????what carb????

[76cheetah]

i have a 350 hp 455, got my hands on a old torker intake and need to know what carb will work good on it. it currently has a stock intake manifold and a rochester quadrajet. thank you very much.

[455maveric]

750 Holley

[D.B.S]

750 Holley

[Bies]

A good tuned Q-jet is reliable, they are 750CFM, some 850, people give them a bad name because they don't know how to tune them, I think Holley's are a pain, love to leak and flood, just my .02

[SS-201]

Edelbrock 750, simple,no leaks, will run right out of the box.

[Jacob]

Holley/ Edelbrock you will get the ol ford vs chavy opinions. Both good carbs IMO the Edelbrock is a little more user friendly. Bies is right about your q-jet.
Good luck!

[76cheetah]

going with a holley 3310 750 cfm vacuum secondary. i think it will run alot harder and get better fuel mileage. thanks for your help

[TIMINATOR]

Bad idea, use an 800 or 850 dp holley, the larger primaries allow a reasonable cruise speed without the secondaries being open. With the primaries and secondaries partially both open, but at differing amounts, the mixture distribution suffers as does power and fuel mileage. IMHO the Q-jet is the worst jetboat carb in this regard. The front cylinders will tend to pull fuel from the small primaries at a high velocity, and the back cylinders will pull fuel at a low velocity from those huge secondaries. This upsets the balance of mixure and flow, thats why you can sometimes feel a vibration at cuise that goes away at full throttle. Part throttle secondary metering is dependent on the taper of the metering rods and hanger height which varies with wear and poor quality rebuilding. Put a Q-jet on a flow bench at part throttle and use a directional pitot and cotton tuft indicator and you will never use a Q-jet again except in an economy situation. We like to use the HP 920 on even mostly stock jets because it will allow a faster part throttle cruise. We like to also use a dominator carb with modified secondary linkage for the same reason. My 21 Daytona with the 572 would run about 78 on the primaries and got better fuel economy than the 454 it replaced. It could also pull a much larger impeller too. Again, this is my opinion, yours may vary. 1TIMINATOR

[sleekcrafter]

850 DP very hard to over carb a jet boat

[Cobra1racer]

Bad idea, use an 800 or 850 dp holley, the larger primaries allow a reasonable cruise speed without the secondaries being open. With the primaries and secondaries partially both open, but at differing amounts, the mixture distribution suffers as does power and fuel mileage. IMHO the Q-jet is the worst jetboat carb in this regard. The front cylinders will tend to pull fuel from the small primaries at a high velocity, and the back cylinders will pull fuel at a low velocity from those huge secondaries. This upsets the balance of mixure and flow, thats why you can sometimes feel a vibration at cuise that goes away at full throttle. Part throttle secondary metering is dependent on the taper of the metering rods and hanger height which varies with wear and poor quality rebuilding. Put a Q-jet on a flow bench at part throttle and use a directional pitot and cotton tuft indicator and you will never use a Q-jet again except in an economy situation. We like to use the HP 920 on even mostly stock jets because it will allow a faster part throttle cruise. We like to also use a dominator carb with modified secondary linkage for the same reason. My 21 Daytona with the 572 would run about 78 on the primaries and got better fuel economy than the 454 it replaced. It could also pull a much larger impeller too. Again, this is my opinion, yours may vary. 1TIMINATOR

You can take this info to the BANK, Tim knows his shiat.

[Dave01]

My Eliminator has a stock 454 and Quadrajet. While it runs well overall, there is a definite hesitation when getting onto plane and again when accelerating from 3000 rpm. You can get through it by pumping the pedal a bit, or it will smooth out in a few seconds, but still needs to be fixed.

My last boat, with 455 Olds and 750 Holley mechanical secondaries, was smooth as could be at any speed, any rpm. So, I'm in the same situation as 76Cheetah, do I rebuild the Qjet and see if I can smooth it out, or go to the 750 or 850 Holley. After running both I'm leaning toward the mechanical secondaries over vacuum, just seems more predictable, but then again I don't want to burn a ton more fuel either.

[Bies]

Tighten the secondary air valve, the hesitation comes from opening the air valve to soon, this pulls the needles out of the secondary jets and is like flushing the pot. This is usually why people call them quadrabogs. There is a small screw that hold a spring.
This adjustment is in any carb kit, or get me the serial number on yours and I can look up the adjustment. It is about like setting an automatic choke.

[TIMINATOR]

Also the choke pulloff pod on the opposite side of the throttle is used as a "shock absorber"/slow down device to slow the secondary opening rate. It has about a .020 restrictor in the vacuum tube that the short hose fits onto. Remove the hose (is the hose in good condition?), and fully compress the pod link, put your finger over the vacuum hose barb and verify that it will hold vacuum for at least 30-45 seconds without bleeding off. If it bleeds off replace it before you do any changes that you are not sure of. If the pod holds vac ok, then firmly depress the pod again (without your finger over the barb)and see how long it takes to fully extend. It should take about 10 sec to fully extend. Go to a parts store and play with a new pod and get familiar with its operation before deciding to replace the old one. There is more than one pod application.The sec spring can get softer, but it won't make an immediate difference, only the pod failure or linkage falling off will do that. The pod does NOT have to be removed from the carb to do these tests. Also, there is a spec for the pod linkage compression holding the sec airvalve closed. Often these problems start when someone decides to remove the choke for a performance gain and doesn't realize that the pod must stay. Some dragracers remove the pod and compensate by tightening the airvalve spring, but that only works well in a fully open or closed condition as in racing. Call me if you have any questions during business hrs at 623-877-8553 if you have any questions. TIMM

[Dave01]

Bies and Timm, thanks for the suggestions. I'll take a look in a few days when I get time to work on the boat and let you know what I find.