400EX Head studs will pull the threads loose in the cylinder anytime that the cylinder gets too hot breaking down the aluminum. There are several causes of this including overheating of the cylinder during resleaving and poor matching of fuel octane to the engine.

Critical Note:

These heavy duty studs cannot be used if the cylinder was drilled and tapped for Helicoils or drilled and tapped for any other oversize studs with a differant thread diameter and pitch.

Installation Instructions

  You need to first drill and tap the cylinder to accept the new studs. 

Hole machining

7/16-inch course thread. Drill holes with a 3/8 inch bit. It is always best to have a machine shop do this procedure in a vertical mill to ensure proper alignment.

Be sure to hone cylinder after studs are installed. 

Install the new studs using Permatex sleeve retainer on the threads. 

Be sure to install to the correct height. 

The studs must be the correct distance out of the top of the cylinder. 

Front – 2.436”

Rear – 3.188”

Sides – 1.929”

Stock vs. Heavy duty

400EX Exhaust

Highest Power Exhaust for the 400EX!!

Back in the day - we built a great High Performance exhaust that out performed every exhaust out there.

I hand built each one of these - tried to get several exhaust companies to make exact copies of it for me many times with no luck.

With a 400EX project we have here - we are building another one for it.

Yes its loud!!

It will not pass any sound tests - it is a pure high performance pipe only.

We again offer them for sale.

Raw 400EX Racing Exhaust...#01-002.........$450.00

Chrome 400EX Racing Exhaust...#01-003...........$750.00

For Chrome - Please allow an extra 4-8 weeks.

Over 4 hp gain over a popular 400EX exhaust.