Super Stock/GT Fuel Injection Rules

[Frechles71]

So I am hoping to pick some brains and gain some knowledge on Super Stock/GT fuel injection rules/regulations. I’m confused with what I have seen at the track compared to how I read the rules. I’m looking at maybe putting a FI combo together so any incite is appreciated! Sorry if this gets too long, hopefully you stay interested until the end haha.

OK, the way I interpret the rulebook with my lawyer hat on: Both Super Stock and GT sections of the rulebook are completely silent on anything dealing with fuel injection. The Intake Manifold segment under Super Stock (Section 11A) does say that any intake manifold can be used, however; it has to be of the same configuration as original for carburetor used. No mention of throttle body, plenum, runners, etc.

This falls back to the Super Stock Section 11A intro caveat that: Requirements and specifications for all Super Stock categories are the same as those for Stock Cars unless otherwise specified herein. This leads to the Fuel Injection segment under Stock (Section 10A) which requires: “Fuel injection must retain OEM throttle body(s), plenum and manifold.” There is no mention of modification restrictions for the throttle body(s), plenum and manifold in this section.

So to sum it up with my verbatim interpretation: A Super Stock/GT car running a fuel injected combo should be running the OEM throttle body, plenum and manifold for the year motor claimed, as directed by the Stock car rules since the Super Stock/GT rules are silent. The Super Stock/GT Intake Manifold segment is not applicable since fuel injection is not mentioned and only carburetors are specified. I do not see any aftermarket fuel injection manifold/throttle body stuff on the NHRA acceptable aftermarket parts/sizes page, but may have missed something, so used OEM is golden. Since the rules are silent on fuel injection OEM part modification, the throttle body, plenum and manifold can be massaged in any way imaginable.

Just curious how everyone else running FI on Super Stock/GT cars see the rules? I have noticed a few cars this past year running a Victor Jr style intake to a Wilson elbow to a factory type throttle body and I do not see how that is technically legal but was told it is acceptable. Am I wrong with the assumption that the throttle body can be massaged since the rules are silent on the matter? I know there are throttle bore size requirements on the Engine Spec pages but there is no specified +/-.

Thanks!

[Ed Wright]

Any intake manifold that keeps the stock throttle body in it's original location.
What do you have in mind?

[ALMACK]

Originally Posted by Frechles71

So I am hoping to pick some brains and gain some knowledge on Super Stock/GT fuel injection rules/regulations. I’m confused with what I have seen at the track compared to how I read the rules. I’m looking at maybe putting a FI combo together so any incite is appreciated! Sorry if this gets too long, hopefully you stay interested until the end haha.

OK, the way I interpret the rulebook with my lawyer hat on: Both Super Stock and GT sections of the rulebook are completely silent on anything dealing with fuel injection. The Intake Manifold segment under Super Stock (Section 11A) does say that any intake manifold can be used, however; it has to be of the same configuration as original for carburetor used. No mention of throttle body, plenum, runners, etc.

This falls back to the Super Stock Section 11A intro caveat that: Requirements and specifications for all Super Stock categories are the same as those for Stock Cars unless otherwise specified herein. This leads to the Fuel Injection segment under Stock (Section 10A) which requires: “Fuel injection must retain OEM throttle body(s), plenum and manifold.” There is no mention of modification restrictions for the throttle body(s), plenum and manifold in this section.

So to sum it up with my verbatim interpretation: A Super Stock/GT car running a fuel injected combo should be running the OEM throttle body, plenum and manifold for the year motor claimed, as directed by the Stock car rules since the Super Stock/GT rules are silent. The Super Stock/GT Intake Manifold segment is not applicable since fuel injection is not mentioned and only carburetors are specified. I do not see any aftermarket fuel injection manifold/throttle body stuff on the NHRA acceptable aftermarket parts/sizes page, but may have missed something, so used OEM is golden. Since the rules are silent on fuel injection OEM part modification, the throttle body, plenum and manifold can be massaged in any way imaginable.

Just curious how everyone else running FI on Super Stock/GT cars see the rules? I have noticed a few cars this past year running a Victor Jr style intake to a Wilson elbow to a factory type throttle body and I do not see how that is technically legal but was told it is acceptable. Am I wrong with the assumption that the throttle body can be massaged since the rules are silent on the matter? I know there are throttle bore size requirements on the Engine Spec pages but there is no specified +/-.

Thanks!

Great question.

I know the throttle body diameter(s) have to be the size as per the engine spec sheet.

Going by what Ed posted above, I suppose the only Ford SS EFI engine that could use a carb style e.f.i. intake is the CJ.

[Jim Caughlin]

Don't want to tell you it's legal or not but in SS, I have seen throttle bodies bolted directly onto the top of fabricated single plane type manifolds. In other words, I don't think you have to keep the original plenum configuration, just the throttle body itself.

[fordteacherguy]

I asked the same question of intake configurations to Bruce Bachelder when I first was putting my 89 5.0 SS/MA Mustang together.

Bruce's comments at that time were that since we even allowed sheet metal intakes with no defined configuration (Any intake design per rule) the carb type intakes with adapters were perfectly legal. Where the throttle body is located is not very defined in the current rule, but most SS EFI cars (not many) I have seen keep it close to stock.

I assumed no TB mods as expected in stock.

Brian Thompson

[Ed Wright]

Unless something has changed recently, the throttle body had to be stock, (more to it than bore size, ask Travis LOL) and in the stock location. Single plane, carb intakes can be used with an elbow to put the TB back to it's original location. You can use any flow rate injectors.

[Crew Chief]

When I asked the same question, here's what I was told.

Any intake can be used. The unmodified OEM throttle body must be located in the original position for the engine claimed. Larger injectors may be used but must be in same position as original.

[Ed Wright]

Originally Posted by Crew Chief

When I asked the same question, here's what I was told.

Any intake can be used. The unmodified OEM throttle body must be located in the original position for the engine claimed. Larger injectors may be used but must be in same position as original.

That is how it has been since I started this foolishness again.

[Frechles71]

Thanks a lot guys!

Ed - Looking at putting together either an L98 or LT1 combo.

[Ed Wright]

John, lots of guys going fast with Edelbrock VictorEFI manifolds and either an Edelbrock or Wilson elbow. I never could make one run as fast as my sheet metal Hogan.

Probably doing something wrong. LOL

Don't drill the idle air hole between the throttle bores too much, they will nail ya. Ask me how I know, right Travis? LOL