When do you to start thinking about upgrading to a 58mm throttle body? I've seen a lot of answers on this on this site. Some say stick with the factory 48mm throttle body and others say upgrade to a larger after market throttle body.

I'm upgrading all my stock TPI intake system now. I have custom ram-air, gutted air filter box, K&N air filters, and a BBK 52mm throttle body.

I am in the process of purchasing a ported plenum. I have a TPIS big mouth base sitting in my garage. I want to find some TPIS intake runners and port match them to the intake.

I also have hooker 1 5/8'' ceramic coated hooker headers and y-pipe, 3'' high flow cat and 3'' flowmaster cat back exhaust.

Other than those basic bolt on mods my L98 is 100% stock. I don't plan to do a lot of other modifications other than upgrading the intake system for the time being.

I may get a set of Edlebrock alumimum heads and aftermarket cam at some point down the road but as of right now the rest of the engine is going to stay stock. I want to see what kind of performance gains I can get from doing thse additional intake mods before I decide to start digging into the motor.

I don't really want to crack open the motor just yet. I have an A/C Delco remanufatured L98 and I've only got 30,000 miles on it.

 

Keep the 52mm. If you were making over 420whp then you would need a 58mm.

 

Nothing you are doing is going to have a dramatic effect on max flow
Calc max airflow of a 350 here ( TPI intakes flatline @ 5500 )
http://www.4secondsflat.com/Carb_CFM_Calculator.html

and compare with the airflow potential of parts here
http://www.gmtuners.com/flow/index.htm

The TB is not going to be a restriction on a TPI based 350

 

Thanks for the advice. Yeah I was planning on keeping the 52mm throttle body after I do all the intake stuff. Especially since the rest of my motor is still all stock. Even if I do eventually put in heads and a cam they are going to be mild and I'm also planning sticking with the 350 cubic inch size motor for right now too.

I've also thought about building up a 383 TPI small block at some point that wouldn't be so focused on being a mild mannered street motor. Yeah the 58mm throttle body would probably work better for that set up.

Vince, I saw the video of your car after you put the mini-ram on it. Thats a pretty stout set-up did you have in your car. When you had the stock style long-tube-runner TPI set up what intake mods worked best for your car?

 

Thanks for the links. They have good information in there. Yeah I am going to stick with the long tube runner TPI set-up in my car so I'm keeping my build focused more on low-midrange torque and power. That's what stock style TPI was designed for and I'm trying to keep my modifications applicable to the idle-5500rpm range.

Ha the good news is that I won't have to come up with money for a larger throttle body since the one I already have will work for the goals that I am trying to reach at this point.

 

TPI will work on a 383 but you are leaving a lot of potential on the table

Compare intake choices here ; nearly 100Hp difference from intake style change
http://xtremecarzone.com.au/index.php?showtopic=386

 

Thanks for the info. Yeah I know that TPI will not make as much power up top as a shorter runner system but I still like the long tube runner TPI set ups. A ported and opened up intake system will still make good torque and power in the low-midrange rpm band and will still pull up top to around 5500rpm-6000rpm. Thats what I am looking for.

 

I agree with vetteoz that a 383 with TPI is leaving a lot of untapped potential on the table. A bored 30 over 350 would serve you better and cost less because you do not need a new crank and very expensive rods especially if you go full bore stoker.
383 is a very expensive motor to build correctly. It would be a waist of money unless you were going to go with a carb, BECAUSE with are carb a 383 can make some sick power well over 450HP.
A 383 PROPERLY built will with all the goodies can run well over 5k and up to 10k.
I currently have my 350 in for machining and I am keeping the 52mm TPI on top of 30 over boring and new ZZ4 heads. Ditching SMOG / Power Steering / CATS. Installing a new tubular k fame w manual steering.
Loos some weight and engine drag and increase your HP to weight ratio.
If your only looking for a weekend driver, show car and a track day once in awhile it will still be plenty effin fast to make you smile without going 383.