1HZ HEAD TO 1HDT HEAD CONVERSION CAN IT BE DONE?

HomeBlog1HZ HEAD TO 1HDT HEAD CONVERSION CAN IT BE DONE?
Posted on 23 July 2018

Something Shane and the Noordeman team get asked quite alot is can i fit a 1hdt head onto my 1hz?

Short answer is  you can’t just swap over to a 1hdt head on its own, but with almost a complete damaged 1HDT you can convert over to a 1HDT, the differences and what you can use we have listed below to try and help you see if its worth the effort or if you just buy a complete 1HDT and rebuild it in place of the 1HZ.

You can use the 1HZ block but you will need to drill and tap the block for the oil return line

The conrods and pistons you use are the 1HDT ones

The cranks are the same

The head can be bolted on and you can use your 1hz valves and springs and guides assembly

The camshafts are different the 1hz one is a bigger camshaft on the intake lobe

The injectors can’t be used from the 1hz for the 1hdt as the 1hz is indirect injection and the 1hdt is direct injection

The fuel pump can’t be used from the 1hz for the 1hdt as the 1hz is completely different to the 12mm 1hdt pump

Fuel pump timing is different between the 1hz and the 1hdt

The injector lines are different between the 1hz and 1hdt so they can’t be used either due to the way they mount to the pump and also the injectors

The rear section of the manifold can be used from the 1hz but you will need to use a 1hdt front section of the manifold

Water pumps are the same

Timing kits are the same for the early 1hz up to 1997

The timing gears are the same

Rocker covers are the same

Intake manifolds are the same

Engine mounts are the same

Flywheel for the 1hz is smaller at 275mm diameter  and the 1hdt is 300mm diameter but both will bolt up to the back of the engine the 300mm will only work with a H151 gearbox

The clutches are different also due to the sizes the 1hz one is 275mm diameter and the 1hdt is a 300mm diameter clutch

Oil pump assemblies are the same upto 1997

Plastic timing covers and backing plates are different due to clips or bolts but both can be used as a set

Noordeman 1hz 1hdt