350 for torque/mileage

[1972GMCsierra4x4]

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.

[67 chevelle]

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 .

[1972GMCsierra4x4]

When you say 268 are you referring to the lift or duration?

[Longhorn 70]

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

[airdale94]

Here's what you want.

http://www.jegs.com/i/JEGS-Performan...d=#moreDetails

[MARKDTN]

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.

[HSRACER]

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.

[alsriv2]

Don't discount the Lunati offerings. They have many cams that sound good at idle, and have great pulling power as well.

[airdale94]

Originally Posted by HSRACER

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.

Yes, with 4.56 gears it's going to be hard to get any significant milage improvement for long distance driving. 3.08-3.42 are good all around gears. Once you get up to 3.73 your milage starts to suffer. Since you have 4wd and if you have larger (I think) tires, 3.73 might be the sweet spot.

[cool68]

if gear ratio too low just put some 24" rims/tires on it - Ha!

[zeldman]

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.

[dsy1]

Originally Posted by zeldman

Whatever you do, go with 2 1/2 inch exhaust, or even 3 inch.

If you go too big on the exhaust you will lose the torque you are after.

[airdale94]

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

[1972GMCsierra4x4]

Originally Posted by airdale94

Here's what you want.

http://www.jegs.com/i/JEGS-Performan...d=#moreDetails

Yeah but if I put that cam in, will that put my redline at 3000 rpm

[1972GMCsierra4x4]

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

[zeldman]

Originally Posted by dsy1

If you go too big on the exhaust you will lose the torque you are after.

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.

[71K20chevy]

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

[1972GMCsierra4x4]

Originally Posted by 71K20chevy

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

That's what I think. The highest I want to take my truck ever is about 4000 rpm. Plus, my headers have a 2 1/4" collector diameter (hey, they were free I'm not gonna complain) so it wouldn't make much sense to put 3" exhaust on something smaller

[71K20chevy]

Or, kill two birds with one stone, just run open headers

Also, what size are the primaries on the headers?

[1972GMCsierra4x4]

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

[airdale94]

Originally Posted by 1972GMCsierra4x4

Yeah but if I put that cam in, will that put my redline at 3000 rpm

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.

[67 chevelle]

Originally Posted by airdale94

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.

x2 your redline will be around 5500 or 6000 , depending on the rest of your components , it should pull well up to around 5000

[71K20chevy]

Originally Posted by 1972GMCsierra4x4

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

I'd say probably 1 1/2", 1 3/8" seems pretty small.

[1972GMCsierra4x4]

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.