Cubic inches and Boost Correlation
Thread Starter
Staging Lane
Joined: Apr 2019
Posts: 63
Likes: 4
Cubic inches and Boost Correlation I am new to the boost scene, and have questions.....
I have been told that all things the same (as in properly sized cam, injectors, same compression, properly sized Turbo etc) a 5.3 is "easier" to make boost with than a 6.0. What is the truth of this and if so the reasoning?
I have also been told that using ported heads makes it harder to make boost? Again if so why?
The fact is I have both a 5.3 and a 6.0 in my shop, one of which will get built (forged rotating) for Turbo use. I also have a set of 243's that have been "stage III" CNC ported with 2.08 intake valves, and of course some 317's, and a set of 862's. This is a 95% track vehicle on race fuel and planning to spray meth, currently backed with a TH400 with RVMB and a brake, followed by a 9". Trying to understand and be able to make the "right" choice of build! Goals are to see 850ish whp
I have been told that all things the same (as in properly sized cam, injectors, same compression, properly sized Turbo etc) a 5.3 is "easier" to make boost with than a 6.0. What is the truth of this and if so the reasoning?
I have also been told that using ported heads makes it harder to make boost? Again if so why?
The fact is I have both a 5.3 and a 6.0 in my shop, one of which will get built (forged rotating) for Turbo use. I also have a set of 243's that have been "stage III" CNC ported with 2.08 intake valves, and of course some 317's, and a set of 862's. This is a 95% track vehicle on race fuel and planning to spray meth, currently backed with a TH400 with RVMB and a brake, followed by a 9". Trying to understand and be able to make the "right" choice of build! Goals are to see 850ish whp
A turbo is a centrifugal air pump. "Boost" is pressure reading inside the intake manifold. The cylinder heads are basically 8 holes where air can escape the manifold. The more air that escapes, the less pressure inside the intake manifold. So an engine that can move more air (like ported heads) might read lower pressure inside the intake manifold.
It's actually more complex than that because exhaust drives the turbo. But you get the basic idea why an engine that makes more power doesn't necessarily make more "boost". (It does move more air volume though)
It's actually more complex than that because exhaust drives the turbo. But you get the basic idea why an engine that makes more power doesn't necessarily make more "boost". (It does move more air volume though)
Launching!
Joined: Mar 2019
Posts: 267
Likes: 171
Don't confuse boost for air flow. Boost is just a measure of the air backed up against the intake valves. The same turbo on a larger displacement engine or the same displacement with better flowing heads will take longer to make boost because it's actually moving the air into the cylinders instead of just backing up. It's why you can do H/C/I on an engine that already had a centrifugal supercharger, keep the pulley ratio the same, and it shows less boost but makes more power. Flow is more important than boost pressure.
Thread Starter
Staging Lane
Joined: Apr 2019
Posts: 63
Likes: 4
Ultimately its not the boost numbers I care about, its the power to the wheels. What I am trying to decipher is that I was basically informed that I would make more power and make it easier putting a cam and injectors on an otherwise stock 5.3 turbo, than if I used my ported heads on a 6.0 with a cam, injectors, and turbo. Making 1000+whp is out of reach for my wallet right now, so I'm not trying to accomplish that, but I'd like to make 850 and not feel light I'm wringing the crap out of it to do it!
TECH Resident
Joined: Sep 2013
Posts: 994
Likes: 119
From: Mechanicsburg, PA
If power is the goal, go 6.0 and be done with it. Stock heads are capable of that power as well. But as stated the ported heads will as well at a lower pressure. Both motors will make that power. So keep the 5.3 in case you hurt the 6.0.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
The only thing "better" about a 5.3 vs a 6.0, is typically the blocks are stronger simply from the smaller bore diameter, meaning thicker wall liners. Plus perhaps they seem so readily available for very little money ( in the US )
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Something fishy about this post, lol-Myself I always go for a 6.0 (cant afford a 6.2) because
my vehs. are usually on the heavy side, fig the extra torq would help move it-but if a 6 isnt
in the cards, then I have no problem using a 5.3. The correct parts, tune is prob more important
than engine size. Stock 48 (nova) went 8.19 on a 6.0 with stock inners, 317 heads, won Drag Week.
If you have Facebook, ck out Richard Holdener, he has done a ton of dyno vids comparing parts.
my vehs. are usually on the heavy side, fig the extra torq would help move it-but if a 6 isnt
in the cards, then I have no problem using a 5.3. The correct parts, tune is prob more important
than engine size. Stock 48 (nova) went 8.19 on a 6.0 with stock inners, 317 heads, won Drag Week.
If you have Facebook, ck out Richard Holdener, he has done a ton of dyno vids comparing parts.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
RH has really been stepping it up with the videos lately. All great work, and hopefully it will continue ! Puts Engine Masters to shame, which whilst still good, has been a little disappointing lately
Surely there's enough money in TV for it to be a more regular, and longer show ?
Surely there's enough money in TV for it to be a more regular, and longer show ?
Thread Starter
Staging Lane
Joined: Apr 2019
Posts: 63
Likes: 4
Not sure what would be fishy...
I was literally told that because a 5.3 has a smaller volume, and because unported heads have a smaller volume that it is "easier" to make boost and that translates to power. Obviously there comes a point where you can put more cyl volume, bigger ports, more fuel, bigger turbo, etc. to make big power, nobody is arguing that. Question is what is the point where that is necessary? 1000hp? 1500hp? With so many people throwing together an untouched 5.3 (other than cam), with a chinese turbo, and making 750ish, or spending big bucks on forged assemblies, Frankenstein heads, monster turbos and on and on to make 1100hp..... it gets hard to navigate and decide the best route.
