[mmm]

Hello PY,
I just got the 455 back in my Firebird last week. The combo is the same as it was before, just a new shortblock. Anyway, what unfolded was this: just before my old shortblock ate the #6 rod bearing, I had installed a Delco stock fuel pump because I was sick of listening to the buzz of my Holley Red. It (the Delco) ran good, but not soon after, I noticed a slight knocking from the engine. I know it was coincidental, but I tried pulling the Delco and rigged the Holley onto the radiator support as a temporary test to see if for some reason the noise was eminating from the mechanical pump I had recently installed. No luck, so I found the real problem & swapped the shortblock. The maiden voyage after reassembly showed a major bog in the upper rpm's, and I think it is due to the fact that the Holley pump is mounted in a location that does not match the way it was engineered (pusher / puller, too high up etc...). I am going to put the Delco back in because I believe it will handle my fuel needs- but after this long winded intro I have this question: I have a Felpro fuel filter mounted on my passenger side fender well. Since it is higher than the stock pump location, would I be hurting performance by routing fuel "up" to the filter, then "down" to the pump, then back "up" to the engine? Also, is a stock pump more resilient to lack of a filter prior to its inlet? I was thinking of just going straight into the stock pump down low, then thru the filter on the way up to the carb. Isn't that basically how it was stock? That's funny to waste a bunch of time trying to route things all over only to return to the way it was designed over 30 years ago!
Thanks, Mike

I'm right at home in a filthy garage

[mmm]

Hello PY,
I just got the 455 back in my Firebird last week. The combo is the same as it was before, just a new shortblock. Anyway, what unfolded was this: just before my old shortblock ate the #6 rod bearing, I had installed a Delco stock fuel pump because I was sick of listening to the buzz of my Holley Red. It (the Delco) ran good, but not soon after, I noticed a slight knocking from the engine. I know it was coincidental, but I tried pulling the Delco and rigged the Holley onto the radiator support as a temporary test to see if for some reason the noise was eminating from the mechanical pump I had recently installed. No luck, so I found the real problem & swapped the shortblock. The maiden voyage after reassembly showed a major bog in the upper rpm's, and I think it is due to the fact that the Holley pump is mounted in a location that does not match the way it was engineered (pusher / puller, too high up etc...). I am going to put the Delco back in because I believe it will handle my fuel needs- but after this long winded intro I have this question: I have a Felpro fuel filter mounted on my passenger side fender well. Since it is higher than the stock pump location, would I be hurting performance by routing fuel "up" to the filter, then "down" to the pump, then back "up" to the engine? Also, is a stock pump more resilient to lack of a filter prior to its inlet? I was thinking of just going straight into the stock pump down low, then thru the filter on the way up to the carb. Isn't that basically how it was stock? That's funny to waste a bunch of time trying to route things all over only to return to the way it was designed over 30 years ago!
Thanks, Mike

I'm right at home in a filthy garage

[george kujanski]

Pumps in general provide more pressure than suction, i.e. it's easier for the pump to pump up thru the filter rather than provide suction to get fuel out of the tank and up to the filter.

Consider the old problem of pumping water out of a pond up to a higher elevation. If you were to take a perfect pump and put it up top, it would provide, say, 29" of vacuum (equiv to a gauge pressure difference of approx. 15 psi. The height of water equal to about 15 psi is about 34 feet, meaning that this perfect pump could suck up water a max of 34 feet. Put a pump down at the water level, instead, and it can provide enuf head pressure to pump the water much higher.

Regards, George

[cscottfergus]

I thought you were supposed to mount the electric pump as close as possible to the tank( in safe location), then the filter comes after the pump. Have you tried that? Or checked with manufacturer?

[mmm]

Exactly. Anyway, my decision to forget about the electric is made up, so I'm just more concerned about the routing of the lines to and from the Delco. From what I remember about first installing the Holley, the instructions seemed to want a filter prior to the pump. On a stock pump though, the filter seems to be on the outlet side if I am not mistaken.
Thanks, Mike

I'm right at home in a filthy garage

[cscottfergus]

From the way I understand it there is a nylon sock in the tank to catch big stuff. Then a fuel line to the pump then to the fuel filter which is an integral part of the rochester carburetor. Then a line to the carb. I have a holley carb on mine now and have an inline canister metal filter that works fine. I think it is about 8 inches from the carb. I would stay away from see through glass fuel filters, the threads can strip out and a fire can result from leaks.

I am not an expert, but I can only imagine that the factory pumps are more resistant to trash due to their positive displacement type action vs. the centrifugal of electrics. At least it think that is right. Someone correct me if I am wrong about why they are more tolerant to trash.

You might want to think about the best routing of the lines to reduce heating of the fuel and insulation.

I think it is bettert to have all Steel lines from pump to filter to carb since they have less chance of leaking than anything else. I beleieve some 60's firebirds had external metal filters with a bracket that held it away form the engine.

Provided there is clearance with your hood. A phenolic carb spacer under the carb would reduce heat transfer also. If you have modified your engine and you are starving for fuel maybe this is a good time to increase fuel line diameter. Talk to the experts about that.

[mmm]

I don't have much of a technical basis for believing so, but I would also like to think that the stock type pump could handle anything that gets past the fuel sock. Well, I think I have a plan now, so we'll see what happens. I do keep the upper part of my fuel line covered with Mallory's heat resistant sleeve just to keep the boomjuice cool.
Thanks for the input!
Mike
Oh yeah, I did at one time use a glass filter, but it now lives at the bottom of one of the many cardboard boxes in the corner of my garage!

I'm right at home in a filthy garage

[cscottfergus]

I think the fact that the engineers didn't see a need to include a filter in the design indicates that they were very comfortable with the ability of the pump to handle trash. You can pump some nasty stuff with diaphragm pumps.

look at picture of diaphragm
http://www.nationalchevyassoc.com/te...og.cfm/2/20/14

You should have an automatic emergency shut down switch triggered to oil pressure I think, if you are gonna keep running your electric for a little while. Safety issue. Ask others. Topic was discussed somewhere around here recently.

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Knowledge is Power