1970 455 q-jet info help

hey guys i gotta 1970 buick lesabre 455 bored 30 over ta112 cam stock replacement pistons pocket port and polish job ta hei distributor rebuilt original 750cfm q-jet didnt replace any of the diaphragms or anything but she's been running pretty good got about 8k on her since the rebuild....initially had some timing woes ive calculated my compression ratio to be somewhere between 9.6 and 9.8 to 1 using a few different online calculators. got a 2.73 open rear end running 4 degrees initial 22 mechanical all in at like 4800 and 10 degrees vacuum advance i know i know it sounds like not enuf but i tweaked and tweaked on this thing and couldnt get it to stop pinging till i got a block off plate for the vacuum advance, the heaviest springs i could find for the mechanical advance and turned the initial down to 4 and trust me it hauls pretty damn good averaged 13-15 mpg from arkansas to virginia and left a few 50-60 ft one legged burnouts on some back roads...........alrighty so to the question what jets are in my stock q-jet and what would you guys suggest because i keep getting a lag or a bog it seems like sometimes the secondaries just dont want to open when im starting from 10 mph below but especially at a dead stop but then when i get out and take the breather off and slam the thottle wide open they seem to open just fine but still a bit of a stumble lag bog hesitation whatever you wanna call it alright well that was probably entirely to much information but hopefully somebodies got some tricks up there sleeve's thanks ahead time guys

 

I think the 70 quad (non stage) has 67's in it. For the secondaries, you can adjust the flap by loosening the spring tension and tightening it up until the flap closes and give it half or 3/4 turn more. It had a set screw to loosen first.

 

We have a similar set up: my 70 455 is bored .38 over, TA284-88h cam, headers, SP1, stock iron heads freshly built, hei(14 initial, 20 mechanical, no vacuum advance)all in by 2500rpm (see Larry's power time thread). I run a later 800cfm qjet (170...something) and I'm running 75 jets, 47k primary rods, DA secondary rods, APT is 2.5 turns out, secondary spring tension is .75 turns past spring seat. 3.42 position rear and anot extreme automatics 2004r Trans w/ reverse manual valvebody.

Not much different from you, but sounds to me like you could use a bigger (800cfm) qjet if you stay with the Rochester. And if you do, increase the air bleed diameter for a better idle. Mark Northcutt (carmantx) on the forum will handle all your qjet woes flawlessly. This combo dynod at 416hp and 500tq on the engine dyno. Torque was better than 400 from 2450rpm up.

 

According to my notes, the 7040240 1970 455 Quadrajet came with 67 jets and 41B primary rods. If you haven't modified the idle circuits, then it will load up at idle and hesitate when you accelerate.

 

I know larry70GS you commented on one of my posts a few months back when i was pulling my hair out trying to time this thing and by the way i appreciate it otherwise i'd prolly still be lost......damn compression ratio, at the time i was building i had only briefed over that thread about dynamic vs static cuz i was pretty sure i was in the clear but i guess not lol. I just knew that big blocks dont like to rev so i didnt want a cam that was gonna give me 25 extra hp at an rpm i was never gonna reach whilst taking away some of my torque but i guess i was slightly mistaken hell i could probably run 12 initial for a 30 to 34 total mechanical if i had stuck with my guns and went for the TA212 but oh well i run 91 in her and no pinging and thanks carmantx if you guys think its worth a shot i'll look at the spring tension and secondary adjustment and maybe order a jet kit with some slightly largger options thanks again fellas