School me on 550 hp fuel system please.. i’ve got a 70 GS with the Robbmc 1/2 -1/2 ..barb fuel sending unit with robbmc big anodized fuel filter near the tank... 1/2 (inline tube prebent like factory) stainless and 3/8 stainless metal lines between the fuel pump in the tank. connected with Fuel injection hose where it’s not metal on each end of the car.. i have a 6an line from Fuel pump exit with an in-line filter up to the Quadra jet (factory style Quadra jet filter removed) I have the “vapor return 1/8 port tied into the 3/8 Stainless line back to the tank when I take the gas cap off I get a pressure woosh of air fuel vapor Is there something I’m missing here is it’ done correctly ?
Stop taking off fast and hazing your tires down my street! I'm joking. Keep entertaining me Milton!!!
The 70 tank is vented on the passenger side top. Is that plugged? I agree with Ethan, put a 71 or 72 cap on it, they are vented. That is what I did just for the extra venting.
Are you having and issue Milton? Your setup should support your engine combo. If there is a question, then the installation of a fuel pressure gauge, sourced right at the carbin inlet is highly recommended for testing and diagnostic. It does not have to be a big deal, can be temporary, even just a good vacuum/pressure gauge setup will work... just use your head, your dealing with flamable liquids. JW
I added an electrical fuel pressure gauge to my set up as Jim advised. They are expensive though, https://www.autometer.com/2-fuel-press-0-15-psi-w-o-peak-valley.html
Thanks to everybody who replied.. yes I’m having an issue JW ...and yes i have the hose barb on the Passenger side plugged there’s actually two Barb’s there I plugged them both ..Car ran excellent except last time I ran it when I put my foot in it it’s starved at least it seemed like it .and it scared me .I know that’s not good JW warned me about that.. I’m going to order the gauge that was suggested AEM fuel pressure gauge I already have 4 AEM gauges oil/temp/airfuel/volts - I will report back after adding a vented cap and the addition of the fuel pressure gauge
Sooo i installed a AEM fuel pressure Guage with a 6an tee at the inlet of the Qjet on my 482 Initially it ran as high as 10 pounds bounced around between 8 to 10 pounds after driving for a while It dropped a little maybe down for 7 pounds if I put my foot in it it drops off pretty good at one point under demand it went down to 3lbs I also installed 3 ft 5/16 fuel hose on the smaller of the 2 hose barbs on passenger side top of fuel tank I plugged the large hose barb coiled up with a see thru plastic fuel filter on it to use as a vent it’s seems to be working there is no more pressure when I removed the gas cap ... i also tried a 1971 vented gas cap (disaster) to allowed fuel to leak out badly under acceleration ... im thinking my new robbmc fuel pump is not working properly I would appreciate any advice to help solve this problem thanks in advance
Sounds like the fuel may be getting hot and partially vaporizing. Are any of your fuel lines near the exhaust? If so, try insulating the fuel line. One of the downsides of a mechanical pump is that the fuel is heated more. I have the CV products pump, and I have noticed that prolonged stop and go driving in hot weather will drop my fuel pressure some. This is way more pronounced if I have winter blend fuel which is more volatile. I try to keep as little fuel as possible in my tank over the winter. I use non ethanol fuel. As soon as they switch over to summer blend E10, I fill up. There is a very noticeable difference in fuel pressure in warmer weather.
View attachment 510607 I wrapped the fuel lines with top-of-the-line fiberglass and heat reflective wrap .. didn’t make much difference I noticed this on robbmc website View attachment 510607
I have a 6 an line from the pump to carb with inline jeggs aluminum filter holder.. filter in q jet removed ... robb mc Recomemds a 8 AN for my HP range .... i’m going to change the line to 8AN .. what micron inline filter should i run ? Is 30 micron adequate
No feed line is tank to pump. I have -8AN from tank to pump, and -6AN from pump to carburetor. That is plenty. Rob recommends his #1024 which is 100 micron. https://www.robbmcperformance.com/products/filters.html
I have the large hundred micron rob MC strapped above the tank I’m talking about the filter from the pump to the carburetor they recommend A 8an i’m running a 6 An my engine dynode at 549 hp at peak how much horsepower is yours making and still running at six an pump to carb ?
No you are misreading it. The feed line is from tank to pump. You should have -8AN there. From pump to carburetor, -6AN is plenty, that is what I have. 602HP/589TQ.
Thanks for clarifying.. some times i just dont get it .....you are a great Asset to V8 board & buick community larry
