dyno

O.K heres the deal SuperV and I have identical motors except for one thing he has 800 Holleys on his and I have 850's on mine. We dynoed his motor and got it dialed in with the 800 we ran the jetting as follows 75 primary and 89 secondary's how much smaller should I go with the larger carb? I'm accutually jetted fatter than him now with the bigger carb so I'm way rich....Help! any Idea? I was going to set mine up with the same jets as him but if I can get closer it would be great.

blown1500

DO NOT USE THE SAME OR SMALLER JETS IN THE 830 THAN ARE IN THE 800!!!! You must set up your carb for your motor. All the metering of the 800 is different than the 830. Bigger air flow carbs almost always require bigger jets even to get the same air/fuel ratio. Best is to use the jets that came in the carb untill you can test and check the plugs. If you don't know how to read plugs, pm or post for help.

dyno

Thanks Blown1500 you the man! I'll wait till till I get back on the water and do some testing!

tomcat

Right on blown1500 - Same air flow through bigger venturis = less signal or suction on the fuel metering passages. Therefore bigger jets are needed just to stay even. I love it when science and real life experience agree! Of course this is assuming that the boosters are the same style, which I think is the case between 800 and 850.

You mention the 830, which I believe has annnular discharge boosters. These are in a class by themselves aren't they? I think they send a stronger signal to the fuel metering passages, even though the booster design reduces total air flow (850 to 830). In your experience does the 830 require less jet than the 850?

No substitute for testing, just asking.

Scott72

Dyno, what size motors are your running the 850's on? I set my 850 on my built up 454 to the specs I got from you guys a year or so ago (motor is built very close to the 330's on Steriods in terms of Cam/Heads). Did you build some new motors? Mine runs pretty good on a 454 (.030 over) but is still a little rich and I have a slight stumble getting on plane. May try an 800 because my 850 is a bit much (but got a deal on it I couldn't pass up at the time).

Scott

KAAMA

Scott, I would think you're going to like the 800 more than the 850 on your particular engine---better throttle response.

dyno

Scott the same motors as before...I'm just like you got a good deal on the 850's so that what I'm running....no stumble at all just rich. Never dynoed with the 850's so we dont have a good idea on the jetting it runs real good but always looking to improve.

Scott72

I agree with you that an 800 would be better. I've decided to try the same thing. Do you remember what Jets you were running in the 850? I think I followed your setup, but I can't remember what I put in there. I too am running a tad rich.

dyno

Scott I'm running 83's in the front and 90's in the rear on my 850's.

audacity

i'll be on the west side this weekend....let me know if you need a hand...i have jets/carb parts and also some brand new trick carbs we can try if yad like??? let me know...if it's **** out i'm not go'n out...i'll let someone else go out...

it needs to be set-up for your app....