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post #1 of (permalink) Old 05-17-2004, 09:55 AM Thread Starter
 
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please help with carb issues...

This is related to the 302 in my samurai. ok, I have a double pumper holley 600 cfm with vacuum secondaries. The truck first off will start up fine, idle like a damn champ. Then if I smash the gas pedal it stumbles at around 2k or so and backfires out of the carb (sometimes a straight backfire, other times actual fire lol). If I rev up the engine slowly through small gas thrusts it will eventually spit out of the carb. Checked timing, good base and seemed to be good advance in timing. Screwed with float screws (havent checked needle and seat pins yet). I want to guess an unadjusted/ dirt/ fouled accelerator pump? Im down to the nitty gritty and nearly ready to buy a new carb, but would like to try and make this one work. I will check to make sure the valves arent sticking or its ignition related. But being as those signs might all be good, is there any good guesses besides that? I've heard the accel pumps will blow and the carbs will run Rich as hell. I've also heard of the rear needle and seat pins sticking and leaning out the carb making it backfire also.Im stumped and tired of giving the neighberhood kids this free fireworks show I got going on here.
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post #2 of (permalink) Old 05-17-2004, 02:48 PM
 
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Re: please help with carb issues...

First off IMO Holley carbs suck for anything other than drag racing. You can make them work but you will constantly be fiddling with it. For the Street I love Carter's/Eddlebrocks AFB carb. It's easy to tune and extremely forgiving. I'm not too fond of it for an off camber carb but I know a guy who made it work by blocking a fuel passage. I think the Autolite 2100 carb would work great in your sammy. It's a little 2V carb but the old timers seem to love it as an offroad carb. There is the 2150 too. This one has an air adjustment to the back of it. Here's a good link on the 2100. That's all carb info. Too me it sounds like you are having some kind of timing issue. Is your Vacuum advance working right? Try adjusting the timing at different spots making notes on each change. I'd be willing to bet that it's advanced too much. Also try richening to accelerator pump as you might not be getting enough fuel under hard acceleration. Check for Vacuum leaks as this can cause stumbling as well. If you haven't changed your power valve yet you may want to try that too as each backfire can destroy one powervalve in a Holley and other types of carbs as well. Keep in mind that every adjustment to the carb you make will effect timing and the opposite applys as well. If you know any hot rodders that spend all day trying to find that "sweet spot" you will truely start to understand that tuning is an artform in itself. A change in air pressure can screw all the work up again. Setting things at stock specs is an easier route (which will only work if you have not already swapped cams, ect.) but what fun would that be?
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post #3 of (permalink) Old 05-17-2004, 04:19 PM Thread Starter
 
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Re: please help with carb issues...

I'd relate it to time advance myself, before we actually set it with a really nice timing light it would always do the "stumble" until you pumped the gas up frequently and built up either pressure or something, after that could slam the pedal and it would rev up everytime, so Imma check timing advance first cause it almost seems like those secondaries are not opening cause it just folds out like its being richened up...I like the way that carb sounds, but Im worried about the 2b setup being as I spray on this engine..
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post #4 of (permalink) Old 05-17-2004, 04:45 PM
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Re: please help with carb issues...

Been a while since worked on a carbed engine, but when I had a holley 4 barrel on a 351 W I had similar symptoms and it was the power valve in the holley. Easy to change and it fixed it.

My carb experience:

The autolite 2150 was on my 71 Bronco 302 factory and it ran like a champ. It would just about run inverted. When I went to the 351 W I first put on the holley and as stated earlier it needed TLC. I changed everything in it several times. When they came out with the Edlbrock carb I jumped on it. fuel leaked out of it while on a hill and caught my engine on fire. Now if have EFI. I love my fuel injection!
post #5 of (permalink) Old 05-17-2004, 05:29 PM Thread Starter
 
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Re: please help with carb issues...

I do like how the autolite sounds, but I currently have a 4 barrel intake (maybe could get a 2), and plus I spray a 125 shot of nitrous on this motor, I dont know if the CFMs would provide ample fuel/air ratio to safely run that. I'll chat with a friend, from what it looks the most that those carbs put out is 424 cfms...I rescently replaced the power valve in this carb but from the backfires/ dirt and grime that might have breached in there it just might have messed it up, I took the needle and seats out..wasnt to happy with how there acting either...I have a full fuel injection setup in the garage (minus the harness and ECU), I might just convert to damn EFI..
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post #6 of (permalink) Old 05-17-2004, 08:36 PM Thread Starter
 
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Re: please help with carb issues...

ok so after rescent research Im told that the 2 barrels that came on old fords are quite the pick, the 302's claiming to have 350 cfm's and the 351w's having 500 cfm...Whats the difference the jets? I would really like the 500 cfm to try and keep a higher end stronghold...Has anyone ever noticed a significant decrease in power between 4b and 2b? cause what Im thinking is using the 500 cfm Im only loosing 100 cfm but is there a significant unrelated difference with those 2 extra barrels?
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post #7 of (permalink) Old 05-18-2004, 01:24 AM
 
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Re: please help with carb issues...

2V= reduced fuel economy because you are running more gas consistantly than you would in a 4V setup unless you are on it constantly. You must be mud bogging because I can not imagine what else you would want/need nitrous for. In that case I'd probably stick with a 4V carb. Every mechanic I've ever talked to likes the Quadrajet for power. I wasn't too impressed with mine. I got a Qjet off a boat (Chevy 305). It's been rebuilt and it ran OK. I still wasn't too impressed running with the front end aproaching vertical. I could sell you the Qjet cheap if you were interested in it. Both the Qjet and autolite could be installed on a square bore intake relatively easy using an adapter.
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post #8 of (permalink) Old 05-18-2004, 09:06 AM Thread Starter
 
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Re: please help with carb issues...

well I was offered a 2v factory carb off of a 351 for free, and after matching the numbers we could most definitely juice that (in fact 2v nitrous plates are quite cheap)and being there's only a 100cfm difference it wouldnt hurt me to bad top end, the only reason I have to consider that is on nitrous your forced to stay at higher RPMs. But how much would you be looking to get for the qjet? I havent completely made up my mind yet. Thank you, Billy

Yes the nitrous was typically for mud, but I do still climb, oh and catch a few ricers at redlights [img]images/graemlins/smile.gif[/img]
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post #9 of (permalink) Old 05-18-2004, 04:34 PM Thread Starter
 
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Re: please help with carb issues...

Ok turns out the hand me down 2b carb I was talking about in fact is a damn holley..is it still any good? I believe its the 500 cfm one. Ok lemme narrow this down, my buddy has a yard full of 69-71 2 barrel carbs, I need to get at least 500 cfm's out of the 2 barrel carb itself. Is it possible to just rejet stockers to 500 cfm? He has them from I6's to 390 stock old 2 barrel carbs. I just need to get as many CFM's out of the carbs as possible..
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post #10 of (permalink) Old 05-19-2004, 02:11 AM
 
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Re: please help with carb issues...

I'd sell the Qjet for $30+shipping. You are looking for an autolite/motocraft 2100 or 2150. Check out that link I posted it has alot of good stuff. These carbs were put on everything from 6 cylinders to 460s with different ventury sizes. The number is stamped on the side accordingly. Plus make sure you get one that has the inspection tag attatched so you can get the right rebuild kit for it. Ford used alot of different carbs.
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