I am searching for a block and crank configuration for a non-Z related project and I think I have found it in the RB family of Nissan engines. I have a few technical questions and if anyone can help me I would appreciate it.

What I want is an I6 with as short of stroke as possible and a high rod/stroke ratio. In my bearing catalog there is an engine that is 1998cc with a bore and stroke of 78mm x 69.7mm (2.75"). I am particularly interested in the short stroke of the crank in this engine and not much more. Now is there a Nissan block that will accommodate this crank that has a higher deck? I want to achieve a rod/stroke ratio of 2.25:1 or even 2.5:1. I can buy rods of the length of my choosing but maybe Nissan has already has a 6.25" rod that would fit this crank.

Also I have noticed there are two different variations of this short stroke crank, there is a 2" rod journal on the older ones and a 1.75" journal on the latter cranks. What are your thoughts on taking the large journal crank and de-stroking it .25" at the machine shop and still have the common smaller diameter journal left. I would be even more interested in a 2.5" stroke, then I would only need a rod 5.625" center to center.

Kevin

 

uhm. iono that's just confusing eny help guys?

 

I don't know all the bore/stroke specs on each engine but there are two 2.0L inline six engines by Nissan that are short stroke.

L20 is an old engine found only in the JDM Fairlady Z. The deck height is the same as the 4-cyl L16/L18 and the L24/L26/L28 six cylinder.
RB20E and RB20ET are SOHC inline six engines found in the mid to late 80's Skyline.

If you want to go 4-cyl, you can try the L20b block. It has a taller deck than all the rest (stroked) but possibly you can fit the L16 crank in there (shortest stroke) and some custom rods. Possibly L20(a) rods from the six cylinder block with some taller flat top pistons out of another car. 280ZX pistons are only 1mm over in the L20b block.

 

Thanks for the help and sorry about the confusion guys, I will try to be more clear.

If I read you right Bleach you are saying the deck heights are very close if not the same on all the Inline 6 engines and the only high deck block Nissan has is a 4 banger, please correct me if I am wrong.

What is the rod length (center to center) in the RB20 engine?

What is the deck height on the RB20 engine?

Not trying to be confusing here but the components I am seeking will not be used as an IC engine. I do need an I6 though, a 4-cylinder crank will not produce the events I need and I have to have a short stroke. I am trying to use as many off-the-shelf components as possible. I have not looked into having a crank made but I don’t think it’s cheap.

Also I am curious how robust the Nissan sixes are, are they built to take a beating or are the BMW engines tougher?

Thanks again for your help.

Kevin