700 double pumper on a road car

GJUK · Post by **GJUK** » Mon Sep 01, 14 9:25 pm

JohnS wrote:Definately sounds lean, sounds like you need mighty Mick to pop round again

Failing that you should now be able to go through the carb tuning sticky

Bigger primary jets and bigger front shooter

I'm pleased it ran and didnt flood with fuel. Good carb, just needs a fettle now.

Jon

Mick · Post by **Mick** » Mon Sep 01, 14 10:44 pm

I've got a 29 and 35 shooters, 6.5 pv and numerous jets but 35 seems quite big for your car. Put your vac gauge on and tune it for max vac, what are the idle screws set at ? Also you could try different positions on the pump cams.
Mick

GJUK · Post by **GJUK** » Mon Sep 01, 14 11:27 pm

Mick wrote:I've got a 29 and 35 shooters, 6.5 pv and numerous jets but 35 seems quite big for your car. Put your vac gauge on and tune it for max vac, what are the idle screws set at ? Also you could try different positions on the pump cams.
Mick

Thanks Mick, Will try tomorrow night with setting to max vac.

Can I ask, I assume the Vac 2ndry carb does not need any kind of vac linkage to the engine does it, no pipes to the carb from the engine? As mine has none linked up at the moment, not sure if this would affect the running of the carb.

I've been told the power valve is large, so Im going to change it to a 6.5

Also you could try different positions on the pump cams.

What do you mean by this mate?

Cheers dude.

Jon

Guy · Post by **Guy** » Tue Sep 02, 14 4:49 am

GJUK wrote:
Can I ask, I assume the Vac 2ndry carb does not need any kind of vac linkage to the engine does it, no pipes to the carb from the engine? As mine has none linked up at the moment, not sure if this would affect the running of the carb.

Jon

The secondaries get their vacuum internally so no need for extra pipes

GJUK wrote:
Also you could try different positions on the pump cams

What do you mean by this mate?
Jon

Holley use various pump cams to alter the timing and duration of the pump shot through the accelerator jets. These quite often have two or sometimes three holes in a cam so the shot can be advance or retarded to help with tuning

MilesnMiles · Post by **MilesnMiles** » Tue Sep 02, 14 6:43 am

I'm with Mick on the squirter. I recently went down to a 28 on my car and it seems to like it more than the 31 and 35 I tried. Take a look at the squirter, they are not like jets where a bigger size simply gives more flow. The squirters have different durations of flow and sometimes a smaller squirter will give a pro longed flow whereas a bigger squirter gives a shorter duration, bigger squirt.
Hope that makes sense

GJUK · Post by **GJUK** » Tue Sep 02, 14 8:35 am

Thanks guys

Jon

MilesnMiles · Post by **MilesnMiles** » Tue Sep 02, 14 8:53 am

Jon, to add to what Guy said; the vacuum secondary's are controlled by engine vacuum and open on demand. The point they open at can be changed by changing the spring to make the secondary's come in sooner or later. Look at your carb, does it have a black top thingy on the passenger side which screws down? If so, you have a carb with quick change secondary's

http://www.jegs.com/p/Holley/Holley-Vac ... 7/10002/-1

GJUK · Post by **GJUK** » Tue Sep 02, 14 9:32 am

MilesnMiles wrote:Jon, to add to what Guy said; the vacuum secondary's are controlled by engine vacuum and open on demand. The point they open at can be changed by changing the spring to make the secondary's come in sooner or later. Look at your carb, does it have a black top thingy on the passenger side which screws down? If so, you have a carb with quick change secondary's

http://www.jegs.com/p/Holley/Holley-Vac ... 7/10002/-1

Thanks, yes it does and I have a load of springs with the carb also.

There is a very 'light' spring in there at the moment.

Due to the large cam in my car the PV is probably too high, i get about 10 IOM when the car idles, the 8.5pv should be around a 6.5 so I have read.

Next I'll tune the car to max vac on idle.

No idea what the idle mixture screws are set to, the car ran as it was so I will set these up also.

I know there is a light spring in the vac advance not sure on much else.

Thanks.

Jon

MilesnMiles · Post by **MilesnMiles** » Tue Sep 02, 14 10:12 am

Jon, when you change out the power valve be careful to ensure that the gasket is seated correctly or the car will flood in seconds. I did that. I know

GJUK · Post by **GJUK** » Tue Sep 02, 14 11:07 am

Thanks

Mick · Post by **Mick** » Tue Sep 02, 14 11:27 am

What colour are the plugs ?

GJUK · Post by **GJUK** » Tue Sep 02, 14 11:34 am

Silver

Sorry, they're a light tan still.

I've just left a VM for John Sleath, the car drove okay last night I think I might just take a day off work and drive it up to him to setup for me. I hear good things mentioned about his work. I think my neighbors are getting a bit Bananarama! off with the noise every evening.

MilesnMiles · Post by **MilesnMiles** » Tue Sep 02, 14 12:19 pm

Be careful, he'll have twin turbos on it before you can blink!

GJUK · Post by **GJUK** » Tue Sep 02, 14 12:22 pm

MilesnMiles wrote:Be careful, he'll have twin turbos on it before you can blink!

Mixture screws, set the vac, check the plugs for lean/richness tonight.
Then change the power valve to a 6.5 if the above doesnt work.

If its still not 100% going to a rolling road with both carbs, maybe he can get the 700 dp back on and working 100%?!

J

Adrian Worman · Post by **Adrian Worman** » Tue Sep 02, 14 12:45 pm

A session on the rollers could be a good move Jon, because the cam is giving a poor signal at idle speeds it may be better to tune to max vac readings on a light throttle or low speed cruise condition.
You may find that the motor is making easy 12-14" at a little above idle speed so your 8.5 PV won't be far behind. A good performance tune for a PV would be to have it opening as soon as possible to avoid any lean bog condition, usually 2" Hg below. A test on the rollers with a vac gauge hooked up will show this easily. Poor idle quality is an unfortunate trade off on a big cam, then you're forced to modify/drill throttle blades etc

Hey, at least it don't leak