ok got the 390 crank and rods for my '73 f100. the shop that i work at has a few spair 4v quadrajets laying around. has anyone ever run a quadrajet on a 390 or any fe for that matter? are they any good for fords at all?? thanks

 

Man, I wouldn't try it. I thought those were spread-bore carburetors anyway?

If the shop has them laying around, there's probably a good reason.

Get yourself a good Holley 600cfm vacuum secondary.

 

i concure with rusty... holley 600 vacuum secondary is hard to beat...

 

I use a quadrajet on my 410 fe in my 4by.Imho there the best carb ever made.yea it will take some mods to make it work but these things are the next best thing to fuel injection on a 4by.If you can keep your foot out off it, the tiny primaries can save you some gas.but if the power is needed those monster secondarys are there.

 

ford actually used quadrajets on early 70s cobrajets and all you need is a 1" spacer that convets squarebore to spreadbore and dont knock em till ya try em the 800cfm ones work well on a 267 chev all the way up to a 500 caddy
they are a pain to rebuild till you get used to em and there are many metering rods sizes to go from luxury boat to full on race

 

The people in the carb rebuild industry call them "Quadre-junk" for a reason. Because there are very few people out there that can really make the work well (they are a b!tch to tune if they don't work when you bolt them on and they are a fuel economy and emmissions carb). I have a buddy that does magic with them, but other than him I know of no one the makes the sing like a Holley will with a bunch less messing around. An adapter is a poor subsitute for the correct manifold for you carb. The ealy 70s CJs were all 429s and the carbs were a special version of the Q-jet at 760 CFM, not the normal 650 or the very rare 850 CFM.

 

Hmm I always called them "Quadraflops." Every vehicle Ive drove or ridden in seems to have a bog when you kick in the secondaries. And plus I cant see the need for that many cfm's on stock motors . Maybe Im bias to a square bore design though.

 

The beauty of the Q-jet was they were all around 750CFM, you would set how far the secondaries open at WOT to meter the CFMs. So a small block Q-jet might only open the secondaries half way, where a big block would open them all the way. There is an adjustment on them for it. I'm thinking of rebuilding the one in my garage and throwing it on the 351w in my LTD. They are GREAT carbs when setup properly, but a real pain when not.

 

Actually the standard Q-jet was a 650 CFM and the big Hi-po one was 850 CFM and very rare. There has been a lot of misinformation put out about the Q-jets. Most people are unaware than you can adjust the opening of the secondary's air valve. The throttle plates are mechanical and tied thru linkage to the primaries. The secondary metering rods are tied to the air valve.

 

I have a carter thermoquad that still works.now those are a pain.I also have an autolite 4100,this has got to be the easyest carb ever to rebuild or tune.
Like most car guys i have a stack of carbs in my shop like carter afb's,avs and the afor mentioned.also hollys of varius sizes and styles as well as edelbrocks,but after the headach of trying to get the quadrajet to work im happy to say that ill never go back to the other carbs again,it just works to well for what i use it for.