3500 LX9 Throttlebody choices

[jmgtp]

I can't use the LX9 tb since it is drive by wire.

I have a 75mm LS1 tb which I think is too big, will have too much flow at small throttle angles and make tuning a complete pain.

I have an LQ1 tb, which I believe is 63-64mm. This is a bit smaller than the stock LX9 tb which I believe is 65mm. Good enough? Is it worth my trouble and the cost to find a ~70mm tb. The rest of the motor is going to stay stock, I don't need MAX power out of the thing but I don't want to choke it any either. I know I'm going to have to fab an adapter plate.

[mickaz]

LX5 3.5 dohc shortstar or

wot-tech 62-65mm throttlebody.

both need an adapter plate. ( wot-tech)

[2.8-350TBI]

If you make your own adapter you can also use the TB from a 96+ 4.3 V6, but thats 70MM, which may be too big for a lightly modded engine.

[jmgtp]

I am considering the 4.3 throttlebody. It seems like it is large enough for a bump in power but not overkill that would cause small throttle angle and tuning issues. My only gripe with it is that the 'snout' portion that the air filter hose would clamp on to is extremely shallow and I'd worry about the hose slipping off.

[2.8-350TBI]

Well, its kinda meant to be held on with bolts so it would be best to fabricate a bolt on snout for it too.

and 4.3's are all too common too.

[SappySE107]

why is it assumed that a larger TB is a bump in power? You have a 3.5 liter engine, pushrod based, that has 65mm stock. The 3.4 liter engine is 56mm stock. Don't you think the 65 might be all you need? You should also remember the drive by wire doesn't let the throttle open as much as your foot tells it, so the tuning can make that 65 act like a 48 or a 56 or a 65. Same reason the used a 72mm on the equinox 3400. You do that on a cable driven TB and throttle resolution will be insane. Touch the pedal, spin the tires. floor it, meh, feels about the same as 75% throttle.

You can go 70mm if you want, but I don't recommend it for what you are doing. You would be better off with the 64mm 3.4 DOHC throttle body off the 96-97 motors.

[bob442]

I'm with this guy on this one /l\

[jmgtp]

Sounds good, especially since i already have the 3.4dohc throttle body sitting in a parts box.
I guess I'm just thinking of my LQ1, it definitely had a bump in WOT power with the larger TB, but it had other mods as well.

While we are on the subject, I have read that the stock 3500 plenum flows less than the stock 3400 plenum but with mild porting it flows more. What is the restriction, is this something I can open up fairly easily/quickly with a die grinder?

[SappySE107]

The 3.4 DOHC has a tiny plenum area and a stupid plenum to runner design (IMO). They called it tuned, I call it detuned.

[bob442]

maybe on paper/theory tuned, kind of like more intake volume=higher RPM curve