Mud truck carb ?

[djd220]

Hope someone on here can help. I am fairly new to the mud truck world. I have a jeep on rockwells, with ag tires. Powered by a mystery 383 chevy. I call it a mystery because I have no idea what has been done to it. I bought the jeep and added the ag tires. When I got it it had a horrible worn out edlebrock carb. I have since added a 750 cfm demon carb. The problem I'm having is that it only runs good when wide open. The timing is spot on (I have set it at all different settings) but it never makes a difference. It also stalls at least 75% of the time when putting it into gear. I have to feather the throttle to get it to start going but once its going especially at w.o.t it is a total screamer. What am I missing here? Do you guys runs fuel injection, special carbs, some kind of tricks of the trade?

Now here is something else, My brother in law is running an 86 k30 chevy on 14 bolt and d60 with a heavy built 357 chevy. Its about 20" of lift on 44" boggers with 5.13s. He is having the same problem. Now I have not wrenched on his motor nor has he wrenched on mine. He just had a very good drag race engine builder come and tune his carb and set up his timing and his motor runs just like mine. This leads us to believe that we are missing something. Does all the bouncing cause fuel to spill out into the center of the carb? Is there some trick to this. We both dabbled in drag racing and never had these kind of carb problems. Any help would be greatly appreciated as I am ready to can the 383 and go with a newer fuel injected motor.

Btw I am a mechanic for a living and feel like an azz for not being able to figure this out. I am a newb in the mud truck world but not in the automotive/wrenching world. Thanks in advance, Dan.

[millerxc]

predator

[mustange70]

diddo on the predator. Holleys, demons, etc usually don't like boucing to much, predators seem to be best suited (fewest number of moving parts).

[gsgrisso]

I have a 850 barry grant, and did have the same problem. Ol boy next door came over one day when i was messing with it in the driveway, he told me that the four corner idle adjustment was off??? OK... I'm pretty sure that is what he called it anyways mine has the little i thought they were called accelater pumps on all four corners. Im sure some one will give the correct term and flame me for it.. But he adjusted them for me and i have had no problems with mine to date. Now as for the how he adjusted it to what it was i have now idea, but i will tell you they are dam near tight against the linkage to wear as soon as you move the throttle they will move at the same time. Good luck..

[Adamsoffroad]

Predator all the way. Or you could run 2 Predators. Mine likes 2 predators on a tunnel ram. mmmmm That baby is nasty quick acceleration and great torque.

[GubNi]

When I was racing I won consistantly because I had a holley fuel injection kit on mine and didn't stall at the bumps. I got it on ebay used for about $400

[Brent Foster]

It also stalls at least 75% of the time when putting it into gear.

stalling when you put it in gear typically means the converter is too tight. switch to a higher stall speed. It may not be much of a carb problem..

Does all the bouncing cause fuel to spill out into the center of the carb?

yes id does... take a 2"-3" long 3/8 rubber fuel line and extend the vent tubes on each end of the carb... or connect them and cut an hole at the top

[flatblack83]

I have a decently built 358, i mud, wheel etc with mine, I had a 750 holley double pumper and just changed to a 670 holley truck avenger. I had to jet it up, change the nozzle and change the accel pump cams. Then the secondary springs to a stiffer one and it runs perfect up steep trails, rough trails and real good and healthy in the mud. It pulls in the rpm range to about 5800, might not be the best for mud but it works excellent for all around.

[mackdaddy]

I'm not a carb guy but I read that the Holley Lo rider series carb was a good carb for the guys with hydraulics. All they do is bounce around

Mack

[Hillbilly Rockstar]

1095cfm demon, mech. secondaries with a 5000 stall, I can bounce it through a pit as hard as I want, no issues at all. I would have to say it needs a higher stall converter as well.

[Adamsoffroad]

Originally Posted by flatblack83

I have a decently built 358, i mud, wheel etc with mine, I had a 750 holley double pumper and just changed to a 670 holley truck avenger. I had to jet it up, change the nozzle and change the accel pump cams. Then the secondary springs to a stiffer one and it runs perfect up steep trails, rough trails and real good and healthy in the mud. It pulls in the rpm range to about 5800, might not be the best for mud but it works excellent for all around.

Wow thats alot a crap to change. lol A predator takes a flat screwdriver and a finger to make 90% of the adjustments.

[flatblack83]

Originally Posted by Adamsoffroad

Wow thats alot a crap to change. lol A predator takes a flat screwdriver and a finger to make 90% of the adjustments.

.........you are right on that, that part sucked...but the carb was new in the box, never used and 150.00. I have like 40.00 into it... I couldnt pass it up for that cheap, a 770 would of been better but its prob better on the 105 octane to and from the trails with the smaller carb jetted up. I still wonder tho how good or better it would run with a predator but im not sure that carb would like the inclines like the double pumper didnt.

[Brent Foster]

The holley on the Willy's I help with works fine on inclines and the bounce it takes if it comes down hard..... Haven't seen a whole lot of Predators in the class.

