posted November 23, 2006 09:37               

Firstly I would like to correct a common error you make. You do not have a Perkins engine in your Dexta. It was made by Ford and assembled by Perkins. There are differences and Perkins parts are not always a direct replacement.

You are coming up against a problem that seems to be common on all types of engine. Pistons are not being made to the full design specification and need to be machined to spec. The piston should not protrude more than around 0.02" above the surface of the block.

Your engineering workshop should be able to get the information about the clearance and machine the pistons to spec.

posted November 24, 2006 15:57               

You are highlighting the point I was trying to make. Original Dexta pistons did not need any extra machining. They were made to fit, as were all the Ford engine pistons I have worked on.

As you say, all Perkins pistons have to be measured and topped.

But this is something that is turning up on other Ford items.

Only last week I was helping someone with a Ford 4000 engine specifications.

The pistons they had been supplied from a well known company who specialises in parts for these engines, supplied pistons that were, again, nearly 1mm proud of the block.

They also claimed that the engine required a piston protrution of 0.50" above the surface of the block. This in no way, was detailed in the Ford repair manual and did not match the piston height of the original pistons that were removed.

Seems as if the aftermarket parts manufacturer are changing the original manufactures specifications.