Next problem....Carb

Ok next thing to tackle.....as i said in my other thread i have the 304 with the edlebrock performer manifold and performer 1405 carb. The carb is a great carb on the street but the second the jeep even looks at an incline it stalls out...the PO before my dad had all this already in the jeep. this is not good for me as the only plans i have for the jeep is offroad stuff.

My question is what is the best offroad carb to get?

Any suggestions you guys have would be great!

i already have the offroad springs in the carb and they dont do much.

 

Too bad you are set up for a square bore carb.
If you want to get the best off road four barrel, you would need a spread bore manifold so you could go with a Rochester Quadra-jet.

 

I'm not super familiar with square bore vs spread, but look into the holly truck avenger. They are very well regarded.


If you're not married to the 4bbl, the factory motorcraft 2100 can be a great off road carb.

 

IIRC the the AMC Performer won't accept a QJet, but you could use an adapter. Or as previously posted, get a Holley truck Avenger. I have one on my Jeep & it works well off road.

 

I also have a truck avenger on my 360. i like but but it likes gas.

 

If you want a new carburetor, I think your only choices are the Edelbrock or a Holley. The Holley Truck Avenger (TA) is well regarded, and works well off the pavement.

Try lowering the float bowl level a lot in your Edelbrock and see if it improves.

 

x2 for avenger carb...or go back to the motorcraft 2100...never seen both 304 and 360 i use to have in my jeep miss or stop the engine. For me nothing can beat the 2100 in offroading!!!

 

Exactly. I wheeled for 2 days straight this past weekend, rocks, mud, water, hill climbs, off-camber, and the 2100 never missed a beat. I NEVER stalled due to flooding or fuel starvation. I'm running a slightly lowered float and a pressure regulator, and this carb runs like its fuel injected.

 

How will that affect drive-ablity on the road? this is mostly an offroad jeep but i do drive around town at times and dont have a trailer so i do have to drive it to trails

Will lowering the floats affect daily driving or idle? would i have to redjust the idle screws? or rejet?

I dont have to have a NEW carb just want something that wont cut out on hills. My dad has a 79 custom deluxe with a q-jet, its 2wd drive and he offered to swap carbs. would that be the best option? will i need an adaptor plate for the edlebrock performer manifold? i dont think i want to do the motorcraft as i dont have the original manifold and dont really want to change it out anyways.

Cheapest is just swap my dad, unless bending my floats work, but is the TA a better carb? would it be worth it?

 

Lowering the float level will lean out the mixture some. A shallower bowl pool means less pressure at the jets, which makes everything a little leaner. If you have not dialed-in this carb yourself, I would try it with no other changes.

The main issue the lowered level will address is gas sloshing out of the bowl, and flooding the engine. The spring-loaded seats keep the float from bouncing and prevent gas from gushing into the float bowl. Make sure they are properly installed. A fuel pressure regulator, set low, will also help with this.

Unless the PO was a carb guru, the current state of the Edelbrock is likely a lot less than optimal. Any carb other than the original one needs to be adjusted to match the engine's needs when installed. I suspect the PO just plopped this carb down on the manifold and ran it. What do your plugs look like?

The QuadraJet is a great carburetor, but it's complicated as carbs go. You'll need an adapter to mount it on your manifold, and you'll have to sort out the linkage and such. Holleys are rather easy to tune, and the 470CFM TA will be close to the right tune, straight from the box. And you won't need an adapter.

http://www.edelbrock.com/automotive_new/mc/install_items/adapters_spacers.shtml
http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000/1465.pdf

 

Interesting, I’ve never heard of that before.
What would you call “a lot”? The factory setting is seated at 7/16” from float top to air horn bottom and drop out to 1”. How far from that are you talking?
Page 8 and 9 in this manual, if anyone else is following along.

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

 

7/16" is the same float drop as spec'd in the off-road needles/seats note that I linked to above.

I've done it before on Holleys and Motorcrafts, but not on an Edelbrock. I'd reduce the fuel depth by a third and try that. As long as all the ports are covered, the carb will still function.

 

So you're thinking an extra 3/16", 5/8" from float to air horn seated?
I've been planning to get into my carb and set it up more for the cold weather anyway so I'm going to try this. I'll report back what I find.

 

Yes Tim i think you were right about the PO just plopping it in, but I have done tuning on the carb myself, like i said i have the off-road needles and springs that you have linked above. Also i brought the jeep down about 3000 feet in elevation so i did re-jet and new metering rods. Maybe ill pull it and mess with the floats a bit and see if that helps...I just have my doubts as i think even with a decreased bowl level on a even a slightly rough trail id think it will still slosh around to much...

Ill look at the TA also, is 470 big enough? i calculate 480CFM with 100% VE although i know im probably closer to 80% but isnt it better to have more CFM and re-jet then have to little CFM?

 

The trade-off is that more CFM means higher VE but a lower vacuum. Higher vacuum will make fuel control better, and provide the opportunity for better drivability and more economy. You may need to run richer with a bigger carb, to prevent flat spots and such. I would err on the lower CFM side, for a trail vehicle.

The TA has annular booster venturis, which make higher vacuum and better mixture control compared to the plain boosters with higher VE (I forget what they are called - Google "annular booster venturi" for some discussion). Again, it's a trade-off between VE and control. EFI gets around this by just sensing the vacuum and not using it to do work - thus TBs generally have very high CFM ratings when compared to 'equivalent' carburetors.

 

Thats good to know thanks tim!!!!

I need to have my dad confirm the q-jet on his chevy, the TA seems nice but dang its expensive....if i can i think ill just swap with my pops. not sure what exactly he has though.

 

Ok, so it’s been a while but I haven’t forgotten this. Just ran into a vacuum leak at the carb spacer that I had to sort out before proceeding.
Anyway, I’ve lowered the float height from 11/32” to about 20/32” or 5/8” and have seen no ill effects during street and highway driving. I’ll have to report back on how it works off road though, just haven’t had the time to get out yet.

 

So far so good.
Took it out for a bit this weekend and though I didn’t wheel it to heavy I did point it up a couple of hills so I could push in the clutch and see if it would continue idling and it did.
So I’ve found some improvement off road with no ill effects I could see on road, I’m pretty happy with this.

 

Just as an aside, Drop a Motorcraft 4100 on it. Same float bowl and general design as a MC2100, and it's a square bore. If they came off of a mid-sixties small block, they're 480cfm, and likely won't require any crazy linkage modifications. And you can usually pick them up off ebay/craigslist for sub-$100 if you look around, and if necessary a rebuild kit runs like $20.....

 

I have a little experience with the 4100. I expect it would work well on the trail, since it is basically a 2100 with vacuum secondaries added. They were indeed used on the small block Fords, but I thought that the small venturi models were only used on 289 Mustangs (and maybe Comets?), and they are now made of unobtainium. Certainly the bigger carb from the 352s and 390s should be readily available. I recall that Pony Carbs was selling the bigger model converted to the smaller venturis, since OEM examples were so scarce.

The primary shaft on the one I had on my 352 was so worn that it would not idle consistently. I replaced it with a 4160 Holley that I found at the Pick-A-Part.