More pulling power from my K2500

[JimsK2500]

I have a GMC K2500 7200 gvw .
It has a NV4500, 5.7 and a 14 bolt with I think 3.42 gears.
When I got the truck I already had an Edlebrock intake, TB spacer and air raid air intake. I have milled the top of the TB and added an injector pod spacer.
I would like to have more pulling power.
Some options I am looking into are swapping to 4:10 gears or swapping Vortec heads and a cam.
Which option would would give me the most for my money, or should I do both?

 

[Schurkey]

I have a GMC K2500 7200 gvw .

WHAT YEAR?

It has a NV4500, 5.7 and a 14 bolt with I think 3.42 gears.
When I got the truck I already had an Edlebrock intake, TB spacer and air raid air intake. I have milled the top of the TB and added an injector pod spacer.

First Guess: "Air Raid" intake was a waste of money. Injector pod spacer is a similar waste. Milling the top of the TB could even be counterproductive. I've never seen any documentation that the typical TBI mods make any difference.

I would like to have more pulling power.
Some options I am looking into are swapping to 4:10 gears or swapping Vortec heads and a cam.
Which option would would give me the most for my money, or should I do both?

Gear swap would have to be front and rear. Relatively expensive, but very effective.

Vortec heads will be a substantial nightmare; just getting EGR is a problem.

Consider the aluminum TBI heads as sold as a Summit house-brand, but made by Trick Flow. They're a bolt-in upgrade that create no other inherent problems. Either do not use the guideplates (use hardened washers instead) and the OEM self-aligning rocker arms; or use the guideplates and hardened pushrods with non-self-aligning rockers.
www.summitracing.com/parts/sum-162108

 

[b454rat]

swap to 4.10s. 3.42s in anything is a highway gear.

 

[Erik the Awful]

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.

 

[stutaeng]

Gear swap is my vote. 4.10s are really good for towing. 7200 GVWR is the 6 lug 2500 trucks, right?

 

[Anubis]

Agreed. A gear change makes sense but will be painful to do the front and the rear.
Swapping Heads, an appropriate cam for towing and a free-flowing exhaust would help a lot. What transmission do you have and will it lock up in third gear? A toggle switch can be added easily.

 

[stutaeng]

Agreed. A gear change makes sense but will be painful to do the front and the rear.
Swapping Heads, an appropriate cam for towing and a free-flowing exhaust would help a lot. What transmission do you have and will it lock up in third gear? A toggle switch can be added easily.

OP's got a manual...

BTW, would you recommend the head/cam swap over re-gearing (not considering the headache of both differentials?)

A ratio of 4.10/3.42 is almost 1.20, meaning OP will have about 20% more mechanical advantage if he regeared. I think that's pretty good. On Richard Holdener videos I have watched it seems like cams usually make more power (at higher RPM) but often lose torque at lower RPM. Seems to me like a good option for racing, but I don't know how that works for towing? Heck, all of his dyno graphs seem to start at like 3,000 RPM, LOL. Of course, there is myriad of cam variables, stall speeds, etc., which I know nothing about....that's why I ask.

 

[DerekTheGreat]

What size are the stock tires on your truck? Based on my MPG numbers with my half ton 4x4 truck, I'm convinced 3.73's are the perfect ratio for it. Now, I don't do a whole lot of towing but I recently netted 19.5+mpg on the highway a few months back consistently. Although it occurred to me that perhaps my truck already has highway lean cruise enabled? It was originally from Nevada, if that makes a difference.

My truck runs at about 2100 RPM at 70mph.
Wife's C1500 runs about 2300 RPM at 70mph and gets no better than 16mpg.

 

[Anubis]

9 times out of 10 people are swapping cams to build high rpm horsepower and torque but most all cam suppliers provide “RV recreational vehicle” cams for better low RPM and mid range power. He’d be best suited to figure out his gear ratio and tire size and then work with a cam supplier to optimize it.

 

[geeeee89]

Re-gear. Assuming you have an early 90s 4500 with the super low 1st, lower axle gears and that first gear will get a load moving no problem.

Saves money if you can re-gear it yourself. I did one for the first time to my semi float axle, not too hard just tons of precise measurements and a few specialty tools. The 14b should be easier. The factory service manual has the exact procedure shown in detail so if you want me to scan the pages for you just message me.

You could do the rear yourself and get a shop to do the IFS axle since that is way more involved. That's what I did with my truck. $550 in labor for that is what I paid.