Is this a good mod to install in your Z? Never heard of it? Is AAM a good company that sells them? Heard there gains are pretty good for its price...http://www.gruppe-s.com/350z/zeng.htm
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or should I go with a 5/16 Motordyne Spacer?

 

Here is some info on them both.

https://my350z.com/forum/search.php?searchid=1467575

 

AAM all the way!

 

I'm considering either the Crawford Plenum or the Motordyne Spacer. The AAM spacer was eliminated because there are no supports for the six center bolts. This means the upper plenum can deform downward up to a 1/2" in the front. There's been some posts on cracked plenums due to this design.

 

I haven't seen any posts on cracked plenums, at least not metal ones. I would think to be able to deform the stock plenum 1/2" you would have to crank down on the bolts to the point of breaking them first. The stock plenum is very strong, strong enough for you to stand on it.

 

Dave, the cracked plenums were a result of not applying the proper torque to the bolts. There was a thread about it about a year ago. The person that cracked it even admitted to over tightening the bolts.

On a side note. I used to have the AAM spacer and I would have to recommend the MotorDyne over it.

 

Now that you mention it, I do recall that thread. He must have had a defective plenum as I recall because several people pointed out that you can stand on a plenum without it deflecting much.

I too have the AAM space and would recommend the MD spacer. The extra space you gain by the 1/2" vs 5/16" isn't worth the trouble I have with the clearance under the strut bar and hood. The angled spacer also introduced issues with leaking under the 6 center bolts, hence the rubber washers.

I just wanted to clarify that it's not a common or widespread problem of plenum's cracking as a result of there being no support between the halfs. Actually, I worked around that problem by buying Motordynes Isothermal kit which came with the plastic post spacers. I ground a few down and got them to fit on my setup so now I have that extra amount of support between upper and lower. I did it mainly to help dampen vibrations.

 

I have aam and got some serious gains.

 

Everyone's entitled to their own opinion. I gave mine and have yet to find any reason to change it. If you prefer the AAM Spacer then I recommend you buy it. I'll end up with something else thank you.