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Discussion Starter #1
421 sbc afr 220 heads with a custom cnc porting. flows [email protected] CAM IS 279int [email protected] 312int 325exh advertised. .679 int lift .645 exh lift. 4/7 swap .i use 1.5 rockers . 12.1 compression. 2 inch primaries. fogger with ,024 f jet. best has been [email protected] 2900lbs. made [email protected] on engine dyno with same came but no 4/7 swap. also addded vacuum pump since dyno and we ran wrong plugs on dyno(had .450 shank plug and needed .750 shank) so plug was .300 in the plug hole so i proablly make a little more than 662 now

been using a race demon 825 but i think i need a larger carb. going to run two stages this season with around 400 totla nitrous.wnat to stay in a 4150 carb but what size do i need and what am i leaving on table with current carb
 

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Go to Pro Systems website and fill out of the tech cards. I did and the next day had a response. Called up and was surprised how close the price was to a Holley HP or QF.
 

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Discussion Starter #3
i def will do that. the shop i work for we just finished a 363sbf build with a pro systems carb and its a real nice pice. really curious if i need new carb or is this one goodenough. and how much and i lossing power wise for the smaller carb with my setup
 

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a 1000 hp would work out for your combo nicely. when i had a 4150 on my car, i initially had an 850 and when i switched to a 1000 hp prosystems, it picked up over .3 in the 1/8th. now i run a dominator which was worth some additional gain as well.
 

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On my 406, a 750 Demon made 550, and the 850 with no other changes made 575. I would think that your motor moves quite a bit more air than mine and that you would need a true 950 or bigger carb.
 

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Discussion Starter #6
i was told that the race demon 825 flows around 980. but i dont know. the carb just seems small to me. it make good power and runs well just seems like it could runn a little better on nitrous. wants to flatten out on the big end.
 

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What if anything did you notice when you went with the 4/7 swap?
 

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Also i'm no nitrous guru but I believe a carb see's less air through it when its on the jug vs N/A due to the expansion of the N2O. So if you didn't flatten out on motor then it wouldnt be carb related. Could you be reving out the motor too high? Maybe bottle press is dropping a bit on the big end? IDK just a thought.
 

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421 sbc afr 220 heads with a custom cnc porting. flows [email protected] CAM IS 279int [email protected] 312int 325exh advertised. .679 int lift .645 exh lift. 4/7 swap .i use 1.5 rockers . 12.1 compression. 2 inch primaries. fogger with ,024 f jet. best has been [email protected] 2900lbs. made [email protected]pm on engine dyno with same came but no 4/7 swap. also addded vacuum pump since dyno and we ran wrong plugs on dyno(had .450 shank plug and needed .750 shank) so plug was .300 in the plug hole so i proablly make a little more than 662 now

been using a race demon 825 but i think i need a larger carb. going to run two stages this season with around 400 totla nitrous.wnat to stay in a 4150 carb but what size do i need and what am i leaving on table with current carb

This engine can definitely use a 1050 dominator. My 383/406 bracket engines run 13.5 with the same camshaft you have, only I run 1.6's, which will also help on yours as well. Why would you want to stay 4150 out of curiousity? I would go with a Por Systems 1050 dominator. Howvere even if you go with their 1,000hp 4150, you will make a alot more power than the BG Demon, that is for sure. We are making over 700hp with cnc 227 heads, your cam with 1.6's, 1 7/8 x 3.5 headers, Super Vic and an HVH adapter and a dominator at 383/406 inches so you should be right up there with the changes.
 

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Discussion Starter #10
im def lookign at a new carb. do you think i should run 1.6 rockers. i have jesel shaft on it now.but only 1.5 ratio.also have 2" primaries. it made 662hp at 6600 rpm and 535ftlbs at5900rpm. it was fairly flat throughout curve and made over 630hp from 5800rpm to 7200rpm. but i did loose a lifter after dyno and required some work so we swapped out to the same came in 4/7 swap. also added vaccum pump. and when we dynoed we had a short shank plug so the electrode wasnt even in the chamber. im thinking now its making 680hp
 

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Discussion Starter #11
Also i'm no nitrous guru but I believe a carb see's less air through it when its on the jug vs N/A due to the expansion of the N2O. So if you didn't flatten out on motor then it wouldnt be carb related. Could you be reving out the motor too high? Maybe bottle press is dropping a bit on the big end? IDK just a thought.
only go through traps at 6400rpm on gas. converter isnt a great converter but doesnt seem to be slipping. and bottle pressure i leave at 925psi so it should drop awhole lot. i def feel it needs a bigger carb. want to stay with 4150 series since i can run in bboth x275 and the real street 275
 

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put 1.6s on the exhaust cam kina small on exhaust duration and lift for a 421 and try shifting at 6500 0r 6700 nos likes to fill chamber with more time of valve open
 

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I will buck the trend here, but your not spinning it up, and a 4150 is going to go quicker at the track. The spray will support itself. Buy a better 4150 it will ET better than the Dom.
 

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Discussion Starter #14
put 1.6s on the exhaust cam kina small on exhaust duration and lift for a 421 and try shifting at 6500 0r 6700 nos likes to fill chamber with more time of valve open
shift now at 7000 on gas and 6800 on motor. love the rpms on gas,
 

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Have tried 4150-4500's on a 15* sbc with 400ci,s and on the dyno the 4500 made a touch more power, at the track the 4150 ET'd better. So like what was said above, the 4500 is not alway's the winner. We run a 1050-4150 style carb, Patrick will get you set-up. He's the man!
 

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I will buck the trend here, but your not spinning it up, and a 4150 is going to go quicker at the track. The spray will support itself. Buy a better 4150 it will ET better than the Dom.
X2 i have ran both good 4150s and 4500s on the dyno and everytime the 4500 made just alittle more power and take it to the track and they run pretty much the same..i guess the 4500 doesnt recover as good on the gear change...maybe needed different converter all 7 times ive tried it..not sure. as for the nos imo with in reason the only thing the carb does is get you to the starting line..so there is a good chance you could spend a grand on a carb and see nothing on nos...
 

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Discussion Starter #18
i realyy just want a good carb without isusues. the rtace demon i have worked good then out of the blue started bogging and ive lost 2-3 tenths. but im more worryed that i could be leaving a tenth on the table becuase this carb is too small. i did call patrick and he recomeed and large throttleblade small venturi carb. he said a 950 base carb. what i didnt understand is he said my cam was pretty big and if it was smaller he would go with a 1050 body carb. can someone help me understand that
 

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The thing about a new carb is that if you have a good dyno operator and he takes the time to tune the carb right on the dyno just about any good brand will be fine. Most ads say their carb will pick you a certain amount but that is normally versus an out of the box carb. If your setup is already optimized no carb should pick you up that much more.
 
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