Dropping compression for supercharger install

The 1UZFE EGR Delete Kit is available for sale here.

quadcam boat

Emerald, Qld Australia
I have a 1UZFE in a ski boat.
It’s a stock early motor with the heavy rods and pistons fitted with a M90 eaton.
The blower locked up years ago and damaged the rotors and housings and put some metal through the engine. It still actually runs fine, but is starting to get a bit sad and has a fair bit of blow by.
Anyway, I’ve had a second engine sitting here for 20 odd years along with a M112 Eaton off a V12 Jag.
So i’m going to set up a new motor and blower for it!
I haven’t been on this forum
for years, so am keen to get up to speed on how best to set it up.
I’m not looking at a big budget, but I am going to pull the heads off the motor and have a look to see if the internals are ok. The rags that were plugging the inlet ports somehow disappeared so it has some dust in it that needs to be cleaned out.
So I’m already up for a set of head bolts and a head gaskets.
Are thicker head gaskets still available to drop the compression and are they a good solution? I’m thinking of running somewhere between 8 and 10 psi (probably with an air to water intercooler since it’s in a boat). I figure thicker head gaskets will upset the valve timing somewhat.
The other option would be to fit lower compression pistons. What options are out there?
Thanks in advance for the help and advice!


Super Moderator
Staff member
Sydney, Australia
Getting anything but stock parts is harder now than 10 years ago. Even stock parts from Toyota are getting thinner.

If only looking at 8-10 psi I would leave the head gaskets alone and run stock compression.

With the cold water you have access to you should be ale to get down to good intake temps.

Rather than taking the heads off why not use a Borescope and check to see if any dirt has snuck in.

If you think about not all the inlet valves will be open so you could be lucky.