The piston debacle

Sheesh! Finding proper 4A-G(Z)E pistons is a mess!

The following pistons are listed with 20mm pin and 30.68mm (1.208″) compression height

  • Wiseco K506M815
  • CP/Carrillo SC7653
  • Wössner 9035D050
  • Wössner 9191D050 is strange. It has a 30.6mm compression height. WTF?
  • Wössner 9278D050

…and following pistons have 20mm pin and 30.5mm (1.200″) compression height

  • Supertech P4-T4AG16-20-81.5-CR11
  • Toda 13010-4AG-001
  • Toda 13020-4AG-001
  • Toda 13040-4AG-001
  • Arias AP331669
  • Arias 3721070
  • Arias 3731220

If my current pistons can be shaved a bit, I’ll keep them. I’d love to get the compression height from 30.68mm to 30.5mm and shave a bit off the piston crown to get dome volume somewhere around 2-3cc. This would drop the compression rate little bit below 11:1.

Otherwise I’ll get the Supertech pistons. They’re pretty damn near perfect. 🙂

Difference in compression height numbers probably comes from two pin sizes. Early 4A-GE engines had 18mm pin, later models had 20mm. Some of the companies dont seem to care about this.

I promised myself that I wouldnt get any parts from a country, which still uses imperial units. Meh…

  • Supertech = imperial
  • Toda = metric
  • Arias = imperial
  • Wiseco = imperial
  • CP = imperial
  • Wössner = metric

Wössner would do, they’re from Germany, but why do they have that compression height error too?

Matrix Garage has some pistons too, based on their own design.

Guesstimates about compression ratio 2

Well, I might have to buy new pistons. I made a mistake when doing calculations about compression ratio.

First of all, I dont know my current deck height. Internet says it is 191mm, but Wiseco uses 192mm. That one millimeter is going to make a huge difference. We’re talking here something above 12:1 compression ratio if the deck height is 191mm.

Also, Wiseco pistons have compression height of 30.68mm and as far as I can tell, stock pistons have 30,5mm. With a small end pin, I set a stock piston next to Wiseco piston to show the slight 0.18mm height difference. Hope the photo is clear enough:

I have to find a good source for either deck height or deck clearance.

Edit: New calculation

  • Bore: 81.5mm
  • Stroke: 77mm
  • HG thickness: 1mm
  • HG bore: 82mm
  • Deck clearance: 0mm
    • (this is a rough guesstimate. Many sites give a 0.38mm deck clearance. Wiseco pistons are 0.18mm taller than stock, which means 0.2mm deck clearance. Also, my block is shaved slightly (guessing 0.2mm) so total will be 0mm)
  • Piston volume: 5.9cc (domed)
  • Combustion chamber: 36cc (not measured yet)

With these values my static compression ratio is 12.3:1, which is slightly high 😀

If I change the head gasket to 2mm thick, CR goes down to 10.8:1. Only problem then is the squish cap, which is way more than optimum.

  • 1mm headgasket – 12.3:1 CR
  • 1.2mm headgasket – 12:1 CR
  • 1.4mm headgasket – 11.7:1 CR
  • 1.6mm headgasket – 11.4:1 CR
  • 1.8mm headgasket – 11.1:1 CR
  • 2mm headgasket – 10.8:1 CR

Guesstimates about compression ratio

This is what I came up with Wisecos calculator. Why o why is the calculator using both imperial and metric??

ok, anyhow, my guesstimates were between 10.5:1 and 11.9:1. With stock values I got 11.1:1, which sounds just perfect.

Slightly related, I just read about an aquaintance of mine who had used 135mm long conrods instead of stock 122mm in his 4A-GE. Wonder what kind of pistons he used…?

(they were custom made by Wiseco + longer conrods from auto verdi)

Oh! Edit 7.9.2017 – where did I get these numbers

Bore diameter: 81,5mm

Engine stroke: 77mm

Head volume: 36cc (stock)

Gasket bore dia: 82mm (HKS)

Compressed gasket thickness: 1mm (HKS)

Deck clearance: 0.7mm (about)

Dome volume: -5.9cc, compared to stock (Wiseco)


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

Parts from coating

Got some parts back from coating!

Cylinder head has some white crud all over it. No idea what it is and how to get it off.

Valves and everything (I mean everything, even the plugs) were coated in heat resistant stuff. Outside, cylinder head got a coat of stuff that helps heat to radiate away from it.

This is a Ferrari F360 flywheel if I remember correctly. Widric found it from our stash. 🙂

Pistons got three different coatings on them. Top of the piston was coated with heat resistant, skirts with friction stuff and the underside with that same stuff as cylinder head that will radiate heat away.

Some bits are now sandblasted and powdercoated. I will have to find some nice paint(s) to do the letters.

Not pictured here are the new camshafts, all the bearings and the block. Camshafts and bearings got a coat of that friction reducing stuff, while the cylinders were rubber with tungsten powder to… well.. reduce friction 🙂

I will get my exhaust manifold and turbo coated as well.

Piston rings + crank girdle

Checking pistons and rings:

Gap on fourth cylinder is 0.35mm.

Pistons seem to fit into block. That is a good thing.

A package from Manon Racing Products arrived, containing Toda timing belt and oil pump gears, N2 style additional timing belt tensioner (or guide) and a crank girdle.

Timing belt tensioner. Fitment is very good.

And the crank girdle. A serious piece of hardware. I needed only some stiffening but now the engine will be bombproof.

Veeery nice 🙂

Buttloads of stuff

Lots of stuff coming in!

The cutest package from Thailand:

Cute box contained connectors for Toyota coil on plugs. Most likely fake as fuck but hopefully they work enough.

Pistons, again.

Arp hardware – studs and bolts. No cat this time.

Engine management unit from MaxxECU, with long loom, lambda sensor and stickers!

The turbo – BorgWarner EFR 6258. Hardware kit needed.

Toyota coil on plugs (dirty and used) – look how the last one is bit short and stubby compared to the rest of the coils. The last one is from Yaris and the long and skinny ones are from Lexus. Funny thing is that I ordered four Yaris ones but got three Lexus coils and one Yaris.

Not going to complain, because the Lexus coils seem to fit pretty well into 4A head. 🙂

Lexus coil part number – 90919-02246