Got new autolite and hooked it up yhe other vday on my 71 351 clv 4v she has good idle but secondaries wount open they are vac

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yea i got a 570 street avenger put it on about a month ago and havnt touched the tuning at all and it runs great still. but my secondaries dont open untill you tune it so im lookin foward to gettin it tuned.

 

Why do you think you're secondaries are not opening?

What diagnostics do you do to determine this?

 

I've heard of others that claim the secondaries don't open. They must sit in the engine bay and watch while an assistant drives the vehicle.

 

im standing over the carb and cant see them open took for a drive around the block and you can deffinatly tell there not opening.

 

If i remember correctly that’s not a valid test.

The engine must be under load not free revving, technically the engine isn’t making HP in neutral ** it only makes HP when it does work.**

Try this for a test:

I’m guessing there should be some type of arm that connect the 2nd butterflies to the vac system, we know that the arm must move if the 2nds are going to open.

So we need to find a way to discover if that arm is moving while you drive the car under load.

Does the arm have to pull or push to open the 2nd?

If it has to pull that makes life easy because you can make/ find some type of loose fitting collar that you can place around the arm that fits flush to the vacuum housing. When the 2nd open it will move that collar down the rod (remember it fits loose) then you can pop the hood and see how far it moved down then you can tell how far the 2nd opened.

Hope that helps or at least makes sence


PS I have manual seconds with a counterweighted baffle to stop flooding and the baffle isn’t fully open until 4,000 rpm. Air velocity forces the baffle open and it takes 4,000 rpm to generate enough velocity to fully open it.
Gun

 

well you always could remove the arm that connects to the secondaries and go drive it and if it is the same then your secondaries dont oepn

 

I agree that there's not enough load to open them at idle. You have to go for a drive.

Make sure there's no vacuum leaks, then try replacing the tension spring with a lighter one.

Justin

 

Thanks for the advice secondaries are opening up now but it seems to have a big drawn out bog before they kick in you know you step on it and it bogs then slowly builds up rpms all the way to redline could this be vacum advance and how do i adjust it?

 

If you only get the "Bog" when you mash the gas to the floor you need to adjust the spring on the vac diaphragm for the 2nd. Its either starving for fuel (opens too late) or loading up (opens too soon). I dont know which (check for excessive back smoke from rich burn during the bog down)

If it bogs down all the time you have further issues than the 2nds alone.

hopes this helps

Gun