Recently installed Holley afpr w/Autometer gauge under hood. i was adjusting pressure w/vacuum line off and forgot to hook it back up-woops!! Went to local track and only ran best time of 14.57. would vacuum line off make a lot of difference? opinions please!

 

im not 100%, and anyone can jump in and correct me, but with the vacuum line off, doesnt the pressure get affected? i think it would stay teh constant psi you set it at instead of it varying when the line is attached. You could of ran a little rich, and then evened out, but im really just taking a guess, im not sure about the fuel system.

 

i just installed a holley AFPR. the instructions say to adjust it with the line off. with the line on the gauge read about 43. unplugged it and it jumped to 50. thats where i left it at.

 

I do believe you are correct, from the looks of things in my car, through trial and error, when you disconnect the vacuum line, you are setting maximum fuel pressure. So running with the line off, is something I really wouldn't recommend. You'll be running rich at idle and low speeds which from what I've read, isn't a good thing to do to you engine.

 

cool... i really wana get a holley unit. i might get one cause im tearing apart the motor for the heads and cam im putting in, so why not take care of any fuel problems i might have, and get a afpr. hope theres some money left in the budget.

 

what i really meent to ask was, Would line off have slowed me down?

 

I would have to say yes, not by much of course, but as long as the engine isn't running at optimum performance all the time, there's going to be a little lag. In your case though, the only thing I would think that may have bothered it, assuming your foot hits the floor when the light turns green, is in the later gears. Even though you're still flooring it, 2nd doesn't need as much fuel as 1st, 3rd doesn't need as much as 2nd, ...etc. So I would say that there is a possibility of you getting richer in fuel mixutre further along that could be slowing you down.

I'm no expert so I could be wrong on this, I have an interior fuel pressure guage and when in 1st and foot to floor, it rockets to about 48 PSI, and during every shift, lowers a little, bit until 4th where I have 42-43 PSI.

 

It wouldn't slow you down much, if any.


You're at WOT when racing. With the line off, you're at no vacuum. (which is why you adjust for WOT by no line attached)