big block versus small block

[redneck joe]

So as some of you know having (I believe) carb troubles and ordered a rebuilt one. That company, while in Jacksonville FL and allowing for the storm, has not shipped in almost three weeks. 'it will ship soon and you will get an email' is the customer service response. So, trying another company and he had me read of the car number plus one on the side which is 17059288. Main carb # on the tag is 1347-7362.

So talking to the guy, told him what his part number was when he asked for the 17059288 and he said oh that's a B model for a big block.

Question is - I always thought BB was 454 CI motor and up and 350 and smaller was SB. Just did some interneting and appears I am wrong.


How do I tell what I have and does it matter? Boat is in sig line below.

 

[redneck joe]

just looked on the carb site and yes it does list the 454 7.4 liter as the BB that takes that model of carb. So thinking, if you all tell me it matters, that the people I paid last year to work on the carb may have just done as I am and ordered a rebuilt and ordered the wrong one?

 

[Scott Danforth]

the 454 is a big block. the 350 is a small block.

now here is a kicker. my small block volvo came with a bigger carb than the big blocks did until you started getting into big power. go off what carb your application needs.

the people could have ordered the wrong carb however when I look up 1347-7362, I get a Rochester carb for a 260hp MCM

 

[redneck joe]

well talked to my guy and he thinks I should go edelbrok but then will need a spacer of some sort and been reading here really should use a new manifold and the fuel line and of course more labor blah blah.


that said, would you go edelbrock? I keep seeing that is is a simpler one with less issues. I think I even saw where bondo recommended it so can't be all bad...

 

[redneck joe]

actually don't answer that here that should go on my carb thread.

 

[Scott Danforth]

the Edelbrock 1409 is good carb, however Im a died in the wool Holley carb guy (they are a bit simpler than a kohler toilet) and much easier to tune than the Edelbrock or the Q-jet

here is a discussion from going from the Q-jet to the 1409.

http://forums.iboats.com/forum/engi...ng-to-edelbrock-1409-from-rochester-quadrajet

and yes, the 1409 is a square bore and the Q-jet is a spread boar so you will need a 1" adapter or a different manifold (2" will give you a bit more torque if you have the room). if you would be going to a different manifold, I would look for a set of vortec heads to go with it and pick up about 30hp. new vortec heads are about $900 a pair, used and reconditioned are about $400

new fuel line is easy (its brake line), however with a single inlet, it should easily be able to bend

 

[boatman37]

from what i remember the small block q-jet is 600cfm and the big block is 750cfm but i could be wrong.

small block/big block is determined by the actual block that is used...sort of. if you set them side by side you can tell the difference. chevy small blocks are 265, 283, 302, 305, 307, 327, 350, and 400. big blocks were 396, 402, 427, 454, and the monster variants like 502, etc. i may have forgot some along the way there

 

[redneck joe]

great manifold, now heads...... Scott - should I just drop in a new crate unit with some fuel injection and maybe bump to a 7.4 with a B3 since you all are so freely spending my money??? I know I said it wasn't an issue and it wouldn't be, until my wife found out then she would be collecting all the insurance money after figuring out how to make it look like an accident....

 

[Bondo]

Ayuh,.... I ain't a Q-Jet guy, But,....
I believe the Q-Jet is the same carb body, jetted differently for whatever motor ya bolt it too,....
The Q-Jet flows up to something like 800 cfms,... All of 'em,...

The 1409 AFB carb is actually sorta a spread-bore, in that the primaries are in fact smaller than the secondaries,....
It's also a dual bolt pattern carb,...
While I ain't tried it, I believe it'll bolt right onto a spread-bore manifold,....
The 1410 for big blocks, is a square bore carb as the primaries are much bigger than the 1409 primaries,...
But again, it's also a dual bolt pattern carb,....
The 1409 with the smaller primaries is rated 650 cfms, the 1410 with the larger primaries is rated at 750 cfms,...

Donno which way ya oughta go, 'n I hope I muddied the water enough for ya to make yer decision,.....

If ya go with a AFB carb, the Merc throttle cable bracket for the later Merc/ Weber AFB carb might help with the cable attachment,....

 

[Scott Danforth]

Joe, if you want to do it cheap and fast, get your Q-jet rebuilt locally.

I just thought i would suggest options. But the 454/B3 would get the boat scooting right along

 

[redneck joe]

Yeah it hits 40 plus now prob 50 pkus with that.

 

[Baylinerchuck]

Ayuh,.... I ain't a Q-Jet guy, But,....
I believe the Q-Jet is the same carb body, jetted differently for whatever motor ya bolt it too,....
The Q-Jet flows up to something like 800 cfms,... All of 'em,....

I never really measured this myself, but I was told the q-jet bodies are different between the V6 and V8 carbs. The bore of the primary throat at the venturis is smaller for the V6. I'm not sure if that holds true from the SB to the BB. My reman carb on my 4.3 is actually a jetted down V8 carb. I was told that 4.3 q-jet is getting to be more rare, and cores to rebuild don't turn up often. I kept my core for that reason. Just FYI.

 

[Faztbullet]

There are only 2 types of Q-jets...750 and 800 CFM. Only difference in V-6 ,SB and BB is jetting.

 

[jimmbo]

There are only 2 types of Q-jets...750 and 800 CFM. Only difference in V-6 ,SB and BB is jetting.

That over simplifies by a considerable amount. True there were only two different airflow ratings, but the Q-jets calibration between engine sizes involved more than jetting. Idle and off-idle requirements are different, power piston springs, secondary meeting rod hangers, secondary air valve preload, air bleeds and emulsion tubes, are some, but not all differences

 

[Faztbullet]

Here is good reading.... and all the bodys the same.
http://www.chevyhardcore.com/tech-stories/choose-your-quadrajet-number-identification-guide/

 

[harleyman1975]

I remember reading in hotrod as a kid that Q-jet is next best thing to F.I.