Quadrajet offroad modification builds?

[gm500hprat]

I remember reading a post a while back about modifying a quad for offroading, it had pics of the fuel bowl vent tube and part #'s for offroad kit, i searched through 20 pages of quadrajet related stuff but couldnt find it. Anybody got info on that build or info/pics of what I can do to my carb to prepare it for offroading, mosty will be in sand dunes.

 

[jms]

You can start by extending the vent tube; a simple piece of silicone hose has worked well for me. The Doug Roe book has a good section on how to modify a Q-jet, including effects of different float shapes. Float settings determine to a large extent how well the carb does uphill vs downhill; setting the float a little higher than spec helps on climbs.

 

[Kenny78]

I think you might be thinking about edelbrocks. My Doug Roe book says very little about offroad tuning because these Quadrajets are very capable already. He does mention float shape tuning if you are going in a continuous direction(up, circling left) and inlet valve tuning but I doubt almost anyone would need to do these. He also mentionsextending vent tubes but I can almost guarantee that a properly operating, tuned Qjet will handle anything you throw at it.

 

[ryoken]

they occasionally run the "J" style vent tubes on the marine quad apps to dump any bowl overflow down the primaries... it's about "the" only "offroad mod" i can think of for offroading, outside of standard rod, etc tuning...

 

[TerryD]

A friend of mine and I actually experimented with different float shapes. We tried a few floats from older carbs modified to fit the later (75+) bowls. We took the truck to Harlan and it stalled out on a V-notch climb in Lower Rock Garden. Had to spray ether down the carb so the truck would back off the notch. We swapped back to the factory float (carb #17056213) and it then went directly through the notch w/o any problems. His truck has been together for 5 years and the only trouble we had was with low quality fuel filters and a bad fuel pump right after we got it together. I know it's not a GM, but here's his build.

We're still working on ideas to improve little things. I'm going to take the Roe book and go through my Q-Jet. I usually lower the float a little and richen up the idle circuit to compensate for the lower static pressure in the bowl. A step up on Jet may be necessary if you change the float setting too much.

 

[gm500hprat]

they occasionally run the "J" style vent tubes on the marine quad apps to dump any bowl overflow down the primaries... it's about "the" only "offroad mod" i can think of for offroading, outside of standard rod, etc tuning...

Maybe that's what it was, I remember the tube looking like the one on the offroad Holley's. ANybody know the part # for the edelbrock offroad needle and seat kit for the qjet?

 

[Hogback Fabrication]

Mine always ran awesome just with the factory specs.

 

[gm500hprat]

Mine always ran awesome just with the factory specs.

What do you run now?

 

[Hogback Fabrication]

What do you run now?

Propane, haven't actually taken it out yet

 

[gm500hprat]

Propane, haven't actually taken it out yet

I wanted to run propane, but I talked with the propane guy and he said with my engine specs I would run out of cfm in my upper rpm range. SO my buddy gave me a qjet, I have had 2 holleys on this engine and they both were crap offroading.

 

[ryoken]

Maybe that's what it was, I remember the tube looking like the one on the offroad Holley's. ANybody know the part # for the edelbrock offroad needle and seat kit for the qjet?

no such thing... 2 totally different carbs... i wouldn't worry about offroad mods on a quadrabog.... run it stock... if your really getting off camber down the road, you can add a j-vent...

 

[Blue85]

You've got it backwards. The off-road mod for a Holley carb is swapping to a QuadraJet.

 

[Hogback Fabrication]

I wanted to run propane, but I talked with the propane guy and he said with my engine specs I would run out of cfm in my upper rpm range. SO my buddy gave me a qjet, I have had 2 holleys on this engine and they both were crap offroading.

Possible, depends on the motor, I'm not really afraid of losing top end with my motor (full roller 383, vortec heads).

This is the worst I've had my Q-jet run (I had broken a front stub shaft and hub):

 

[gm500hprat]

Possible, depends on the motor, I'm not really afraid of losing top end with my motor (full roller 383, vortec heads).

This is the worst I've had my Q-jet run (I had broken a front stub shaft and hub):

Thats one heck of an angle, very awesome! My BBC is pretty decently built I shift @ about 6k RPM when I'm playing in the sand, dont do any slow rock stuff.

 

[gm500hprat]

You've got it backwards. The off-road mod for a Holley carb is swapping to a QuadraJet.

Thats foresure, the Holley's I have had suck offroad for me.

 

[boz42]

I have a stage 2 Jet Performance q-jet. I had to swap float shape to get it to run on steep angles. Other than that no problems.

 

[gm500hprat]

I have a stage 2 Jet Performance q-jet. I had to swap float shape to get it to run on steep angles. Other than that no problems.

Got any pics of the float I should get?

 

[Hogback Fabrication]

I wanted to run propane, but I talked with the propane guy and he said with my engine specs I would run out of cfm in my upper rpm range. SO my buddy gave me a qjet, I have had 2 holleys on this engine and they both were crap offroading.

Also, it's easy enough to run two mixers if you need more flow. My Q-jet served me very well for the most part though.

 

[boz42]

Got any pics of the float I should get?

I would try the one that is in it before I swapped it just for the heck of it. The float that was stock in mine was fat towards the rear of the carb. I swapped it for one that was bigger in the front. This way the float would not rise in the gas as fast on steep inclines. I had to modify it to make it fit. because it was not excactly the right float for my year of carb.

top float was stock to my carb. i swapped to one that looks like the ones in the picture. By the way that picture is of a page from Doug Roe's book.

http://s220.photobucket.com/albums/dd239/K5Boz/Misc/?action=view&current=p1010002.jpg

 

[gm500hprat]

I would try the one that is in it before I swapped it just for the heck of it. The float that was stock in mine was fat towards the rear of the carb. I swapped it for one that was bigger in the front. This way the float would not rise in the gas as fast on steep inclines. I had to modify it to make it fit. because it was not excactly the right float for my year of carb.

top float was stock to my carb. i swapped to one that looks like the ones in the picture. By the way that picture is of a page from Doug Roe's book.

Thats a great comparison shot, thanks.