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58MM Throttle Body

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LarryBible

Guest
Will a 58MM BBK throttle body work okay on a basically stock L98? It looks like I must buy a new throttle body and I would like to buy the larger one if it will work okay. I plan on doing quite alot when it comes engine time and would definitely like to have the 58MM at that time.

Until then will the larger body work out okay with the stock TPS?

It seems to me that cruising in closed loop mode, it won't matter. In Open Loop mode at WOT, is when it seems it would really throw a wrench in the works.

Any comments or experiences?

Have a great day,
 

-=Jeff=-

Well-known member
Joined
Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
Corvette
1990 ZR-1
58mm TB will be too big for a stock TPI. I would just go to a 52mm..
 
Joined
Jun 20, 2002
Messages
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Location
Tallahassee, FL
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none right now :(
jeff is correct, 52 MM willl work, 58 is too big... you will actually lose HP with the 58 because it is too big, and the plenum is not ported that large anyway.
 
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resto75

Guest
I supposely have a 58mm throttle body on my stock LT1. It was on the car when I bought it. The prev. owner put it on for the same reason you are talking about (future mods). I don't think it's needed either but I also don't see any problems with it. I don't race my can but I occassionally like to stomp it. It runs fine and dosen't have any hesitation. I do have a a non stock rear end and some transmission work, but don't know it that has much to do with it.
 
Joined
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Messages
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Location
Tallahassee, FL
Corvette
none right now :(
even a pretty wild 350 couldn't use a 58 MM throttle body... It should only be used in very high horsepower applications... The problem with it is the size of the throttle plates... it flows so much air, and the engine needs so much less than it can flow that the large plates are actually restrictive to the engine... basically it is tough to get the air to move around such large plates...
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
58mm Mucho MAS!

I wouldn't do it.... unless the mods ( in other area's) are right around the corner ( meaning UNDER 4 months )



Vig!
 
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LarryBible

Guest
Thanks for your replies.

What I plan on doing to the engine when it comes engine time may very well warrant the 58MM TB. But, my engine is mostly healthy right now, so it may be quite some time before I will need the 58.

When it comes time, my plans are 383, port the Vette aluminum heads, as much cam as I can get by with for the combination, Intake and Runners, probably the Edelbrock, and open up the front of the plenum to take advantage of a larger TB. Will this warrant a 58MM?

Also, will there be any significant flow advantage with the 52MM BBK over the stock TB?

Thanks everyone,
 
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resto75

Guest
Ok now that I'm thinking about it I have two questions.

1. How can I tell for sure what size TB I have. I was told 58 but I never confirmed that to be true.

2. What MM is a stock TB ?

My car runs great so I'm happy with it the way it is. I am curious now to the TB size however.
 

-=Jeff=-

Well-known member
Joined
Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
Corvette
1990 ZR-1
resto75 said:
Ok now that I'm thinking about it I have two questions.

1. How can I tell for sure what size TB I have. I was told 58 but I never confirmed that to be true.

2. What MM is a stock TB ?

My car runs great so I'm happy with it the way it is. I am curious now to the TB size however.

1) You can take the Air duct off and measure the Diameter of the Each Blade and that will give you an idea of the size.

2) Stock TB for all TPI and all LT1/4 is 48mm

Also there are only 4 TB sizes 48, 52, 54, and 58mm
 

vettn94

Well-known member
Joined
Aug 9, 2002
Messages
181
Location
Warrenville, IL.USA
Corvette
1994 Polo Green Convertible
LarryBible said:
When it comes time, my plans are 383, port the Vette aluminum heads, as much cam as I can get by with for the combination, Intake and Runners, probably the Edelbrock, and open up the front of the plenum to take advantage of a larger TB. Will this warrant a 58MM?

If you plan on leaving your current setup alone then save your money and leave the stock one in.
If you're going to a 383 with a big cam at that point you should consider ditching the TPI for a Miniram or Superram.
just my .02
 
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LarryBible

Guest
Good replies, I appreciate them.

I guess this thread started by my assuming that everyone knew that my TB needs replacing.

I did not realize that the stock TB is 48MM. This means the 52 would be an upgrade for my money rather than just the replacement of a stock part.

As far as my choice of long runners for the 383, what I really like in a street car is gut busting low to mid range torque. The opened up TPI type runners along with not too much cam should give me the dump truck low/mid range torque that I'm looking for.

Thanks again for all the enlightening replies.

Have a great day,
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
52mm; no doubt

Larry is an informative pal to many, here. Thanks. :BOW

You only need the extra flow of the 58mm at very high rpm and/or displacement. I'd check with BBK, but I expect you'll find they recommend the 52mm for your proposed 383, stump puller. The BBK needs no airfoil; it's made smooth.

Remember, only so much air goes through the engine at a given RPM. Opening up the runners (oversizing headers, too) slows the airflow. You can kill the low end with too low of an intake charge velocity. Similarly, the scavenge effect of the headers is reduced by going too big on the tubes. 1 1/2" tubes is fine on a SBC.

Get expert advice; follow ONE expert's formula. ;worship

Bigger ain't always better!

I trust TPIS for results. A pal has excellent results with Arizona Speed/Marine runners, stock plenum and the Ling/Accel intake.


Check this: http://corvetteactioncenter.com/forums/showthread.php?s=&postid=111186#post111186

:w

Gawd, does it ever RUN! :_rock
 

Harold Kelvington

New member
Joined
Mar 29, 2006
Messages
3
Location
Apple Valley, CA
Corvette
2006 Z06 Black on Black
58 mm

jeff is correct, 52 MM willl work, 58 is too big... you will actually lose HP with the 58 because it is too big, and the plenum is not ported that large anyway.

I installed a 58mm throttle body on my L98 and the top speed went from 156 mph to 165 mph.
Note: I matched the TB to the plenum and removed the hump that is just in front of the EGR injection holes, which I welded closed.
Also I matched the runners to the heads, small amount to make them match.
Inside the plenum I did some clean-up, not polishing.
 

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