Carburetor on H.O. engines

[kustomkyle]

What parts/settings on the Rochester Quadrajets make them the H.O. versions, in particular, the ones on the 442/Hurst Cutlass 307's (later roller engines, if there is a difference)? Additionally, it is possible to turn a regular Quadrajet from the era into the richer mixture version?

 

[Minion1186]

all rochester quadrajets from 81-88 were ccc controlled,the ccc quadrajets i believe were all casted from 800cfm models,but had their airvalve door stops adjusted so they only got about 590-650cfm.The H/O 442 qjets seemed to be a richer-mixture ccc carb then the regular ones on cutlasses,they may have had an airvalve door stop set to open 90% so they'd be rated for 825cfm,plus they may also have the airvalve spring tension set to open 1-2 seconds after WOT,unlike the regular ccc qjets,which opened 3-4 seconds after WOT.I hope this helps.For moding a stock ccc qjet,to allow the engine and the computer contols to run right,dont piss with the primary side of the carby,many people changed out the primary jets and often complained to dealerships that their cars werent running good after the jet swap since the primary side is computer mixture contolled.The only mods you really can do is to the secondary side of the carby,first off grab a file and file away at the airvalve door stop located on the passenger side of the carby,stop and see how much you've removed and see if the airvalve flaps open a 90% down.Change the secondary metering rods and hanger out,the rods in the ccc carbs in gbodies were mostly DD's a very fat tipped rod which are lean rods,get a good pair of skinny long tipped rods,these rods allow more fuel into the venturi of the carby and makes WOTperformance better.The hangers are very easy,they made 20 different models,lettered B-V,B being very rich and V being very lean,junkyards are full of qjets,steal some hangers and rods and decide which combo runs best on your car.For example i have a 307 olds,slightly moded and still abtaining the stock ccc carby,I filed the airvalve stop away,threw a K hanger and rich CV rods into mine and it runs way better.Find the mods here in my build thread
viewtopic.php?f=10&t=12639

 

[kustomkyle]

Thanks, that's exactly what I was looking for.

 

[mheath717]

all rochester quadrajets from 81-88 were ccc controlled

My friend has a 1986 Buick Regal with a 307 and a rochester Q-Jet. The car doesn't have the computer controlled carb. He claims it came factory like that, but I'm not sure if they did.

 

[Minion1186]

I really doubt that,like i said ALL qjets from 81-88 came ccc controlled,he may have put an older carb on it

all rochester quadrajets from 81-88 were ccc controlled

My friend has a 1986 Buick Regal with a 307 and a rochester Q-Jet. The car doesn't have the computer controlled carb. He claims it came factory like that, but I'm not sure if they did.

 

[83cutlasssedan]

If it was a Canadian made car it could have come factory with no computer. I have an 83 dualjet with no computer from the factory. I see some q-jets without the computer in the junkyard every now and then up here.

 

[kustomkyle]

all rochester quadrajets from 81-88 were ccc controlled,the ccc quadrajets i believe were all casted from 800cfm models,but had their airvalve door stops adjusted so they only got about 590-650cfm.The H/O 442 qjets seemed to be a richer-mixture ccc carb then the regular ones on cutlasses,they may have had an airvalve door stop set to open 90% so they'd be rated for 825cfm,plus they may also have the airvalve spring tension set to open 1-2 seconds after WOT,unlike the regular ccc qjets,which opened 3-4 seconds after WOT.I hope this helps.For moding a stock ccc qjet,to allow the engine and the computer contols to run right,dont piss with the primary side of the carby,many people changed out the primary jets and often complained to dealerships that their cars werent running good after the jet swap since the primary side is computer mixture contolled.The only mods you really can do is to the secondary side of the carby,first off grab a file and file away at the airvalve door stop located on the passenger side of the carby,stop and see how much you've removed and see if the airvalve flaps open a 90% down.Change the secondary metering rods and hanger out,the rods in the ccc carbs in gbodies were mostly DD's a very fat tipped rod which are lean rods,get a good pair of skinny long tipped rods,these rods allow more fuel into the venturi of the carby and makes WOTperformance better.The hangers are very easy,they made 20 different models,lettered B-V,B being very rich and V being very lean,junkyards are full of qjets,steal some hangers and rods and decide which combo runs best on your car.For example i have a 307 olds,slightly moded and still abtaining the stock ccc carby,I filed the airvalve stop away,threw a K hanger and rich CV rods into mine and it runs way better.Find the mods here in my build thread
viewtopic.php?f=10&t=12639

