Reply With Quote- 8 is 1/2" ID Plenty of fuel for a gasoline blown small block. Just make sure the fuel tank outlet is big enough also.
I ran a B&M 250 blown 406 with the same.
i'am going to feed a small block chevy with aluminum heads, solid roller cam, 4 to 5 lbs of boost with fuel. how do i know if a -8 fittings for the fuel system will work. I bought a barry grant fuel pump (preset at 7.5 to 8 psi) and am probably going to buy the barry grant inline fuel filter both have -8 fittings in them. Will these be big enough, i have never plumbed anything with AN fittings before any help would be appreciated!
- 8 is 1/2" ID Plenty of fuel for a gasoline blown small block. Just make sure the fuel tank outlet is big enough also.
I ran a B&M 250 blown 406 with the same.
I concur -8 is adequate. Just make sure you have no restrictions and stay away from sharp 90ยบ adapter fittings if possible. They reduce flow substantially and typically have much smaller than 1/2" holes through them. Use tubular -8 hose ends to make your bends wherever possible.
i looked at a -8 fitting and the opening didn't look like 1/2 inch maybe i need to look again. do you guys run a bypass so that anything over your desired pressure goes back to the fuel tank?
-8 AN size refers to the inside diameter of the hose, not the fittings. In reality the hose even runs about 1/16 smaller normally, like 7/16. So any fitting that fits inside the hose (hose end fitting) will obviously have a smaller ID than the hose ID. That's why flow and plumbing configuration become so important. Sharp 90's kill flow.
The typical id of a -8 hose end fitting will be around 3/8" or slightly larger.
A bypass regulator is the most effective and best setup because it circulates the fuel keeping it cool and they are generally less restrictive in terms of flow than deadhead style regulators. Put it after the carbs.
There are good deadhead regulators as well but you lose the cooling effect of the bypass. Also they are harder on electric pumps. Deadhead setups work fine most the time, they are just not the optimum setup IMO.
if you had a bypass and you ran 2 tanks how would you prevent it from filling one tank more than the other?
I'm not too fermiliar with the tank situation on boats but one thing i know that has to happen is that the tank needs to be able to breath so you dont cause a vacume in the tank. Seams like overfilling a tank would be a bad thing.
Originally posted by Shaun
if you had a bypass and you ran 2 tanks how would you prevent it from filling one tank more than the other?
I'm not too fermiliar with the tank situation on boats but one thing i know that has to happen is that the tank needs to be able to breath so you dont cause a vacume in the tank. Seams like overfilling a tank would be a bad thing.
Excellent question Shaun. I will attempt to answer it.
There are a couple ways to prevent overfilling from the return.
The first which is not legal for production boats is to run a balance line between the bottoms of the two gas tanks. We do this in alot of the ski race boats and pull off the center of this line for feed and return to either tank... doesn't matter with the self balancing line. Now since this option isn't available on most performance production boats because of USCG regulation I'm going to discount it's usefulness for this discussion.
The best way for the average boat to accomplish it is presently to use the IMCO 6-way fuel valve set up. It switches both the supply and return at the same time. The downside is its very expensive. The same effect can be accomplished by using two 3-way valves although it is not a clean plumbing arrangement normally. I know there is going to be a single manual valve on the market in the relatively near future that will be a 6-way valve to accomplish this task. I do not have price or exact availability details yet.
Those are the only fool-proof methods I know of to guarantee you won't overfill a tank from the return line.
One other method I've seen posted is to run the return line back into the supply line with a check valve. While this I'm sure works it pretty much negates the positive effect of recirculating to the tank for cooling the fuel so it would not be my choice if I could do it another way.
Hmm, i dont see why having a line between each tank would be illegal in a production boat, i mean whats the diffrence if you have a device inbetween it, what so if one tank blows the other does, shit if one tank blows the other one might as well
I have to check but i think i have a T fitting right now that connects both thanks and supplys the pump
The balance line I'm talking about runs between the bottoms of the tanks with the center of the line lower than either tank. This center point is where the tee for the supply is located effectively creating one large gas tank as far as the fuel pump sees. The tanks then balance themselves from gravity no matter where the fuel is returned to either tank.
Coast Guard regs for new boats specify that the pickup has to come through the top and have a pickup tube inside the tank. The purpose of this regulation is to eliminate any hoses having a leak and draining raw fuel in the bilge (not a good thing). So you're not going to find any production boats out there with what I've described above. That's why I discounted it as being relevant or useful for most people. Hope that better explains.
Ahh, that makes alot of sense!
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