Hi folks,

I'm having a rare minor difference of opinion with my mechanic over how to best plumb the fuel system for my yet to be started 496. I rarely second guess Mike given he is a good experienced professional mechanic whereas I'm merely the hobbyist. I have however recently had opportunity to do some reading on the subject and found that when mounting a fuel filter when using a mechanical pump it should be placed on the pressure side given a mechanical pump will by design push much better than it can can pull potentially avoiding a fuel starvation issue. When I asked Mike to mount the new Aeromotive cannister type filter on the front of the motor adjacent to the pressure regulator he objected stating the aluminum cannister would act as a heat synch. He's right in principle of course, however, I question how hot it actually gets there apart from some radiator heat being introduced from the fan. Mike wants to instead plumb the filter directly onto the 3/8 hard-line coming from the tank placing it against the fenderwell away from all heat sources before the Edelbrock mechanical fuel pump. I am concerned that having it on the low pressure side of the pump may in fact be a greater potential problem than what any radiator heat may introduce having it mounted on the high pressure side on the front of the engine?

Ideally I suppose I would be using an electric pump rather than the mechanical and this would be a non issue. I have found the mechanical pump to be reliable, I like to keep things in their stock location as much as possible and the 140 GPM rating of the pump should be more than sufficient for the ballpark 550HP requirement. Mike may also be under the impression that the cannister is larger than what it truly is given I didn't have the measurements at the time.

Thoughts, opinions and experiences very much appreciated!!

-Andre

 

I have never seen an OE set up with the filter before the pump. What's wrong with mounting the filter in the spot Mike wants and plumbing to it from the pump?

RACE ON!!!

 

i to like the idea of a Pre-Filter but it needs to be a free flowing (not fine) type ... everything iv'e read say's don't but i have done it on off-road cars.. they had a ped-**** to open every so often... the main
filter after the pump cought the real trash

 

It could certainly be done that way it just isn't as neat as fuel lines would be running back and forth the engine bay which introduces a lot more pressurized line into the engine bay which makes me a little uncomfortable. I want to keep it neat and simple as possible is possible but may end up doing something like that though. Want to do it once and right.

Thanks for your input.

 

I also like the idea of a prefilter but this is intended to be the only filter installed in the system. It she should be a pretty free flowing design given it is advertised as as being for street/strip performance but I'm not sold that it is a good idea to have just a single filter before the pump.

Thanks

 

The "correct" technical answer is to have it on the pressure side. Any restriction on the suction side can cause unusual issues. The boiling point of the fuel will lower as you pull a vaccum on it and if there is a restriction, it can literally boil and form bubbles. This will cause pump to cavitate and pump very little. You can chase the problem for a long time because under normal conditions it will pass all the volume/pressure tests.

All that being said, I can tell you I ran a simple basic cheapo in line filter on my 427 combo with mechanical Holley pump for a long time with no issues. I had some silicone type junk that was on the new fuel filler neck gasket that got in fuel tank once and continued to end up under the needle and seat of carb. Silicone doesn't like gas....no idea why it came with the coating...I took a shot and figured it might be some new whizbang stuff. It wasn't! So I stuck the filter on it to catch junk.....it ended up staying there for a long time and the car regularly ran low 11's@123+ mph in TX heat.


JIM

 

Thank you Jim,

I totally agree with you and everything everyone has said so far. I am just more paranoid than usual given this setup is going on my new motor on which I have spent a bunch of money and don't want to sabotage it before it even starts. I'm also into boats, Donzi's specifically, a buddy built a similar engine to mine, broke it in correctly then first time out on the lake ran it at sustained high RPM's, leaned it out and completely toasted the engine in an hour. Just don't want to skimp on any final details I could later regret. I'll have the filter placed on the pressure side as I intended. It really isn't substantially larger than a normal inline filter and will monitor it closely for heat to ensure it isn't a factor. I am planning on installing a pressure gauge inside the car as well so I can actively monitor it when driving. I also think that when Mike sees the filter he will probably say "Oh, that's no big deal, I thought it was bigger".

 

Just to close this up.

Went to look at the car today with a bag full of plumbing parts in hand with plumbing diagrams in pocket. Mike (mechanic) looked at the filter and said "Oh good, it's nothing like as big as I had imagined it to be, It won't be an issue at all".

All the same, to clean it all up we decided to mount the filter and regulator on the back inside of the passenger fenderwell (after the pump of course) with the the fuel rail facing the firewall rather than off the front of the motor. Actually doesn't take that much more line as it needs not "back-track" again, everything will remain nice and cool away from the headers and any potential heat sources. Much much happier with this configuration and will do it all is SS steel hoses rather than hardline for added flexibility given the motor is anticipates to move a little independantly from the fenderwell/chasis.

Thanks to those who provided input. It was very helpful and enabled me to come up with a better solution which I had not previously considered.