With heads and cam I can believe something more than 48MM was benificial.

 

I raise the question again to those planning on or currently have 345 or better crank hp as to why the factory put 80mm t.b.s on ls1 Btw I'm not convinced the big block mentioned earlier had that small of a t.b.

 

I went with the Holley 52 for the performance as well as the looks, I guess you could say that looks were 75% of the motivation, 25% performance. Really sets the engine off to have that Holley tb plate. Now that I have a complete top end setup I think its alot more benificial to the setup than a stock piece.

 

I am running 10.5's at 3200 lbs with an untouched factory 48mm throttle body. You do the math on the HP.
I don't doubt that these guys when they say that they picked up with a bigger throttle body. I would like a good explanation as to why. Is it because they are running pump gas, etc?


Daren

 

GMPP 502 Ram Jet description. Note where they got the throttle body from (The L98 uses a twin 48mm throttle body). Also note the positive results of running a smaller throttle body.

Daren


P/N 12499121 [Old P/N 12497323]
The recipe is simple; one part attitude, one part driving perfection, one part leading factory technology, and five hundred and two parts hungry rat motor. Ram Jet 502, you either have one, or you want one! When the idea of an all new big block fuel injection system first came up, we all thought it was a good one. When it was proposed that it be integrated with our 502 crate engine, we thought someone had clearly lost their mind. Who could possibly need the awesome, flat, broad torque curve only available with a long runner dry manifold? And who would want the neck-snapping throttle response of MEFI 3 controlled port fuel injectors? And what would be the need for aggressive tunnel ram styling? But then we remembered we?re not building 100 mile per gallon, 0 to 60 in a week, eco scooters. We?re in the hot rod business! So we called together engine management system experts from GM Powertrain, our own GMPP engineers, and fuel injected race engine builder and GMPP Pro Mod racer Harold Martin. After some great discussions, a little debate, a lot of late nights and 50 gallons of coffee we had an intake manifold design like no other. By leveraging leading fuel management technology, numerous production developed components, the industry standard MEFI 3 controller and the great Ram Jet name from the 50?s, the Ram Jet 502 is reality.
The new undisputed heavy weight champion, the Ram Jet 502, makes 502 horsepower at 5100 rpm and 565 ft.lbs. of torque at 3200 rpm. The instantly throttle responsive Ram Jet 502 drives like no other big block you?ve ever driven. With over 500 ft. lbs. of torque from 2,200 to 5200 rpm, the Ram Jet 502 is a tire shredding monster making more torque throughout its operating range. This is possible because Ram Jet has a larger plenum and runners than would ever be possible in a carbureted application. This means greater intake efficiency and greater torque without sacrificing driveability. The Ram Jet manifold is so efficient that we?re able to make all of this horsepower and torque with a production L98 throttle body assembly, you know, the one that Firebird and Camaro owners always replace when trying to make more power in their 350 engines. It?s all about airflow quality, velocity, and fuel and spark management. You?ll just have to drive one to appreciate it. If the one-second cold starts, no stalling, instant throttle response, and the solid pull from idle to red line don?t convince you that a Ram Jet 502 is for you, then maybe we could interest you in a 100 mile per gallon, 0 to 60 in a week eco scooter.
The Ram Jet 502 is designed for ease of installation needing only 12V, ground, fuel feed and fuel return to run. Included are an instruction sheet, service manual and diagnostic tool for ease of installation and service. As with any GM Performance Parts Ram Jet engine, an in tank fuel pump is recommended to avoid possible vapor lock. See instruction sheet for fuel pump recommendations. Also included is complete throttle linkage that accepts your production throttle cable and transmission cable. Includes pre-programmed MEFI 3 ECM and wiring harness.
The Ram Jet manifold stands eleven inches tall as measured from the front and rear ?china wall? on the cylinder block. That?s just half an inch taller than a typical single plane high rise manifold, Holley carb and air cleaner combo.
For specific internal engine specifications, refer to the ZZ502/502.

 

The stock 48mm tb flows what, 750 cfm? That is enough for a 100% VE 383" at 7000 rpm. I have never seen an aftermarket tb of quality equal to the factory piece. Throttle levers come loose, poorly done IAC passeges etc. Tougher to get a big cam to idle well with an aftermarket tb. as they usually clobber the idle air distribution passage, screwing up cylinder-to-cylinder IAC air. Just another place to throw money away. When you hear of gains with them, it was usually one week with the stock piece, another week with the big one. No A-B-A same day testing. Mine showed absolutely no change either way with a 58mm, all tests run within 15 minutes. Ran the old one, the 58mm, then again with the old one. Swapped them out sitting on the dyno. A more powerful engine would probably show you something, my old turd did not care. Easy enough, as Darren said, to do the math.

 

And he should know.