[my350camaro84]

well guys I'm just taking an opinion. I'm debating on what to do. Currently on my 305 I have a 4 barrel rochester q-jet 500 or so. should I one get this holley double pumper 600cfm for $125 or do you think I should just hold off and get a 670cfm street performer holley for $300? (the carb off this will go on my 350 when I drop it in and it's going to have some nice power. 400-450 range) thanks.

 

[jimfulco]

Stock or mildly modified 305? I'd keep the Q-jet at least until the 350's done, then try it on the 350.

 

[Max Keith]

what carb?

IF your engine is stock, or even slightly modified, going with a 650 or 600 double pumper is way more carb than your engine needs. Either stay in the 500 CFM area or if you are insistant on going larger, I wouldnt go more than a 600 and make it a vacuum secondary.

 

[packratwrecker]

Point of order, My350. The Q-Jet is either 750 or 800 cfm, depending on primary venturi size.

I'd stick with the Q-jet, as you can tune it to run on anything from a 283, to a 454, using standard parts. Changing from a 305 to a 350, will probably be nothing more than stepping up the jet size. :thumbup:

 

[NXS]

ok, after the other carb thread I'm having to rethink everthing I thought I knew about carbs. Please bear with my questions and help me learn more.

Changing from a 305 to a 350, will probably be nothing more than stepping up the jet size.

That is what I would have also said about three days ago but... now it seems like a 350 will have better velocity & better booster signal and in effect more fuel with be drawn thru resulting in the need for smaller jets. ??!!? ok, whatever.

Also in regards to a mild low compression engine needing a small carb is also what I would have said but... now it seems that a larger carb will raise cylinder pressure due to more complete filing of the cylinder...and raised cylinder pressure, as we all know, raises HP at least until detonation occurs.
So a low compression engine needs a larger carb than a high compression engine all other things being equal!!?


I don't know which emonicon best explains it>
:nono: !

 

[Mighty Mouse S-10]

How big is the cam? What kind of heads are you going to use. I have a 350 with a set of phase 2 Bowtie heads ported and polished 3 angle grind on manley racefol's. cam int,224 d at 495 lift ex. 234 d at 518 lift. I run a Holley 770 street avenger and it's perfect. Not to big not to small.

 

[stepside454]

NXS...with a spread bore carb, like a Q-jet, its a differant ballgame. a spread bore is more forgiving ,and can be made to work on a huge range of displacement with tuning.
If it were me with this 305,I assume is stock, Id either keep the Q-jet. If I was insistant on a differant carb for some reason..Id use a 500 Edelbrock.
I had a 570 Holley on the 305 I built in my 86 Caballero, it was mild, but healthy enough to go 13.70s with 3.08s.

 

[NXS]

i really like Q-jets myself. Really like them. I also think the OP should keep the Q-jet.

I was bringing up from another carb thread that thru the current reasoning >

a lower compression engine needs a bigger carb...LOL
and
install a bigger carb on a smaller engine and jet it UP...LOL

everbody i have ran this past has just laughed.

 

[wildman926]

How big is the cam? What kind of heads are you going to use. I have a 350 with a set of phase 2 Bowtie heads ported and polished 3 angle grind on manley racefol's. cam int,224 d at 495 lift ex. 234 d at 518 lift. I run a Holley 770 street avenger and it's perfect. Not to big not to small.

Mighty Mouse,

Would you please describe how your car runs with the 770? Any issues with throttle response? Idle issues? Tuning issues at all?

 

[stepside454]

Heck, Ive got a 770 Holley on my 454...