm leaning towards right now because I know how it performs.
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350 build, cam, gmc, mpgs, torque |
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