My honest guess is the conveter is too tight.
Is the engine "Lugging"? when you flat foot it will it come to life or does it take a second to "wind up" and get into a comfortable power range? if the converter and gearing are right for the combo it should just about blow the tires

[djd220]

From an idle in gear if I stab the throttle wide open it will stall. I have to feather the throttle to get it to move, once its moving I can stab it wide open. It takes a few seconds to clear out but then it hauls. As far as I know the converter is stock. Gearing is standard rockwell 6.72. I'm going to take the carb apart I'm thinking there is something physically wrong inside. It doesn't seem to squirt like it should. Maybe has some dirt in it. What would you guys recommend for a converter. My jeep is more of a bogger than a racer, but I still want to be able to haul azz.

[old ugly 54 chevy]

The stall you need depends on how big your cam is and when it starts making power. Fairly mild motor i would say 2200-2500 would get you where you want to be.

[jhama78]

I ran a hose connecting the bowl vents and spring loaded needle and seats in my 750 vac secondary holley on the 383 in my mud truck. Had an off the shelf tci super streetfighter converter, hydraulic cam .512 lift and it matched up pretty well. I never had any problems with stalling or flooding and ran this combination for 5 years in hill and hole mud pits.

coupla pics of it in the air a little bit

[mustange70]

Haven't seen a whole lot of Predators in the class.

Thats cause they're probably not big enough, pred's are rated for 930 cfm, and when you guys are rrunning mech. fuel injection with big ass blowers, something tells me 930 just might not cut it

[TEX]

Originally Posted by mustange70

Thats cause they're probably not big enough, pred's are rated for 930 cfm, and when you guys are rrunning mech. fuel injection with big ass blowers, something tells me 930 just might not cut it

I think he meant the Pro Stock in the far lane, but that one's gonna have an awful big Dominator too.

[Adamsoffroad]

Afew monster truck guys I know said they always liked the way the trucks ran with 3 predators on top of a blower.

[mustange70]

how the fawk do they fit three on top?

I think he meant the Pro Stock in the far lane, but that one's gonna have an awful big Dominator too.

Yeah somethin tells me he's running something in the 1000+cfm range

[TEX]

Originally Posted by mustange70

how the fawk do they fit three on top?

That's the old Bigfoot setup

[Adamsoffroad]

Here this link is for Bigfoot scroll down there are many pics with 3 Predators atop the blower. http://monsterphoto.iwarp.com/bfoot1t.htm This is also how Everett Jasmer ran his 572 on the USA 1 monster truck. Gives me wood just thinkin about it. lol

[Proeliator]

Originally Posted by TEX

That's the old Bigfoot setup

Yup, tits as hell

Thing could run at angles you'd swear required injection of some sort

[furblog]

Originally Posted by djd220

Hope someone on here can help. I am fairly new to the mud truck world. I have a jeep on rockwells, with ag tires. Powered by a mystery 383 chevy. I call it a mystery because I have no idea what has been done to it. I bought the jeep and added the ag tires. When I got it it had a horrible worn out edlebrock carb. I have since added a 750 cfm demon carb. The problem I'm having is that it only runs good when wide open. The timing is spot on (I have set it at all different settings) but it never makes a difference. It also stalls at least 75% of the time when putting it into gear. I have to feather the throttle to get it to start going but once its going especially at w.o.t it is a total screamer. What am I missing here? Do you guys runs fuel injection, special carbs, some kind of tricks of the trade?

Now here is something else, My brother in law is running an 86 k30 chevy on 14 bolt and d60 with a heavy built 357 chevy. Its about 20" of lift on 44" boggers with 5.13s. He is having the same problem. Now I have not wrenched on his truck parts motor nor has he wrenched on mine. He just had a very good drag race engine builder come and tune his carb and set up his timing and his motor runs just like mine. This leads us to believe that we are missing something. Does all the bouncing cause fuel to spill out into the center of the carb? Is there some trick to this. We both dabbled in drag racing and never had these kind of carb problems. Any help would be greatly appreciated as I am ready to can the 383 and go with a newer fuel injected motor.

Btw I am a mechanic for a living and feel like an azz for not being able to figure this out. I am a newb in the mud truck world but not in the automotive/wrenching world. Thanks in advance, Dan.

Lolz. P.R.E.D.A.T.O.R. You'll gonna love the torque + acceleration combo. ANyways, how's it going right now?

[djd220]

Thanks for all the responses. I ended taking the Demon apart to see if there was anything in it. I found a very small amount of dirt in it. So I cleaned it out blew out all the ports and jets, threw on some new gaskets. I also changed out the harmonic balancer. The old one was separating and I think the line was in the wrong spot which meant I was timing it all wrong. I didn't get a chance to take it out until yesterday. I can say it is now running fantastic! Its running to good now, as I broke my first rockwell axle shaft. I don't have spares so I took it out and ran in 2wd and then twisted up my rear drive shaft. Had some carnage but at least it ran good. Now time to upgrade to u joint shafts and better drive shaft material