View Poll Results: what mpg with 3rd gen and a 4.8 6spd turbo highway
25-30
5
62.50%
30-35
2
25.00%
35-40
1
12.50%
Multiple Choice Poll. Voters: 8. You may not vote on this poll
4.8 in 89 formula with 6spd
4.8 in 89 formula with 6spd well i have a 89 formula 350 tpi that i cant manage to sell for some reason and dont have a car or truck that gets good gas mpg. my car in sig probbley 15mpg and my truck dodge v10 8 mpg on the high, so i decided i might put a turbo 4.8 truck motor in with a 6spd in the old 3rd gen. im woundering what gas milege i would be able to get out of it though before i do it. full weight 3rd gen stock 4.8 mybe with custom cam and ls1 intake i guess and single small turbo. Looking to only make 350hp and 350tq. 2.73 rear end. what do you guys think.
I don't think you need the turbo to make 350rwhp and still get great mileage.
My SS is getting about 32-34 mpg hywy. It's a forged 346, PP LS6 heads, LPE GT-11 cam, MAC mids, LM1, M6, and 3.90s.
I could see a 4.8 with PP or PRC 5.3 heads, a similar cam to mine, an LS1/6 intake and headers making 35+ mpg and 340-360 rwhp. Just make sure you keep it in an efficient operating range while at cruising speeds. For example, in stock form (3.42 gears), my SS got 27-28 mpg hywy. Simply by changing to 3.90 gears, I picked up about 4 mpg. This is because it was running below it's efficient RPMs before.
My SS is getting about 32-34 mpg hywy. It's a forged 346, PP LS6 heads, LPE GT-11 cam, MAC mids, LM1, M6, and 3.90s.
I could see a 4.8 with PP or PRC 5.3 heads, a similar cam to mine, an LS1/6 intake and headers making 35+ mpg and 340-360 rwhp. Just make sure you keep it in an efficient operating range while at cruising speeds. For example, in stock form (3.42 gears), my SS got 27-28 mpg hywy. Simply by changing to 3.90 gears, I picked up about 4 mpg. This is because it was running below it's efficient RPMs before.
im not even looking for 350rwhp but 350 at the crank, i had the most fun when my car was stock unmodded just looking for that again and on the cheap with the best gas milege i can get. thinking of pulling an entire 4.8 and grabbing a wiring harness from an f-body or truck. i can get a small turbo cheap and used intercooler cheap also. i can do the tuning myself and if a 3.42 rear gear would be better i already have ten bolt with it. ill have to do some reseach to find out if truck headers will fit backwards in a 3rd gen also.
If you're only wanting 350 hp at the crank... then why are you even thinking about a turbo? Even a 4.8 will probably make that with just headers, ls6 intake, and a decent tune. No need for turbo at all. Truth be told... I don't think there's many LSx turbo guys getting better than 26 mpg hywy, so why bother for 350 bhp? What psi are you planning on running to only get 350? 1 psi?
i think the 4.8 only makes 270hp stock. i believe its usually around 1 psi for every 20hp mybe with these engines. so 4-5 psi mybe keeping every thing else stock. I believe headers for 3rd gens for these motors are costly i think also. not sure if the smaller motors like 4.8's 5.3's respond to bolt ons as well as the bigger 5.7 6.0 motors would or boost. though im here to learn so you never know also.
LSx motors are typically very underrated from the factory. For example, I seen a crate LS1 (rated at 350 bhp) dyno at 414 bhp on an engine dyno.
I'd imagine the same applies for a 4.8 that's running correctly. From what I've read, the small truck motors repond just as well to mods as the others. If you're gonna run boost, I think you can set your goals much higher than 350 hp.
There's a lot of guys running LSx motors in third gen f-bodies. The headers don't have to be custom made, so they shouldn't set you back too much.
I'd imagine the same applies for a 4.8 that's running correctly. From what I've read, the small truck motors repond just as well to mods as the others. If you're gonna run boost, I think you can set your goals much higher than 350 hp.
There's a lot of guys running LSx motors in third gen f-bodies. The headers don't have to be custom made, so they shouldn't set you back too much.
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im not setting my goals to high as i know the car would end up like the one in my sig setting in my garage guted to the max and awaiting more go fast parts every week
I know i could make alot of power with the turbo,but its not what im after with this one. i think ill put it in n/a for now and see how i like it then mybe a small turbo. What do you think the max mpg that could be had out of it.
I know i could make alot of power with the turbo,but its not what im after with this one. i think ill put it in n/a for now and see how i like it then mybe a small turbo. What do you think the max mpg that could be had out of it. LS1 Tech Stories
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