How far can the stock 48mm Throttle body be bored without blade change. If one could change the blade and Shaft, how far he could go.

I've read that Jeep guys bore the TB and replace the blade and shaft. They go from 58mm to 62mm on the 4.0 I6 engine. I myself had the TB on my 1999 4x4 XJ bored to 60mm, no blade change though. But, it's a stroker 4.6L with 100HP NX shot, shamed some V8's on hill challenge.

 

I'm guessing 52mm. Mine is a stocker modified to 52mm and the sides are prety thin. Don't think you could go any farther. A 52mm throttle body flows 750 CFM which is more than enough air for up to 450 ish RWHP.

How do you bore the throttle body out 2mm and not change the blade? Your gonna have a gap at least on the sides and the blade is going to be prone to jamming at idle.

 

Well, the Jeep TB is tapered towards the blade, so, I just made it straight 60mm upto the blade.

It helped in passing the spot from 2000-3000 RPM in 2nd gear in a quicker time.

 

I think I heard somewhere using 2 blades there is a 54 mm stock bored T/B, but if you go a monoblade I think they flow like 1100 to 1300 cfm.

 

Nice set up, in your sign. Have any dyno numbers or 1/4 mile times.

 

I just ran an 11.8 at 115 something a few weekends ago. I cnat seem to get the traction down (this was with a 1.9 60 footer).

 

Congart. I am sure with more traction, you would get better time.

Was it difficult to tune for GM 847. Was it mail order tune.

 

Yeah its still the mail order tune, so far its pretty good (minus the rev limiter being set too low), But it runs and drives fine theres a little weepy eyes at idle (rich exhaust) but from what I hear everyone with the 847 runs rich at idle. I am going to have it dyno tuned here soon so I'll see if there is any left there. I have been watching it with my freescan software, and I havent had any noticable knock, or any BLMs out of sort , so I'm pretty pleased with PCM for less's initial tune.

 

While we are on the subject. How do you remove the butterfly shaft on a stock throttle body?