GM 3.1 and 3.4 Cylinder Head – Manifold Issues

3.1-3.4 cylinder head
3.1-3.4 cylinder head

GM 3.1-3.4 Cylinder Head and Manifold Issues

Confused about 3.1 / 3.4 Cylinder Head Types. Installers are not finding out until it is too late and the Cylinder Head is already installed.

If you do own a vehicle equipped with a 3.1L or 3.4L engine.. chances are that you have already experienced this ‘intake gaskets leaking coolant’ condition (and have repaired it), or you’re experiencing it right now or will be soon enough. Is there something that can be done to avoid a repeat of this particular problem? The answer is yes and it involves using an updated type of intake manifold gasket made by Felpro and tightening the intake manifold bolts with a torque wrench to specification.

So, in conclusion… I know it sucks that you’re having this particular problem with your 3.1L or 3.4L GM vehicle… but, you can prevent a repeat of the problem by doing two very important things: 1.) Use the updated intake manifold gaskets and 2.) torque the intake manifold bolts with a torque wrench to specification.

Common Issues

  • Too many casting numbers,some are interchangeable and some are not.
  • They come with or without air tube holes.
  • They can have 8mm or 10mm Rocker Bolts and still have the same casting number.
  • There are many suppliers offering Cylinder Heads that fit from 1996 to 2005 but are not explaining the differences.

The most common issue is I have the Head installed but my Rocker Bolts don’t fit ! ( Customers are telling me they went to a wrecking yard to find rockers that would fit )

Find other information on Danny’s Engine Portal Other issues are Rocker Bolts pulling the threads out during installation.

Care should be taken not to torque a rocker with the valve in a open position as this can pull the threads as the spring pressure pulls the thread before the bolt is fully seated.


Exhaust and Intake push rods are different lengths. Quite often I am seeing bent pushrods and valves when they are mixed up.

Exhaust pushrods on G.M. 3.1 and 3.4 engines are longer than their intake counterparts. It’s critical to reinstall the correct length pushrod in the correct place. So, how do you commit to memory which pushrod goes where?

It’s easy if you remember this short phrase… It’s been a long, exhausting day. This should help you remember that the long pushrods belong to the exhaust valves.