Need ideals for an Electric Fuel Pump & location

[1969_Mach1 333]

Did you ever try it without an air filter just to rule that out?  K and N has some information to size their filters.  It's a little surprising how large they specify.  Typically a 14x3 for a 351 at 6000 RPM.  What kind of flow rate it that fuel filter rated at?  10 microns is a fairly fine mesh filter for a carburetor.  Is your fuel pressure gauge before or after the filter?  Just an FYI I run this 40 micron filter between my pump and carb.  https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/filters/carbureted_filters/parts/162-562

Holley also has the identical filter in their Earls line for a lower cost which is the one I use.  I wasn't certain what micron rating fuel filter to use when I purchased it.  The information I found all said 40 microns for carbureted engines and located between the pump and carb and 10 microns for fuel injected engines located between the pump and fuel injectors.  I haven't had any issues with the 40 micron filter.  I wonder if your fuel filter is the whole problem.

 

Because I don't drive mine mush I occasionally remove the carb and spray it off with carb cleaner.  I see residue from fuel evaporation but never a gel.

 

Mike

[MikeStang 247]

You check the float levels? May want to bump them up.

I don't recall what your build is but my best friends 69 with a 393 made 410 hp to the ground through a 5 speed using a 750 Vac sec Holley and Stock Fuel pump and a piece of 1/2" steel line to the carb, and he was running rich through much of the pull.... So unless your making 500 or so HP I can see why a stock pump wont keep up unless its bad or something is going on with the carb or you have a restriction from the tank to the pump.

[1969_Mach1 333]

I thought I mentioned float levels.  Prayers1 seems fairly knowledgeable about that carb and it has sigh glasses on the bowls so I figured it was okay.  Right now, to me, the small screen size of his fuel filter is questionable for a carburetor.  10 micron is more suited for fuel injection and may not flow enough at the lower pressures of a mechanical fuel pump.  I would replace that with a 40 micron filter that flows at least what the fuel pump is rated at.  The air filter is also questionable but I know others here run a shaker with stock size air filters.  I'd also open up the carb and make certain everything is clean.

 

I've done the math in the past and it takes in the range of 33 gallons per hour of fuel to make 400 hp.  33 gallons per hour is about at the limit of a stock fuel pump.

 

Sometimes with me anyway, when several items can cause or contribute to an issue I start making certain everything that can cause the issue is correct instead of trying to find a single item.  That's the approach I was taught and so far it has worked since sometimes it's several small items together causing the problem.

[sportsroof69 13]

What valve springs do you have? How old are they?

[1969_Mach1 333]

What valve springs do you have? How old are they?

That's a good question.  I think his motor is fairly new.  Hopefully the springs match the cam.  I don't know what RPM range the cam has.  The intake duration is not very large and its on a 110 LCA.  The 110 LCA is good for a street performance motor but it will narrow the power curve compared to a 112 LCA.  I imagine the upper end of its power curve is in the 5000 to 5500 RPM range.  But the OP mentioned the issue seems to start at 3500 RPM.

 

 

On a side note:  Not trying to hijack the thread.  But I always thought Isky cams had an interesting tech article on split duration cams.  Here is a link if anybody is interested.  http://www.iskycams.com/tech-tips-2000.html#2003

[sportsroof69 13]

It wouldn't be the first time I've seen someone install a cam and not use the right springs, and if it just stops making power before it should, with no other symptoms, valve springs can be a culprit.

[1969_Mach1 333]

That's true.  The fuel pressure drops off a fair amount at the same time the power starts dropping off, 3500 RPM, with two different mechanical fuel pumps.  Then when the OP mentioned a 10 micron fuel filter is installed I thought possibly the fuel filter may be causing the fuel pressure to drop off.  Everything I have read states a 40 micron fuel filter is recommended for carbureted applications between the pump and carb.  There is also a relatively small air filter as well.  I have seen that limit upper RPM ranges but I don't know for certain how much that would contribute to his issue.

