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New Motor Super Fat
So my rebulit windsor stroker made over 600Hp on the dyno, but using 92 jets in an 850xp carb. This carb comes with 84 jets Square. The plugs are dark and the thing just stinks of fuel. This sure seems like an awful lot of fuel. While it goes like a rocket WFO, drive-ability sucks and it just flat stinks.
Does anyone have a similar motor that would care to share jetting/set up? Motor came with the blue springs and a 21 degree bushing...total 32* initial 11* (seemed way low). Went to a 14* bushing taking initial to 18* but now i get a single knock on start up. Little better but still stinky and jerky... Thanks |
Typical Plug
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Wiener dog thinks its food
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If someone tells you what jets they are using, how will you know it is right for your situation? If it were mine, I'd consder pro dyno tuning on a chassis dyno or some kind of Air/Fuel ratio gauge/meter. .... Not that it will help you, but I installed a full time AFR gauge in my latest build for just that reason.
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431", 850 will make big power at cost of bottom end, vice versa for a 780. Big cams, my experience, do not pull enough vacuum below 1800 rpm for the carb to work well, below 1800. Have you checked into accel pumps? I went through all of this, spent a bunch of money and time, scrapped the carb and went to EFI. BETTER, streetability with a big cam. Recently, change to an EFI cam, bottom end, 1000-1400 greatly improved. GOOD LUCK
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My 438 Windsor ran great with the stock 84 jets. The gas smell is telling you it’s getting way too much gas.
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Holley power valves are junk.
Make sure your power valve ain't blown. If the fuel bowl drains down over night or if you pull the metering block off and there's gas in the power valve well behind it, your PV valve is leaking. |
pull of that carb and go with EFI and a maga squirt/AFR meter. problem solved
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If i've got to drill out for an O2 Sensor...
I might as well do EFI. For along time i thought the retro look of the carb was cool, but im getting tired of always having some sort of drivability issues.
Thanks for the feedback fellas |
signed up
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Do you have adjustable air bleeds for the idle circuit? Maybe you need to introduce more air to overcome those pig rich 84's and lean out the lower rpms? Possibly some similar tuning for the transition circuit, too? Me personally, I'd try to get the car happier at idle and up to 1,800-2,000 rpm first (install an A/F meter) or take it to a dyno. What's your idle vacuum reading? Your PVs might be bleeding open too soon. My $0.02.
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Do some more research, perhaps on the other forums as well. I've read many threads where someone has tried to convert to EFI and had tons of issues. If you get it right it can be great, but sometimes it just doesn't every get there. My engine builder kept me away from EFI. I suspect the 850 cfm carb may be oversized for how you are using the car. I run a 750 cfm carb with a 408 pushing just short of 600 hp. With a good tune a carb will perform well. I've used the Air fuel ratio systems and they can help a lot as well. Like Tommy said, try a professional tuner perhaps before taking the plunge.
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I wasn't suggesting dyno tuning for peak horsepower. You already know the carb is setup for that. I was thinking of running on a dyno with a cruising load and an AFR readout so you could check things at 1800 RPM, 2500, 3000, etc without wide open throttle. With a few sets of jets and some tuning of the idle and midrange circuits you may be able to get it where you like. It's definitely cheaper than an EFI.
BTW, I mentioned earlier that I put an AFR gauge in my latest project. It has a 427 ci small block Chevy with a Holley Ultra 850 XP carburetor. It hit 600 HP peak on an engine dyno. I haven't opened up the carb to check the jets because the AFRs look ok at all the normal operating RPMs. It is challenging to start in cold weather due to the lack of a choke and I get a lot of gas odors during warm up. But it seems like other Holley carbed V8s when warm. |
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Tuning and setting up a carb is a diminishing skill. I am 69. I grew up working on them, especially Holleys. If you are unfamiliar with setting up and maintaining a carburetor, fuel injection is the way to go. My 2014 Backdraft has a Roush 427R and an 870 Holley. Jets are 78/82 P/S. I thought it was too much carburation when I got it from the original owner but Roush told me otherwise. It was the way they designed it. Strong, noticeable gas smell especially when sitting ...ran a little rich, some black smoke. I have seen it before. Turns out it was nothing more than a carb that needed a good adjustment and cleaning including the air bleeds. All probably caused by the bad gas that was run through it for years. There are plenty of threads about it on here or the Holley forum. Only change I made was to remove the original vacuum secondary pot and install a Quick Fuel one. Car runs like a champ. No gas smell.
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Do what you want you do not need a dyno just your blue jeans plug readings some jets air bleeds a little help from the boys here on this site and a little time. I believe you will find a lot of satisfaction fixing it yourself . Think of it of the joys of owning a cobra . Fyi I have a quickfuel 780 with vacuum secondaries and can tell you while it is not perfect I am quite happy with it. Thanks to the above mentioned comments.;)
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