Is 8 psi too much?

[matt63]

I finally installed a fuel pressure gauge on the 408.  It reads 8 psi after the filter.  The engine has a mechanical pump.  Is 8 psi too high? If so, where is the best place to mount a regulator.  I was trying to stay away from an inner fender mounted regulator set-up.

[pink panther]

I'm setting at 6/12 on the guage running a 6 pack.  Think I heard somewhere you only need about 4 pounds or so

[MEK-Dangerfield]

I would prefer to see 5 or 6 PSI. You are kind of pushing it at 8 PSI. If your car is running fine, then I guess you are good to go. Otherwise, gas would be forced down your carb., and I think you would notice it running bad.

  Mike


EDIT- I have a hi-volume mechanical pump. At start-up, I generally am getting 8-9 PSI. Once I drive it around, it drops to 5-6 PSI, which is where I have my regulator adjusted for. If you are getting 8 PSI at start-up, then your's is probably dropping a little like mine too.

[360 'CUDA]

Staying at 8 psi though is bad.
It could stick the needle valve open on the carb and fill up the bowl too fast.
Then the gas has no place to go but out the vent.
(don't ask me how I know this)

[matt63]

I think the engine is running a little rich although not extremely.  I've adjusted the idle mixture.  What would cause the fuel pressure to drop after driving it awhile?

[70nos340 barracuda]

if u don't want to put the reg. on the fender u could put it close to the carb use a carb bolt to hold the bracket, or on the valve cover bolt etc. i may be wrong but i think the closer to the carb the better anyway.

[matt63]

I'll try and find a compact non-return type regulator so I can do this.  I might have to move the filter and put it down low nearer the pump.  I should of gone electric!

[pink panther]

mine is on the passenger inner fender and like I said 6 1/2 psi.

[augie]

I finally installed a fuel pressure gauge on the 408.  It reads 8 psi after the filter.  The engine has a mechanical pump.  Is 8 psi too high? If so, where is the best place to mount a regulator.  I was trying to stay away from an inner fender mounted regulator set-up.

Are you running a Holley? If so, How modified is your engine? Do you have a high compression ratio? What rear end gear do you use? What size of accelerator pump do you have? 50cc or 30cc? What size of convertor? All of these factors plus some will determine your pressure. On anything modified, single 4, 8 or 9 psi is where I'd keep it IMO. 
 Reason: You do not want your bowls drained or low during a pass. DAMAGE. My example is a extreme one (My Challenger) 13:5 compression ratio, 4:88 gear, 8 inch stall, 50cc pumps etc.. I run two 660 center squirters at 10 psi and have for over 12 years. I'll drain the bowls right after launch at 8 psi from the regulator. Car will just fall on it's face! I must have 10 psi or else. I also use a Mallory 250 gph pump. I set the pump at 20psi to the regulator, from the regulator to the carbs I set it at 10 psi. With a 250 gph you need a special regulator that will handle higher pressures also from the pump.
 A stock fuel pump you'd be lucky to see 6 psi, and there's no way on earth you should be using a stock pressure on a modified engine. Too lean will create an issue remember. Also a Holley needle and seat should take up to 12 psi without blowing gas. If you are blowing gas at that pressure, then you should consider a new needle and seat. Hope this helps some.

Here's the regulator I use
http://www.jegs.com/webapp/wcs/stores/servlet/CategoryDisplay?storeId=10001&catalogId=10002&catalogIdentifier=Jegs_Direct&categoryId=14185&parentCategoryId=10323

here's the pump
I use the 250 gph
http://www.jegs.com/webapp/wcs/stores/servlet/CategoryDisplay?storeId=10001&catalogId=10002&catalogIdentifier=Jegs_Direct&categoryId=17279&parentCategoryId=10307

[Fast Finch]

I have a PSI regulator on my engine set to 6. My engines a 440, 60 over with an edelbrock 750cfm 4 barrel. I have an electric pump.

Michael

[Chryco Psycho]

with most carbs in most applications 6 psi is correct

[matt63]

My fuel pressure does drop to 4-5 psi when the engine is hot.  I still don't understand why it would do this.

[Fast Finch]

My fuel pressure does drop to 4-5 psi when the engine is hot.  I still don't understand why it would do this.

Matt,

You may be suffering from a small vapor lock problem.  Wrap your fuel lines near high heat sources, i.e. headers and exhaust.  This should fix the problem and it's easy to do.

Take care
Michael

[MEK-Dangerfield]

Matt,

You may be suffering from a small vapor lock problem.  Wrap your fuel lines near high heat sources, i.e. headers and exhaust.  This should fix the problem and it's easy to do.

Take care
Michael

Michael,

    As I mentioned, I get 8-9 PSI at start-up, with my regulator set at 6(mechanical hi-volume pump). After driving a few miles, it does drop to 6. I can't explain it. Maybe some initial surge, or something?  As long as his pressure drops to 4-5, that should be fine. Get lower than 3, and I would worry. 


  Mike

[Morris'_Mopars]

I run 8-8.5 on my cuda. -No Problems