Thread: Fuel...

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Hi my name is Dennis Im new here. I dont own any hot rods but hot boat...
I have 555ci Chevy built by Dave Ebbert in Costa Mesa CA. 802hp about 40hrs on it.

I have two 750 Holleys on it. Optimal fuel pressure is @ 7psi. It gets flooded really easy at start up. Usaully will get up to 8 or 9psi while cranking it when flooded, but goes down a few seconds after idle. Im looking at from the mechanical gauge.

So usually I will let it sit till I see the gauge drop down to 2 or 3 psi then crank it. Im new to big engines.. my question is.. Is is bad to fire up the motor with the fuel pressure higher than normal. Should i let the pressure go down or just fire it up?? Will this cause it to backfire?

Engine specs..
- 555 cubic inch, naturally aspirated
- Runs on 91 octane pump gas
- 802hp @ 6500rpms
- 648ft/lbs of torque @ 6500rpms
- Edelbrock tunnel ram
- Twin Holley 750cfm double-pumpers
- Brodix aluminum heads - over $1000 in porting
- Brodix stud girdle
- CP forged pistons
- Fuller solid roller system (lifters and rockers)
- DNE propietary Cam spec and build
- Eagle 4340 crank
- Eagle 4340 connecting rods
- Dart Big M block
- System 1 remote oil filter
- Injegtor butterfly scoop
- Barry Grant fuel pressure regulator
- Edelbrock mechanical fuel pump
- MSD 7AL Ignition
- MSD crank trigger
- MSD distributor
- oil cooler
- Miloden 10qt racing oil pan with windage tray

Originally Posted by DennyW

The big block guys will be along. I would cut my pressure to 6 max. Sounds like you are forcing the floats off there seat, and getting extra fuel in the intake. Yes, this would cause it to act up, and flood. And, yes, if the pressure is above that 6 psi, wait until it drops to 6 before starting. Sounds like maybe a fuel line heat problem causing expansion of the fuel, increasing pressure.

Welcome to the forum.

Denny has got this one.
I think you are pushing fuel past the needle and seat.

Try running a small return line from the low pressure side of the reg. back to the tank. Bleed off the pressure before it floods the engine.

Thanks for the advise guys! I appreciate it being that im new to this thing.
I'll try the return line and drop my pressure back to 6psi.

Im just really affraid of it backfiring in the 110 degree weather in Arizona where I boat.

DO you think my carb floats might be out of adjustment too?

Sometimes when its anchored in on the water for an hour or more, it wont start. Is this this due to the bouncing around? The engine seems flooded.
Could I prevent this with a fuel shut off valve??..or??

Didnt Dave have your carbs B/P? I would call Dave and ask him what he thinks first.That little 555 isnt making the power the smaller combos are making. What is your compression? Not trying to burst your bubble or stir any chit, Just wondering. I see alot of DNE motors running alot more HP with less inchs.

My little 548 will make more than 850 HP on pump gas and 10.2:1

Ive seen your boat cruisin in needles,nice looking ride.

Good info above though, get that regulator turned down and check the float levels. Set them up as if the boat was on a WOT pass to get the attitude where it rides and set them.

As for it not starting after siting, you might want to check your tank vents and make sure they are working. With the heat out there it will exspand the fuel and force the fuel right past the floats and it wont want to start, but for the most part, it sounds like you have some carb Issues. I would for sure call Dave and ask him what he thinks.

Hey Futs,

Im in Willow Valley, So im always on that stretch of river. In fact I will be up there this Monday - Sunday.

I need to talk to Dave, because when I talk to him before he said check the float levels. He said that should be my problem.

I was looking through the huge file of reciepts the old owner gave me.....
I he see took it to a shop in september (at the end of the season) to have the valves adjusted and the float level set. I have the invoice right next to me. So they should be on right???
I did check the foats today and they are accurate. hmmm..

I didnt check the vent. hmmm?? Ill grab a flash light and go outside.
remeber.. Im a rookie. haha

This is my boat...Wave next time
http://img263.imageshack.us/img263/3...dowtiedqc8.jpg

when you checked the float did you make sure the boat was sitting as it does in the water on a WFO pass? if not then they are wrong if so then Id say fuel vents. I know some of the newer caps have venting problems.

nice ride cant tell for sure by the pic but is it an Ultra?

I'd be seriously thinking about a return line off the regulator like Pope said to bleed off some of that pressure when you shut the boat off. A fuel shut off is a good plan, too, but IMO it would work best to run the shut off in the line before the regulator, then at shut down close the fuel shutoff, let the engine run 5 to 10 seconds more to bleed off the pressure, then hit the kill switch. With all the heat, plus the heat sink off the engine, the fuel is going to be expanding a lot after shut down and probably flooding the engine..... We've used the shutoff valve and return line method for years on drag and circle track engines. No reason it won't help out a boat, too!

Yes Fourq, the boat is an Ultra.

I just got back from a 6 day trip. Didnt have this problem once. I ran another vent from the tanks. Boat ran great and never acted up. I spent about an hour on the phone with Dave Ebbert before I left. He walked me through everything.

If you are running Two carbs you might consider to try reduce the squrtter jet. You may be getting too much gas when you pumping the carbs.