. I turned into a side street and opened the hood. use a 1/16 - 1/8" restrictor in the end of your fuel line to see if you can set the pressure then. Too much fuel pressure for a given needle and seat . FREE SHIPPING on most orders of $35+ & FREE PICKUP IN STORE. It is a measure, as I understand it, of how readily the fuel will evaporate in open air. From that time on octane ratings slowly rose, helped by the addition of more and more tetraethyl lead. The pressure regulator works fine when mounted flat, but should work ok when mounted on it. A vapor lock condition would be caused. The reliable, albiet slower, stovebolts never suffered vapor lock because the fuel pump and lines were up front in the airstream of the engine fan. There was a problem adding this item to Cart. I can start my car instantly after sitting in a cool garage at about 75 deg F. Drive 30 miles and then park for 20 minutes. Worked well out of the box. Rusty, thanks so much for this information. The float has a needle that projects through the top of the carburettor so it is possible to see whether the float is "floating" or not. So, I take the reg apart to see if it is all clean and looks good. Holley Fuel Pressure Regulators 12-803 HLY-12-803. P/N 12-803, 12-803BP, & 12-804 Installation Instructions 199R7914-3 NOTE: 12-803BP IS NOT TO BE USED WITH MECHANICAL FUEL PUMPS! There is a light spring that helps push the ball against the the seat in the direction of the fuel flow. I do not have a pressure regulating valve to reduce the pressure from the pump but it works fine with no flooding under normal conditions and I have fitted a modern soft seat to the float cut off needle. From propelling the LS-, Coyote-, and Gen 3 Hemi-swap trends, to continuously innovating late-model and vintage vehicle performance, Holleys commitment to its customers and their cars is at the core of everything we do. Changing the vapor pressure (and thus the boiling point) of gasoline is not new. Rusty, if you can find a cooperative local high school chemistry class, take a small amount of gasoline, split it into 2 portions, add 5% or so kerosene to one half, and have them do a fractional distillation on both. I would like to try IMCT, how is it sold? Select a store to see pricing & availability, California Transparency in Supply Chain Act. All Holley regulators are pre-set at the factory so there is no guesswork when first installing the regulator. December - February gas mixture begins to vaporize at 11-15psi at 105 deg F, April gasoline is 9-11.5 psi at 124 deg F. If you had winter gasoline in your Antique car on a 100 deg day you would only be about 5 degrees from vapor bubbles in the fuel. Is there a brand name? If your having pressure controll issues with the Holley regulators you can eliminate most problems with stability by installing a by pass line back to the tank and usualy a street car can use 1/8 copper. Going to check my VW bus fuel pump pressure. Any of these heavier than gasoline petroleum distillates above will raise the vapor point of gasoline if mixed into it. Lots of Chinese Holley 12-803, 804 etc knock-offs are available. Discussion in 'The Hokey Ass Message Board' started by oldrelics, Oct 12, 2010. Check the status of your Shipping was fairly fast. The higher the RVP, the greater the tendency to vaporize or vapor lock. Purchased the regulator from Baxter, unit arrived in 4 days.. Unfortunately, these FPR are now made in Korea and they no longer include an alternate spring. The summer gasoline vaporizes in the line and the heat soak is quicker and longer on hot day's. [endif]-->,