Calling pete...or anyone really.

['80RegalT-type]

I'm doing pete's alternative pecv replacement but am unsure about where to run the vacume line to the "carb vent".

 

[Peter]

Originally posted by '80RegalT-type
I'm doing pete's alternative pecv replacement but am unsure about where to run the vacume line to the "carb vent".

The original PECV has a vac. line to the carb. vent. The vent is located at the rear of the carb. close to the top. There are are other vac. lines at the bottom which should not be disturbed.

 

['80RegalT-type]

Well......there is no line to the top nor is there a place to put a vac line. Another thing, i think i've determined which switch controls the yellow light. It has a blue wire and the other has a yellowish one. The one with the blue has two prongs on it like there should be another wire but i don't have it. Is mine missing?

 

[Peter]

My car is a 78 'B' chassis, and I can only make referance to that.
I know that 78's are different to all other years in many respects,so your 80 will probably be different to mine.

If the PECV is still present ,trace the lines. One of them should go to the vent, probably repositioned on an 80 carb.. If the vent is left open it will only suck air, and dirt, but will not effect the running of the car. Look for an unused port?

Maybe someone else can locate this port on an 80 carb.?

On my car the switch that operates the the yellow light, the one you are looking for, has two wires. One yellow and one blue. The other switch has one white wire .

Both of these switches make a connection to ground when switched on. The Buick diagram shows the ground is made through the body of the switch. However, mine have a ground terminal with a black wire attached. Check to see if one side of the switch is grounded. Maybe you don't need this ground wire in your case. Do the lights work? If they do, no problem.

 

['80RegalT-type]

Ok, now that you got me thinking there "WAS" a port on the back top of the carb that looked like it needed a vac line but had nothing to it. (the old pecv is long gone) But i bought a remanufactured carb and i'm seeing that it isn't there. I remember taking both my old carb and this new one and inspecting them before i exchanged them and everything looked the same. seems i missed something i didn't think mattered. I guess i just need to know why this thing needs to go to a carb vent? it must not just need any old air, but specifically from the carb.

As for the the boost guage lights i have seen the yellow one work. My motor has about 10 miles on it and i have yet to take it into boost. i've been having a problem with no bottom end power though. But when i get her up to 1500 rpms she takes off. Bugs, bugs, bugs. What a pick for a first time motor build aye?

 

[Peter]

The reason for venting into the carb. vent is that air/fuel mixture is discharged. However, this is a very minimal amount, not like a blow-off valve. You could vent this anywhere into the intake system,without a problem.

 

[Peter]

PS.

Of course before the throttle valves.

 

[b4black]

Why is there a vent? The power valve is usually plumbed internally. On a Turbo carb, it's plumbed externally with the PECV valve inserted in-line. The PECV blocks the vacuum or allows it to pass, based upon the pressure it sees through the bottom intake port.

There is also a thermal switch and plenty of other things t'd into this line, but it seems preety straight forward. Here's the diagram for a '80:
http://home.flash.net/~rjgeorge/images/vac80abfed.JPG

The problem may be the replacement carb. It may have an internally plumbed power valve (in other words, not a Turbo carb). Which could explain the missing port.


DISCLAIMER - I have all electronic carbs without PECV's and power valves, so I might not know what the hell I'm talking about. Just going by what I've read.

 

[b4black]

Oh, get a boost gauge! It will really help you diagnois the car (and the lights).

 

['80RegalT-type]

The carb base is a turbo. I made sure it had the extra port for the power valve unlike all my other Q-jets. I have a boost guage, I worked it into the dash where the old clock used to be.

 

[Peter]

Originally posted by b4black
http://home.flash.net/~rjgeorge/images/vac80abfed.JPG

[/i]

This 80 diagram is different to the 78 diagram. The 78 PECV has three connections to the top as well as the bottom connection to the manifold, where as this 80 diagram only shows two on top. The two connections shown are the same. The vent connection is no longer used it appears.

It would appear that the back side of the wastegate is connected to the carb. vent on the 80 diagram. The back side of the wastegate on the 78 diagram goes to the PCV line.

I think the purpose of connecting the the power control valve to the vent under boost conditions [as in the 78 version], was to ensure that no boost or vac. was left in the line. Presumably Buick considered this unnecessary in the later version.

I like the idea of venting the power valve line on boost, as it ensures that the power valve goes to full rich under boost conditions. Just my opinion.

 

[b4black]

Originally posted by '80RegalT-type
The carb base is a turbo.

But the power valve isn't in the base. I belive the vacuum source starts at the base, but it's plumbed to the top to suck the valve closed. You may have a mismatch in plumbing. Drilling a hole and adding the port may be all you need to do.

Do you still have the old carb?

There are two books you may want to buy. The first is Rochcester Carburetors by Doug Roe. The other in Turbochargers by Hugh MacInnes. Try a major bookstrore like Border's or even ebay.

 

['80RegalT-type]

That's true that the power valve isn't in the base. It's hard to tell by the diagram but it looks like the pecv goes to the carb's base. I don't have the old carb (i had to turn in the core because i was low on cash or i would have kept it) but i remember the port on the back just stuck in from the side above the secondaries, that's it. It didn't look like anything special to me. It's been kind of hard for me to match things up. I got this motor from a friend with no vac lines or anthing to go off of so please bare with me if i come up with something off the wall.