I have put dual quads on my 65 Skylark GS . They are the dual quad set-up for the 401/425 with the stock manifold and carbs. I just last night took it out for the first time and nailed it . I found that at about 60 - 65 mph + while floored it almost seemed the motor was running out of gas . Do I need to change the fuel lines or fuel pump due to the dual quads ? Thank you , George Bednar fxandhds94@aol.com
Fuel starvation George - some things to check The fuel tank pickup sock can get plugged up. I finally took the one out of my '68 because it was falling apart and kept causing this problem. You can try blowing back through the fuel line with low pressure compressed air, just take the gas cap off first. You might have some other restriction like a partly plugged filter or your fuel pump may be on the down slope. Did you rebuild the carbs? Are the float levels set right? If they are too low you might be sucking the float bowls dry, not enough gas in the carb. I don't know how strong your motor is, but unless it's huge horsepower your stock line and pump should be fine (at least at 65 mph!)
Good information .... txgwildcat ..... I have done nothing to the distributor . Would like to know some specs as to what to do . John ..... I'll check pickup sock , fuel filter and pump . Carbs were rebuilt but I'll have to check float level . Basically a stock motor with some work to the heads , pistons , rings , bearings but nothing radical . Thanks for the info . George
Did it run fine before the Dual Quads were put on? The centrifugal advance on a dual quad should start at 900 RPM and advance to 10@3800 as opposed to the single carb advance starting @800 and be 15@3900 when at full advance.
Actually, the curves are different, as noted above, more info: Single 4 engine: Initial timing: 2.5 deg/BTDC Mechanical curve: 30 crahkshaft degrees Total: 32/5 degrees 2x4 engines: Initial: 12 deg/BTDC Mechanical curve: 20 crankshaft degrees Total: 32 degrees Both engines like no more than 10 crankshaft vacuum advance degrees, build stop to stop pin pull at .86 travel.
Is the spec given, correct for a 2x4 401 or should it be 2800 ? If it is 10 at 3800, at what RPM should the total mechanical advance be all the way in? I always thought the total (20 mechanical + 12 initial) advance was supposed to be in by 2800 RPM. ou: By the way, when I first added the 2x4's, I also thought the fuel pump was the problem as it was dying at higher RPM's when I was on it. The stock pump is sufficient and it was the distributor curve and accelerator pump setting that was giving the problems. Thanks, -Bob
10@3800 has inconsistent units should either be 10dist. deg@1900 dist rpm or 20crank deg.@3800crank rpm. Don't mean to confuse you, sorry.
George, What about checking the fuel lines up near the tank towards the top. I had found a crack in mine where you cant see it from on the ground, you must feel it on the top. Just a thought. Good luck with it George. Bill Bailey
