i have a 93 z28 and i am looking to buy a larger throttle body, i was wondering if a 52mm is big enough or if i should go with a 58mm, i am running about 350hp now with bolt ons, and i have heard that it can sometimes be detremental to go too big on the tb and i plan on getting nitrous in the near future as well.

 

why do u even think you have 350hp with only bolt ons... ?

 

I wouldn't waste any money going above stock at this time.

 

He prolly meant BHP not at the wheels.
I wouldn't waste my money on that. Stock is all you need for the power you're pushing.

 

I agree, its not really worth the money at this stage of the game. Maybe you can post a signature with some basic info on your car along with the mods you have done so far.

 

Just as 2000gtp said maybe post up what mods you have and then we can point you to the right direction.

 

Unless you really increase the breathing (boost, N2O, or Heads/Cam), you would not likely reap the benefits of a larger TB. I installed a 58mm TB when I did my heads/cam and it seems to help a lot. We recorded the MAP on a dyno while pulling runs for the tune, there was little to no restriction in the intake. If the TB was a restriction, then I would have seen more vacuum present.

In my opinion, unless you are planning on more mods in the future, you may feel disappointed.

I did notice that my clutch engagement seems to have changed. I used to launch with about 1/2 throttle at about 3/4 engagement. Now I launch with about 3/4 throttle at near full engagement... the TB acts differently. It kind of lags, then rockets hard so if you have a clutch, you may need to learn to drive it differently than you used to or you may stall a few times. No big deal, just something to get used to.

 

So, what are your guy's opinion on the TBs? Is it hp based or RPM or both? I am rebuilding my engine and trying to keep most of the stock parts there. I'm getting the heads machined and a new cam put in. I'm hoping to hit between 350-400 rwhp while staying below 6000 rpm. I didn't start this thread but maybe if you can answer my question it'll help kohl as well.

 

I hope this helps.

 

What is being done to the heads? Machine work as in rebuilt head or port work? 400hp will be hard with just a cam alone and stock heads.Same goes with staying below 6k rpm. Not impossible but you had best pick your stuff and make sure you have a combo that works well together. Unless you spray....

 

Can't the stock throttle body be ported to 52MM?

 

yes, and can be had for cheap on ebay

 

WTH: wait til you boost or juice and go with a mono-blade. JMHO

 

I was originally going to send them to AI for there CNC work, but my castings aren't what they like to work on. So, I'm having the local machine shop check them out and if they're okay, we'll do some port work and valvetrain upgrades. If they're bogus I'll be giving AFR a call. I'm really looking for 350rwhp and won't complain about any extra that I might get. The stock 2-bolt mains and cast crank worry me a little, so I want to keep the rpms low.

 

I've went thru two of those in the past year...They both had a habitual problem with sticking. I'd stay away from them. I'm at almost 6,000 ft in elevation don't know if that matters or not, but after I threw my 58mm Edelbrock on and tuned the throttle body I noticed my throttle response/ acceleration was considerably better than stock. *shrugs*