700 double pumper on a road car

GJUK · Post by **GJUK** » Thu Aug 21, 14 10:25 am

Thanks I hope to have it all lashed up tonight.

GJUK · Post by **GJUK** » Thu Aug 21, 14 10:42 pm

Alas, I missed some parts off the shopping list

Should have them for Saturday now as long as Royal Fail get them here.

Meh.

Mick · Post by **Mick** » Thu Aug 21, 14 11:18 pm

They took a lot of rocking to make them weep at all, so i raised them one flat, maybe i overdid it but it was having problems before i adjusted them. I think opening the transfer slot on the secondaries, backing the idle screw off and regulating the fuel pressure will help.
Mick

GJUK · Post by **GJUK** » Fri Aug 22, 14 10:56 pm

GJUK · Post by **GJUK** » Sat Aug 23, 14 7:14 pm

Update (6,009?)

Fuel regulator on and pressure gauge.

Set this up while idling at just under 6 psi...

Stayed like that for a while, all happy.
Got up to tempreture and still 6 psi...

...Another 5 minutes or running and revving it starts to drop...

... 5 psi...

...4.5....

4...... 3.5.... 3.2.... 3.....

Then the engine starts to sounds a bit crappy, not quite as good as it was.

Huge pop from the carb and I stopped there.

My tank is not vented, though running it with no fuel cap in made no difference.

Fuel pump?

Bozwell · Post by **Bozwell** » Sat Aug 23, 14 8:39 pm

or blockage in fuel feed pipe to pump or blockage in pickup in tank or blocked fuel filter.

may as well get a new pump as i have seen the seals/valves swell up due to ethanol in the fuel.

Edlebrock fuel pumps are supposed to be ethonol proof.

clean out fuel lines to be sure as well.

GJUK · Post by **GJUK** » Sat Aug 23, 14 8:45 pm

Bozwell wrote:or blockage in fuel feed pipe to pump or blockage in pickup in tank or blocked fuel filter.

I hear you on that one.

may as well get a new pump as i have seen the seals/valves swell up due to ethanol in the fuel.

Edlebrock fuel pumps are supposed to be ethonol proof.

clean out fuel lines to be sure as well.

My friend is brining an electric pump over tomorrow to try.

Can anyone first hand relate to low psi and shocking running engines, would 3psi be causing my issues?

Have I found *THE* problem?

Thanks

Jon

Bozwell · Post by **Bozwell** » Sat Aug 23, 14 8:59 pm

if your losing pressure your losing flow. (flooding must have been a seperate issue)

holley carbs are rated at 7 psi and most mechanical fuel pumps will be 6 to 7 psi. you can bench test them with moving the lever to just pump air through to a pressure gauge

i did a lot of testing when the MK3 GT40 i rebuilt a few years ago broke down. i had four spare pumps to play with and upon stripping them down the rubber valves had swollen up by about 20% in the one off the car.

the owner did some research and although we wanted to keep the original type of pump for originality we ended up with an Edlebrock for reliability. has been good as gold since.

Bozwell · Post by **Bozwell** » Sat Aug 23, 14 9:03 pm

said GT40

GJUK · Post by **GJUK** » Sat Aug 23, 14 9:06 pm

Very nice car.
I am aware of fuel eating away rubber, I have mused R9 class fuel hoses so far, though.... The car has only done 500 mile or so in the UK.

Perhaps its just a faulty pump.

More tomorrow guys

Bozwell · Post by **Bozwell** » Sat Aug 23, 14 9:11 pm

the GT40 did less than 100 miles when it broke down on a new pump. (it only has 7000 miles since it was built in 1969)

GJUK · Post by **GJUK** » Sat Aug 23, 14 9:59 pm

Bozwell wrote:the GT40 did less than 100 miles when it broke down on a new pump. (it only has 7000 miles since it was built in 1969)

It's pointing towards the pump now...

we'll see.

Dave-R · Post by **Dave-R** » Sun Aug 24, 14 10:19 am

Check again that the fuel line is not getting hot from the exhaust somewhere.

GJUK · Post by **GJUK** » Sun Aug 24, 14 6:31 pm

The problem appears to be the secondary float.

It get stuck at the bottom of the carb, though I (and two other people that know holley carbs) can see no reason for this.

Sometimes its sticks, lets loads of fuel in and it comes out of the boosters. Take the sight out and you can see fuel flooding out.

With it off and checking it dry everything appears to work. You add fuel and it all goes tits up. The primary is fine.

Just going to buy a new carb and lob this one as far over the fence next door as I can. Shot put style.

dustymopar · Post by **dustymopar** » Sun Aug 24, 14 7:14 pm

Replace the sec needle valve