Am I underpowered?

twebuh said:

I did just spend a good chunk of money on the posi 3.73 gears so :/ idk if I can swing it

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I have an Eaton true track in my 97, with 373s. Thing is, I'm running 275/60/15 tires. The 373s on that OE, or close to the same high as OE tires are grate. You could always sale you 373s. As for the posi, you should be able to just swap the gear set. If you don't know how to do the rear end work, do what I did, teach yourself. Of course keep in mind that your front dif gears, and your rear diff gears, need to match.

Wow.. amazing it came with 3.73's. That's what's sucking up your power, trying to turn over those 35's with that gearing.

Richard

twebuh said:

So I have a ‘99 C2500. Big boy. 6.5 inch lift on 35s, cammed, built top end, posi 3.73 rear end, among other thing. My question is, from a dig should I be breaking loose my tires. I feel like it’s down on power but I’m not sure, I’ve never owned a lifted older vehicle before so I have no reference. It can do burnouts (I haven’t tried since I got the posi but it did it with the open diff). Kinda a weird question but I wanna know if it’s just slow or if I’m probably down on power. My assumption would be a fuel issue if that’s the case. My injectors ARE on max duty cycle

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Your injectors should not be anywhere close to max duty cycle on a stock L31 or even a L31 with some bolt-ons. Mine once was running lean, discovered the fuel pressure was dropping at WOT. The OE square 4 pin fuel pump connector was melting. I replaced the pump with a new Delphi pump assembly that used the upgraded flat oval 4 pin connector and added a matching Racetronix harness that powers the pump off the alternators charge wire post. Restored my fuel pressure to factory spec, fixed the lean condition and added a considerable amount of power back. I am still running the same pump to this day, the Racetronix E85 high flow Camaro pump I have is still sitting new in the box at the shop.

L31MaxExpress said:

Your injectors should not be anywhere close to max duty cycle on a stock L31 or even a L31 with some bolt-ons. Mine once was running lean, discovered the fuel pressure was dropping at WOT.

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Yeah,more like he said. How old is the fuel filter? My want to check your fuel pressure.

Scooterwrench said:

Yeah,more like he said. How old is the fuel filter? My want to check your fuel pressure.

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New fuel filter. I’ll check it at some point. I have a new fuel pump and everything. I’ve been chasing it for a while now

kennythewelder said:

I have an Eaton true track in my 97, with 373s. Thing is, I'm running 275/60/15 tires. The 373s on that OE, or close to the same high as OE tires are grate. You could always sale you 373s. As for the posi, you should be able to just swap the gear set. If you don't know how to do the rear end work, do what I did, teach yourself. Of course keep in mind that your front dif gears, and your rear diff gears, need to match.

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I found some USA standard 4.56 gears on Summit. I’ll try those, thanks. I don’t know why I forgot I wasn’t difficult to swap lol

I agree with the others who said that you need more gear.

Also, if you really want to know if you're engine is making expected power levels, MEASURE IT. And I don't mean by using the famous "Peel-O-Meter". Put it on a chassis dyno or down the 1/4 mile to get a trap speed, and calc your HP...then you'll know.

Tom400CFI said:

I agree with the others who said that you need more gear.

Also, if you really want to know if you're engine is making expected power levels, MEASURE IT. And I don't mean by using the famous "Peel-O-Meter". Put it on a chassis dyno or down the 1/4 mile to get a trap speed, and calc your HP...then you'll know.

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I second this. Trucks should only be pulled in 2nd gear though. Many un-familiar dyno operators will try to pull them in 3rd.

Scooterwrench said:

Yeah,more like he said. How old is the fuel filter? My want to check your fuel pressure.

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While I do agree a fuel pressure check is valid troubleshooting procedure in many cases (esp. lack of power complaints) - being a small block Vortec, I'd bet if he had even marginally low fuel pressure, he'd also have no-start complaints. That is, unless the original poppet valve setup has already been upgraded.

Richard

someotherguy said:

While I do agree a fuel pressure check is valid troubleshooting procedure in many cases (esp. lack of power complaints) - being a small block Vortec, I'd bet if he had even marginally low fuel pressure, he'd also have no-start complaints. That is, unless the original poppet valve setup has already been upgraded.

Richard

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I had zero drivability issues, just low power under load. The only time the pressure was low was under throttle.