Plenum install mishap

[GWhiz35]

Hey guys, I installed a Motordyne 5/16 spacer yesterday and now my car is making a hissing noise (but not from the engine) sounds like its comming out of the rear of the car on the passenger side. Anyone have a clue what this could be?

[joe603]

Make sure all of your vacuum lines are connected properly. Also, make sure that you didn't pinch anything between the new gasket (spacer) and the plenum.

[toddnos]

hopefully you used a torque wrench, and did all the plenum bolts to spec...i had issues because i overtightened my bolts..i cracked the upper plenum cover...sounds like a vacuum leak...spray some carb cleaner around the plenum spacer with the car running...the idle will change(jump) if you spray the cleaner near the source of the vacuum leak.

good luck

[tollboothwilley]

I agree. Sounds like you didnt torque them to spec. I don't use a torque wrench but I'm very careful with how tight I torque all the bolts down. Too much = very bad. You will notice with a plenum leak that your idle will typically be lower than normal.

[GWhiz35]

Hey thanks guys, I had to go out and buy a inch/lbs torque wrench and do it at 40in/lbs 80in/lbs and then 100in/lbs and the hissing stopped. My G sounds meaner than ever now! Can't wait to get my HFCs, anyone have a recommended brand??

Appreciate the help guys, I love this site!!

[tollboothwilley]

I'm running Kinetix HFC, everything has been great for me.

The general consensus is that Fast Intentions has some of the best HFC out there. Too much $$ for me though.

[kmckis1029]

hmmmmm i get a hissing noise (sound comes from the front left)... ever since i installed my z-tube and k&n filter.... way before i installed my spacer... i torqued my spacer 40/80/100 like you suppose to...

this hiss/sucking noise only comes when i get to 4k rpm... i have no engine light and my idle is 650-800 rpm which is what its been since i got the car...

i have checked the z-tube install for leaks many times... am i right in assuming that that is just the engine sucking in more air after 4k rpms?

[joe603]

I'd check the air tube connections...maybe take it off and re-install to make sure that you have a tight seal. Better yet, get a JWT or Stillen PopCharger!

[kmckis1029]

i thought about getting one of those... but not worth the money for 6-7 hp on the top end... versus 4-6 hp with the k&N/z-tube combo...

i have recently reinstalled when i got my spacer and i made sure i got a nice seal... but even with the slight hiss/sucking noise the power bump in the 3-6k rpm range is still there

i wont my head over it... ill take another look today... for the fourth time since i noticed it...

maybe ill try and get video of the sound...

on the positive note... since its always at 4k... i dont have to look at the rpm gauge to know when to shift lol

[JeromeS13]

You shift at 4k? Boooooo.

Haha. j/k

[kmckis1029]

no i dont, but i know im getting close to the 6600 i shift at lol

but if im crusing i will shift at 4k right when i hear the hiss...

[GWhiz35]

That hissing sound is from the air intake, My JWT does the same thing at the same RPMs. Nothing to worry about, and it seems that the spacer takes a little while to really get a good seal, i drove mine for a couple hundred miles before it stopped making noise.

[tollboothwilley]

i thought about getting one of those... but not worth the money for 6-7 hp on the top end... versus 4-6 hp with the k&N/z-tube combo...

I've got an extra JWT pop-charger and heatshield...email me.

[tollboothwilley]

That hissing sound is from the air intake, My JWT does the same thing at the same RPMs. Nothing to worry about, and it seems that the spacer takes a little while to really get a good seal, i drove mine for a couple hundred miles before it stopped making noise.

Spacer should not take any # of miles to stop hissing. If you are hissing then something is wrong.

Also, the stock airbox with the K&N...I've never heard anybody have hissing noises.

KMICKIS - what is your idle at in P when fully warm? What is it at in D when warm? 650-800 is too wide of a range. With a vaccum leak you will notice a decrease in rpms...by about 50 normally.