My motor is a 400 bored .040 over, shaved clylinder heads for more compression, a comp cam 268/280 duration & 477/480 lift, weiand dual plane intake, a 750 cfm holley carb, and stock electronic ignition with MSD blaster coil and new taylor spark plug wires. It will cruise above 3,000 rpm fine until I stomp on the gas then it sound like it keeps misfiring, not a problem below 3,000. Ive tried adjusting the timing with little improvement. Could it be some sought of fuel problem because I'm running the smaller 5/16 fuel line?
5/16 fuel line on a 400
- Thread starter moparguy
- Start date
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66dartgt
Well-Known Member
Are you using a high volume fuel pump ? If not - try one, if that doesnt help then look at the fuel line, and increase it to 3/8. Keep in mind that the pick up in the tank needs to be 3/8 as well. By the way, how is the sock filter in the tank and the fuel filter near the carb, clean ? Maybe they are clogged partly or something. Make sure your float setting in the carb is spot on as well. I would also look at your electronic ignition reluctor gap, is it in spec ?
flyboy01
Its almost done!
I just bought a 3/8 pickup and sender on ebay for $58 tw days ago, I also got a new Gas tank for $180 a few weeks ago. I am changing the fule line next with 3/8. I currently have a 318, but I am working on getting it swapped to a 451 by this summer so I am getting things in place to do so.
flyboy01
Its almost done!
Have not had it more than two months, and it has been on jackstands since, so no drag for me yet. I will probably do some when I get the new engine in. I still am not sure 100%, budget will dictate the engine. My budget this summer will be around $4K, so I am definately going to be hitting swap meets looking for deals.
demon seed
The Original Demon Seed
Regardless what fuel pump you run you should go to the 3/8 fuel pickup and fuel line with that engine and carb. First though check your bowl levels and fuel filters cause if the engine is cutting out at only 3000 I'd supect one of the above first. Your mechanical fuel pump could also be crapping out and yes they do make high volume mechanical fuel pumps but plan on installing a fuel regulator at the carb to limit the pressure to 7 PSI.
Terry
Terry
OldVart
Well-Known Member
Before changing out the fuel line, I'd go over the basic tuning steps for the timing, distributor, and carb. While a 3/8" line right from the tank to the carb is desirable, it's definitely not a requirement with the build you have there. Have you tried running the engine rpm up past 3000 while you're parked, to see it it does it then, or if it just happens under full load? The guys also gave some good advice about checking for dirt in the fuel system, and you can also static check this with a jerry can of gas with a known good line direct to your fuel pump. Make yourself up a logic-tree type list, and then follow it until you get to the root of the problem, then change what NEEDS to be changed to aleviate the current problem. Hope this helps.
flyboy01
Its almost done!
This is also a good reason to change you pickup and tank. Here is a picture I took through the filler of the tank.
WoW! Thats a dirty Mo-Fo for sure.
Try the carb tuning and float levels first to be sure. Then go back over the ignition system. Be sure, do not assume.
A 5/16 should be enuff for what you have. The fuel pump after many years can be crapping out for several reasons. We'll just call it old age for now.
Carte/Fed-Mougal makes hi-volume pumps at streetable pressures for use with out regulators. Though a regulator is under a $40 total expenditure by installs end.
I did a 3/8th line in my E body Cuda from sender to carb. Thats enuff for most every street build. Easy install job.
Try the carb tuning and float levels first to be sure. Then go back over the ignition system. Be sure, do not assume.
A 5/16 should be enuff for what you have. The fuel pump after many years can be crapping out for several reasons. We'll just call it old age for now.
Carte/Fed-Mougal makes hi-volume pumps at streetable pressures for use with out regulators. Though a regulator is under a $40 total expenditure by installs end.
I did a 3/8th line in my E body Cuda from sender to carb. Thats enuff for most every street build. Easy install job.
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