do i need need a bigger carb

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vkute265

vkute265

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Hey I run a 850 demon on my 318/392 stroker with 11.7 comp, mopar purpleshaft .557 with 1.6 rockers, Eddie heads tti step headers. With no pipes I run 83 and 96 jets and could step the front upto 86. Car has run 11.65 @ 114.5 mph. Should I step up the carb ??
 
A bigger carb is over kill! If your car runs those numbers, just start fine tuning the carb. Need more info. How do the plugs look after a pass? Timing? Much more to racing than just the carburetor. I run a 750 Holley on mine and it does just fine.
 
Seems soft. What geats and convertor? What are the 60' times? Are they consistent?
 
Runs 4.10 gears, 275/50 tire, 4000 stall. 60 foots are consistent low 1.6's.last time I checked plugs I was running octane booster so it made it hard to read but I do run an afr gauge which said I could go slightly richer, I haven't stopped makin mph yet, timing is 32 total
Car weighs aRound 3500lb
 
vacuum gauge...if it doesn't reach zero on a WOT pass, can use a bigger carb
 
That should be enough carb imo. I don't think you too far off as far as ET vs. MPH. But if it's still lean according to your meter i would look at fuel supply? Is the pressure consistant thruout the run?
 
I run a holley hp125 with -8 out of my cell through an inline filter through the pump upto the reg then into the carb, I have a pressure gauge out of the reg it doesn't move off 7psi
 
What kind of inline filter? And what is the air fuel ratio read at high revs? I just realized your in Australia. Your altitude might have some thing to do with the problem maybe even the temperature it can be a killer in power!
 
cant remember off the top of my head exactly what filter or how many micron, but its -8 all the way, its our winter at the moment, and i dunno what altitude our local is, but its not overly high like another one we race at, fuel pressure at the reg doesnt move, from memory arfs where low 13's at WOT, id like to see it in the high 12's. last couple of meets after pulling the pipes off and the motor requiring more fuel ive picked up 4mph, but after stepping up from 73's and 83's which is what i had it dyno'd with the pipes on. to 83's and 96's, i was thinking do i need a 950? i noticed also at around 6300-6400 is has a pop or a miss, it still wants to go but somethings holding up, ive been shifting at 6200rpm. plugs are a heat range of 7 and gapped at 35thou and a run a msd 6al 2 progamable with a blaster 3 coil, limiter set at 7000rpm, the next day after running we had the car on the highway and every now and then at crusing speeds (3400rpm) the motor would miss like you let of the gas for a split sec then went back to where u were. did it every 10km or so, fuel pressure was 7lb ive never had this issue before, around town with revs moving up and down all the time its ok, just sitting at consistant revs, im considering a new coil, maybe a hvc one ?
 
If you have a carb you can try it might be worth a shot. My 410 stroker only has a 750dp on it (and about 1 point less compression), and it runs 10.8's at 123 MPH....I would love to try a bigger carb, I just have not had time to mess with it.

Something seems off though...did you degree that cam when you installed it? I would think your car should be about a half second faster.
 
Yes cam was degreed spot on. I'll b back out at the track at the end of the Month, a similar combo in has run 11.20 @120 mph in a 3300lb car. I honestly think I Need more head work, they flow 250 and 190 at .550
 
vkute265 said:
cant remember off the top of my head exactly what filter or how many micron, but its -8 all the way, its our winter at the moment, and i dunno what altitude our local is, but its not overly high like another one we race at, fuel pressure at the reg doesnt move, from memory arfs where low 13's at WOT, id like to see it in the high 12's. last couple of meets after pulling the pipes off and the motor requiring more fuel ive picked up 4mph, but after stepping up from 73's and 83's which is what i had it dyno'd with the pipes on. to 83's and 96's, i was thinking do i need a 950? i noticed also at around 6300-6400 is has a pop or a miss, it still wants to go but somethings holding up, ive been shifting at 6200rpm. plugs are a heat range of 7 and gapped at 35thou and a run a msd 6al 2 progamable with a blaster 3 coil, limiter set at 7000rpm, the next day after running we had the car on the highway and every now and then at crusing speeds (3400rpm) the motor would miss like you let of the gas for a split sec then went back to where u were. did it every 10km or so, fuel pressure was 7lb ive never had this issue before, around town with revs moving up and down all the time its ok, just sitting at consistant revs, im considering a new coil, maybe a hvc one ?
Click to expand...

I'd start adding more timing, 32 * seems a tad low, run it up untill the MPH falls off, then start jetting it up untill the same thing, That 850 should be more then enough carb, i'll bet it runs better with a 750hp.
 
its been suggusted to run more timing, i run pump gas which is 98ron and sometimes octance booster. i was under the impression that 32 was about it, ill try stepping it up a deg at a time, i just dont wanna do what my mate did with his 410, pop head gaskets with 35 deg
 
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