Looks like a great product and look forward to getting it installed to see if it can mitigate intake manifold heat soak issues further.  At the time of this write-up, he didn’t have it listed on his website (X35Design) but emailing Steve over there will get you the info you need.

When I mocked it up and placed the hardware in the holes so I can see if I would need to do any port matching, I found it suffered from the same issue as the BBK throttle body.  Not the fault of the spacer, but more the fault of the intake manifold.  The bolts holes are just too large for the hardware and allow for a lot of play.  This would make any attempt at port matching it futile as it would be difficult to place properly when installing it.  So…just as with the BBK, I used the same logic here. And it worked perfect…

Spacer with gaskets installed.
Thickness of spacer for those curious.

Dowels created for improvement. I now sell these already made to spec, so if interested in buying a set, click here:

5/16″ OD, 0.035″ wall thickness, 304 stainless tubing, cut to about 0.8″ length (can’t be any longer than 0.9″)

Picked any 2 holes far apart from each other and drilled with 5/16″ drill bit:

Drilled matching holes in spacer, same 5/16″ drill bit:

Dowels installed into spacer:

Perfect tight fit onto IM:

It’ll need minimal port matching, mostly just a little of the spacer needs to be matched to the ports, but Steve did a great job of getting it super close.

There ya go.  I can probably drill the bolt hole very slightly using the same 5/16″ drill bit for the match holes in the heads and push those dowels through the spacer slightly.  That would get this setup 100% dead-nuts tight and centered from head to spacer to intake manifold…

Here is a video showing the port matching done on the intake manifold side of the spacer:

On the head side, another 5/16 hole only slightly drilled to accept the alignment dowels:

Both holes drilled (hey, easy now…this is a family oriented forum!):

This is all you need it pushed through on the head side to get it to line up:

Rags stuffed into runners to minimize getting the dust into them while doing the port matching:

Used the dowels and the hardware to keep it secured down while porting:

Video on doing the porting on the head side of the spacer…

All done and ready to mount:

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