Head Flow Comparison Via Power Difference (1G, 2G)

[OverKillGSX]

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This is more of a specific question than looking at flow numbers, so here's a thread.

I know a 2G head will "outflow" a 1G head (as far as velocity goes due to the ports' "floor" being higher in the 2G head giving the air a direct shot passed the intake valves increasing air velocity and ultimately flow). Question is as far as extremities go, which one will become restrictive first in a high HP application?

For example. Lets take a 6 bolt engine with a 1G head that's been deburred and polished. JMF manifold, Q45 throttle body, GT42R turbo. Puts out 780HP at 30PSI on e85. Throw on a 2G head with the same cams that has the same debur and polish job on the ports and change nothing else. Which head will be able to make the most power?

 

[2GFWDbeast]

What sort of scientific proof has "look at it" been turned into? What makes you think that you will gain HP with a 1G head over a 2G head just because the intake runners are larger?

The larger runners on a 1G head have a much larger angle into the valve, this actually slows the air entering the cylinder chambers. Generally on a port job of a normal head for racing they raise the chambers not lower them so the entry into the valve is a straight as possible. The angle into a 1G head is horrible because the port is so low already in the head.

The HP increase from a 2g head to a 1g head is from the Cams, and Intake manifold. If your using aftermarket cams and plan on buying a SMIM don't put on a 1g head because you'll end up with no gain and a head that has horrible port design.

Most major racers now using DSM's are using a 2G head and 2g style intake manifold and raising the runners in V8 styles so the air is hitting the top of the valve as straight on as possible. Air flow has nothing to do with the size of the chamber and EVERYTHING to do with the shape and design.

Putting a 1g head on a 2g block is the OPPOSITE of what you want to do. Replace your 2g block with a 1g block and keep your 2g head. Have it ported and port raised and add a set of HKS or Comp cams with a SMIM. This will provide you with a much more potent street engine.

The castings on 2g heads are far superior to 1g castings. They have more alluminum in the lifter bulkhead to reduce flexing and less problems with casting shifts than 1g heads. The intake ports are smaller yes, but they do not seem to be a restriction of any sort. The Evo 8 heads have the exact same intake ports and we are making 600+ whp constantly on completly stock unported ones. Our shop car's intake ports arent opened up that much at all and it makes over 800 awhp.

Use the 2g head, drill the head bolt holes out to fit the larger 12mm studs, find yourself an Evo 3 intake manifold, and you'll have the same top end package as an Evo 8, which has been proven to consistantly outperform 1gs. It will save you money, make your swap far easier and WILL outperform a swap with a 1g head/intake, much to everyones dismay

 

[OverKillGSX]

What sort of scientific proof has "look at it" been turned into? What makes you think that you will gain HP with a 1G head over a 2G head just because the intake runners are larger?

Errr...what? I said that? I said a 2G head overflows due to velocity. I said the opposite. Where is the read icon.

The larger runners on a 1G head have a much larger angle into the valve, this actually slows the air entering the cylinder chambers. Generally on a port job of a normal head for racing they raise the chambers not lower them so the entry into the valve is a straight as possible. The angle into a 1G head is horrible because the port is so low already in the head.

Exactly!

The HP increase from a 2g head to a 1g head is from the Cams, and Intake manifold. If your using aftermarket cams and plan on buying a SMIM don't put on a 1g head because you'll end up with no gain and a head that has horrible port design.

My plan is a SMIM, pte6262, 280 cams. I want to use a 2g head for a few reasons, the added velocity being one. I need to make sure that the smaller ports will not become a restriction at high HP as opposed to the 1g head with the larger runners.

Putting a 1g head on a 2g block is the OPPOSITE of what you want to do. Replace your 2g block with a 1g block and keep your 2g head. Have it ported and port raised and add a set of HKS or Comp cams with a SMIM. This will provide you with a much more potent street engine.

Yup, that would be the opposite of what I want to do. .

Just trying to confirm what I already know. Thanks man.

 

[2GFWDbeast]

what you asked what head will make more power i answered it in a detailed description for you.

 

[OverKillGSX]

what you asked what head will make more power i answered it in a detailed description for you.

I understand where you're coming from. 90% of people say "bigger ports = better" and even worse 50% of people say "1g = better"

 

[2GFWDbeast]

just trying to give you the run down. I know of people say oh ya umm 1g or 2g but dont say the reasons and what not