I have a 85 TPI 305 LB9, 48 mm throttle body, 50,000 actual with the following mods: ported plenum, runners matched, gutted air boxes, K&N's, cold / forced air, Maf screens & fins removed , air foil, throttle body coolant by-pass ,44 lbs fuel pressure, 170* t-stadt, cooling fan on toggle switch, gutted cat, Dynomax cat-back, timing 10*, 92 octane, 3:42 posi, 700R4 with Corvette servo,etc. Nothing radical, but the car runs well. My question is: would a 52 mm throttle body improve performance off idle up to 4800-5000 or so? Or would throttle response / torque suffer below, say, 2500, with little improvement from there to redline? I seem to hear many conflicting opinions / ideas on this. It seems to me that a 52mm would improve throttle response AND torque all around, just because the EEC will, with aid of the oxygen sensor, maintain the correct ratio of fuel to air, allowing more hp / torque. It stands to reason that a 58 would be over kill, but how about 52 with the above mods. I've seen 50 mm throttle bodys available also. Any ideas, Yes, No, Maybe? Thanks in advance!

 

I don't think it'd be worth the $$$$ for your combo......

 

Stay stock, the 305 doesn't need and can't use that much air.

~M~

 

Definetly stay with the 48mm TB.

 

Stay 48mm untill you have around 300HP HAS ANYONE ACTUALLY BEEN AT A TRACK AND SWITCHED TO A LARGER TB AND MADE GAINS?????????????????

 

Thats a good question. I got my stock one. I'll try it this season.

 

The stock 48mm flows like 725 cfm or a little more. A 305 can not
draw in that much air. It would take a 350 turning over 6k to
pull that much air.

Save your money and upgrade your ignition or something that
WILL add power.

 

Thanks for the response guys. I've heard this before, especially on a rather stock 305, and its probably right on. Still, I'd love to hear from someone who actually made the swap, and what the result was. Either on a 305 or a 350. Later.

 

Hey 1991 RS 305 have u done the 1/4 mile in ur car. I am planning around the same mods as u and I want to know how i will do at the track

 

Hey Iroc_cragg, here ya go:


60 '.....2.59
330.....6.81
1/8......10.27
MPH.....71.18
1000....13.26
1/4.......15.72
MPH......89.96

This was last fall, prior to the ported plenum, TPIS wires, hollowed-out cat, new cap & rotor, and Corvette servo. I am not proud of these numbers,.....however, I feel it is now capable of low 15's and hopefully high 14's or so. In all fairness, I must say that the car got NO traction out of the hole...I really had to feather it up to 10-15 mph or so, then mash it, otherwise I went sideways. The 700R4 1st gear is REALLY deep (3:06 or something) At WOT, my 700R4 does the 1-2 shift at 5000, the 2-3 shift I did manually at 4900 or so, otherwise it would upshift at 4400-4500 and kinda dog out. This is not a cop-out excuse, but I think that with a moderate burnout for a decent hole-shot and the over the winter mods, it should be slightly stronger next time out.

 

1991 RS 305

Where do u live. How high above sea level is the track u race at. Is that time corrected at all.

 

No, not corrected at all. I ran it at Rock Falls Raceway in beautiful Rock Falls, Wisconsin. No idea what sea level is there. Planning to go again soon on a Muffler Day, or Tune & Run day, or whatever.

 

sea level there should be 0 feet like everywhere else

 

Results of tb swap and nothing else below. Of course, I have a LOT more cubes.

 

Ahhh, I didnt have to even Jump In On this one

Good people.

Desert Roc, Your 406 is a far cry from a stock Lb9

 

IIRC, Rock Falls (Eau Claire) is about 852' ASL, FWIW.

BTW, A 48mm TB feeds a RamJet 502 at 5,400 RPM just fine, unless you don't like the idea of 500HP and 520 ft/lbs.... So what's up with that? I guess throwing numbers around is only part of the science of horsepower, eh?

 

Gotta remember the Laminer Flow effect though.....

 

don't waste your $ you won't see any gains..

 

Numbers Mean Nothing, The only TRue Measure of performance is the Butt-Dyno.