alecsammy

Hello ,
I have a 502 with some mods, I have a brand new holley 850 marine carb , The engine stumbles off idle the plugs show to be rich. Tried a couple of jets changes and timing adjustments but I'm unable to tunr this carb. I want to change this carb to either a BG or Quick fuel carb. I don't want to run a holley 800 any suggestions on a carb selection.

tinman565

What jets are in it now ? Is there a choke on the carb ? How many numbers did you go down ? These are 4150 style carbs...the BG and QF are the same style. If your having trouble tuning the Holley....you'll have trouble tuning the others also. Save your money sir. That Holley will work perfect for you...you just need to make some simple adjustments. These carbs are EASY to work on. I got faith in you brotha....you can do this.

ezstriper

exactly...you are going to need to work on primary accel pump shot with the cam and sqirters, not hard unhook throttle linkage, move throttle about 1/2"(not running) while looking down in into carb, see when you accel shot comes in and how much. differnt intakes/cams/timing need different shots..also ck the size of the squirter, #'s on them, start with a 31 or so, buy a pack of them along with pack of plastic cams...just takes time...after that work on jetting....full throttle runs with GPS, the start jetting down both sides, go 4#s at a time at 1st...that will get you going...need to makes changes while you are in the water and can make back to back runs..not days apart...Rob

stevesxm

isn't there a lot more to this question ?

did the motor ever run correctly since " mods" ?

was it ever on a dyno and set up properly ?

does it have sufficient manifold vacuum to give the carb correct signal ?

have you looked at the timing at all ?

there are about a billion things to check before you just throw the carb over the side and start over with another one you don't know any better than the one you have. thqat carb is a bog standard and as simple as it gets. and certainly none of your complaints seem to be about how the thing runs across the water . i think you look at the general mechanical set up... vaccum gage , timing and initial advance for sure... if you stall the intake charge in the manifold because of no velocity which can occur for a lot of reasons, you get what you have now... no transistional response. i wouldn't exactly condemn the carb out of hand. i mean , really ... short of the float breaking off and sinking, what can go wrong with an 850 holly ?