More torque for my GMC Sierra 4.8?

[H20Rat]

I work at a speedshop (parts). IMO, there isn't much you can do to upgrade that engine. Sure, you can get a tuner, but IMO, for gas engines they don't do much. Maybe you'll grab an extra 10-15HP, but this usually comes at the top end.

And to go along with that, most of the 'tuner' mods on a non-turbo/supercharged gas engines are nothing but a resistor that screws with what the computer thinks the air temp is. You gain power by leaning out the engine!


(turbo gas engine on the other hand... Lots of power left on the table there!)

 

[smokeonthewater]

Eh often tuners for n/a gas engines make more power by advancing ign timing and specifying high octane fuel.

 

[Maclin]

Yeah, certainly not looking for more top end. I will just save my money and downshift as needed. I can't find the exact number, but I believe the red line is around 6000. Keeping it at or below 4000 on the long steep hills will keep me moving just fine.

That will be one of your best options, and it is free more or less. Plus, if you do increase torque and do not change the final drive ratio by physical gear swap or downshifting the tranny will take more abuse.

 

[bruceb58]

I used to work for an electronics division of GM. When I was at the proving grounds once I stoppedd off in the lab of the group that was doing the ECM programming for one of the engines in the trucks. They always laughed at the tuner people. Said there was no way they knew enough of the whole system to do an overall good job.

 

[Volphin]

I've read the other responses and some good points were made. If you want some more low end grunt without breaking the bank, you need to free up some ft/lbs. of torque. One way of doing that is adding long tube headers to the engine. (Not shorties!) Here's a bolt on pair:

http://www.summitracing.com/parts/psm-72c2267/overview/make/gmc

 

[bruceb58]

I've read the other responses and some good points were made. If you want some more low end grunt without breaking the bank, you need to free up some ft/lbs. of torque. One way of doing that is adding long tube headers to the engine. (Not shorties!) Here's a bolt on pair:

http://www.summitracing.com/parts/ps...rview/make/gmc

If you live in a state that has smog inspections like the OP does, you will fail your inspection.

 

[Volphin]

Depends on whether they sprung for the CARB sticker. Mike Leach headers are CARB compliant as they have paid the extortion fee.

 

[bruceb58]

Depends on whether they sprung for the CARB sticker. Mike Leach headers are CARB compliant as they have paid the extortion fee.

Says off-road use in the description.

 

[Scott Danforth]

Could always unbolt the 4.8 and bolt in a 6.0

 

[Volphin]

Says off-road use in the description.

Bruce, I was not referring to my link, rather offering up another vendor for him to check out. I was not aware he was in a CARB heavy state.

 

[bruceb58]

Bruce, I was not referring to my link

I thought you were when you said depends on if they sprung for the CARB sticker.

In any case, slapping headers on an engine is no guarantee it will help. In fact, sometimes headers like these will actually make performance worse.

 

[Volphin]

Really Bruce? Do you have any examples you would like to share? I'd be very interested in hearing them, along with the dyno sheets.

 

[bruceb58]

Really Bruce? Do you have any examples you would like to share? I'd be very interested in hearing them, along with the dyno sheets.

The stock exhaust on the 4.8 is actually a pretty free flowing design. Depending on tube diameters and length, you can get a header that will give gains at high RPMS and hurt low RPM performance(less than 4000RPM) which is what you need for towing.

The stock exhaust is actually a pretty well designed exhaust manifold. Way better than what used to come on 5.7L engines.

 

[MTboatguy]

Okay

:fish2:opcorn::laser::yield:

 

[SDSeville]

I just returned from a 700 mile trip with plenty of long steep inclines. I tried manually keeping it in lower gears on the inclines and it worked perfectly. No more stress of listening to the tranny search for gears and I even got an extra couple miles per gallon. Thanks for the help!!

 

[SDSeville]

Ohhhhh the irony of my previous post!!! We returned from our trip yesterday afternoon and everything seemed fine. Transmission failed after about 10 miles of driving around today. Everything seemed great on the trip. I took most hills at about 3500 RPM, only going over 4000 a few times and just for a minute or 2. I am assuming the failure was a result of 14 years of letting the tranny search for the right gear, lugging and continuously shifting back and forth. That and 100k+ miles with the big tires.

This really sucks, but thank God we made it all the way home before the failure. My family could have been stranded in the middle of the desert for hours.

 

[smokeonthewater]

that sux

 

[bruceb58]

After seeing higher temps than I normally would like to see with my tranny, I just purchased a new cooler to prevent what you just had happen.

 

[SDSeville]

After seeing higher temps than I normally would like to see with my tranny, I just purchased a new cooler to prevent what you just had happen.

Which cooler did you get? I think I will have them install one with the new (rebuilt) tranny.

 

[bruceb58]

http://www.amazon.com/gp/product/B00...ilpage_o01_s00

I have been changing my fluid regularly including a manual full flush a couple years ago which included using a Dexron VI rated fluid vs the Dexron III that came in these trucks originally up to 2005. Dexron VI is rated for higher temps that Dexron III fluids.