1-3/4 vs. 1-7/8.

[foghat]

I've seen LS3 heads flow 320+ stock and LS7 heads have been known to flow roughly 360cfm where as with a stock Coyote you are lucky to see 300cfm on the intake side.

'Better flowing heads' is just not accurate.

It certainly could be accurate.

I don't pretend to know which heads are better - but just because the mustang heads don't flow as much due to the 302's smaller displacement, does not mean they aren't a better flowing head (all else being equal) than what comes on the LS3/LS7.

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[Matte Black]

It certainly could be accurate.

I don't pretend to know which heads are better - but just because the mustang heads don't flow as much due to the 302's smaller displacement, does not mean they aren't a better flowing head (all else being equal) than what comes on the LS3/LS7.

Ummm, that's exactly what it means...

A 'flow bench' prove this. Thats the entire point of a flow bench lol. A Flow bench doesn't take into account engine displacement- it simply measures the amount of air (CFM) that is able to flow through any given item.

 

[Zemedici]

It certainly could be accurate.

I don't pretend to know which heads are better - but just because the mustang heads don't flow as much due to the 302's smaller displacement, does not mean they aren't a better flowing head (all else being equal) than what comes on the LS3/LS7.

What are we comparing then? How the heads LOOK?

CFM is CFM is CFM, same as HP is HP.

'well, 300hp is good for a 4 cylinder' when in reality 300hp isn't shit. Know what I mean?

The 4v heads flow well for their size, yes. However, they don't have the DISPLACEMENT to support a header size that big. Plain and simple. The dyno data provided above is awesome, except it is for a 6.2l LS engine, and the bigger displacement could utilize the larger header diameter better than a 5.0. If there was data similar except utilizing a 302, it would prove something. However, I feel you'd be hard pressed to find an answer stating this explicitly ;)

 

[Ultrakla$$ic]

Get the 1-7/8" just because they're easier to resell. LOL.

 

[Major League Infidel]

Go with the 1-7/8" primaries and don't look back. You won't regret it nor will you have to purchase another set if you decide to build a 800+rwhp monster down the road. :cheers:

QFT :amen:

 

[beefcake]

these cars really like to breathe, we typically go for the 1 7/8 right out of the gate, just because alot of guys grow later down the road to power adders

ets will be pretty much identical,

we have the stainless power on sale right now, very good pricing

 

[Zemedici]

these cars really like to breathe, we typically go for the 1 7/8 right out of the gate, just because alot of guys grow later down the road to power adders

ets will be pretty much identical,

we have the stainless power on sale right now, very good pricing

and there you go, OP :cheers:

 

[foghat]

Ummm, that's exactly what it means...

A 'flow bench' prove this. Thats the entire point of a flow bench lol. A Flow bench doesn't take into account engine displacement- it simply measures the amount of air (CFM) that is able to flow through any given item.

What are we comparing then? How the heads LOOK?

CFM is CFM is CFM, same as HP is HP.

'well, 300hp is good for a 4 cylinder' when in reality 300hp isn't shit. Know what I mean?

The 4v heads flow well for their size, yes. However, they don't have the DISPLACEMENT to support a header size that big. Plain and simple. The dyno data provided above is awesome, except it is for a 6.2l LS engine, and the bigger displacement could utilize the larger header diameter better than a 5.0. If there was data similar except utilizing a 302, it would prove something. However, I feel you'd be hard pressed to find an answer stating this explicitly ;)

I'll admit I am a bit out of my element and should probably stop talking now.

With my comment about all else being equal, what I was trying to get at is overall head design vs LS3.

In absolute terms yes, the LS3 head flows more, but does that automatically make it a 'better flowing' head? Same way you can't say the car with the most hp (cfm) is the best performing (best flowing) - at the very least you need to take weight (displacement) into consideration.

Does it make sense to compare flow rate to displacement to determine a flow per cubic inch number? Similar to the way you often see lbs per hp to determine how well a car will perform. Seems to me such a number is what one would look at to determine the best flowing head.

