[Just_Another_Mike]

I finally got this procharger D1SC running on my 502. However, although it sounds good after a dozen setbacks, my boost gauge is reading about 12.5 at idle......I dare not gun the thing as I don't want "ka-boom". However, just slightly revving it, the boost remains fairly constant at 12-13 pounds. The problem is that I specfied to ATI that I want to run only 8 pounds of boost. Is this a problem? I have my boost gauge hooked up to the large vacuum port on the rear of the carb. I'm going to call them tomorrow, but their tech support is less than great. The diameter of the D1SC pulley is approximately 4 inches.

Thanks,

Mike

 

[camcojb]

Sounds like you have your boost gauge hooked up to the wrong place, like in the carb hat. You want the boost gauge hooked in the intake or somewhere below the throttle blades. There's always boost above the blades, but you need to see the boost the engine is seeing which is below the throttle blades. The only line running into the carb hat should be the boost reference line to the pump or regulator.

Jody

 

[Just_Another_Mike]

Jody, no the boost gauge is hooked up below the throttle blades. You know, the large port that most people either hook up to a PCV or power steering booster. I have my boost reference line running from the carb hat to the reference port on the regulator. Before, I had this stuff all hooked up wrong and was seeing little or no boost, but now I am seeing what appears to be too much.

Mike

 

[Wolfplace]

Jody, no the boost gauge is hooked up below the throttle blades. You know, the large port that most people either hook up to a PCV or power steering booster. I have my boost reference line running from the carb hat to the reference port on the regulator. Before, I had this stuff all hooked up wrong and was seeing little or no boost, but now I am seeing what appears to be too much.

Mike

=
Sounds to me like you are seeing vacuum not boost on the gauge.
There is no way you will have 12 lbs of boost at idle??
Pull the line off & see what you have with your trusty finger

 

[camcojb]

Yes, you cannot have boost at idle. It will be vacuum at idle/cruise no matter what. So either you are reading the gauge wrong, bad gauge, or it is not hooked up correctly.

Jody

 

[forcd ind]

you will see a small amount of boost @ idle, you may not be able to measure it, but if you pull your sight plug out of the carb with it running, you could get a spray of fuel coming out (did that once) i prefer the gauge in the hat, with a 502 and a disc, your prob going to be close to the 8 lbs, depending on max rpm's(if its a serpentine belt, belt slippage could come into play also)
you are boost ref your fuel system, right

 

[camcojb]

you will see a small amount of boost @ idle, you may not be able to measure it, but if you pull your sight plug out of the carb with it running, you could get a spray of fuel coming out (did that once) i prefer the gauge in the hat, with a 502 and a disc, your prob going to be close to the 8 lbs, depending on max rpm's(if its a serpentine belt, belt slippage could come into play also)
you are boost ref your fuel system, right

You will not see boost at idle with that blower. You will see some pressure ABOVE the throttle blades; you cannot set the floats with the blower hooked to the hat as you have seen as there's air from the blower pushing into the vents/float bowls. That's the reason for the boost-referenced pump/regulator, to add a pound of fuel pressure for every pound of boost in the bowls so the fuel can still flow into the carb. But BELOW the blades in the intake manifold (which is where you hook for a boost reading) it will not be showing boost at idle.

You do not want your boost gauge in the hat. You want to know what the engine is seeing, not what is in the hat above the engine. It's the same as if you run a boost retard and run the vacuum line to the hat; it will always be retarding the timing, and you wouldn't want it to. You want it to reference to what the ENGINE is seeing, nothing else.

Jody

 

[Just_Another_Mike]

You guys are correct, it is vacuum that I am seeing. My problem was that I do not have the gauge mounted and I'm in a extremely confined space and was reading the gauge sideways......finally realizing that the gauge goes both from vacuum to boost. So thanks for the replies:thumbsup:

Mike