More pulling power from my K2500

b454rat

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Look for a truck in a junkyard with 4.10s. They made 6 lug K2500 with them. Might be tough to find, but they will be bolt in. Went up to 95. After that 3.73s was the steepest for 1/2t light 3/4t. Guy was parting a truck, but didn't want to sell the axles....
 

Supercharged111

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You're specifying pulling power, not "I want 500 hp so I can boil my tires!" Good thing, that's cheaper.

From what I can tell, there are two valve sizes on the TBI heads. I believe the 305s got 1.84" intake valves and the 350s got 1.94s. I'd bet you have 1.94" valves, but if you take the heads off, verify. GM does silly stuff on a whim. If you have the 1.94s, I'd do a cleanup port on the heads. Don't touch the swirl ramps except to clean them up. Headbytes Porting on Youtube has a good video series on TBI heads, but I'll say enlarging the combustion chamber to unshroud the intake valve is pretty difficult - I skipped that part on my heads.

Call your favorite cam manufacturer and ask them for a cam. In my truck, Lunati recommended a big lift, short duration cam for me that's very impressive down low.

What does your exhaust look like? Pencil thin pipes, crushed down to half size with crinkle bends? Headers and a crossover make a nice difference.

Finally, consider tire size alongside your gearing. If you're running tall tires and don't expect to swap down in size, you'll want a higher rear ratio. If you're interested in shorter tires, gears might not be necessary. When I autocross my Mustang, I swap on tires with 2" shorter height. It puts me right in my power band at autocross speeds.

I'm pretty sure the headbytes guy is full of ****. Last I watched his videos he seemed to make wild claims that nobody else does.
 

JimsK2500

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Thanks for all the info and opinions. My truck is a 1995 with 265/75-16 tires a couple size bigger than stock witch is not helping my situation. I have been going back and forth between 3:73 and 4:10 and have decided on 4:10. This truck is not my daily driver. I pull a 22' camper a few times a year and a boat that weighs about 4000 LBS. Pulling around town is not bad but, going up grades on the interstate I have to really work it to keep the speed up. If I let the rpm's drop below 2500 it wont keep up. The truck is geared too high and the fuel mileage is not good either. I am looking for a junkyard front differential and just do a gear swap in the rear. With the TBI 5.7 it stops pulling a little over 3000 rpm's. I had considered a 5.3 swap but,when I tow with my 04 suburban and start up a grade it really starts pulling hard above 3000 rpm's 4500 to 5000 when it down shifts at 65 mph I am not real fond of that either. I like the low rpm torque of the 5.7 so I am not ready to move away from that yet. I have briefly looked into a cam swap but, I need to do more research for the best option as I don't want to move the power band up the rpm range very much.
 

Schurkey

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I'd say a 5.3L is a step backwards.

If this were me, I'd be looking for good-condition axles with proper gears, front and rear. This might be a good opportunity to upgrade to a full-float rear axle with Gov-Lock, for example.

When you find this donor vehicle, consider grabbing whatever else you need for a gear swap--which may include some computer "chips". You'll need to assure the accuracy of your speedometer, for example.
 

L31MaxExpress

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Thanks for all the info and opinions. My truck is a 1995 with 265/75-16 tires a couple size bigger than stock witch is not helping my situation. I have been going back and forth between 3:73 and 4:10 and have decided on 4:10. This truck is not my daily driver. I pull a 22' camper a few times a year and a boat that weighs about 4000 LBS. Pulling around town is not bad but, going up grades on the interstate I have to really work it to keep the speed up. If I let the rpm's drop below 2500 it wont keep up. The truck is geared too high and the fuel mileage is not good either. I am looking for a junkyard front differential and just do a gear swap in the rear. With the TBI 5.7 it stops pulling a little over 3000 rpm's. I had considered a 5.3 swap but,when I tow with my 04 suburban and start up a grade it really starts pulling hard above 3000 rpm's 4500 to 5000 when it down shifts at 65 mph I am not real fond of that either. I like the low rpm torque of the 5.7 so I am not ready to move away from that yet. I have briefly looked into a cam swap but, I need to do more research for the best option as I don't want to move the power band up the rpm range very much.

Something is wrong if it stops pulling at 3,000 rpm. Mine was quickest shifting a tad over 5,000 rpm. I had factory shorty headers and catless true duals that came on my 83 G-van on the 350 TBI though. Also had ultimate TBI mods, a hypertech powerbowl, 1" open center spacer and 1.6 full roller rockers. I have seen many plugged cats on older TBI trucks and vans.
 

Supercharged111

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My TBI with longtubes, ultimate TBI mods, and bumped timing was still lifeless above 4000 RPMs. This with almost 15psi of fuel pressure, no improvement over the 11.5 on the maxed stock regulator.
 

Erik the Awful

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I'm pretty sure the headbytes guy is full of ****. Last I watched his videos he seemed to make wild claims that nobody else does.
I haven't watched many of his videos, so I don't doubt it, but the TBI head videos seem fairly solid. He explains why he's making the cuts and showing how to do it.
 

JimsK2500

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If I down shift to third it will rev to 3800 rpm but it’s not pulling. Then when I shift back to fourth the rpms drop too much. I am talking going up a slight grade pulling 4500 lbs. I am sure I could wind it 4000 rpm but I don’t as there is no benefit to doing that. I just gave the truck a tune up. It is running good.
 

Erik the Awful

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A cam swap does not necessarily mean moving your power band upwards. When I bought my cam I initially ordered the wrong cam, which definitely would have put the cam's power band well above the heads' capability. I called Lunati and told the advisor that my truck would primarily be used for towing, but that I certainly wanted more power. I let him know I was going to be able to run up to .530" lift, and he specified a cam with high lift and a shorter duration. I have to say, the torque is impressive, but I'm also running Vortec heads, 9.7:1 compression, headers, and Holley Sniper on a dual-plane Summit intake. https://www.lunatipower.com/voodoo-hydraulic-roller-cam-lt1-lt4-262-270.html

** Even though the cam says it runs fine with stock injection, the stock TBI couldn't handle the fuel requirements. If you're not interested in reprogramming your TBI, I wouldn't mess with a cam. **

I plugged your tire size into a calculator, and you're at about 31.5". An inch or two shorter tire diameter would make a noticeable difference, but if you use your 4wd often, I'd go with the gear reduction.
 
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