If you were to put an equivalently designed head on the LS3 would it flow better than what the current LS3 heads flows? If yes, wouldn't one conclude they are a better flowing head? Just, in the mustangs case, the displacement isn't there to realize more flow than the LS3.

Could this make any sense, or have I made myself sound like a complete know nothing asshat? Which honestly is not far off the mark in this case. :cheers:

 

[dubster99]

I've seen LS3 heads flow 320+ stock and LS7 heads have been known to flow roughly 360cfm where as with a stock Coyote you are lucky to see 300cfm on the intake side.

'Better flowing heads' is just not accurate.

Have you tested the heads from the boss, or the 2015?

 

[Zemedici]

I'll admit I am a bit out of my element and should probably stop talking now.

With my comment about all else being equal, what I was trying to get at is overall head design vs LS3.

In absolute terms yes, the LS3 head flows more, but does that automatically make it a 'better flowing' head? Same way you can't say the car with the most hp (cfm) is the best performing (best flowing) - at the very least you need to take weight (displacement) into consideration.

Does it make sense to compare flow rate to displacement to determine a flow per cubic inch number? Similar to the way you often see lbs per hp to determine how well a car will perform. Seems to me such a number is what one would look at to determine the best flowing head.

If you were to put an equivalently designed head on the LS3 would it flow better than what the current LS3 heads flows? If yes, wouldn't one conclude they are a better flowing head? Just, in the mustangs case, the displacement isn't there to realize more flow than the LS3.

Could this make any sense, or have I made myself sound like a complete know nothing asshat? Which honestly is not far off the mark in this case. :cheers:

Cylinder head flow is directly related/proportional to displacement/cubic inches. You're making it more complicated than it needs to be. :cheers: let's simplify it.

Header size also has to do with power, which is why we're saying IF OP plans to go Forced induction to get the bigger, as he'll be making the power to utilize it correctly, make sense?

However if he plans on staying NA (my car will never be FI, so I'd get the smaller headers as they would 'match' the other components of the engine better (head flow, cam, intake, etc etc) the smaller ones will work.

No worries man, we're all here to learn/spread knowledge :cheers:

 

[daniel_94kg]

I have 1 3/4 because I got a killer deal(otherwise I'd have probably went with 1 7/8) on them. I'm planning on running a blower but only looking for the 600hp range. . Right now the car still sounds great and makes Good power with them. My et went from 112mph to 115mph after the install and tune.

 

[bluebeastsrt]

these cars really like to breathe, we typically go for the 1 7/8 right out of the gate, just because alot of guys grow later down the road to power adders

ets will be pretty much identical,

we have the stainless power on sale right now, very good pricing

That is a pretty sick price!:clap2::clap2::clap2:

 

[Cascadia_302]

I was recently told that the larger diameter headers produce the most power at the higher RPMs as opposed to the smaller diameter headers (1-3/4) which produce the most power at lower RPMs. Opinions?

As a side note: I do understand the reason for having a larger diameter header set up for FI, but is that where the benefit ends?

I think for street use 1.75" is a good choice (huge improvement over stock) but as mentioned above if later you go down the FI road OR you plan on higher RPM use aka strip or track just go with the 1.875".

 

[Derek@Lethal]

Although that is true the 302 does not flow NEARLY enough air to warrant a 1 7/8 header, it just doesn't. Save for a FI build, which seems to be where everyone is headed nowadays, in which case it would be beneficial to pick up the bigger set just so you don't have to purchase different ones in the future.

Its nice to be able to discuss tech with someone whos not talking out of their ass, thank you sir :cheers:

The Coyote flows way more than enough to warrant the 1-7/8" in NA form. As bluebeastsrt pointed out, the head flow on the Coyote is one of the reasons. You also have to consider the cam profile, compression AND RPM. The Coyote has healthy compression and can turn some RPM, two of the main reasons to go with the larger primary.

 

[beefcake]

and there you go, OP :cheers:

That is a pretty sick price!:clap2::clap2::clap2:

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