Piston Measurements

[kachel 5]

Hi all,

 

I have d6b pistons with measurements 82.86 to 82.91. Is this usable in new liners?

[petert 591]

Depends what the bore of the liners are. For example, if they're were all 83.00, then you'd have 0.14mm (0.0055") clearance on the smallest piston, which is way too much for a strutted, cast piston. You need to measure both parts to make a value judgement. Ideally you want 0.02-0.04mm (0.0008-0.0015") clearance.

[kachel 5]

Thanks Peter, excellent info.

I might get my hands on some 1.9DFZ pistons. But these are more flat than the d6b pistons. Is this ok for the d6b engine with a skimmed head?

[petert 591]

DFZ pistons come in 3 size ranges, just like a D6B piston. So you're no further ahead in terms of working out sizes. However, they will give a decent increase in compression. You'll probably have 10.75-11.25:1, depending on how much your head is skimmed. Great if you have 98RON (or better) fuel.

[kachel 5]

Ok, thanks again Peter. I now have class B pistons. Unfortunately I cannot find the class on my new liners from Goetze. There's no marking but on the box it is mentioned that the cylinder bore is 83:00. So I can make the calculation of 83:00 -0.04 =82.96 for the minimum size of the pistons?

To be sure, I take the size from the pistons on the two bottom 'flaps' of the piston.

[kachel 5]

Is there a difference between DKZ and D6B pistons? Are the dishes different?

Edited October 11, 2015 by kachel

[petert 591]

Yes, DKZ has 16cc dish, D6B 15cc, from memory.

[kachel 5]

Ah, ok thanks again Peter. I guess with a skimmed head i'll have the D6B compression then.