Choosing an intake manifold
There are 3 major groups:
- Dual plane
- Single plane
- Tunnel rams
Dual plane manifolds are what most engines came with originally. Dual plane manifolds are in fact 2 manifolds, each using one side of the carburetor and feeding 4 cylinders. All engineered into one aluminum manifold. Dual planes are the way to go up to 6500 rpm, they make power in the full rpm band and they have good throttle response. They’re the best choice for 90% of engines.
Single plane manifolds “look” faster when looking into them, there’s one big hole under the carburettor, and normally straight runners to the cylinder heads. Looks very unrestrictive compared to the dual plane where the runners snake around. But the large plenum (hole) under the carb is only helping in high rpm. In the 1500-5000 rpm range it’s not size that helps, it’s actually keeping the runners down in size, the venturi effect will then speed up the air/fuel mixture towards the cylinder heads. Single plane manifolds are best above 5500 rpm, so if that’s where your engine is to make power, 5500-7500 rpm, and has the internals to not break down, then a single plane is for you.
Tunnel rams are for show mostly. We’ve run them and having 2 carburettors sticking out of the hood and shaking is a pleasure to look at. If you want to run them, carburetor choice is even more critical than ever, we’d recommend buying a tunnel ram with carb kit, and even then, don’t expect the same drivability as with the more ordinary set ups. Do they produce more power? Rarely, but hey, looks are important too…