Fuel system update on 67 Coronet 440cid

[mopar67440]

Good morning all,

I'm looking to perform a fuel system upgrade to rectify issues related to engine compartment heat and E10 fuel (non-eth. not avail in Mass).
I've dug into all the info I could find on this subject, and looking for feedback on my current plan.

This is for a moderately built street 440 currently with a Carter high volume mechanical pump feeding dual Edelbrock AVS2 carb. with 5/16" line, no regulation, no vapor separation filter and no return line. The fuel pressure is a consistent 6 PSI (boarder line with these carbs), and engine runs strong and consistent with air temps below 85*F. Any higher and we have a problem!

My off-season upgrade plan is to replace the sending unit with a Spectra 3/8" (I'm aware of the resistance issue) reworked with a 3/8" return line and a Tank Meter Match. Mechanical pump will be removed and replaced with a Carter P4395 electric. After pump 40 micron filter at pump for serviceability (maybe 100 micron before), 3/8" supply/return lines routed along frame (insulated) up behind alt brackets like factory to fuel log, then pressure gauge, then Holley Bypass Regulator (set to 5.5PSI), returned via 3/8" to tank.
Attached is a diagram.

Anyone see an issue with components selected or routing issues?
Thank in advance!!!

 

[ckessel]

I have a 67 wagon w/440 out here. We've got E15 and so far it's not bad. When I do get into warmer areas, there is some percolation, but it hasn't been a massive issue. The car has just a standard oe style pump on it. Down the road I want to do multi point efi. I would put a better after pump filter on though. At least 10 micron to keep the junk out of the carbs. I'm using a WIX 33032 5/16" inline between the pump and carb. One thing I did on it was put a Mopar trans pan magnet on the inlet side of the filter for rust. Rust and Holley's, using a 3310-2, are a bad combo since its almost impossible to clean out the metering blocks were the crud hides. Not so with AFB's. On the upcoming fresh engine, it'll have 440 Source heads which will eliminate the heat crossover so the manifold runs cooler. If you're running iron heads, you could use the Fel Pro 1215 pan which has blocked heat ports. That helps too. The addition of Ethanol and other stuff, we have the CARB additive in ours too, drastically lowers the boiling point of the fuel. Last I heard, it's 150* on the boiling point for our swill. And as you know, the underhood temps are much higher than that.

 

[lewtot184]

I use a ch28 with two 1407 carbs. I use a 6903 pump, 3/8" hard line, 1/4" return line with .040" resriction orific. Works great and is very simple.

 

[mopar67440]

10 Micron filter-check
Magnet on filter for rust-check
Thanks!

I have no EGR xover on intake so this is not an issue. I also have 3/16" insulator gaskets on both carbs which helped. Hood has a hemi hood scoop for cooler engine compartment temps when driving. This also helped.

I performed a test with a thermal coupler on the front carb bowl while driving on an 85* day which was right at the thresh hold of fuel issues. I also have an AFR gauge installed. At 30mph and greater carb was below 90*F and engine ran good. AFR near 14. Stop and idle for 15 minutes, and bowl temp rose to 102*F and idle suffered with AFR in the 16's. Shut the engine off for 15 minutes with hood down and bowl temp rose to 125*F. Starting was an issue and idle went to hell (AFR's >17) until driving for another 15 minutes where temp dropped back down to the 90s, AFR returned to high 13s, and all was well again.

My goal is to modernize the fuel system using carbs to minimize any radiational or conductive heat to the fuel system. Meaning no standing fuel in engine compartment, bypass to allow cooler fuel to circulate from tank to carbs, and insulating all lines.

In the future carbs will eventually be sealed to hood scoop once I design a functional but nice looking cold air system... but that's for another topic.

 

[mopar67440]

lewtot184​

I like it. I was leaning towards the same simple approach I read above...maybe even your post. I also have the CH28 with dual AVS2 (650s).

This would allow me to use the current 5/16" line as a return and update the supply to 3/8" with one less component being the regulator. How did you discharge into the tank...gas filler tube or sending unit?

I still think I will use the elec pump to eliminate conductive heat from the mechanical pump. I have leads on an old stock Carter 4594 made in USA pump and avoid the new Chinese crap.

How did you arrive at the 0.040" orifice size?

 

[lewtot184]

I put a 1/4" tube nipple in the sending unit and fabbed supply and return lines. I also use a felpro 13834 insulator gasket under each carb. Real nice driver.

 

[mopar67440]

Like this photo?
Again, how did you arrive at the 0.040" orifice size? I see no gauge on your lines, so did you bleed the return fuel into a bucket and measure it, set a specific PSI or just wing it and say let's try this?

 

[lewtot184]

I use .060" as a bypass go to number because that's what the factory used with high pressure mechanical pumps. I use a 6903 pump which isn't high pressure. I know from track experience and monitoring pressure swings that lower pressure pumps bypass too much fuel to make top end power. I took pumps apart playing with them, i rigged some testing and tried different orifice sizes vs pressure. Anyhow, it was time consuming trail and error, but i knew i didn't want all the electric pump stuff that can stifle reliability. I worked hard to keep it simple. If i were to go to the higher pressure pump i'd just adjust the bypass size to get the pressure i want. Kinda like using the pills on mechanical fuel injection to regulate the system. It's simple and reliable.

 

[lewtot184]

Like this photo?
Again, how did you arrive at the 0.040" orifice size? I see no gauge on your lines, so did you bleed the return fuel into a bucket and measure it, set a specific PSI or just wing it and say let's try this?
View attachment 1957921

i soldered in a piece of tubeing.

 

[mopar67440]

And drill the orifice too size, depending on pump pressure. Got it!
Did you arrive at 0.040" for a carb pressure of 5.5PSI at the Edelbrocks?

 

[lewtot184]

And drill the orifice too size, depending on pump pressure. Got it!
Did you arrive at 0.040" for a carb pressure of 5.5PSI at the Edelbrocks?

Yep. I know .060" or larger will drive but won't perform. I do the math on the area of different orifice diameters looking for percentage changes

 

[lewtot184]

I don't think there are any aftermarket electric pumps that are rated for continuous duty. Modern electric pumps and mechanical pumps aren't compatiable together. Mechanical is more relisble.

 

[mopar1967440]

I don't think there are any aftermarket electric pumps that are rated for continuous duty. Modern electric pumps and mechanical pumps aren't compatiable together. Mechanical is more relisble.

I thought electric pumps were made for continuous duty. They aren't pressure switched, just regulated whether with bypass with cooling or dead headed which slow stalls the pump causing heat.

 

[lewtot184]

I thought electric pumps were made for continuous duty. They aren't pressure switched, just regulated whether with bypass with cooling or dead headed which slow stalls the pump causing heat.

Not aftermarket pumps. You may find a generic in- tank pump thats good but wouldn't trust any holley, carter, or whoever for long term reliability. I chased in my mind what your trying to do and of all the senarios i came up with the answer was always no.