View Single Post
billjam billjam is online now
Certified User
billjam's Avatar
Join Date: Aug 2007
Location: Perth, Western Australia
Posts: 1,985
Stupid inlet spacers

Having joined the dark side from a NA background, I am dumbfounded by the pathetic size of the inlet tract on our turbo motors. 32mm !!!!
I know that with a bit of boost this restriction can be overcome, but let’s get real here, as much as we don’t like to admit it, a large percentage of our driving really is in the rev range where we are off boost (and way down the power curve).
While I have my motor apart I’m doing lots of “while I’m in there” type stuff and one thing that’s high on my list of things to do is to improve power below 3,000 rpm.

It just seems so obvious to me that the inlet manifold branches, inlet spacers and head ports should be opened up. There’s plenty of room to do this in the manifold and the heads but the stupid plastic inlet spacers are a real problem.

Bruce Anderson notes in his book that the inlets should be opened up from 32mm to 36mm but doesn’t elaborate further. Boring out the spacers by 4mm will reduce the wall thickness from 4mm to 2mm.
Can anyone report on the longevity of spacers that have been bored out to 36mm?

I’d like to go as far as possible here – maybe bore out to 38mm. This would leave a wall thickness of 1mm, which on its own is getting a bit flimsy. To reinstate some strength, I am looking at filling the spaces between the flanges with some kind of epoxy or liquid metal (see shaded areas in photos).
Has anyone else tried this? If so, what type of material is best to use? Obviously it has to be able to handle head temperatures and be compatible with the plastic spacer.

I have also considered boring out the entire center tube in the spacer and replacing it with a steel tube. 1-5/8” ERW tube with a 1/16” wall would be good (for the ROW, that’s about 41.3mm OD x 1.5mm WT).
If I did this, I would still need to bond what’s left over of the original spacer flanges and injector mount to the steel tubing. I’d need to notch the tube to clear the injector as well.
Has anyone tried this approach?
Old 07-02-2008, 08:13 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)