mechanical pump questions...olds 455

[NautiII]

I am going to route of a mechanical pump for my olds 455. now, question 1, any particular brand? holley, clay smith, mr. gasket, etc. question 2, what size lines from the tanks to the pump, and pump to carb? question 3, is 80 gph enough, or do I need to go higher. motor is mildy built. I see that most 80 gph have 1/4 inlet/outlet, and 110 and above have 3/8. difference??? thanks ya'll!

[Wet Dream]

What carb are you running? I ran a single 750 Holley on mine with a stock mechanical pump and never had a flow or pressure problem at all.

[Keyser]

i Have a stock pump on mine and it has a 3/8 inlet/outlet.

[SmokinLowriderSS]

I am running 3/8" lines, I wouldn't advise going smaller. My 454 is running a "stock" unit ordered from a boating supply warehouse in OKC (don't recall the name). I did specify one for "non-stock" High-HP aplications but have no idea the GPH on it. At 5-grand, my fuel pressure is 9psi tho, and no shortage of flow volume. Don't even know the brand. Factory original one went south in 2002 after 24 years.

[maxwedge]

I'm running the $15 NAPA automotive replacement pump on my 455. It doesn't have the extra vent for marine use, but I couldn't find a marine 455 pump and my engine isn't enclosed anymore. So far I haven't had any bildge explosions or anything yet and it keeps up with my mild 455 just fine.

[TIMINATOR]

It takes 1/2 lb of fuel per horsepower per hour. 80 gallons/hr X 7 lbs/gallon=560 lbs/fuel, divide that by two and THEORETICALLY it will feed 1120 HP! I have run the Edelbrock mechanical pump# 1712 on a roller cammed, aluminum headed, 1050 Dominatored, 250 HP CHEATER KITTED! 572 Big Block Chevy in my 21 Daytona. for three + years, trouble free. YES the single pump for BOTH the motor AND the CHEATER KIT!!! I ran -8 lines from the tanks to the "T", -10 line from the "T" to the pump and -8 from the pump to the fuel log and -4 to the fuel solenoid. The formula will keep you pointed in the right direction, but keep in mind that some pumps are rated free-flow, at no back pressure. Make sure that the GPH rating is at 4 or 5 lbs. before you try the formula. Another way to tell if you are OK, is install a temporary fuel pressure gauge where you can see it in the boat, make sure you have a minimum of 4 Lbs. at wide open throttle. TIMINATOR

[TIMINATOR]

Hey MAXWEDGE! Where in ILL. are you? I lived in Springfield for ten years before I moved to the Phx,AZ. area. I ran around with a bunch of people from the Auburn area. I ran Lake Springfield, Taylorville, Lou Yeager(Litchfield), and occasionally Shelbyville too. TIMINATOR

[maxwedge]

I live in Bloomington. Been to Springfield Lake once last year, but I usually run Clinton Lake and the IL river because they are closer and I try to stick with bodies of water that have a lot of toxic and nuclear waste in them. :D Going to venture out a little and maybe try to hook up with Sidewound on the Mississippi this summer. I also lived in Vegas for a few years before I moved back here to freeze my ass off in zub zero weather for some reason, so I've been on a few lakes in AZ area too.

[396_WAYS_TO_SPIT]

It takes 1/2 lb of fuel per horsepower per hour. 80 gallons/hr X 7 lbs/gallon=560 lbs/fuel, divide that by two and THEORETICALLY it will feed 1120 HP! I have run the Edelbrock mechanical pump# 1712 on a roller cammed, aluminum headed, 1050 Dominatored, 250 HP CHEATER KITTED! 572 Big Block Chevy in my 21 Daytona. for three + years, trouble free. YES the single pump for BOTH the motor AND the CHEATER KIT!!! I ran -8 lines from the tanks to the "T", -10 line from the "T" to the pump and -8 from the pump to the fuel log and -4 to the fuel solenoid. The formula will keep you pointed in the right direction, but keep in mind that some pumps are rated free-flow, at no back pressure. Make sure that the GPH rating is at 4 or 5 lbs. before you try the formula. Another way to tell if you are OK, is install a temporary fuel pressure gauge where you can see it in the boat, make sure you have a minimum of 4 Lbs. at wide open throttle. TIMINATOR
Good advice tim;) I have the same pump and it never skips a beat;) No wiring to run or overheated pumps to worry about. Oh did I mention I hate electric fuel pumps:D

[Taylorman]

I am going to route of a mechanical pump for my olds 455. now, question 1, any particular brand? holley, clay smith, mr. gasket, etc. question 2, what size lines from the tanks to the pump, and pump to carb? question 3, is 80 gph enough, or do I need to go higher. motor is mildy built. I see that most 80 gph have 1/4 inlet/outlet, and 110 and above have 3/8. difference??? thanks ya'll!
You have two choices in an aftermarket pump, a Robbmc or a Mr. Gasket. The Mr. Gasket fed my dual carb tunnel ram 455 just fine with 3/8" lines and 1/4 NPT fittings. You can buy it from Summit. The part # is MRG-7709. The pump has 1/4 NPT fittings. 3/8 lines from tank to carb will do just fine for you. Hope that helps.

[RobbMc]

WWW.ROBBMCPERFORMANCE.COM

[Taylorman]

I have a Robbmc pump now. I put a new intake and carb on this summer and the Mr. Gasket pump could not keep up. I bought a Robbmc pump and no problems since.
Hey Rob, question for you. I have the 110 gph pump. What is the difference in fuel lines sucking from the top of the fuel tank vs sucking from the bottom? My tanks have the fuel fittings at the top of the tanks and a tube that goes down into the tanks. The fuel pump has to suck the fuel up to the top of the tank.

[RobbMc]

I have a Robbmc pump now. I put a new intake and carb on this summer and the Mr. Gasket pump could not keep up. I bought a Robbmc pump and no problems since.
Hey Rob, question for you. I have the 110 gph pump. What is the difference in fuel lines sucking from the top of the fuel tank vs sucking from the bottom? My tanks have the fuel fittings at the top of the tanks and a tube that goes down into the tanks. The fuel pump has to suck the fuel up to the top of the tank.
Naturally it would be better if the fuel didn't have to be sucked up to the top of the fuel tank however, when the tank is full (or nearly so) it really isn't so bad because of the siphoning effect. The weight of the fuel creates a pressure near the bottom that helps push the fuel out. Of course as the tank is drained the pressure decreases forcing the pump to create a higher vacuum to draw the fuel out of the tank. On a hot day this means the fuel is more likely to vaporize as the tank nears empty. If you start noticing pressure fluctuations when the tank is less than half full on a hot day, you will know what is happening.

[victorfb]

stock (napa) pump on a mild 455 and never had a problem.

[NautiII]

thanks everyone! I appreciate the help. boat should be done in a month!! will post pics. just got interior back! looks great so far!