75 mm throttle body on Cobra intake?
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Taken from this article.
The GT40/Cobra/Explorer intake entrances can easily be ported to 70mm, which brings us to our next throttle body size, the 70mm. If you don't want to do any porting whatsoever, stick with a 65mm throttle body on your GT40 style intake. Most aftermarket intakes have at least a 70mm entrance, and usually 75mm. The 70mm throttle body has an effective area of 3,149 mm², a 52.7% increase over stock.
If you don't mind heavily porting your GT40 style intake entrance, you can go all the way up to 75mm. Likewise, several aftermarket intake manifolds already come with a 75mm entrance. The 75mm throttle body has an effective area of 3,668 mm², which is an increase of 77.9% over stock.
The GT40/Cobra/Explorer intake entrances can easily be ported to 70mm, which brings us to our next throttle body size, the 70mm. If you don't want to do any porting whatsoever, stick with a 65mm throttle body on your GT40 style intake. Most aftermarket intakes have at least a 70mm entrance, and usually 75mm. The 70mm throttle body has an effective area of 3,149 mm², a 52.7% increase over stock.
If you don't mind heavily porting your GT40 style intake entrance, you can go all the way up to 75mm. Likewise, several aftermarket intake manifolds already come with a 75mm entrance. The 75mm throttle body has an effective area of 3,668 mm², which is an increase of 77.9% over stock.
What throttle body do you have now? If a 65mm or 70mm, i wouldn't spend the money to go to a 75mm TB at all. Put that money elsewhere.
I run a 65mm on my 93 cobra intake with TFS170 heads. I did buy a 70mm for it, but haven't put it on yet.
I run a 65mm on my 93 cobra intake with TFS170 heads. I did buy a 70mm for it, but haven't put it on yet.
I would skip the BBK, save my money and get an Accufab. Question is whether to get a 65mm or 70mm. If you are going to leave thing pretty much stock and stay with a 302 inch motor then 65mm.
The issue I would have with the 75mm on an unported upper is the mismatch between the opening on the upper and the trottle body which would create some hella turbulent air flow into the upper. I try and maximize everything I can as hp is not cheap.
The issue I would have with the 75mm on an unported upper is the mismatch between the opening on the upper and the trottle body which would create some hella turbulent air flow into the upper. I try and maximize everything I can as hp is not cheap.
I bought the Accufab. It's a damn fine piece. Only reason i didn't buy a 65mm is because i felt like if i was spending the $$ i might as well allow for future growth. HP difference between a 65mm and 70mm are likely nil on a N/A car.
One thing to be weary of is what's called "tip-in stumble" that occurs in off-idle situations. It's been debating that a large throttle body and it's larger blade creates a very sensitive situation when coming off idle, because it doesn't take much to let more air in. This can be tuned out, but if you are running a stock tune you may have issues with it. Hit or miss, some folks stick a 90mm and claim they don't have a problem.
For better drivability, the smaller TB might give you better "resolution" when driving at near idle conditions. For a race car that spends it's time at WOT...it doesn't matter.
One thing to be weary of is what's called "tip-in stumble" that occurs in off-idle situations. It's been debating that a large throttle body and it's larger blade creates a very sensitive situation when coming off idle, because it doesn't take much to let more air in. This can be tuned out, but if you are running a stock tune you may have issues with it. Hit or miss, some folks stick a 90mm and claim they don't have a problem.
For better drivability, the smaller TB might give you better "resolution" when driving at near idle conditions. For a race car that spends it's time at WOT...it doesn't matter.
Stay away from the Professional Products. The BBK is fine. Accufab is a lot more money, and unneccesary. I've never seen any problems with an oversize throttle body like 75mm. The toughest part is getting the inlet hose on that big throttle body.
Kurt
Unless sc or turbo the 70 mm tb is all that a 5.0 can use. Anything more is hype
foxbodybill89
Active Member
You had a BBK cold air intake with which MAF? I've had the same 70mm BBK/Edelbrock throttle body on my car for 23 years now and it works absolutely fine. I've never had to fix anything on it. Your results might be atypical, and this is not the place to air your grievance.
Kurt
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