Jazzman’s #8745 "Flip Top" Build

[edwardb]

Sorry for being late to the party on fuel line size and filter usage. Often when I'm browsing thru posts, I see something that I want to be certain about for my anniversary build. First the fuel line size. I have a Forte supplied Dart 351stroker (427) with a mild cam -450 hp. I have read a few postings on the fuel line size but want to be certain. I am running an engine mounted fuel pump with no return line. And, of course, no in-tank fuel pump. The kit comes with a 5/16" size fuel line which I have already run. Will I regret not switching to 3/8".

Second, I have read that installing the supplied ffr fuel filter, for my set up, between the fuel tank and mechanical pump is a no no as it could lead to fuel pump failer. Mike Forte tells me he installed an in line filter at the carburetor. Am I correct on this topic?

I am probably not the best expert on this topic, ThickCobra, but I will share what I have learned. I am going with the Coyote engine, and there seems to be consensus that the 5/16" lines are adequate for "mid range" builds. EdwardB (certainly an expert far beyond my own knowledge) is a proponent of the 3/8" lines and has used them on two builds. His current and previous build threads have a good discussion on the reasons he believes that the larger lines provide a larger margin of safety for higher horsepower installations. The reason for the concern about the in line filter has to do with unnecessary strain on the fuel pump leading to premature pump failure. I went with an in tank fuel pump, but a higher volume pump. I'm sorry I can't give you specific information about your setup.

Let me give a couple responses to this. I'm far from an expert. Several builds and the resultant experience, yes. But I'm learning as I go too. My first build, a Mk3 with a pretty strong 306 SBF, used the stock 5/16 FF lines. (See, I can use the parts that come with the kit. Sometimes...) It's a mechanical pump/carb setup, and certainly has never had a fuel delivery issue. Runs great, now with another owner. I spent a long time looking at multiple forums and data when planning my last Mk4 with the DART 347. Found everything from the 5/16 stock lines are fine to guys that went with 1/2 inch lines. (Really!) When all was said and done, 5/16 probably would have been OK, but 3/8 was probably safer. But the tipping point was I wanted to do SS lines, just because, and there was little/no difference in 5/16 versus 3/8 at that point buying the material, bending the lines, doing the installation, etc. Very similar rationale with the current Coyote built. The data shows 5/16 feed and 1/4 return flow enough fuel. But several pump and regulator instructions suggested using 3/8 lines for both, and again because I decided to use SS for the lines (I can't seem to get enough punishment) it was a no-brainer just to do them in 3/8. So in both cases, was 3/8 really needed? Maybe not. But it was what I wanted to do and eliminated any possibility of the lines being undersized. Needless to say, having to change them after the build is done would not be fun.

So those were the reasons behind what I did. I would be inclined to suggest 3/8 lines for a 351 based 427, but I can't say with data you would ever outrun the 5/16 lines. If you do a search for HP suggestions for various fuel line sizes, you will find the recommendations all over the map. Over on the other forum you will find some of that too. You're describing a pretty mild 427, probably even a bit less than the pretty strong 347 in my Mk4. But I personally would still lean towards the 3/8 inch lines. But then you've seen my rationale, so you can decide if that means anything to you.

What I can say with confidence though is for mechanical fuel pump systems, do not put the filter between the tank and the pump. That is only for EFI systems. For a mechanical fuel pump setup, the filter should be between the fuel pump and the carb. In both cases there should be a rough filter or screen on the pickup (or pump) in the tank.