Large bore 8valve

[Rallyace 3]

I would like to build a large capacity engine using an 8 valve cylinder head. Which block, piston and crankshaft combination do I need and what capacity can I achieve? 

[SRDT 232]

For the bottom end you can find a few 16v builds on the forum ; it's basically XU10 iron block bored to 87 or 88mm + 96mm stroke DW10 forged crank.

The XU10 head has bigger intake valves than the others, the round intake ports can be enlarged to match the square ports from XU5/7/9 intake manifolds.

There is a 8v turbo head with better exhaust valves and maybe updated internal cooling, n/a heads should have the same casting as long as they have provisions for the two extra threaded holes on each side of the turbo exhaust manifold. Turbo and n/a spare parts bare heads are exactly the same.

[petert 630]

Also, the XU10J2 head is better for this as it has a wider chamber, better suiting the 86+ mm bore, which unshrouds the inlet valve better than the XU9 head.

[SRDT 232]

9 hours ago, SRDT said:

96mm stroke DW10 forged crank.

*DW12, aka 2.2 HDI.

[Rallyace 3]

Thanks for the info. I’ll start to locate the parts.

[SRDT 232]

If you want a XU10 block with oil jets to cool the pistons you need a XU10J4, XU10J4RS or XU10J2TE block.

The jets on the XU10J2TE are diesel style and better suited for a 8v, the 16v jets will aim where the 16v exaust valves should be.

[Rallyace 3]

Thank you for your help so far.

I have sourced a S16 engine. I have also got a GTi6 inlet manifold, which I believe is the preferred option. I’m beginning to question whether I should go for the 2.2 crank due to the additional mass of the balance shaft gear. I like to hear your thoughts on this.

So lots of doubts at the moment. Stick with the S16 head with some basic porting and perhaps a better inlet cam, which some seem to suggest is a useful mod. Or look for an XU10J2 head (which cars was this fitted to) for the sensible reasons outlined by PeterT. To reiterate, this engine is intended for Targa Rallying. I’m not necessarily looking for high revs, the limit set on the standard engine would be fine, but happy to be advised. What I’m really after is as much torque as I can reasonably get. There’s a lot of stop/start from controls and slow turns around markers and chicanes are commonplace. I look forward to your responses. I’m sure that I’ll have lots more questions in the future.

[petert 630]

S16 head? I thought you were staying with 8V? A standard S16 head will outflow the very best 8V head. It’s not even a close contest.

[Rallyace 3]

The original plan was to stay 8 v, but as I’m getting a S16 donor engine , it probably makes sense to stick with it.

[petert 630]

Easy to rebuild and easy hp.

[Rallyace 3]

I have been offered a set of Maxspeeding forged rods for the XU10J4 RS engine (158mm) complete with ARP bolts. Would these be useful to use with any of the longer stroke cranks as part of the build of  my S16 engine? 

[petert 630]

What size pin? Maybe use with an XUD11 crank, K20/24 pistons and skim 1mm off the block?

 

ie

46 + 158 + 30 = 234mm

[Rallyace 3]

The pin diameter is 20mm. Are the Honda pistons 22mm diameter ?

[petert 630]

9 hours ago, Rallyace said:

Are the Honda pistons 22mm diameter ?

Yes.