Do you see a fuel supply problem with my current setup ? My system includes Mallory 110 pump into Mallory canister style filter, out of the filter with 1/2 inch line up to the Holley regulator. The regulator is set at 7 1/2 lbs, out of the regulator with -6an (3/8) line to inline banjo fittings to the carbs. The engine is a 383 stroker sbc, 10 1/2 -1, Edelbrock rpm heads with a 238/538 cam, cam is good to about 6500 rpm. I'm curious if the supply will be there at the top of the rpm going through the lights on a 1/4 mile track ?
1/2" line will support up to about 700 HP, the 3/8" line, about 375 HP. Your pump will max out at 478.261 HP.
The set up you have will work, but in my opinion you should have run 2 singles from the regulator, (dual outlet reg) then 1 up to each carb. The way you have it now you are stealin from peter to pay paul. At 6500 rpm, your gonna use alot of fuel.
I think that he might be skirting the edge of that not being enough pump, and dual lines to the carburetors. Dropping to a p***-through 3/8" line creates a choke point.
Maybe some other points not already mentioned..... * technically the regulator and guage should be at same height as fuel bowls. * even though the motor is probably mounted solid, there is still movement/vibration working on the line and your fitting especially at every shift. Isolation with a flexible section would be desired
Main problem I see is your fuel tank is going to be running dry all the time and you'll be constantly having to refill it.
I was just wondering because I just had the engine on a run in stand with a standard inline electric pump that only showed 3 1/2 lbs on the regulator. The thing sounded like it was running out of fuel at 5700 rpm, shut it down and checked the sight screws and no fuel coming out. I had set the floats dry with the top of the float parallel to the top of the bowl and using the old pencil trick to check it. I was surprised these floats were not closer than what they were and was wondering if the small electric pump was not giving it the fuel to fill the bowls. That then got me thinking that I should have run the dual lines out of the regulator in a similar fashion as to what I did on my truck. I had bought that tunnel ram with a pair of 600's on it with the upper piece of braided line with the two banjo fittings. I just had the lower section made down to the regulator, figured the guy said he was racing with the setup prior and it would work. Now I'm thinking of changing it after the run in deal.
IMO, the big block is set up the way it "should" be done... Keep in mind that all the fuel going to the back carb has to flow around the banjo bolt on the front carb. Could be a real supply issue.
swade, that looks like the 12803 reguulator, with dash-6 lines, I'd run one for each carb, and be able to adjust and verify fuel pressure at each carb. I'm **** that way, but never melted one down from inadequate fuel, TR
Going with Jeff355's answer regarding fuel supply. I don't think air flow would be an issue as it is being forced into both carbs and each carb can only "take in" as much air "volume" as the openings will allow. You would need to adjust the fuel air mixture's on both carb's once the engine is running for optimal performance.
Just talked to my friend at Holley, I'm correct, one regulator per carb, I'd never give you wrong advice buddy, TR
So how would you run two regulators in series off of one line and not get restricted fuel to the second regulator ? Also if the regulator I have now is set at 7 1/2 lbs would that change with the second line aded if I use just one regulator ?
Pump, tee, regulator on each branch, single line to each carb. However, i think you'd be just fine doing what you did on the big-block, just running one line to each carb. Those little single feed carbs should work fine off a single big regulator (yeah, I know it's not what Holley recommends).
I've been running thru a single reg. [w/ a line to each carb] for a number of years now, but , the main restriction is the reg, IIRC it's only 'bout .250. There are "big port" regs. available from various sources. I'd start w/ 5# fuel pressure so as not to overpower the needle valves, you can always raise it if your gauge shows too much drop[you do have a gauge you can read going down the road ,right? dave
That gauge on the regulator is the only gauge I had on the car. So get rid of the banjo fittings and go with regular straights is a good move on that as well as running dual lines ?
Sorry swade, been busy at the doctors, yes T the lines into the two # 12803 regs, OR you can go to the bigger reg single inlet and w/ 2- 1/2" outlet's reg from Holley # 12704. If you go the T route, dont be cheap on the T block, you want unrestricted flow, O.K. If you build your own, go into the block with a little die grinder and smooth all of the p***ages out where they meet and intersect. Stay warm buddy, I know N.Y. is cold as a witches t$t today- I'm 81 degrees, ****s right? TR
my opinion is your gonna run outta fuel at 5000 rpms. I did not read all the posts, but your pump is to small to start with. If it where me, I would have a pump capable of 280gpm, and at least 14 psi. I would run 3/4 line from tank to pump, 1/2 from pump to reg, adjust pre***ure to 7 psi and then 3/8 to each carb float bowl, or at least to each carb. The best illistration is swades pic which is correct. Bottom line, if your cruizin around town lookin cool you should be fine. If you heat that engine up and run her lean at 6grand your gonna swell the pistons and cause premature wear and even damage.
Sorry, bro, but that is WAY overkill. Those are the line sizes I run on my 900hp injected big block...on methanol. And I think you meant 280 gpH on the pump...I think. 3/8 line from pump through reg. to carbs is fine. Remember, the secondary feed on those is 1/4". They just don't use as much fuel as a dual feed carb...
Well it looks like I have some refiguring to do, I think I've got a Moroso "Y" block out there somewhere that has 1/2 in inlet but not sure on the outlets.
Perfect, get another 12803 regulator, out of the pump into the Moroso Y block, Y block into each of the regulators, 3/8" or Dash 6 into each carb, your done! The Moroso units will either be 3/8" or 1/2" . Keep everything away from the heat as much as possible, and the shortest lines and least amount of bends and fittings as possible. You will be glad you did it this way!! TR
Can't go wrong with that setup... I still think 1 big regulator would be ok, and one less thing to screw with / fail.
Yes exwestracer agreed either or will be fine, I gave swade the part# for the single inlet and dual outlet regulator, same range of adjustment, perfect for his application. You guys have a great Christmas.
that is more than enoug for your set up. U can run carbs twice that big with what u have. You will be fine.
How about a couple ideas on how to plumb this ? I will have the "Y" block attached to the end of the fuel line where the regulator is in the earlier pictures. Now I could make a wider bar to attach both regulators to, keeping them both in the location of the single regulator now. Or where else could these be mounted ?
You do not need another regulator. Take the gauge out and run from that port to the other carb. If you feel that you need a gauge to monitor the fuel presure they make a fitting that will go inline for the gauge to screw into.
So in my quest for more knowledge I had sent an e-mail to the tech section of CarCraft mag. a while ago when we were discussing it here. Well I was quite surprised to see it in print with a half page spread of the ol Henry J's engine in the latest (June) issue. Jeff Smith gave a pretty good diagnoses of some possibilities and it was a good read to hopefully help someone else out. Now of course I had switched to dual lines to the carbs in the meantime...lol
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