demon tuning help

[berk]

just got my new engine running with the sea demon 650. seems to work well enough out of the box but one problem we encounteres several times yesterday was after a big bounce, or flight , the floats seemed to chug fuel and left us flooded. my fancy new fuel system is pumping 6 psi, with electric holley blue and a homemade return bypass circulation sys. my redneck buddy said lower the fuel levels in bowls, and he also said maybe connect the bowl bypass tubes that dump into the throats to each other, so fuel sloshes between bowls and not down the intake. any thoughts?

[bp]

do you have that carb sitting front to back or side to side?

[SmokinLowriderSS]

How the heck do you connect the float bowl bypass tubes to each other? Oh well, I have a holley, not a sea demon.
I'd lower the float levels a bit. My Holley is at the "right" levels and gives no troubles. My mech pump delivers as much as 8 to 9 pounds at WOT and we have never had any bounce or surge troubles.

[cave]

berk I have a Demon 850. I added the Barry Grant off road float needles to my carb along with Oval track beveled floats. The needles have a small spring mounted to them. The floats are carbon type with the bottom corners shaved in the shape of a V. I still get the sputter on late afternoon chop. But no as bad as before. Saguaro gets real rough.

[berk]

its mounted front/back and sits at an angle all the time. i just had it out and the water was REAL rough, the thing was coughing every time i let out the throttle too. restart would be a bit slow too, some cranking. i will try lowering the floats, could a rich idle mix cause a stall after closing throttles abruptly? thanks=

[bp]

i don't know about 650 sea demons, i run 850 mightys. but i wouldn't lower the float level.. if anything, you may have them too low, depending on how much angle the boat is sitting at when you set the float level, and how much angle the carb is sitting at when you're running along. demon recommends running them at the top of the glass. what do they have on that carb for bowl vent extensions?

[berk]

top of glass ? they said in the docs middle of glass but is that fuel level or do you use the line in the float?i assume actual fuel, in which case its right in the middle now. the bowl vents come up and do an upside down J into the throats.
cave: i get the springs on needles, i think i need those. what do the beveled floats accomplish?

[cave]

I had a problem in tight turns. The motor would starve for fuel so while I was ordering the springs I ordered the floats. Haven't had a problem in quick or tight turns since.
I'm definitely not an expert on this but all these little fixes worked for me. I've had my Demon since 1999 and love it. It does eat fuel but when I hit the throttle it pulls hard.

[berk]

just pulled plugs for a reading and found most wet with fuel and 1 and 6 had melted electrodes. :frown: WTF? if i melted another motor its back to outboards for me- serious :cry:

[87 rogers]

I would check the timing thats why you run a hot plug so it burns the plug first. For your carb problem you could try to lower the float level below the window what is going on is when you hit a wave the fuel is sloughing around gets up to high in the bowl and because of the vent tube hanging over the barrels it sucks the fuel out of the bowl. :cool:

[berk]

i am running cold autolites. i think they are the second from coldest in the range.

[87 rogers]

then you probably got a problam a cold plug puts the heat in the piston

[berk]

i thought it was the opposite? cold plug draws heat away. i was told and have read to start cold and get warmer as i do readings.

[87 rogers]

Hot plugs mean they're hot any other questions just ask run mid range plugs

[GUGS102]

I'd be more concerned about the burned plugs than the carb at this point. What timing numbers are you running bottom and top. What dist and have you had it curved? What compression ratio, cam etc. There is such a thing as too much timing, you can detonate any motor, the trick is to find what it likes. Above a certain amount of timing you won't see any performance gain, just hotter cylinder temps.
Did the electodes break off? If so, make sure you get them out of the cylinders, it'll wipe out the seats and possibly valves.

[berk]

yes am worried about the material in the cylinders, very. the ratio is about 9.5/1 and iron heads. total timing was 30 degs, all in at 3000. i had the dist. checked out by a shop right before this. its a mallory hei. new carb was intended to cure a lean out but looks like it is a plague that will follow me in this boat. :frown: the plugs look like they just melted like a stick welder, the ceramic remains but the center is burned out doown to abut 1/8 below the tip. some of it was welded to the hook thing, but i am sure the rest has burrowed into eery bad part in the engine and i am now probably out another motor. my chevy guy said just do comp check and leak down, if ok, run it.
rogers, i still dont understand what you are saying completely, hotter plug means hotter plug but what does that mean for combustion temps/ detonation? i read a colder plug draws heat away from the combustion chamber and thus would get fouled easier and detonate less. hotter plug would make the cyl hotter too>? so at this point i think i want a colder plug?
my plan now is to go two jets bigger on secondaries and lean out the idle a bit. primaries seem ok i guess. i also plan to do real plug readings at each rpm range and try not to fork up this motor. is 30 degs safe? is 3000 rpm a good point to have it all in? what plugs should i run? gap em? does gap make the plug hotter or colder? these were about .043" out of the box.
thanks for your inputs! :skull:

[87 rogers]

running a hotter plug is just safer it will burn the plug first it did not burn the plug because it was to cold. I would leave the gap wher it's at put a higher vacum power valve like a 8.5 or 10.5 this will make the power valve open sooner and give you more fuel in the mid range then up the timing 2 to 4 degres 30 is a little slow and can put more heat up higher in the chamber it exausting early witch could burn the plug. what is your engine. I work m&s engine works a custom engine shop in north Idaho I do not now everything . But you can call if you like. my name is Dale 1 208 597 0700 west cost

[87 rogers]

You could also call barry grant tech line 1 706 864 8544

[SmokinLowriderSS]

Plug heat range is not at all related to gap. It is relative to how fast the plug cools the ground electrode. Used to be the longer taper center insulator was one of the things that was done to help slow the plug cooling. In these days of extended reach plugs, I am not sure any visual cue can help you. There is a number in the plug # code that represents it's place in that design's heat range (like an AC delco R41T / R42T / R43T / R44T / R45T / R46T / R47T series for the BBC) the higher ### is a hotter plug (shunts it's heat off to the cyl head slower)