I have the HT383 with a Holley 650dp and a Carter 6900 mechanical pump. I've been losing pressure (see previous posts). I've read on the pusher pumps to assist the gas flow. Any recommendations? I have a Holley in line, came from a pro jection 670cfm, pushes 43gph. Will this be ok? Run this to the carter to a regulator and hook up the return?

 

A Carter P4594 make a good "pusher pump" , no regulator is required. Reroute your fuel lines away from the exhaust heat. Check any rubber hose joints in the system. Especially on the inlet Feed side of the pump. The low pressure on the feed side combined with engine heat makes these rubber line joints collapse and restrict flow. Especialy on bends.

The low presssure/ near vacuum condition on the feed side of a mechanical pump make the fuel more likely to boil in the lines from heat soak.
Pressureizing the line and getting it away from engine heat should cure the loss of fuel pressure you're seeing.

The engine mounted mechanical pump also picks up heat from the engine block. Try one of these heat shield gaskets.

Canton Racing Products #85-000 and #85-010

These heat isolators used to come installed on cars but often get thrown away and are hard to find replacements.

Essential stuff.

 

Fuel pump seal and heat spacer with special bolts

 

here's a pic

You can get one from Bicknell Racing Products (USA or Canada)

 

I've used 2 different ones over the years. My old stand-by is a Carter 5PSI street pump (72GPH). Worked reliably for me for many years. When used in combination with a high volume block-mounted mechanical pump it's been good for well past 500HP. It is rather noisy, though, even when used with the supplied rubber isolators.

That's when I started using the Holley "Red" pump with 7PSI and 90 GPH. More volume than the Carter and runs a lot quieter, too!

Either one will work well if used in combination with a block-mounted mechanical pump. Both are low enough pressure that you don't need to use a separate regulator- the mechanical fuel pump will do the pressure regulation for you.

If you choose to use a high pressure electrical pump (such as one designed for a fuel injection application) then yes, you will need to use a regulator with a return line. I think, however, you'll be money and labor ahead to simply use one of the pumps I recommend, above.

 

Wow, thank you so much F-bird and Damon.

I tried the pusher pump (Holley Projection pump with Aeromotive reg) with the mechanical and the pressure slowly went to "0" again. I looked at the floats and the rear went dry before the first did. Shut the car down and So then I took off the mechanical just to test and the TBI pump did the same thing...started up with 6 psi and after 15minutes it slowly goes to 1 (this is where I shut it off and just walked away).

I just put on also a Aeromotive bypass reg. 13301. To send the fuel back to the return and made 100% sure it's hooked up right. I have a filter, from Zone, right before the electric.

I re-routed all my lines and even put heat barrier material and then put a heater hose over that. The line feels cool to the touch. I have two pressure gauges and both read the same, one is on the line and the other is routed to under my cowl hood. The carb also has an insulator so it's away from the intake.

I pinched the return line and pressure jumps up in the feed line.

I'm searching for an answer and appreciate the help. I just want to drive the car without any worries on this pressure.

 

A re you sure there is not a piece of rubber fuel line up near the fuel tank that is collapsing?

 

For a good, reliable setup I would run a Mallory 140 or 240 pump with a 4307 regulator.

 

F-bird, that is a possibility. I also think that maybe since the tank sat for 5 years that it could have some senditment. I tried to clean it out before it sat but you know how that goes...so I plan to run a line into a gas container (like for the lawn mower) and see how it runs. If pressure stays, then it's the tank and the project continues.