All right you got me there. But still. I think people get hung up that 48 means only that! And it actually means more. That’s all I was trying to illustrate.

 

This particular topic is of interest to me for a couple of reasons. The first is I have owned stock, 52, 58 and monoblade TB’s. The second is that a well known shop recommended that I replace my monoblade with a 52 mm TB on a 383 engine I bought from them.

What I do know……….. On a stock LT4 engine replacing the stock TB with a 58 mm TB made absolutely no gains on the dyno. It also produced no loss. After a rebuild on a 396 making around 450 rwhp, I replaced a 58mm TB with a monoblade and also saw no gains. I'll also admit there was a few problems encounter during the rebuild.

Could care less about theory….. hardcore dyno numbers are what I’m looking for.

Downsides I encountered.......No doubt the monoblade is a bit tricky to drive as it opens so quick, besides that…… why would this “name shop” tell me to ditch the monoblade on it’s 400 rwhp 383?? Any clues?

 

THis is what i believe...
Excluding forced induction etc. Basically if a throttle body is adequate in CFM's of air it will work just as well as a larger one that flows more but the difference would be how much throttle you have to apply to get the WOT reading. Basically since the openings are larger you only have to open up a fraction of the butterflies to flow the same amount as a stock 48 Somthing like
100%open 48mm 80%open 52mm 60%open 58mm 20%open monoblade

That is just a guess but I'm trying to get the mechanics of it across. I don't have exact measurments. Most of us can polish up our stock ones and add an air foil (which doesn't add much power either), and be fine with that. If you wanna feelk big go witha bigger one but you will have less pedal travel or more touchiness on the throttle. It's probably just personal preference. I simply know I could spend that $300 somewhere else fisrt!

 

Look here, I do not understand what the debate is here! We all know that the faster you get the air in, and the faster you get the air out, thats where your HP gains are gonna be.

On a stock motor, I agree that there is no need to upgrade your TB. But on a heads/cam/1.6rr motor I feel this mod is more than worth it.

 

Go for it Brent !!!!!!!!

 

Not More Throttle Response!!!!!!

 

This threads kinda tired but I have to ask,
Did you guys with the 58mm and/or the monoblades port the intake where the t.b. mounts? (I know Brent did). If so, how much for the monoblade? Those are 52mm openings so they would be a restriction beyond a 52mm t.b. Since you may have dyno #'s that makes it more interesting.

 

So what kind of intakes are you guys using for these test. Stock unported runners or what? Is the air that entering the intake enough but the intake(runners) are choking the motor down?

Lets shed some light on the intake itself. I see alot of people welding the intakes up above the injectors holes and porting the hell out of them....

 

Taken from my thread here-
http://web.camaross.com/forums/showt...hreadid=189363

Some calculations to help-

------------

To determine how much air your engine can consume at peak rpm complete this simple formula-
CFM = (rpm x displacement x VE) /3456

rpm=max rpm you will shift at (6700 for example)
displacement= cubic inches of your engine (350 for example)
VE= Volumetric Effeciency (90% = .9, 104% = 1.04)
So a 383 that shifted at 6800rpms with a VE of 100% would consume 753cfm.
CFM = (6800 x 383 x 1) /3456

------------

Now carbs and throttle bodies are flow rated at a pressure drop of 1.5" Hg, you need to convert this to 1" Hg. So use this formula-

sq root (new pressure drop / old pressure drop) x flow at original pressure drop

So a 58mm TB that is rated at 1050cfm would flow 857cfm actually.
sq root (1.0/1.5) x 1050 = 857cfm

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So you can see for the mentioned 383 a 58mm TB would be enough for it. Try your combo out...

 

I’m one of those whom appreciates the automotive physics/math, but I’m just to plain dumb to really put it into proper perspective. Can’t really relate very well.

Frankly what floats my boat is objective information either in best new times (same track – same conditions) or even better, dyno data. I’m honestly surprised that virtually no one on this list has actual dyno sheets comparing throttle bodies.

As mentioned, I dynoed a 58mm TB vs a 48mm TB on a basically stock LT4 making 331 rwhp and there was no difference. This was same day with the throttle body exchanged while the car was still on the dyno and retuned to see it it would help. I also dynoed a 58 mmTB vs monoblade on a solid roller 396 and felt there was no gains to be had. But this was not a scientific test as it was two different combo’s almost a year apart.

I bought the very expensive monoblade and reported my intake based upon other peoples subjective suggestion. In my mind, that very much appears to have been a waste of time and money and something I got suckered into. This is why I don’t trust anything that is not objective results oriented and not performed in at least a semi-scientific manner..

I’m redoing my current 383 combo to a completely different 385 setup. I currently have a 52 mm TB and the first thing I’m going to do when it’s done is to borrow a 58mm TB and see if the car responds. How else do you know if you’re wasting your money or not?