J13 wet sleeve

[Ken75]

Hi,

 

did anyone ever try to wet sleeve a J13? My plan is to run 81mm pistons (=1599cc) on modified cylinder centers so they will be equally spaced. This will bring the combustion chamber inside the cylinder. With 0.135” sleeve wall thickness that would result in 0.2” spacing between the sleeves.

It’s for a ‘68 520. Please don’t suggest engine swaps. The challenge is to start from the original J13 engine and go all the way from there 😉

 

Thanks,

Ken

[Stoffregen Motorsports]

Instead of going to all that trouble, why not just install a 1.8L out of an MGB? They are virtually identical to the J series.

[datzenmike]

What are the 81mm pistons from? They would need to be the same pin height as the original J13.

[Ken75]

Pistons and rods would be custom made to suit, as it looks now with 27mm pin height and 156.2mm rod length. I would only have production started after succesful boring and sleeving the block.

 

I actually have 2 blocks, one stamped with “1300” (from my 520) and a spare one stamped with “B34” which I still need to disassemble.

Any known differences between those?

 

Thanks,

Ken

[Ken75]

3 hours ago, Stoffregen Motorsports said:

Instead of going to all that trouble, why not just install a 1.8L out of an MGB? They are virtually identical to the J series.

 

I know but the point is to start from the original engine. I’d call it a challenge, not trouble. At least or now, I may change my mind later on 🤣

 

Ken

[datzenmike]

Rebuild to stock specifications. If wanting larger displacement, check out the MG and what can be done to increase performance like cam and dual SUs..

[Stoffregen Motorsports]

On 8/15/2022 at 12:11 PM, Ken75 said:

 

I know but the point is to start from the original engine. I’d call it a challenge, not trouble. At least or now, I may change my mind later on 🤣

 

Ken

I get it, but for me the end result is the point. Some people love the exercise, but in the long term, a goal that's easier to achieve costs less, which means I get to spend more on other things.

[Ken75]

The J18 has a 80.5mm piston so pretty close to the 81mm target. In fact, a +020 oversize is even spot on.

So that’s an option for at least a proof of concept before moving to expensive custom pistons.

 

Anybody any idea on following J18 dimensions:

- piston pin diameter

- piston compression height

- rod length C/C

- rod big end diameter

 

I’ve become even more sceptical on online info lately: I measured the J13 rod length to be 150mm (as written in the workshop manual) but engine-spec.net indicates 142.67mm 😖

 

thanks,

Ken

[datzenmike]

J18 over bore pistons (81mm) on J13 rods and crankshaft make a 1598.6cc engine. Assumes J18 pin heights are same as J13. (probably) Piston dish is an unknown but if J13 and J18 heads are identical then it will have a larger dish than the J13 piston. As it's only cramming 1.6 liters instead of 1.8 liters the compression will be lower.  If you have the combustion chamber volume you can work out how much to shave the head to bring it back up into the 8.5 range.

[Ken75]

I would assume that the J18 rods are a bit shorter compared to the J15 rods to compensate the extra stroke. Maybe the combination of the J18 piston with a J15 rod could work out. The J13 rods have the bolted smaller 17.45mm piston pin so that is no option.

 

So lots of loose ends information wise, and if I have to make a few shipments to Antwerp before I get it right on the parts configuration, I may be better off just going with custom parts straight away - with the option of reproduction in case of interest.

 

BR,

Ken

[datzenmike]

The J15 is just an over bore J13. Rods and stroke should be the same.

 

The J16 shares the same bore as the J15 but uses a longer stroke and likely shorter rods.... although if there's room the pin height could be reduced 4.4mm and the J13/J15 rod kept. Too many unknowns.

[Ken75]

I’m getting ready for a surprise. I have a 520 engine manual which only discusses the 1.3L engine. My 520 has the block with “1300” embossed.

The manual indicates a rod length of 150mm, wich is exactly what I measured in my block. I also checked the cylinder wall thickness, and at most locations it is 5.5mm so a diameter of 84mm. For this reason I always had my doubts that the J15 is just a bored version of the J13, because the wall thickness would only be 2mm at 78mm bore.

 

Then there is the engine manual for the 620 truck. This manual discusses the J13-15-16 engines, and also says that the J15 in essence is a bored J13 and the J16 is a “longer version” of the J15. Unclear if that refers to the stroke or maybe deck height as well. Anyway, the J13 version is written to have “B34” embossed on the block, and indeed so has my spare engine which is said to originate from a South African 620. But most interestingly, the rod length in this manual is said to be 142.67mm as opposed to the 150mm written and verified rod from the 520 block. So maybe engine-specs.net wasn’t all wrong!

 

I’ll be taking the “B34” apart somewhere in the next weeks to see what’s really in there. The rod length will be interesting, as well as the cylinder wall thickness!

 

To be continued…

Ken

[datzenmike]

It should be understood that a J15 uses the same crankshaft and rods and only the piston diameter and bore are increased from 73mm to 78mm. Naturally the casting would be modified to allow for the increased cylinder size to retain a suitable wall thickness and to reduce milling of the bore.

 

The J16 is basically a J15 but with an increased stroke crankshaft (77.6 up to 82mm) and the rods would have to be shorter by about 4.4/2=2.2mm

 or 150mm - 2.2mm = 147.8mm. Now you say that the manual says 142.67mm rod length on the J16 and this can be explained by using a reduced pin height piston (piston is taller) but the same bore as the J15's 78mm. This assumes the deck height for the J13/115/16 are all the same.

[Ken75]

I apologize for my writing being incomplete: the 620 engine manual indicates a rod length of 142.67mm for the J13-J15, and a 139.85mm rod length for the J16 version. So the half stroke difference of 2.2mm as you calculated is pretty close to the 2.8mm difference in rod length. The compression height of the J16 piston could be slightly different, or the piston could sit 0.6mm deeper to adjust the CR using the same head. So that all adds up.

 

But the puzzling thing is that the 150mm rod length for the older 520 J13 “1300” block appears to be different from the 142.67mm rod length for the 620 J13 “B34” block.

 

So the question is where that comes from: the stroke is identical so it must be a difference in deck height or a different piston compression height.

And if the block is different indeed, it is possible that the cylinder wall thickness was increased as well to allow for the 73mm and 78mm bores.

I will post my findings when I open the 620 J13

 

BR,

Ken

[datzenmike]

Good info, I always wondered. We only got the J13 so all the others are a mystery. May have been used in some lift trucks. I saw a DATSUN lift truck once. Looking through the grill it did look like an OHV engine maybe A series but could have been a J

 

 

If so might be a good source of rebuild parts.

[Stoffregen Motorsports]

I believe the J motor was the forklift motor of choice. Many industrial suppliers list parts for J engines. Try doing a google search for Datsun or Nissan forklift engine parts.