Vacuum Secondaries don't seem to be coming in

[Sixt8Chrgr]

I have my new Holley 600 installed on my stock 68 383 H code, transmission linkage is hooked up and adjusted. I am pretty sure that the secondaries are not coming in. While the car was off, I had my daughter hold the gas pedal to the floor and I looked in at the primaries butterflies and they were all the way open. I am expecting a slight hesitation and the sound of the 4 barrell coming in. At least with the Eddy I felt the four barrell come in but did not really here much. Perhaps the sound is being drowned out with the xterminator mufflers?

Any ideas on what to do next?

Thanks,

Lawrence

[FLG]

Vac secondaries wont open while the car is off  (as far as i know, atleast with my thermoquad they dont)

What kind of problems are you experiencing?

[maxwellwedge]

A 600 on a 383 should easily open the secondaries. With the car turned off, hold the throttle wide open. Now, move by hand, the secondaries open. Do they open and then close by themselves? If they feel tight the carb mounting bolts may be over-torqued. If they do open and close freely you need to look for carb/engine vacuum leaks. The secondary diaphram may be leaking/ripped.

[Sixt8Chrgr]

I agree, I should have been more clear. I had my daughter hold the pedal to the floor to make sure I had the accelerator linkage adjusted for WOT.

The problem I am having is that the secondaries are not coming in while the car is at WOT...or it does not seem like they are. I am use to hearing that 4 barrell moan when the secondaries come in. Not hearing this and dont feel a surge of power.

[Sixt8Chrgr]

A 600 on a 383 should easily open the secondaries. With the car turned off, hold the throttle wide open. Now, move by hand, the secondaries open. Do they open and then close by themselves? If they feel tight the carb mounting bolts may be over-torqued. If they do open and close freely you need to look for carb/engine vacuum leaks. The secondary diaphram may be leaking/ripped.

I did that and they seem to open freely. I will check again and pay attention to how freely they open. I may have over torqued the bolts. I will then look for vacuum leaks. I had this carb on my Corvette years ago and it worked fine.

Thanks,

[Just 6T9 CHGR]

Use the paper clip trick......put a paper clip tight on the vac sec rod up close to the vacuum pod.  Take the car out for a WOT blast.  Come back & check the clip.   If the clip is now further down on the rod, then the secondaries opened.
If not you have to play with the different tension springs to dial it in....

[firefighter3931]

With a vac secondary carb the engine needs to be under load to open the secondaries. If the car is sitting stationary in park/neutral and you're blipping the throttle they won't open completely if at all.



Ron

[elacruze]

....The secondary diaphram may be leaking/ripped.

...I had this carb on my Corvette years ago and it worked fine.

Thanks,

Check the diaphragm with a length of hose and a vacuum pump, or suck on the hose to be sure the pot still works. Alcohol in gasoline eats rubber over time, and it may have hardened up and perforated since you last used it.

[TylerCharger69]

Sounds to me like it could be a few things.....Vacuum diaphragm is bad...check ball underneath it is either stuck or missing....Diaphragm itself makes the gasket around the mating surface, so there could be a vacuum leak there....or...a long shot...the spring may be too stiff and needs a lighter spring.  Engine must be running in order for them to open as to supply vacuum.

[Sixt8Chrgr]

With a vac secondary carb the engine needs to be under load to open the secondaries. If the car is sitting stationary in park/neutral and you're blipping the throttle they won't open completely if at all.



Ron

I agree, I was not clear on my earlier post. The reason I was looking at the primaries with the car in park, turned off and at WOT, I wanted to make sure that I had the accelerator linkage hooked up right. I was making sure with the gas pedal on the floor carb was at WOT.

[R2]

Found this on the Holley site,,,,,,,,,,,,,,

QUESTION I can rev the engine when it is in park and the secondaries will not open. Why is this?
ANSWER The secondaries will not open by free revving the engine. The engine needs to be under a load before they will open. If you are still uncertain if they are opening or not you can take a normal paperclip and clip it onto the secondary diaphram rod. You will then push it up against the bottom of the secondary diaphram housing, now you will need to go out and drive the vehicle. When you return you will be able to look at the position of the paperclip on the rod. If it is lower on the rod then you can tell the secondaries opened and how far they opened. This is useful in determining if you need a heavier or lighter secondary spring.

[Sixt8Chrgr]

Found this on the Holley site,,,,,,,,,,,,,,

QUESTION I can rev the engine when it is in park and the secondaries will not open. Why is this?
ANSWER The secondaries will not open by free revving the engine. The engine needs to be under a load before they will open. If you are still uncertain if they are opening or not you can take a normal paperclip and clip it onto the secondary diaphram rod. You will then push it up against the bottom of the secondary diaphram housing, now you will need to go out and drive the vehicle. When you return you will be able to look at the position of the paperclip on the rod. If it is lower on the rod then you can tell the secondaries opened and how far they opened. This is useful in determining if you need a heavier or lighter secondary spring.

Thanks

[Sixt8Chrgr]

I did the paper clip trick and of course the paper clip was missing when I can back home. Either it fell off because the secondaries were coming in or otherwise. I will use a bigger clip tomorrow.

[Sixt8Chrgr]

I got a good read and the secondaries are coming in. I used a haripin clip instead of a paper clip. The paper clip kept falling off.