By the way, did you know how much horsepower your 307 has/had? I read in your build thread 180HP/275 torque but I think you were talking about the factory specifications for the 350 you have? I plan on having an overbore and etc. like yours and was just wondering what it was like. My car has 2 dead cylinders, smokes, and chugs but I don't think the power is that bad considering it was only supposed to have 140 from the factory. All I am really concerned about is to have it running like new again, but I want to make it run as strong as possible while it is apart. I have a new VIN 9 cam, .30 pistons and rings, and headers to put on. I have 2.56 gears which I plan to keep, I guess most of these cars had worse (2.14s or whatever they are).

 

[85 Cutlass Brougham]

I will also add that it is not just the rod you need to be concerned about. The rod is set up to flow a certain way with a certain jet. So, it is the rod/jet pairing that matters. I would try the factory calibration for a ZZ1 crate engine in a Camaro which was AH rods and a G hanger. I tried a set of rods from a 500 Caddy in my Q-jet and it ran dead rich. I think maximum power is around a 12.7:1 A/F ratio and anything richer will make less power. As far as it goes, mine has no computer running it (it's off a 350 Chevy van from 1979), and I left the primary side stock. All I wound up doing was to change the secondary metering rod hanger (bought from Edelbrock) and cut off the air valve stop. Remember too that you can vary the size of the carburetor by adjusting the secondary air valve return spring tension. This will not affect the theoretical max CFM like chopping the stop will, but it will change the actual max the engine can pull it open. Remember too that most of the time, even at WOT, the secondaries are not flowing their maximum CFM.

As for part throttle, an engine car run leaner than the stoich. ideal of 14.7:1 and be fine. It just can't run too much leaner than that (maybe 16:1 or so) without running poorly. That is why I leave the primaries stock on a Quadrajet, but I also try to pull one from a engine of roughly the same displacement as the engine it is going on. Otherwise, the idle feed restriction will be wrong and the idle could end up stinky rich or too lean. This is why a Caddy 500 carb is not a good idea on a 350, and nor is one intended for a Buick V6.

 

[jrm81bu]

all rochester quadrajets from 81-88 were ccc controlled

Are you just talking about cars? I believe the you could get a non ccc quadrajet into the early-mid 80's on trucks.

 

[Minion1186]

KustomKyle-my 307 olds was rebuilt by the P.O. around 68k miles,bored .40 over,mildly ported heads (which are the economy 7A heads).It still retains the stock (rebuilt)ccc carburetor which is cracked in two places on the air horn!.I moded the secondary side of the carburetor just as i mentioned above and i'm running a dual snorkel air cleaner i rednecked to make look identical to a 442 one.I am also running 2.56 ratio gears and a 2004r.As for performance,since you have .30 pistons already,get a .30 overbore,rebuild the engine,carb (if needed,then modify) and the VIN 9 cam should be good (i'm not intirely sure).The headers may be a problem,running a slightly richer carby will allow better performance with the headers,as the headers will lean the carburetor out.With all the modifications done to my 307,i would say it makes about 200 hp,290 ft.lbs torque,love to get a dyno reading on it to have accurate numbers.With the gears being so high,it really doesnt show much for itself but it is a tad bit better than a stock 307.By adding 373 gears performance will be much better.BTW it probably needs a rebuild when you have 2 dead cylinders!lol
JRM81BU-I really dont know,i think you could like on mid 80s surburbans and silverados,defintely on cars though