 

There could be a few things a little off contributing to the issue. 

[prayers1 153]

1969_Mach1----Your right on that 10 Micron, SORRY my bad, its not a 10 Micron, it's a 35 Micron

 

At first I had one of those Jegs 40 micron from pump to carb with the Fuel Pick up sock still on.  I just recently took the Sock Filter off, about 1ft from the Fuel tank I put in a Holley trash filter 100 micron and a Earls 35 Micron filter from pump to carb per Summit Tech advise.

 

1500 miles on motor

 

Cam rpm range 6000

 

Carb fuel window is 3/4's

 

Check out spring rate below

 

Here's my build:
351 4v Iron Closed Chamber 63cc heads, SS valves
Scorpion Pedestal roller rockers
Bullet grind 541/559, 270/283, 50@ 220/231, lsa 110
Springs #145@1.800 & #350@1.200
RobbMc Fuel Pump.
Blue Thunder Intake
Carb- Quick Fuel 735 Vac Sec
Sandersons Shorty headers
FlowMaster 40 out to tail pipe
4 speed AOD and 2600 stall
Mallory 47 ser. Unilite Dist w/ ProMaster E-Coil 41000 volts
4:11 trac-lok 9" rear

[Rsmach1 71]

Just a thought, have you thoroughly checked and blown out the hard line from the tank to the pump? Also verify it's 3/8 and not 5/16.

[1969_Mach1 333]

Good point RSmach1 since it was an original 302 car.  If that is okay it is proving to be difficult.  There are a lot of good parts on the motor.  I think at this point, if it were mine I would go back to looking at the secondaries on the carb.  How much are they opening.  Like I mentioned I've read about rigging up a paper clip on the secondary dashpot actuator rod.  With it snug against the bottom of the dashpot it will slide on the rod as they are opening and thus indicate how far they are opening. Also, open the carb to clean it and be certain everything is okay.  Ideally, if there was another carb to try that would confirm whether or not there are any issues with yours.  I still question the air filter size. 

 

It's a lot of work to install an electric pump and new 1/2" fuel line like your original plan not knowing for certain that is the cause.  I still don't understand why the fuel pressure drops off so much.  Did you ever try it without any filter on the suction side to see if there was any difference at all? 

[prayers1 153]

The 3/8s fuel line from tank to pump is new as well as a new SS tank and Scott Drake SS pickup.

 

I can remove the filter elements on both and try it w/o. Since all components are new, I feel w/o any filter element I shouldn't have any problems with debris.

[Rsmach1 71]

A 302 car should of had 3/8 as well, but unless you're the original owner you never know what's been done by PO's. For that matter who knows if Ford was out of 3/8 lines that day lol. But I would definitely check and blow the lines with compressed air.

 

Edit. Just saw your post, wouldn't hurt to try that. Maybe just get a cheep inline filter right before the carb just to be safe.

[sportsroof69 13]

I think you're taking a false security in new parts. Lol

[1969_Mach1 333]

A 302 car should of had 3/8 as well, but unless you're the original owner you never know what's been done by PO's. For that matter who knows if Ford was out of 3/8 lines that day lol. But I would definitely check and blow the lines with compressed air.

 

Edit. Just saw your post, wouldn't hurt to try that. Maybe just get a cheep inline filter right before the carb just to be safe.

Good idea, I would first try it with a filter between the pump and carburetor.  Is this the type of fuel filter you have between the pump and carburetor?  http://www.summitracing.com/parts/ear-230106erl/overview/  I had one for a while, I replaced it, it just seemed physically small.  I don't know if it would have caused any issues for me but I replaced it with a this larger 40 micron filter http://www.summitracing.com/parts/ear-230616erl/overview/

[prayers1 153]

Yes that is the exact one I just put on, but I had a 40 micron JEGS style before that.  Been to busy at this point to get to the car but first chance I try those experiments . In the mean time any other ideals please drop a note.

