305 to 4.8 worth it?

[bucket]

The original 305 in my '84 DD runs fine and averages 16 mpg. It has around 130K on it and it uses some oil, but nothing excessive. I'll say the power is just "OK".

I can get a good running, non-oil-burning '99 4.8 for free. It also runs well but it has an internal noise that doesn't seem to be getting any worse. It doesn't sound like a rod knock, but it doesn't sound like a valve tick either. Not sure what might be causing it.

Would I just be wasting time and money replacing my 305 with this 4.8 motor? I know I would need the right headers, mounts, fuel system, etc but that would be the case with any LS swap. I'm more concerned with an increase in power and mileage, if both are significant then I think it might be worth dropping in the little 4.8 motor.

 

[Old77]

For free I'd say yes it's worth it! With that said you can get a good, complete 5.3 these days for fairly cheap and the performance increase over 4.8 is significant.

But I'd have a hard time turning down a free 4.8....

 

[bucket]

It's not so much about increasing the power, but the mileage too. I have no experience with this motor in a regular cab 2wd shorty, they have all been extended cabs, 4x4's, or both. I'm wondering if I could average 18 or 19 mpg and gain a little power too.

 

[Old77]

The 4.8's get excellent mpg so I definitely think it'd be a huge improvement over the 305. I'd expect low 20's out of the 4.8 especially if you got a custom tune on your PCM. Blackbear Performance is a great resource for this!

 

[bucket]

I like what you're telling me! If I start now looking for deals on all the parts I would need, maybe I could have everything gathered by summer. The cheaper the better!

 

[Old77]

That'd be cool! If you get a blackbear tune on that it'll get more performance wise but also give you better mpg so you might be able to attain mid 20's around town at that point. Those are the numbers I've heard from others who've tuned a 4.8 from blackbear

 

[Jims86]

If its an LR4, I would say yes. 270 HP would be a nice little jump from the 160 that your engine was factory rated at in 84...especially for a DD.

4800 LR4
The Vortec 4800 LR4 is a Generation III small block V8 truck engine. Displacement is 4.8 L (290 cu in) with a 96.01 mm (3.78 inch) bore and 83 mm (3.27 inch) stroke. It is the smallest of the Generation III Vortec truck engines and was the replacement for the 5.0 L 5000 L30. The LR4 produces 270 horsepower (200 kW) to 290 horsepower (220 kW) and 285 lbf·ft (386 N·m) to 305 lbf·ft (414 N·m), depending on the model year and application. LR4s are manufactured at St. Catharines, Ontario and Romulus, Michigan.
LR4 applications:
1999 & 2002–2006 Chevrolet Silverado 1500/GMC Sierra 1500
1999–2006 Chevrolet Tahoe/GMC Yukon

 

[foamypirate]

I like what you're telling me! If I start now looking for deals on all the parts I would need, maybe I could have everything gathered by summer. The cheaper the better!

You can check the last page or so of my build thread. I have some of my LSx fuel system thoughts/parts listed out, along with how they go together, all PNs listed.

 

[Old77]

You can check the last page or so of my build thread. I have some of my LSx fuel system thoughts/parts listed out, along with how they go together, all PNs listed.

You are the man!!! Stuff like that is a huge help!

 

[78shortandwide]

If i was swaping engines i would want to make sure the one im putting in was in good or great running condition. No reason to put something in that has to be rebuilt in the near future. Might as well fix that noise before it goes in.

 

[89Suburban]

Will that bolt up to his trans or will he need to change that too?

 

[Old77]

Not sure. I know that it uses the 4L60E normally. I'm not a transmission guru....

 

[oneluckypops]

SOME 99 4.8 and 5.3's had a small engine noise. I cant remember for sure which cylinder it is but I am thinking it was #3 cylinder. The problem was from the manufacture the castings on the heads were undersized where the push tubes go and theres been some motors reported that the push tube will rub the head.

Not saying that is 100% for sure what your noise is but it is defintly something I would look in to.

 

[foamypirate]

Not sure. I know that it uses the 4L60E normally. I'm not a transmission guru....

GM sells a flywheel with a spacer that was used on 6.0L w/ 4L80Es after 01' or so that will allow the use of an older-style transmission. The 99-01 6.0L's actually had a longer crank flange to make up the difference, but they changed to the flywheel w/ spacer around 02' or so.

 

[Old77]

Yeah but the 6.0's are different than the 4.8's with regards to what tranny will bolt to it, right? Will a 700R4 bolt up to a 4.8?