Fuel feed issues
 

OK I believe my new 509 is have some fuel feed issues. It really feels like power falls off on the big end and I have no top end. This motor dynod at 684hp and compression is 165 across the board. I expected to see around 95 mph at 6250rpm with 28 pitch and 1.5 drive...I am no where near that. It wouldnt wind past 5500, put a 26 pitch on and it got worse, couldnt wind even 5000. Performance seems to be diminishing.

My first thought was fuel pump, pulled the pump and there was some fuel in the pulley driven water pump reservoir cam mechanism. I put on another pump but have not tested it. I will tonight.

I dumped the separator out and there was a lot of debris in it. Could any of the debris make it to the carb through my filter water separator? There was no water in it but my mechanic friend said it didnt smell fresh.

What are the possibilities of the screens on the pickups in the tanks being plugged?

Coming from fuel injection here and do not have much carb experience. there is a mechanical gauge on the carb feed line and I am installing a sender to get my gauge working tonight. Last I knew it was at 6psi idle and 4psi under load, is that acceptable?

I am going to drain the fuel tonight and see what it looks like.

Thanks for the help.

Is this the same fuel pump that it was dyno'd with, from your explanation it sounds like a stock merc pump driven off the cam lobe, your under load psi reading sounds low to me.

That seems a little low for your application. I'd rather see 7 to 9 psi.

I think you're on the right track looking at the pump. You will grenade that monster if it's too lean.

It was dynod with an electric and a regulator I believe.

That may be the issue, that stock pump was not made to support the HP that your running, I think if you install a good electric marine pump and regulator you will see a big difference

I agree.

What size lines?

I would have to look. I think the smallest line would be the hard line from the pump to the separator.

I'd run -10 to the pump and minimum -8 after the pump. Volume is the key. 6-7psi will support plenty of power carbed if the volume is there .

I know for a fact the lines are not that size. I think the hoses are 1/2" to the pump and the hard line after is maybe 3/8".

Is this motor N/A pr blown ?

Na

Please explain the 684 HP / hair dryer ??

What do you mean? I just posted N/A...

Jim Valako Dart Race heads matched with intake...he is no joke. There are many here on oso to verify. Not sure why you are even going here.

Just went thru this today on my 555 NA motors. -8 or 1/2 from the tank to pump, -6 the rest of the way. 8 lbs fuel pressure at idle per electric guage on fuel dist. line. Your pressure seems low from what I have seen in the past.

As far as your HP goes, 684 NA isnt that crazy to achieve IMO. I get the 509cid limiting factor however I m sure the heads and intake make up a bunch. What carb and compression are you at?

Get your azz in bed, we've got a hard day in front of us tomorrow.

Had to replace my fuel line on bone stock 502 this summer and it was 5\8 or an 10.
your fuel line is probably way undersized, and or pump worn.
edit in tank to low pressure pump

I'm still in Blytheville running crews. Prob won't be home till 2 or 3am. Up at 6 and back to work on the boat though.

Im not knocking on the motor or the builder, those are great numbers for a single carb and no help.

Is there a reasonably priced pump that will support my HP level? It is Gen6 sea pump mounted.

http://www.cvproducts.com/ProdDet.aspx?PN=SPIN-MP-2630

I agree that you may want to upgrade the pump itself. However, if the engine was able to pull 5500 with a 28p prop, then only able to pull 5000 with a 26p prop, you had more going on, than simply a insufficient fuel pump size. I think you may be on to something, as far as the pickup being clogged, a fuel line that collapsed internally, or some junk in the carb. Junk in the carb though, wont show a loss of fuel pressure, where as a clogged screen, filter, line, etc, will.

What I would do, is try to rig up a mechanical gauge, to where someone can see it while you run, temporarily. Forget those electric pieces of crap. Ideally, if you have 6.5-7psi at idle, you dont want to see it drop to 3-4psi at wot. You wanna see it stay around 6 or more at speed. Even most of the mechanical gauges arent very accurate as far as they go. You can take 1 gauge, install it, and see 7psi at idle. Remove it and install another one, and see 8psi at idle. But what you wanna watch is for the pressure drop at high load/speed. If it drops more than 1-2psi say from 3000-5000, you prob have a supply issue.

Your typical holley needle and seat cant take 9psi without being pushed open. The CV product pumps are nice, but, they are not gonna help if the pickup is clogged, lines to small, etc. Also, make sure the tank vent isnt clogged with spider webs.

I have a mechanical gauge on the motor, cell phone and duct tape problem solved!

I wouldn't try to bargain shop on fuel delivery for high hp applications. When I upgraded, I switched to an electric pump, used the existing pickup as a return by bending the pickup tube and removing the screen. Installed a new larger bulkhead fitting in the tank for -10 with a new tube and large in tank strainer. Is grenading a motor worth the $500 you may save?

Found a pump with larger ins and outs off a 600sc that my bud switched to electric. It should support this thing...problem now is the water separator has small ins and outs.

Its always something with these things, good luck

On the bright side it is a 170 gph pump

Sorry to sidetrack - but why would he do that ?

def get a high flow water/fuel filter.... 3/8 line is way undersized... I would say 600HP max with that.... I built my 509 and guess its around 575HP and it does OK with a stock pump and larger lines. I also installed a wide band air/fuel ratio gauge to monitor everything in real time and it is really the way to go to dial in your carb. If you are leaning out and I bet you are, you are running the risk of frying your nice, new motor..... I am running aluminum heads and high compression so I have to run 93 octane from the pump and I am always afraid of the alcohol in the gas creating crud in my fuel system.....
I would also get an AFR gauge, I look at mine all the time. the only thing is you need is to weld an exhaust bung for the O2 sensor. I use a plate with mine as I have the 496 style dry joint exhaust.
I would say going with electric is a good idea. I am going to install an electric setup as a backup just in case my mech pump craps out......

wanted to make sure it had sufficient fuel and he is anal as fuk

Don't tell'm, but my question remains the same..maybe even more so since so anal.

Oh well. Others can learn from this. If you can stay mechanical : ie, you have carb(s) vs EFI, stay mechanical.

My Dirty Floored Shop Opinion. . LOL.