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-   -   Presure, Where Did It Go? (http://www.hotrodders.com/forum/presure-where-did-go-2634.html)

rssschevy2 05-25-2002 03:35 AM

Presure, Where Did It Go?
 
Any body, help me please! A 355 sbc,in a 67' nova,with a mecanical fuel pump. Im getting 6-7 psi when the motor is not at operating temps,185 deg. But when it gets warmed up, the fuel pressure slowley drops to 1 to 2 psi and of course runs like crap! So i have changed the fuel pump,with another performer fuel pump,changed the filter, and a new fuel tank pickup 3/8',all for nothing!There are no leaks, and it was fine for a hundred miles or so. The motor is new,afr heads, holley750dp or edelbrock 750, same problem, 10-1 pistons,performer rpm,headers,hi-per hei dist.gear drive.medium cam, th350 trans.Im so confused, frustrated, because i thouht i could fix it. I thought it was a easy problem!!!Any help would sure be highly appr. :rolleyes:

[ May 25, 2002: Message edited by: rssschevy2 ]</p>

Pontiacman 05-25-2002 06:19 AM

Lets see, easiest stuff could be do you have the
proper gas cap, vented I believe on yours, volume of gas sufficient? fuel line off at carb, connect
to hose watch flow while tuning over, dist. wire dissconnected, does flow change?watch for alittle while.Could fuel line be touching block (from pump to carb. Vapor locking)this happenes after warm -up.I'm guessing wrong cap and vapor locking.Keep up posts and let's what shows up as the coulprit.

78 monte 05-25-2002 01:06 PM

it could be vaporlock.check if the fuel line is to close to the headers. maybe an electric fuel pump would help cause you could mount it away from the engines heat.

rssschevy2 05-25-2002 05:12 PM

Hey,Pontiacman & 78Monte,thanks for the replies! This site is a cool place to ask questions and get answers to when you dont have many people to ask. Any how I did last year put aluminum fuel lines, out from any heat source,all the fancy,smancy fuel fittings,then hid all that hi-dollar stuff in the engine compartment area with a thermol-tec sleeve, just so i wouldnt have a heat problem.Last summer the car ran fine here in chicagoland.also as far as the vapor lock, when the fuel preasure went down to 2 psi, I did loosen the gas cap to check to see if there was a suction or vapor lock going on and it didnt help the fuel preasure any! The gas cap is original, heck most of the car is. The motor does get,and engine conpartment too, a little warm, just like most motors do. Its not even warm outside yet were I live! Thanks again for your help. :rolleyes:

Pontiacman 05-25-2002 07:25 PM

Try again your noticeing pressure decreasing sounds like you have a pressure gauge or pressure
regulator in between pump and carb, if so just for fun remove it and go straight to carb( could have flow direction backwards,mechanical fuel pump I would think either works or not.Oh, just thought of something, your fuel line isn't
up to high( on fender or somewhere else high up)
mechanical fuel pump won't work correctly if line is up high ,loses suction, keep up posts


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