High Flow Heads On Stock Motor

Feb 9, 2017
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So I'm Ben, I'm a new guy with a 92 gt. i have acquired a set of trick flow r series 205 heads from a friends drag car. They supposedly flow 350 cfm on the intake and have 61cc chambers. Would there be any draw back to putting these on my stock 5.0?
 
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CarMichael Angelo

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Potentially poorer performance and loss of current fuel mileage. Port velocity will be slowed because of the larger port.
The end result will be a sluggish, torqueless bottom end.

Now,.....If you add a cam, intake, and exhaust to the mix......Then they'll work.

There are a couple of examples on this forum where somebody else has done it and yielded really good power out of the combo.
here's one:
https://www.stangnet.com/mustang-forums/threads/nikwoacs-commitment-issues-engine-build.833852/
 
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CarMichael Angelo

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Thanks for the reply. Sounds like I'll be better off spending money on the 408 that these heads are meant for.
:shrug:

Where'd you get that from? If you're going to buy a 408, and go through the expense and labor to swap it in, a cam, intake, and exhaust headers for the current engine are way cheaper than a 408.

The engine build I linked is a perfect example of what you could expect from big head on a stock shortblock, provided you add the supporting mods to make it all work cohesively.
I don't know about you, but I'm sure that there are plenty of guys out there that would be giddy w/a N/A 335 whp / 325 ft/lb rwtq out of a 306.
 
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tannerc91gt

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What are the rest of the flow numbers? Peak doesn't mean much out of context
 

tannerc91gt

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I see the 205s are 305cfm but I believe that's at .700. Maybe yours have had some work done?

They'd be better suited on a motor with more cubic inches. Mike summed up why pretty well.
 

tannerc91gt

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Potentially poorer performance and loss of current fuel mileage. Port velocity will be slowed because of the larger port.
The end result will be a sluggish, torqueless bottom end.

Now,.....If you add a cam, intake, and exhaust to the mix......Then they'll work.

There are a couple of examples on this forum where somebody else has done it and yielded really good power out of the combo.
here's one:
https://www.stangnet.com/mustang-forums/threads/nikwoacs-commitment-issues-engine-build.833852/
Nik is who I was thinking of after reading his post as well. Car ran well for the combo IIRC. But that's not to say it wouldn't have run better with more appropriate heads.

As you said, it's heavily dependent on the rest of the combo. You can do a lot with a 300" motor.
Don't like seeing people get wrapped up in peak flow numbers at .700" and then they run a .512 lift camshaft and drive a lazy car around.
 

a91what

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average numbers are what to look for, it's best to get a higher mean flow rate rather than a high peak. This creates an engine that make a high mean torque curve. This translates into better drivability and a fun street car.
 
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5.0specialist

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On a stock 5.0, the stock E7 heads would perform better on the street in the low and mid rev range.. IMO Sell those heads and get a set of gt40p heads or AFR165's if you want to go with aluminum.
 

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