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1969 Mercury 429 fuel line issue w/ dual feed Holley

4K views 9 replies 6 participants last post by  JJU9507 
#1 ·
I am reaching the end of installation of a fresh and mildly upgraded 429 into my old Mercury. I have a Holley 4160 with a dual feed setup and the point of connection from the stock fuel line to the dual feed line are not even close. I plan to put the fuel filter on the line to the stock pump, so that will eliminate one item on top of the engine. I would like to use the stock line if possible, just wondering how others have plumbed for this situation.
 

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#3 ·
Get one of these to put the fitting on the carb line much farther back.
https://www.summitracing.com/parts/hly-34-160
Grab a 3/8 npt X 3/8 inverted flare elbow. I think the OEM fuel pump to carb line ran up the front of the block over the top of the intake next to the valve cover on the other side of the dist.You will need a piece of steel tubing and a double flaring tool because I like hard or braided line on the pressure side of the pump.You will find all the fittings you need on the Parker inverted flare fitting site,get their numbers,buy them anywhere.
 
#4 ·
I don't think you will be able use the stock line without rubber hose,if you want stock lines from the pump to the holley with center pivot bowls you could order the line for a 429 SCJ,this will require replacing the front bowl with one from a 390GT,428cj/scj,or 429 boss or scj or boss 302 carb and replacing the rear bowl fitting to be compatible with a stock ford HP holley crossover tube, obtaining and using the tube.The inlet line will come into the driver side of the front fuel bowl thru a filter and fuel to the rear bowl will go out of the passenger side of the front fuel bowl and thru the crossover tube back to the passenger side of the rear bowl.Using the stock fuel inlet filter will still require a short piece of rubber hose to connect the line to the filter.If you wanted to eliminate the stock fuel inlet filter there are fittings available to replace it with one that accepts a 3/8 inverted flare fitting and I believe a line is available to eliminate it.There are a few companies that make prebent fuel lines that should be able to fix you up or you could fab your own if you have the tools.The original front fuel bowl on your holley is not drilled and tapped for fuel fittings on the drivers side hence the need to replace it unless you know of someone with the ability to do the necessary work.Plumbing it this way would give a clean stock appearing setup that uses hard line all the way to the carb.I believe the fittings and lines are all available as reproduction.You can google images of any of the carbs I listed and get an idea of what it looks like,it won't have quite the fuel flow capability of the dual feed setup you currently have but should have plenty of flow for the mild engine you describe.
 
#5 ·
Thanks for the replies! I gues it never occurred to me that I could get a shorter dual feed line than the one I installed. I think I'll go with a shorter one with a 90 degree barbed fitting, and a rubber hose from the stock steel line. Several more days out from the first start!
 
#8 · (Edited)
I wanted to share an update about the 429 in the Merc that is one of those things that makes you feel like a dunce. The engine developed an intermittent missfire under load two years ago. I don't drive it often at all and work on it even less, so I have changed several items that I thought might be the problem over the past two years. I replaced the fuel pump, the Pertronix module, the coil, cap, rotor, along with resetting the timing and readjusting the carb. Nothing had much effect and the missfire under load got worse over the two years. I was starting to think I had a lobe wearing off the cam. In February I had a wild idea to replace the plugs with copper core and replace the wires with Accel wires. I finished that and didn't test it until this past Sunday. I am pleased to report that my old 429 is back in business! I am amazed that the simplest parts were the culprit all along. This 429 sounds great again!
 

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