kmiller

Well I am getting close to running perfect. My only problem is after driving to a location and sitting for a while, when I go to start the engine I will pump once and crank ( normally starts right-up ) it will crank 10-15 sec. and I have to hold the throttle wide open to start, will start poppy and clear out. Also last time coming off plane it would not idle down right away, and when it idles I have to clear it out as is starts to load-up. I replaced the power valve with a 6.5 same size that came from demon, but the best vac I could get was between 7.5 and 8.5 @ around 750 rpms by adjusting the 4 idle screws. Any Ideals it seems I need a different size power valve.

kmiller

If it helps this is a 350ci sbc, I currently have World Products Sportman II heads 72cc, crane roller rockers 1.5 ratio, .060 over flat top pistons, performer rpm intake, Gill Manifolds Running as true dry exhaust, and a sea demon 650 carb. Does the vacume seem right for this size cam?????

284*/290* @ .006”
223*/234* @ .050”
131*/141* @ .200”
112* LSA
108* ICL
IVO 28* BTDC
IVC 77* ABDC
EVO 79* BBDC
EVC 31* ATDC
59* Overlap
4* Advance
.309” I lift lobe/ .323” E lift lobe
.475”/ .485” valve, with 1.5 ratio which are inverted on the chart

HARDCORE A/O

Have you checked your float level? I seem to recall having this same problem years ago and I found out that the floats were a bit too high and when I shut it down, gas would dribble out of the boosters and flood the engine. If you have to hold the throttle wide open to get it to start, it's flooded and the chief culprit is either a high float level or a stuck needle and seat. Start it up and take the flame arrester off and carefully look down into the carb at the boosters. If you see fuel dripping out of the boosters, take like a screwdriver handle and rap on the needle and seat adjuster nut, this will usually dislodge any debris that might have the needle stuck open. If that doesn't work, you probably need to adjust your float level down a bit.
Another problem I had with a Holley 4010 carb once was that it would heat up so bad that it would percolate the fuel right out of the bowl. If your carb gets really hot, especially when you shut it down and it "heat sinks" , then this might be the problem and you might have to buy a heat shield to put under the carb and/or add some ventilation to your engine compartment..
Hope this somehow helps. Happy boating...

HARDCORE A/O

BTW: I think you have a pretty good combination there but the vacuum does seems a bit on the low side. Have you checked your ignition timing lately? A relatively high idle (static) timiing will increase your vacuum, so you should check both idle and maximun timing. You would probably need like 10-14 dgerees at idle and 32-34 at maximum (all in by about 2500RPM), as a starting point but it varies depending on climate and fuel type.

kmiller

I will check that over, I have a sight glass on my bowls and it is at the center if the glass??? Also I will re-check my timing I think it is lower then that. I will reply back after the weeking of trial. Thanks Kyle

HARDCORE A/O

Be careful with advancing the timing. Do it in small increments and listen carefully for detonation. Iron head motors are particularly sensitive to timing advance but you should be OK at even 34 deg. max timing with 72cc chambers and flat-tops.

formula31

if your level is in the middle of the sight glasses your too high. They should be at the bottom. Just slighly dribbling out the hole (with the screws or sight glasses removed)

formula31

And try starting without touching the throttles until it fires, the accelerator pumps can flood it quickly too. Mine starts without touching the throttles when its warm or hot. If I touch them at all, then I have to go through what you are doing.

kmiller

Well great info I will lower the float levels and retry, I will also check timing and try to figure out the vac problem....

RumRunner

kmiller,

The float levels on your carburetors should be about 1/4 of the windows, or the bottom line on the side of the float bowl. You may be running into a problem with fuel dripping out of the boosters when the engine is shut off based on the angle the boat sits in the water, and pumping throttle probably isn't helping you.
If the problem just started with it coming back to idle take some carburetor cleaner and spray out the air bleeds on the top of the carburetor, and retighten the float bowl screws.