Any Off-Road Tips or Tricks?

[70_Steve]

Hi everyone! I've got a 1970 Ford Bronco with a relatively stock 351W engine. Quite a few off-roaders are singing the praises of the Q-jet for off-road performance. Off-road, we're not looking for 60" times or 1/4 mile ETs. We're looking for a carb that will run at off angles. There are a few carbs on the market that are specially modified for this type performance, including companies that say they prep the Q-jet for this type service.

 I picked up an older Q-jet, #7041208. I disassembled it last night and will clean it up tonight. I'm looking to reassemble it this weekend. Mr. Ruggles, I have your book on order, but haven't received it yet, so I don't know if the information I'm asking is included there. So, are there any modifications that will improve the off-road performance?

Also, I'm running a manual choke on my current carb. The 7041208 is a divorced choke model. There's not nearly enough room to try to install the divorced choke coil below this carb. Is there a way to convert this carb to a manual choke?

[Cliff Ruggles]

NAPA sells several manual choke conversion kits for q-jet carburetors, we don't stock them due to poor demand for them, at most I get a call for one every 10-15 years!

The q-jet makes an excellent off road carburetor, we have set quite a few up for off roaders, mud boggers and rock climbers.

We install a taller front vent, then block off all other venting to the airhorn, and modify the POE venting (if used) in the airhorn so it vents back to the float bowl.  Some q-jets will already have the POE wells vented back to the fuel bowl, some will not.  The carb you are using has the external venting.

We sell complete HP kits for that carburetor number, and recomend installing screw in main airbleeds and completely recalibrating them for high performance use.

I can not stress enough the importance of using good parts, and upgrading all internal components where required for use with modern fuels that contain ethanol.  There isn't a day goes by in the shop that I don't get a phone call from someone who has just rebuilt there carburetor, and shortly after being placed in service, it is giving them NOTHING but troubles.

This happens because currently available over the counter kits are still using rubber and neoprene parts, which do not fair well with ethanol......Cliff

[70_Steve]

Thanks very much for the information. Is there any benefit to modifying the float level, either up or down?

[70_Steve]

We install a taller front vent, then block off all other venting to the airhorn, and modify the POE venting (if used) in the airhorn so it vents back to the float bowl.  Some q-jets will already have the POE wells vented back to the fuel bowl, some will not.  The carb you are using has the external venting.

Cliff, Thanks again for the information. I took a look at the carb last night, trying to visualize the vent modifications you had suggested. The taller front vent shouldn't be a problem. Might even bend it back a little overtop the carb. It seems that this would help when the vehicle is nose down. I did find (what I think are) the POE vents. It may be a bit of an engineering challenge to vent those back to the fuel bowl, as the passenger side vent is right below the choke linkage.

My biggest question is about your suggestion to "block off all other venting to the airhorn " . As I'm looking at the airhorn, I can't help but notice the two (relatively) large holes where the secondary metering rods go through into the float bowl. With the front of the vehicle pointed up (when I really want the engine to run well), it appears that the fuel will move to the rear of the float bowl, where the secondary metering rods are, and potentially spill fuel onto the secondary air valve. I've been trying to understand how the other vent modifications could have much effect if I can't deal with these openings for the secondary metering rods.

Help!!

[Cliff Ruggles]

There are several  methods used to block the round POE vent holes, I've seen some building use screen/epoxy, just plain epoxy, etc.  I like to use screw in set screws, and lock them in place with a drop of loctite for insurance.

The wells themselves need to vented internally back to the main fuel bowl.

The only vent required in the airhorn is the round tube, all others can be blocked off.

Keepig fuel from coming up around the secondary metering rods is simple, use a good quality black electrical tape of the holes during assembly, they push the rods thru them.  Lubricate them with grease so they don't stick.

I've seen foam used there as well, with the rods poked down thru it.

Float level will depend on the size of the fuel inlet seat, float size, and fuel pressure based on engine requirements.  Fuel pressure will have an effect on the level, all else being equal.

A good starting point is apprx 9/32", small float, .135" inlet seat, and 5-6 psi fuel pressure.....Cliff