You guys are great, Thanks!

[sportsroof69 13]

Maybe I missed it. What's your total timing?

[prayers1 153]

initial 16, Mech 20, total 36

[prayers1 153]

I took the rear 100 micron filter out and changed to a quicker advance curve, I didn't feel comfortable taking the front 35 micron filter out.

Took it for a run and the fuel pressure went from 6 to 4 at 4000 rpms. I didn't feel any difference in regards to my shorter advance curve.

 

I did apply the brake and gave it gas to see where it started to move and it was around 1400 rpms, does that mean anything with a 2600 stall.

 

 

[1969_Mach1 333]

If I understand, the fuel pressure was better but the performance was the same?  Or was the performance any better?  It seems at least the fuel pressure will be even more stable if a physically larger 40 (or 35) micron fuel filter replaced the current 35 micron fuel filter.

 

What air filter are you using during these tests?  Here is a link to K&N's formula to determine a suitable K&N filter size.  http://www.knfilters.com/filter_facts.htm  Take a look at it, it may be surprising.  You need to scroll down the page a little to find it.  You also need good clearance between the air cleaner lid and top of carburetor choke horn.  Holley recommends 1" but that's tough to obtain on these cars.  Maybe unrelated to this issue but larger diameter air filters work better.  They allow the air to straighten out more and be a little less turbulent when it enters the carb. 

 

I was wondering a bit if the fuel pump arm was starting to float affecting the fuel pressure.  I know at least on 351W and other Windsor engines the Carter and Edelbrock high volume fuel pumps have an additional return spring installed to assist the arm to return at higher speeds.  Regardless, even without an additional return spring the fuel pressure issue shouldn't start at those low RPM's.  Just a thought that popped into my head.

 

I think I would still open up the carb, clean out the residue, and make certain everything is correct.

 

I am not familiar with high stall torque convertors.  I don't think there is an issue there.  I do know the same convertor on a small block motor will have a lower stall speed than if it were installed on a big block motor.

 

Mike

[prayers1 153]

On that test I ran it w/o the air filter.  i don't know if changing from a 35-40 micron would be any significant difference.

 

The only other explanation could be the eccentric for the fuel pump arm. I brought this question up to an engine builder friend of mine and he said there are two types, one thick and one thin, If I have the thin one then it should of came with a cap to make up the difference. If the guy who built my motor didn't do that then that may be the problem.

 

As for cleaning the carb, I guess it wouldn't do any harm.

 

I gotta pull the oil pan off this weekend due to n oil leak, I'll see if there is anything unusual on the fuel pump arm.

 

I still would like to try an electric pump as per my opening statement.  The only problem is finding a reliable one w/o putting one in the tank since I show the car in Stock Class.

 

1969_Mach1 - Now that you know all the specifics on my build, how many GPH due you think I need on an electric pump.

[1969_Mach1 333]

Well I'm not certain what flow rate electric fuel pump you may need.  It's based on horsepower.  Here is a simple formula based on horsepower that's on Edelbrock's site.  http://www.edelbrock.com/automotive/misc/tech-center/tech-discussion.shtml#fsr  Ford Racing also has the same procedure in their catalog.  Most mechanical street performance pumps are rated at 110 to 120 GPH and support 550 to 600 hp.  I thought of an electric pump for mine as well some time ago because mine sits a lot and the fuel evaporates from the carb bowls.  But it seemed the cost was going to be high because most electric pumps in the $200 or less category had reviews of either too noisy or unreliable or both.  I do know the most reliable electric fuel pumps are in tank pumps.  I think its because being submerged in fuel helps to cool the pump.  

 

I know Windsor's have either a two piece or one piece fuel pump eccentric.  The one piece is the desirable style.  I can understand why there would be an issue if the builder only installed the inner ring of a two piece eccentric.

 

Mike