Boost Referenced Carbs Question

[highlimit9000]

I have 2 1090 King Demon Blower Carbs as seen in pictures. Both Carbs have primary and secondary power valves.
The bases of both carbs have ports for boost referencing tubing. My question is does the primary and secondary sides of carbs both need vacuum tubing to manifold? Right now I have tubing in my secondary side only, and the primary side is just capped off.

 

[fmo24]

Try PMing Denny Valdez. Racerden on the boards

 

[Quick99]

If there is power valves on the primary and secondary I would think they both need to be hooked up to intake manifold vacuum.

 

[Racey]

Paging Denny or Alexi :cool

The intake side of the blower will always see vacuum unlike a Naturally Aspirated motor where when you go wide open the vacuum goes away (as long as the carb is big enough). As vacuum goes away and the manifold pressure rises the power valves begin to open under normal conditions on an NA motor. On A blower motor vacuum may actually increase up there as blower speed comes up with RPM, the inverse of what happens on an NA motor. I would think they should be referenced to below the blower to get the most out of the Carb's operating range, but the power valve is just one piece of the puzzle, you need to make sure the overall mixture is good by putting it on the o2 meter, or being super diligent with plug checks. In other words, Are these new carbs, or have you been running them this way and now changing them?

This is why i love EFI, none of this nonsense to deal with

 

[highlimit9000]

No, they are old carbs but sat for about a year.
All my needle and seats dried out, so I replaced them and adjusted float levels. This is when I discovered power valves in primary and secondary sides. I currently only have vacuum lines on secondary side which go to intake for boost referencing. My primary have always been just capped. Motor has always ran pretty rich at idle though. Was just thinking this might be an issue if power valves on Primary side have always remained open. I would just like to make it right, if it is not currently correct.

Agree EFI would be nice!

 

[Quick99]

Strange that you have power valves on both the primary and secondary circuit. Usually only used on the primary with the secondary power valve plugged. I had a holley 950 blower carb on my 177 and only the primary block was boost referenced to intake vacuum. Same set up on my 420 with duel 800 cfm Holley's and only the primary are boost referenced.

 

[racerden]

I have 2 1090 King Demon Blower Carbs as seen in pictures. Both Carbs have primary and secondary power valves.
The bases of both carbs have ports for boost referencing tubing. My question is does the primary and secondary sides of carbs both need vacuum tubing to manifold? Right now I have tubing in my secondary side only, and the primary side is just capped off.

I would utilize only the primaries for a couple of reasons. First, economy on any forced induction set-up is achieved at lower RPMs & engine loads. Second, referencing secondaries is touchy simply because when most of us are into the secondaries engine life and efficiency via correct tuning is paramount; referenced secondaries can throw in huge variables. If you do follow this program and reference the primaries, be sure to remove the secondary PV's & block them with appropriate plugs and jet up your secondaries 5-6 jet sizes for starters. Another important tip is to note what size PV's you have and closely monitor your vacuum/boost gauge for application tuning parameters. The lower the number, the later the PV opens.
Hope this helps,
DV

 

[highlimit9000]

DV thank you for responding. After doing a lot of research and now seeing your recommendations I will follow that advice. That also seems to be what the majority of research is also doing. Again thanks for the responses. Hopefully see some of the Schiada's in Parker Sept 12th. John

 

[racerden]

DV thank you for responding. After doing a lot of research and now seeing your recommendations I will follow that advice. That also seems to be what the majority of research is also doing. Again thanks for the responses. Hopefully see some of the Schiada's in Parker Sept 12th. John

You are welcome and will be in Parker on the 12th. One last thing, you don't need humongus lines for referencing. Loose the plastic for sure and depending on your wallet go with -4 SS; you'll be glad you did.
197

 

[BoostPower]

I have 2 1090 King Demon Blower Carbs as seen in pictures. Both Carbs have primary and secondary power valves.
The bases of both carbs have ports for boost referencing tubing. My question is does the primary and secondary sides of carbs both need vacuum tubing to manifold? Right now I have tubing in my secondary side only, and the primary side is just capped off.

We use both ports unless you have base area that are merged at the bottom, do the blow test[emoji6][emoji106]🏻