Intake Manifold Bolts

Intake manifold bolts clamp the manifold to the cylinder heads and seal the joint, which on many V engines carries coolant as well as air. The ARP kits in this category come in hex or 12-point form, in stainless steel or 8740 chrome moly, and are listed by engine, sometimes by manifold too.

The joint carries little mechanical load, but it must hold manifold vacuum, boost where fitted, and coolant at the same time. An aluminium manifold also expands differently from the heads, so the gasket is worked on every heat cycle. Uneven clamping lets air in to lean the mixture, or lets coolant into the ports or the oil.

On a V engine the bolts pull the manifold down and inwards into both heads at an angle, so an even, gradual tightening sequence matters. A matched kit gives consistent clamping from bolt to bolt, with threads and heads that survive repeated removal.

Use the title and listing to choose:

• Engine and manifold: kits are listed by engine, and some for a particular aftermarket manifold whose flanges differ from the original. Use the kit made for your manifold.
• Bolt length: some kits are listed by under-head length, such as 45 mm or 55 mm, to suit the manifold’s flange thickness.
• Complete kits: some cover a multi-piece manifold in one kit, and valley cover bolt kits are listed as well.
• Head: hex or 12-point, most taking a 3/8 in socket and some an 8 mm or 10 mm one.
• Material: stainless steel for corrosion resistance and looks, or 8740 chrome moly.

Check each bolt’s length against its hole before fitting: one that bottoms out feels tight but clamps nothing, and one that is too short engages too little thread. Where a bolt enters a coolant or oil passage, seal its threads. Lubricate as the kit specifies, and tighten in the engine maker’s sequence, from the centre outwards, in stages.

Re-check the bolts after the first heat cycle, as new gaskets settle. A smoke test is a quick way to find any vacuum leak that remains.