Fuel Mileage?

Well kinda, even though research has told me the carb I used was a 750, looking down the venturies, says otherwise, it has 800 written all over it. It looks identical to the qjet I use on my V8, which is off a caddy 500. Also, I happen to have a confirmed 750 for comparison, big difference, so I'm sure I have an 800 on my hands. As far as th inline taking all the cfm, not exactly, set up right the q jet will only flow as much as the engine demands, meaning yes the carb can flow upto 800cfm, but it will not actually do it unless circumstances are there. Say I took the carb off my V8 and plopped it on the I6, making no changes to the secondary end, The inline would not have the demand to open the secondaries like the V8 would (speaking of the top flaps which control how much fuel is dumped and when). My 8 will demand secondary asisstance almost right off the line, while the I6 doesn't ask for it until about 3000rpm.  The same carb which flowed say 600 on the 8, may only flow 400 on the 6 (those are random numbers). That's the beauty of the vacuum/mechanical secondaries, unlike a holley or edelbrock, it controls fuel and air on a as needed basis. My favorite thing, is the set and forget tuning, once you have it right, you can just leave it alone, there's no need to mess with it on a weekly basis, I hated my AFB for that, I could never get that thing right for more than a couple days at a time.

14-16 all the way...sometimes less. Bone stock 1976 258/904. Gosh I hate the detuned emissions engines. 

904 isnt bad at all, thats part of why so much trouble was put into it to drag race elephant motor equipped Mopars in leiu of 727.  The 904 is the basic Simpson gear set up that was the thing in the day, so it does sap hp especially on the 1-2 shift.  But , alot less than others and in 1;1 it is fine.  I think some may have worn convertors.  I know that i like to always run an aftermarket convertor with brazed fins.  Efficiency goes up and thats free power all the time as hi pressure fluid isnt sneaking past those fins.  Tolerance is better putting the parts closer, upping efficiency also.  I wasnt this way until I found two of my own convertors to be dogs over the last  few years. They were just  stock repacement tc's and as we all know, it seems workmanship is dead in world. Most dramatically this happened in my lt-1 caprice, trans had to come out for something else, and i put in another tc . It was like a new motor was put in and i was now glad the trans had to come out.  I can only imagine how bad that cars hiway mpg wouldve been except it was a lock up tc, so it just didnt feel right...motor made the right sounds but just didnt move car like it used too.

X2 and alot of gas is used due to chokes being set on rich side, staying on too long.  Idle mix cant be under-estimated . Mech advance curves being slow to locked  due to age, or smogger profiles.  Its no wonder fuel inj is considered so superior...it is consistant.    

 Rear band is wider and a few more clutches in the 998 or 999 vs 904. 999 also had lower first/second gear planetaries that 727 owners WISH they had. (available aftermarket for $$)  

Edited by carnuck - Mar/04/2012 at 1:14pm