Part 1. Preparation and safety
Objective
- Install the intake manifold.
Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection - such as rubber gloves and barrier cream
- Respiratory equipment - such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
Safety check
- Get some assistance to lift the manifold if it is heavy.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- Treat the threads of the bolts with non-hardening sealer.
- Manifold bolts usually have a tightening sequence ensure you tighten bolts in the correct sequence.
Part 2: Step-by-step instruction
- Prepare block and gaskets
The preparation of the block is the same for a carbureted or fuel injected engine. Start with a solvent cleaner, such as lacquer thinner.
For most engines, it's good idea to put a some silicone sealant in the four corners where the heads meet the block. Put some gasket sealer around the water jacket ports and their mating surfaces on the intake gaskets.
When the sealer on the gaskets is tacky, line up the bolt holes and stick them in place . Then, spread some more gasket sealer on the tops of the gaskets around the water jacket ports. On any engine, if the decks of the heads, or the block, or both were machined, the heads will sit a little bit lower and the gap between the intake manifold and the block rail will be smaller.
Some gasket sets have rubber or cork gaskets that will be too thick to allow the intake to seat properly. These are not recommended. Instead, to seal the block rail to the intake, run a solid bead of silicone sealer along the front and rear upper rails of the block. Run the bead evenly from gasket to gasket. This is a good idea for all engines, whether the decks have been machined or not, because it provides a much better seal.
- Install intake manifold
When the block is ready, double check that the oil splash guard is in place on the bottom of the intake, if it has one, and then lower the intake manifold in place.
Get some help if you need it, cast iron manifolds are very heavy and it is important to lower it as close to its final position as you can. The aim is to need very little adjustment to get the bolt holes to line up.
- Torque the manifold bolts
On most engines, the intake manifold bolts lead directly into the oil soaked area under the vale covers. Treat the threads of these bolts with non-hardening sealer to avoid oil leaks.
It's sometimes hard to get to the bolts near the plenum of the intake with a socket. If that is the case, use the ring, or box end, of a wrench. The intake bolts usually have a tightening sequence similar to the heads, but the sequence usually starts with the middle bolts near the plenum.
If you can't get to all the bolts with torque wrench, tighten to the first torque increment one of the bolts that you CAN get to, then put a box end wrench on the same bolt and feel with your hand how tight it is. Now you can guesstimate how tight to make the first few bolts in the sequence. Do this for the first few inaccessible bolts for each of the three increments, and you should end up with all of the bolts torqued to a similar rating.
