Pistons are in – part 2

While I was tightening conrod bolts, I found out that the bolt head was not 10mm.

Totally forgot that ARP does not come from metric world. Almost shat my pants when I felt the tool slip – luckily it was just the socket giving up.

Figured out pretty quickly that the bolt head must be 3/8″, which converts neatly to 9.5mm, and just to make sure that the size wasnt something really weird I also bought a 9mm socket.

Perfect fit – it was 3/8″. I cleaned everything twice and tightened the bolts to 40Nm per instructions from conrod manufacturer.

Heading towards this:

Meanwhile Widric had bought a disco ball.

Pistons are in

After quickly checking the shop manual that I wasnt forgetting anything (like those ring pins), I rummaged through Widrics stash for a piston ring compressor.

Quick check from the internet how the piston ring gaps should align and in they went.

All four went in nicely, no hiccups, very smooth movement and no obivious problems.

From below, bolts are in place but not yet torqued.

After getting back home, a cold surprise from Hokkaido!

Camshafts, bearings and intake

Here are the camshafts. Coatings for more slippery 🙂

Sadly, at the moment they’re the only engine bits I have. Rest of the stuff is at Martelius’

The bearings thing.

I spoke with a friend about conrods in general and also about symmetrical conrods, when I realized what the “always turn the engine to normal rotation direction” means. I’ve thought it had something to do with piston rings but oh boy was I wrong. It’s about bearings.

See the little notch there? The bearings should have a tang that goes into that notch. If the engine is turned “backwards”, the bearings could dislocate and jump off the notch, maybe resulting spun bearings.

Fuck I’m an idiot! I havent ever realized this before 😀

Second peek to the intake! Still much to do.

List of manufacturers

Here are some of the manufacturers I considered for my project:

Pistons: (CR numbers not exact)

  • Wiseco K506M815 81,5mm (CR 11:1) (20mm pin) + piston rings
  • CP/Carrillo SC7653 81,5mm (CR 12:1) (20mm pin) + piston rings
  • Wössner K9035D050 81,5mm (CR 11.8:1) (20mm pin) + piston rings
  • Arias AP331669 81,5mm (CR 8.2:1) (20mm pin) + piston rings
  • Arias 3731320 81,5mm (CR 12.5:1) (20mm pin)
  • Supertech P4-T4AG16-20-81-CR11 81mm (CR 11:1) (20mm pin)
  • Toda 13020-4AG-001 81,25mm (CR 11:1 STD HG) (20mm pin)
  • Tomei 1163815012 (81,5mm) (CR ??) (??mm pin) (not sure if these are available anymore)


  • Auto Verdi (Custom)
  • Manley i-beam (?)
  • Manley h-beam (?)
  • Pauter (TOY-200-450-1220F)
  • Carrillo (???)
  • BC h-beam bc625+ (BC6354)
  • BC h-beam (BC6355)
  • Molnar (TH4803BCB4-A)
  • Arrow Precision (Arrow 142) (these would have been my second choice)
  • Tomei (125007) (not sure if these are available anymore)
  • JUN (1002M-T001)


  • Arrow Precision (Arrow C120) Maybe in the future 🙂
  • BC (bc5359)
  • JUN

Head gasket: (havent yet ordered)

  • HKS (2302-RT002) 82mm bore, 1mm thickness, stopper type
  • Wössner MLS, multiple choices