 Fuel line diameter and fuel pressure |
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| Scott S |
 Oct 20 2011, 04:45 PM
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#1
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Small Member  Group: Members Posts: 1,697 Joined: 30-April 03 From: Colorado Member No.: 633  |
Hi All –
Will reducing the diameter of a fuel line cause an increase in fuel pressure? I am installing my fuel distribution block tonight. The line from the fuel pump is 3/8” and goes to a 3/8 barbed fitting on the inlet. The outputs (two of them) are 1/4” (using a 1/4” to 5/16” barbed fitting on each output). The fuel line is 5/16 from the outlets on the distribution block to the PMO fuel rails on the carbs. Attached is a pic of the block itself. The reason I am asking is that I will be installing a fuel pressure gauge and want to get as accurate of a reading as possible. There is a perfect place to install the gauge on the 3/8” line going into the distribution block. However, if the reduction in line size causes a pressure difference, I will obviously want to find a location on the output side on the lines going to the carbs. Will installing the gauge on the inlet side work? Am I just being too anal? Attached image(s) 
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Replies(1 - 5)
| luskesq |
Oct 20 2011, 05:35 PM
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#2
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Member Group: Members Posts: 276 Joined: 24-October 10 From: Fresno, CA Member No.: 12,303 Region Association: Central California |
I pulled the following out of a discussion on water pressure. It should be applicable to what you are talking about. Reduction in size of the line reduces the flow rate but not the pressure. "No. Pascal's Principle states that a pressure applied to a fluid system at rest is felt throughout the entire system."
As to whether you are being too anal, I can't address that. (IMG:style_emoticons/default/lol-2.gif) Keith Read more: http://wiki.answers.com/Q/Does_decreasing_...e#ixzz1bMrX3ggH |
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| JeffBowlsby |
Oct 20 2011, 06:44 PM
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#3
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914 Wiring Harnesses Group: Members Posts: 8,510 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None 
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Whatever...just adjust the pressure to what you need on the gauge at the regulator...
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| IronHillRestorations |
Oct 20 2011, 06:50 PM
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#4
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I. I. R. C. Group: Members Posts: 6,719 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None
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I wouldn't worry about it.
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| Cap'n Krusty |
Oct 20 2011, 08:09 PM
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#5
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Of course that gauge is apt to be about 10% off, one way or the other, and anything you add to the system increases the possibility of a high pressure leak. It's rare that you need to adjust the fuel pressure, unless it's previously been "adjusted".
The Cap'n |
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| Scott S |
Oct 21 2011, 09:14 AM
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#6
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Small Member Group: Members Posts: 1,697 Joined: 30-April 03 From: Colorado Member No.: 633 |
Thanks All Capn - This is on my carbed -6, so it is a low pressure system. I did a pile of research and decided to go with the Carter 4070, as many folks said a regulator was not needed (here is one of the articles: http://www.racetep.com/webfuelspark.html). I figure I can always add one later if it is an issue - but it makes having the guage fairly important in my opinion. The other issue is the price of fuel injection hose - holy cow. I think I have 100-125.00 into the stuff. To cut it for an inline gauge install that turns out to be wrong would be a bummer. Thanks again - Scott |
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