After installing my new topend (not including heads) I had my head under the hood today adjusting the AFPR and I heard a very distinct hiss like a vacuum leak from the passenger side of the intake plenum towards the rear runners. (nice run on sentence huh )

Anyway, my kpa's are VERY constant according to my data stream and my idle is steady, moving only about 25RPM's at the very most. I've checked for a leak but cannot find one. I thought it maybe a fit problem between the SLP runners and the Accel base on that side.

I don't remember this noise on my old top end. Any ideas???

 

Are you able to monitor IAC counts? If the counts are zero or near it, could be an indication of a vacuum leak...i/e the IAC is extending to close the passage to lower the idle, due to extra incoming air.

Just a thought

 

I have my idle screw set to that at idle in gear my IAC steps are 5 and mt TPS is 0.53. I have it set this low on purpose. It was at like 25 counts until I adjusted the idle screw.

So no but good thought though.

See everything seems perfect but I just hear this loud hiss......

 

Time for a little carb cleaner/propane/water test, huh?