Reply With QuoteI'm sure there are a million different opinions. Mine runs fine without the jets squared. Let the motor tell you how it likes it, not people.
I did a search on this but i did not find an exact answer. I have a 450hp to 500hp 454 with single holley 850 dp. I am running 84's in the front and 86's in the rear. I was told the staggered jetting may not work with the 850. Anybody running yours this way? or should they be even.
I'm sure there are a million different opinions. Mine runs fine without the jets squared. Let the motor tell you how it likes it, not people.
I wouldn't get excited about a jet size or two difference, just for reference here is a link that shows how that List #4781 carb came jetted from Holley, http://www.mortec.com/carbs.htm. 80F/80R with 6.5 powervalves F&R, however, #4781-3, -4 and -5 versions came jetted 80F/78R. My #4780 with 76F/83R jets, 6.5 powervalve in front and plugged rear runs great on my mild 460, nice tan plugs too.
I'm running 84 square with my Holley 850 dp. It's a little fat and might be a tad faster, if I leaned it out some.
THANKS GUYS,
I was running 81 front and 86 rear. When I hit the nitrous button with the bottle turned off and line purged (just using the fuel jet) I picked up about 100 to 200 rpm. I new I was lean so I needed to go up a size or two. I moved to the 84 front to check it out but I also installed the lightning headers last weekend so hopefully off to the lake this weekend if I get them back from the powder coater.
Wow! 100-200 RPM rise on the fuel solonoid is alot. Your are running real lean. Your motor should bobble and bog when you run the fuel solonoid. The fuel sol. dumps LOTS of fuel. Getting that much rpm gain indicates a problem, Maybe. Your jetting doesn't look strange, If anything, it seems like it should be a bit rich. Check all the air bleeds on the top of the venturis, make sure they are not blocked. Also anyone who runs Holleys will tell you they are always fiddling with float levels, you might check this as well. Is your fuel pump up to the task? Running Nitrous you probly have 2 pumps, The carb pump may be gettin' tired. Just .02 but I'd hate to read a post that says you have a gang of melted pistons.
fog
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