Quadrajet jet/metering rod combos:

[Stewart G Griffin]

So, i'm (somewhat reluctantly) shopping for a "new" quadrajet. Why would some come with smaller jets and thinner rods, while some come with larger jets, but fatter rods? So, in other words, it seems the highway cruise fuel delivery settings are going to be similar.

This is just going to be for transportation and to get the thing running. i don't care about performance right now.

[zieg85]

My thoughts are what is the correct CFM needs for your displacement.  I am assuming it is for your 4.3L??  In the early 80's I really played around with 2 barrel on a 350 engine.  I changed the jets till I got the plugs looking/burning right and the tail pipe not black.  It took me several tries but I was getting 15 mpg in a 72 Chevy C10 and it had excellent driving manners and 3 mpg improvement over when I started.  This was probably a 65/35 split of in town/highway driving

[blazer74]

Jet/rod combo's depend on several factors but what your asking is large jets and rods for large main air bleed and single main air bleed carbs,  smaller jets and rods for small main air bleed carbs.

[Stewart G Griffin]

Yes, it is for the 4.3.  i can't get either of my quads or the 2g to run really good.  All 3 probably need to be rebuilt and i'm just really busy.

Jet/rod combo's depend on several factors but what your asking is large jets and rods for large main air bleed and single main air bleed carbs,  smaller jets and rods for small main air bleed carbs.

So...........larger air bleeds for larger engines,  smaller bleeds for smaller engines?

[blazer74]

No,  more air requires more fuel . Large are bleeds require more fuel ( larger jet) for correct fuel ratios. Therefore for requiring a larger rod for correct cruise fuel ratios.

The 4.3 you have came with a Quadrajet?  They were used with them or I should say v6's
Idle tubes, idle channels and jet/ rod combos were tuned for them along with limiting the secondary flap opening for the smaller engines.

[Stewart G Griffin]

No,  more air requires more fuel . Large are bleeds require more fuel ( larger jet) for correct fuel ratios. Therefore for requiring a larger rod for correct cruise fuel ratios.

The 4.3 you have came with a Quadrajet?  They were used with them or I should say v6's
Idle tubes, idle channels and jet/ rod combos were tuned for them along with limiting the secondary flap opening for the smaller engines.

Yes, the quad came on the first two years of the 4.3, for 85 and 86 on trucks.   i don't think the buick v-6 got it, instead they used 2g's or dualjets and i think the smallest 6 to get one was the pontiac straight 6 which was 230 inches!

[blazer74]

The Buick Grand National and v6 turbos had quads under the turbocharger except for the first year which was a 2g

Do you have the original quad off your v6 ?

[Stewart G Griffin]

oh yeah--forgot about the grand national.   So, in that case the monte carlo turbo probably also had it?

i do not have the original carb from the 4.3