Install: KSTech 6.5mm Phenolic Intake Manifold Spacers

A while back, we installed some Grimmspeed Phenolic intake manifold spacers (3mm) onto my EJ207. I didn’t use gaskets on recommendation from a friend, a Subie mechanic, I used grey RTV instead. Unfortunately, I developed a leak at each runner.

Since the spacers were used, I decided to replace them with some fresh units. Instead of going with Grimmspeed again, I decided to try a new brand – KSTech.

KSTech 6.5mm spacers came with longer bolts and optional OEM gaskets as well. Unfortunately, the bolts were too long for the JDM long runner intake manifold (no TGVs). The OEM bolts may have worked, but I didn’t want to chance it. I ordered a set of M8 1.25mm x 4omm JIS bolts from Bolt Depot. The OEM bolts are ~35mm long.

KSTech 6.5mm Phenolic Spacers
KSTech supplied hardware (right) v Bolt Depot bolts (left)
OEM gaskets; P/N 14035AA421

First step is to pull the connector for the fuel relay behind the passenger kick panel. Then start the car until it dies (if it even starts).

We previously went over how to remove the intake manifold with the GS phenolic spacer install so we will be skipping over that process here.

Previous Install

Once the intake manifold was off, I was a little disappointed at how much carbon buildup there was.

It isn’t the worst case of carbon buildup but it doesn’t bode well for the long term. I definitely need to figure out what AOS to go with.

Next up, it is time to clean. We need to clean up mating surfaces and any dirty parts so we can see new leaks. I used Seafoam spray to clean up the ports and intake running a little bit.

The intake manifold has seen better days. The paint is flaking off just about everywhere. If there was time, we could throw a coat of paint on it but that will have to be a project for another day.

Once the mating surfaces were clean we can re-install the lower intake gaskets…

…and then the spacers.

The 6.5mm KSTech spacers have little dowels or pins already in them, which I thought was neat until I tried to install them. I was hoping that they would fit on top of the pins in the head but they didn’t. So, we either need to use the pins in the head or the spacer. I’d rather have the bottom gasket and the spacer locked down so they can’t move so I left the head pins in place.

You can use a couple of nails in the pins to hold the top gasket in place. Just make sure you don’t knock them into your intake ports when repositioning the intake manifold.

From here, reinstallation in the reverse of removal. Then torque your bolts to spec or gutentight, whichever you prefer.

The TMIC sits slightly raised on the driver’s side but nothing too bad. KSTech does not recommend the 6.5mm spacer for TMICs so I was a little worried about the fitment. The passenger side is bolted to the block but the driver’s side is bolted to the intake manifold. To keep the TMIC level we need to modify the driver’s side bracket.

The TMIC is unlevel to the max.

However, it doesn’t interfere with the operation of the hood so we can save that mod for another date. We just need to bend the bracket down to level off the TMIC.


I have been driving for a couple of weeks with the KSTech phenolic spacers in place, with no real expectations other than to plug up the intake manifold leaks.

I have noticed an improved turbo response, even when it is +80°F out, but I can’t really attribute that to the spacers or the fixed intake leaks; it could be a little bit of both but I can’t say with any certainty. The only way to know for sure would be to pull the spacers off and drive around and compare the difference.

While it wouldn’t be too difficult to pull the intake again but I have no interest in determining who is the real hero.

Anecdotally, the Bugeye doesn’t seem to heat soak nearly as often but it is a little early to tell. While it is certainly hot in east Tennessee already (low 90s), summer is still a month away.

Since I don’t and will most likely will never have any hard data to prove whether phenolic spacers actually work, Dom says they don’t, I can’t really recommend them based on any hard data.

I believe these spacers work better as a part of a heat management strategy. I have done the throttle body coolant bypass, the Dom coolant mod, relocated the coolant expansion tank, phenolic spacers, turbo & downpipe blankets, hood vents, and more.

If this is your first mod to manage heat then there are certainly better mods to do first. Keeping the heat in the exhaust and out of the engine bay should be priority #1. Once those items have been tackled then you can move on to less proven mods to experiment with.


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