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[Z06] Cylinder head flows on Mercury 32-valve, DOHC LS7

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[Z06] Cylinder head flows on Mercury 32-valve, DOHC LS7

 
Old 01-17-2019, 04:08 PM
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BigVette427
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Default Cylinder head flows on Mercury 32-valve, DOHC LS7

Saw in my recent SuperChevy magazine an article about the Mercury 32-valve, DOHC LS7. Great article and picutres, the engine is an engineering feat in and of itself.

That said, I'm not exactly impressed with the flow rates of the heads, even compared to stock (already CNC'd) LS7 heads. Additional ported LS7 heads far exceed the SB4 7.0 cylinder head flow rates. Not sure I care much for flow rates below .500 lift on an engine that boasts 8,000 rpm redlines?! My AHP hand-ported LS7 heads flow 390cfm+ at .700 lift.

http://www.superchevy.com/how-to/181...50hp-dohc-ls7/





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Old 01-17-2019, 04:13 PM
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Originally Posted by BigVette427 View Post
Saw in my recent SuperChevy magazine an article about the Mercury 32-valve, DOHC LS7. Great article and picutres, the engine is an engineering feat in and of itself.

That said, I'm not exactly impressed with the flow rates of the heads, even compared to stock (already CNC'd) LS7 heads. Additional ported LS7 heads far exceed the SB4 7.0 cylinder head flow rates. Not sure I care much for flow rates below .500 lift on an engine that boasts 8,000 rpm redlines?! My AHP hand-ported LS7 heads flow 390cfm+ at .700 lift.

http://www.superchevy.com/how-to/181...50hp-dohc-ls7/



I'm no expert but there's 2 (TWO) intake and 2 (TWO) exhaust ports per cylinder, sooooo
Also, flow rates dont really mean much without other data, cylinder bore, with pipe, without pipe ect

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Old 01-17-2019, 04:57 PM
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Originally Posted by Millenium Z06 View Post
I'm no expert but there's 2 (TWO) intake and 2 (TWO) exhaust ports per cylinder, sooooo
Also, flow rates dont really mean much without other data, cylinder bore, with pipe, without pipe ect
Sure, but it's not two of the LS7 2.205" intake valves, they are two of the much smaller 1.70" intake valves. Interesting what the total volume would be. I was thinking the flows would have been in the low 400cfm's like some of the modern Hemi heads or something.


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Old 01-17-2019, 10:38 PM
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Lots of advantages to having separate cams for intake and exhaust. Also no rocker arms or push rods.
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Old 01-18-2019, 08:27 AM
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Would love to see some independent testing of these on a nice LS7 or bigger motor.
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Old 01-18-2019, 08:39 AM
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This illustrates the benefits of being able to rev well beyond 7000 RPM comfortably without concerns about valvetrain stability.
That 750 crank horsepower is a result of an engine that is revving to 7500+ to make that 750 crank horsepower without valve train deflection or crazy big cam shaft profiles.

Awesome engine.
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Old 01-18-2019, 08:43 AM
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Also shows you the value of the mid lift flow numbers.
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Old 01-18-2019, 11:07 AM
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Originally Posted by BigVette427 View Post
Sure, but it's not two of the LS7 2.205" intake valves, they are two of the much smaller 1.70" intake valves. Interesting what the total volume would be. I was thinking the flows would have been in the low 400cfm's like some of the modern Hemi heads or something.

Again, 2 (two) 1.7 valves, thats 2.4 total area and a smaller valve will increase port velocity which equals torque so 2 smaller ports and 2 smaller valves will easily outflow a larger single port/valve. The mid lift numbers, where you are 90% of the time would also be far better than the single port and I'd bet its capable of well over 400cfm.

Modern HEMIS are in the 390's also with the 5.7 Eagle head being the best of the non SRT heads. The SRT 6.2/6.4 heads flow slightly better

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Old 01-18-2019, 12:44 PM
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Originally Posted by Millenium Z06 View Post
Again, 2 (two) 1.7 valves, thats 2.4 total area and a smaller valve will increase port velocity which equals torque so 2 smaller ports and 2 smaller valves will easily outflow a larger single port/valve. The mid lift numbers, where you are 90% of the time would also be far better than the single port and I'd bet its capable of well over 400cfm.
That is my entire point - I would have thought they would have flowed greater, too.

Originally Posted by Millenium Z06 View Post
Modern HEMIS are in the 390's also with the 5.7 Eagle head being the best of the non SRT heads. The SRT 6.2/6.4 heads flow slightly better
Your numbers are a little high, not sure where you are getting those from? Even the Apache heads don't come close the LS7 cylinder head flows. I'm still of the impression the LS7 cylinder heads offer the greatest flows from a production cylinder head. How many production cylinder heads are CNC'd from the factory, and of those, how many of those have Ti valves?

Dodge now offers four different Hemi heads, the early 5.7 (like the ones we tested), the 6.1, the later 5.7 Eagle, and the 6.4 Apache heads. The early 5.7 heads we tested, offered the lowest stock flow-rates of the bunch, topping out at 269 cfm at .700-inch lift. All of the later heads offer significantly more flow in as-cast form, with each easily exceeding 300 cfm. Flow numbers for the 6.4 Apache heads are said to reach 340 cfm, a big number even for ported 5.7 heads, as our ported early castings from Total Engine Airflow (TEA) checked in at 329 cfm. The improvement in airflow offered by the porting from TEA was significant, as the ported heads flow enough to support over 650 horsepower. The question now was; would the mild engine be able to take advantage of the extra head flow when it was making only 400 horsepower? The answer was not really, as the stock heads were already sufficient to support the current power level. The ported heads improved the power output slightly, to 413 horsepower at 5,700 rpm, and 439 lb-ft of torque at 4,600 rpm, but it was another case of the mild combination holding the heads back. The results would change in test two.
https://www.hotrod.com/articles/hemi...mild-and-wild/


https://treperformance.com/i-2390084...-lift-630.html

I was more so referring to the aftermarket Gen II Hemi heads (ex. Edelbrock) for the 426 and up motors; they have heads that flow 400cfm as cast.
https://www.rodauthority.com/tech-st...26-hemi-heads/
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Old 01-18-2019, 06:06 PM
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Because they dont need the lightness of titanium to keep the rpm up...
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Old 01-19-2019, 10:16 PM
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Pro tip - marine heads arenít designed for peak RPM power. They are designed for peak torque in the mid RPMs for sustained use/load.

If those heads could make their way to Greg Good then feelings would be hurt for sure.
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