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Old 11-21-2022, 09:07 AM
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Gary H Gary H is offline
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Default Throttle body size recommendation

I'm building an engine for a customer and the boost arena is something new for me. I'm looking for some recommendations on throttle body size for this combination.
The engine will be a 525" aluminum block, 4.5" stroke, KRE High Port 380 CFM heads, hydraulic roller 255/265 duration, Northwind intake with fuel injection rails added by Wilson manifolds, gooseneck forward to throttle body, 9.25 compression, dual TorqueStorm procharger belt system with two intercoolers
This is a street / show car 79' Trans Am, 6L80E transmission, 3:73 gear 9" rear. I have had recommendations from 90 - 105 MM on the throttle body and I simply don't know. Any thoughts are appreciated

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Old 11-21-2022, 09:28 AM
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What RPM range and how much boost?

Try this calculator:

Induction CFM


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Old 11-21-2022, 02:54 PM
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Hey John, since it's a street car probably see 7000 max. Regarding boost, probably on the 12 lbs range

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62' Lemans, Nostalgia Super Stock, 541 CI, IA2 block, billet 4.5" crank, Ross, Wide port Edelbrocks, Gustram intake, 2 4150 style BLP carbs, 2.10 Turbo 400, 9" w/4:30 gears, 8.76 @153, 3100lbs
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Old 11-21-2022, 03:58 PM
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I'd say it would need around 1900/2000 cfm throttle body. (more for racing, but 'street' use probably good enough)

My 'Toilet Bowl' is 4" diameter (around 101mm I think) which supposedly flows 1500 cfm. You would probably need the 105mm at least?
Probably good for street type use. But I'd try for a little bigger?



Found this on sizes on Killer Ron's website:

Quote:
The biggest throttle body features a purple*throttle blade*and comes in at 1800 CFM (4.100" Butterfly). This unit is set aside for the bigger cubic inch/higher horsepower applications. Engines from 421" to 572"*can put this throttle body to work.*
105mm would be smallest I'd go.

Link to the 'Terminator' style throttle body of Flying Toilet:

Terminator

May give some ideas on the size.



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KRE's MR-1 - 1st 5 second Pontiac block ever!


"Every man has a right to his own opinion, but no man has a right to be wrong in his facts."

"People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates

Last edited by johnta1; 11-21-2022 at 04:07 PM.
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Old 11-21-2022, 05:22 PM
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105 mm is a very common size for the Accufab and Holley throttle bodies (single blade).

The LS Intakes in this intake system can mount a 105 mm Throttle Body as designed right from Holley for LS Chevy engines,
see photo.

I personally would not use anything smaller than the 105mm TB. So you have a choice on either a 4 BBL 105 MM TB flow
or a single 105 mm TB flow set-up.

Tom V.
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Old 12-04-2022, 05:01 PM
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We run a 105mm on our 461 cu.in. twin turbo car. seems to like it.
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Old 12-04-2022, 06:13 PM
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105 or bigger

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