FYI I have no intentions of "throwing" together a junkyard setup, I don't like building things twice. Looking at doing rods and pistons in either a 5.3 or 6.0 (I have both), and then of course trying to decide if I should use the ported big valve heads on the turbo setup, or use them on my 69 Chevelle that has an LQ9 and use some unported 317's on the turbo?
I was literally told that because a 5.3 has a smaller volume, and because unported heads have a smaller volume that it is "easier" to make boost and that translates to power. Obviously there comes a point where you can put more cyl volume, bigger ports, more fuel, bigger turbo, etc. to make big power, nobody is arguing that. Question is what is the point where that is necessary? 1000hp? 1500hp? With so many people throwing together an untouched 5.3 (other than cam), with a chinese turbo, and making 750ish, or spending big bucks on forged assemblies, Frankenstein heads, monster turbos and on and on to make 1100hp..... it gets hard to navigate and decide the best route.
FYI I have no intentions of "throwing" together a junkyard setup, I don't like building things twice. Looking at doing rods and pistons in either a 5.3 or 6.0 (I have both), and then of course trying to decide if I should use the ported big valve heads on the turbo setup, or use them on my 69 Chevelle that has an LQ9 and use some unported 317's on the turbo?
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
But a more efficient non-restrictive setup will make boost easier with the right parts. AND it WILL make more power.
We do not want restrictions.
Launching!
Joined: Mar 2019
Posts: 267
Likes: 171
Not sure what would be fishy...
I was literally told that because a 5.3 has a smaller volume, and because unported heads have a smaller volume that it is "easier" to make boost and that translates to power. Obviously there comes a point where you can put more cyl volume, bigger ports, more fuel, bigger turbo, etc. to make big power, nobody is arguing that. Question is what is the point where that is necessary? 1000hp? 1500hp? With so many people throwing together an untouched 5.3 (other than cam), with a chinese turbo, and making 750ish, or spending big bucks on forged assemblies, Frankenstein heads, monster turbos and on and on to make 1100hp..... it gets hard to navigate and decide the best route.
FYI I have no intentions of "throwing" together a junkyard setup, I don't like building things twice. Looking at doing rods and pistons in either a 5.3 or 6.0 (I have both), and then of course trying to decide if I should use the ported big valve heads on the turbo setup, or use them on my 69 Chevelle that has an LQ9 and use some unported 317's on the turbo?
I was literally told that because a 5.3 has a smaller volume, and because unported heads have a smaller volume that it is "easier" to make boost and that translates to power. Obviously there comes a point where you can put more cyl volume, bigger ports, more fuel, bigger turbo, etc. to make big power, nobody is arguing that. Question is what is the point where that is necessary? 1000hp? 1500hp? With so many people throwing together an untouched 5.3 (other than cam), with a chinese turbo, and making 750ish, or spending big bucks on forged assemblies, Frankenstein heads, monster turbos and on and on to make 1100hp..... it gets hard to navigate and decide the best route.
FYI I have no intentions of "throwing" together a junkyard setup, I don't like building things twice. Looking at doing rods and pistons in either a 5.3 or 6.0 (I have both), and then of course trying to decide if I should use the ported big valve heads on the turbo setup, or use them on my 69 Chevelle that has an LQ9 and use some unported 317's on the turbo?
TECH Resident
Joined: Sep 2013
Posts: 994
Likes: 119
From: Mechanicsburg, PA
I am new to the boost scene, and have questions.....
I have been told that all things the same (as in properly sized cam, injectors, same compression, properly sized Turbo etc) a 5.3 is "easier" to make boost with than a 6.0. What is the truth of this and if so the reasoning?
I have also been told that using ported heads makes it harder to make boost? Again if so why?
The fact is I have both a 5.3 and a 6.0 in my shop, one of which will get built (forged rotating) for Turbo use. I also have a set of 243's that have been "stage III" CNC ported with 2.08 intake valves, and of course some 317's, and a set of 862's. This is a 95% track vehicle on race fuel and planning to spray meth, currently backed with a TH400 with RVMB and a brake, followed by a 9". Trying to understand and be able to make the "right" choice of build! Goals are to see 850ish whp
I have been told that all things the same (as in properly sized cam, injectors, same compression, properly sized Turbo etc) a 5.3 is "easier" to make boost with than a 6.0. What is the truth of this and if so the reasoning?
I have also been told that using ported heads makes it harder to make boost? Again if so why?
The fact is I have both a 5.3 and a 6.0 in my shop, one of which will get built (forged rotating) for Turbo use. I also have a set of 243's that have been "stage III" CNC ported with 2.08 intake valves, and of course some 317's, and a set of 862's. This is a 95% track vehicle on race fuel and planning to spray meth, currently backed with a TH400 with RVMB and a brake, followed by a 9". Trying to understand and be able to make the "right" choice of build! Goals are to see 850ish whp
Questions
1) If each engine has a properly sized cam, injectors, compression ratio and properly sized turbo (different turbo for each application), no truth, so no reasoning.
2) True, in a way. The turbo would have to move more air to achieve the same boost/restiction level.
Just run your ported 243's on the forged 6.0 and let it eat. It'll easily exceed your expectations.