TBI Heads

[KRS1]

It has 385 cubic inches, unsure what you mean by inlet resonance tuning? The"desktop dyno" results have to be taken with a grain of salt

 

[Supercharged111]

Inlet resonance tuning refers to runner length and its effect on flow. Similar to exhaust scavenging, but on the intake side.

 

[KRS1]

Ah so modifying the intake runner length interesting for sure!

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You would need a variable intake runner, I don't think Edelbrock makes one for TBI heads lol

 

[Pinger]

Ah so modifying the intake runner length interesting for sure!

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You would need a variable intake runner, I don't think Edelbrock makes one for TBI heads lol

I confess - I've never seen it theorised like that before.
Where I've encountered it it has been in terms of a negative (suction) pulse travelling back up the runner, encountering the open end, changing polarity to positive, and returning down the runner to ram in more charge.
The four stroke engine that seemed best at exploiting resonance tuning was the rotary Mazda used to win Le Mans which had sliding trombone type inlets. That engine has very rapid inlet opening courtesy of the rotor uncovering the inlet port at its apex peripheral velocity. Such rapid opening combined with an already lowered 'cylinder' pressure is the ideal condition to develop a strong negative pulse. (It also had an open channel between inlet and exhaust port at that point).
A negative pulse from the exhaust system arriving during valve overlap and travelling up the inlet runner would achieve the same on a conventional piston engine.

Back to torque/litre.
Maximum torque is just that. At rpm below it it isn't at a maximum, ditto at rpm above. The former as gas can reverse back out of the cylinder, the latter because it can't get in there fast enough. But any engine will have a speed where it optimally fills its cylinders and that filling will typically be 85-90% of cylinder volume. Thus all and any engine will make torque dependent on its swept volume and that amount of filling and that is typically around 60lbs.ft / litre.
To go higher some (without resorting to supercharging) requires raising volumetric efficiency above 85% ie, by resonance tuning. It is nearly impossible to fall below 60lbs.ft / litre though. Even if you strangle it with small valves, restrictive inlet timing, or undersize throttle body or bodies it will still make 60lbs.ft / litre - just at a much much lower rpm. 60lbs.ft / litre is the base line and it's hard work to raise it much higher. More likely your efforts to raise it will raise the rpm it occurs at - a route to power in itself.

 

[LC2NLS6]

A junkyard 4.8 LS with 500,000 miles makes more power and torque 0 to 6000 rpm than a hemholtz resonance tuned TBI 350 that makes 190hp.

 

[Pinger]

Back to torque/litre.
Maximum torque is just that. At rpm below it it isn't at a maximum, ditto at rpm above. The former as gas can reverse back out of the cylinder, the latter because it can't get in there fast enough. But any engine will have a speed where it optimally fills its cylinders and that filling will typically be 85-90% of cylinder volume. Thus all and any engine will make torque dependent on its swept volume and that amount of filling and that is typically around 60lbs.ft / litre.
To go higher some (without resorting to supercharging) requires raising volumetric efficiency above 85% ie, by resonance tuning. It is nearly impossible to fall below 60lbs.ft / litre though. Even if you strangle it with small valves, restrictive inlet timing, or undersize throttle body or bodies it will still make 60lbs.ft / litre - just at a much much lower rpm. 60lbs.ft / litre is the base line and it's hard work to raise it much higher. More likely your efforts to raise it will raise the rpm it occurs at - a route to power in itself.

Missed a trick - or translation with this. 1 litre is 61 ci - call it 60.
1lb.ft/ci is the base line then.
If maximum power occurs at 5250rpm then 1hp/ci can be expected.

 

[L31MaxExpress]

A junkyard 4.8 LS with 500,000 miles makes more power and torque 0 to 6000 rpm than a hemholtz resonance tuned TBI 350 that makes 190hp.

No it doesn't! Not even close. Under 3,500 rpm the TBI 350 is substantially more powerful. The 4.8 makes 285-295 ft/lbs @ ~4,400 rpm. The TBI 350 makes 300-310 @ 2,400. The 4.8 probably only make 250-260 ft/lbs at 2,400 rpm.

 

[LC2NLS6]

No it doesn't! Not even close. Under 3,500 rpm the TBI 350 is substantially more powerful. The 4.8 makes 285-295 ft/lbs @ ~4,400 rpm. The TBI 350 makes 300-310 @ 2,400. The 4.8 probably only make 250-260 ft/lbs at 2,400 rpm.

What garbage transmission is WOT at 2400 rpm and stays there? The LS in the real world dominates any TBI engine, even the 454.

 

[L31MaxExpress]

What garbage transmission is WOT at 2400 rpm and stays there? The LS in the real world dominates any TBI engine, even the 454.

What delusional world are you in? That 454 will tow circles around a 4.8L while staying in OD most of the time. The 8.1L is far superior to a 6.0L with a trailer behind it. Having more torque down low means you can stay in high gear climbing grades. My 383 has ALOT more grunt in the lower rpm range than a 6.0L and similar HP to a healthy cammed one. Put decent heads and some cam in that 454 and it will destroy any naturally aspirated LS you want to run against it. A bone stock TBI 454 makes 385 ft/lbs of torque and it makes it at a low rpm. The 6.0L makes substantially less and it does not reach peak torque output until the 4,000 rpm range. They spin and spin and spin and pull like a dog.

My buddy has a 98 K3500 crew cab dually with the 7.4/4L80E and 4.10s. Rolling on 37" mud terrains it has no problem pulling a 6,500 lbs travel trailer comfortably at 85 mph down the road in overdrive with the torque converter locked.

I have driven a 2010ish 4.8/4L80E/4.10 geared Express cargo van down the same road and it would double downshift to 2nd gear to try to hold 75-80 mph on the uphill sections of the same road. 4.8 was screaming way up in the rpm range and the empty van was still slowing down. My 350 TBI G-van with 3.08 gears and my 350 Vortec Express van with 3.42 gears never had a problem maintaining that speed in overdrive up those hills.

You do not have to be WOT to reach maximum torque output. All you have to do is hit barometric pressure in the intake manifold and be in power enrichment fueling. At lower rpm you can hit atmospheric pressure in the intake manifold at 1/2 throttle or less. With factory GM transmission programming you hit full load well before the PCM unlocks the torque converter or downshifts.

My uncle owns a farm and his son-in law once talked him into setting up a propane fueled 6.0L in place of an older tbi era 454 on an irrigation well. Lets just say he replaced the 6.0L with an 8.1L. 6.0L was not strong enough to do the job.

I would take Nissans VK56 especially the newer VK56VD over a LS engine or even a LT engine anyday of the week towing. The guys on youtube that test trucks tested a 2014 355 hp 5.3 LT engine against the older 317 hp version of the 5.6L in the Titan. The 2014 Titan was almost 2 seconds quicker to 60 mph pulling the same boat than the Chevy. In a merging situation from a stop that is 20 car lengths. I prefer a big block to the VK56 though.

 

[badco]

4.8 cant tow as good as a tbi 305 nor can the 5.3. My 96 k1500 with nv4500 will out pull my 02 hd 6.0 but the 6.0 will pull harder after its going.

8.1 isnt even a choice, it get bout same mpg as a v10 dodge and not enough power to justify it. Plus only thing it shares with a real bbc is crankshaft would fit. None of the other big parts will.

Wanna ruffle feathers do it with something other than 4.8.