what forged pistons brand

[filh]

As expected , I broke my 6th 4age engine . Always same problem : rings and ringland broken .
It's a rally car and it's a heavy use .
Engine only have 2 small CatCams , and a lighted flywheel.
Always fitted stock pistons ([u:4b59bf6630]oversized 81.5mm bore, 18mm pins[/u:4b59bf6630]), but unavailable now from Toyota.
Mostly use Mahle .
The engine was tuned on a Dyno bench : fuel management and timing were correctly fitted.
Problem seems to come from a too high C.R. due to multiple head surfacing.

I think the best solution could be to fit stronger forged pistons .
But most I found (Wiseco, TODA) are dome top . Impossible for me to use as CR would raise a lot more .
I'm searching for flat top forged pistons, but don't know which manufacturer or supplier could help me .
Any experience with this ?
Saw Arias , but don't know if they can fit my engine .
http://www.ariaspistons.com/products/toyota.html

Phil

[NoHachi]

scat?
http://www.coasthigh.com/Toyota-4AGE-88-.../14497.htm

[filh]

Thanks for the link , it looks like what I'm searching for .
But i'm a bit lost : as I ckeck the bore size (in technical specifications) , they're speaking about 83.5mm.
I thought it was 82mm maximum size?

And If I check the wrist pin, it's 0.866in (looks like 22mm) it's much too large .

But anyway it's what I'm looking for .
I'll try to contact them to know if they can supply what I need in size.
Many thanks for your interest
Phil

[totta Crolla]

Phil, if you have a bigport engine sling it out along with the catcams and fit a smallport engine complete. Expect to make similar power but have some reliability.
Has anyone ever seen a properly timed stock engine break the pistons in the way described above ?

[Project D]

Far as I remember, Arias made pistons only for 4AG with 20mm pin
Find a new head or change your engine. (actualy a complete bluetop 4AG can be found for less than a set of forged pistons)

[apardal]

Try to find out how much you've shaved the head so that you can decide on which head gasket to use.

HKS sells 1.6mm head gaskets.

Although I have them and don't like Wiseco pistons very much, I would recommend them for their cost/quality. Anyways, at stock head height, they don't raise the CR much.

I've got a 0.6mm shaved head, 0.8mm TRD head gasket, 0.1mm shaved block and wiseco pistons. This results in 12.2:1 CR which is in fact too much for stock camshafts. Only with these 296º and 9.4mm kent camshafts I got now I was able to get rid of detonation issues.

Bottom line, Wiseco pistons and 1.6mm HKS head gasket could do the trick

Good luck!

[filh]

Thanks for your interest.
To resume : As I said above , the engine was correctly tuned (timing and injection) and was verified on dyno bench.
This last engine was use in about 1500km of rallye stages .

My machinist mostly work on race engines .
He was the engine builder when Toyota competed in European touring car championship, with the AE86 Fina (Fermine / De liedekerke)
He has a lot of experience and make many engines like Citroen C2R2, winning cars in local rallye here in Belgium.

My head was too much shaved , due to multiple milling (in fact each time the engine broke )head chamber are now 30cc. I think stock head is 37cc.
The headgasket is 1,7mm thick (oem Toyota late 4AGE engine)

The C.R. is 10.6.
Each time the engine was rebuilt , I used new pistons : Mahle , and another Japan brand .
And it was always the same result: broken rings and ringlands

I bought two stock used engines . Opened them and found same spectacle as in mine : broken rings and ringland .
That's why I don't want to buy another used engine , even smallport.

I've decided to change the head , starting from a stock one .
And i'll order Wiseco or Wossner forged Pistons , giving 11.6 CR .
But as the engine is near from stock (only 2 small Catcams and a light flywheel)I'll need more petrol and will have to install bigger injectors and AFR.
Hope it will be more reliable .......
Thanks again .
Phil

[Ivan141]

Filh,
I'm no expert on pistons, but I'm fairly sure the broken ringland syndrome of the standard 4age pistons can be traced directly to the slotted oil channels behind the piston rings. This just introduces an inherent structural weakness. Most aftermarket pistons use round holes for the oil channels, probably for the same reason.

[filh]

I'm not expert in pistons . I'm a serial 4age killer
But I think the stock Toyota pistons were stronger , but it looks like they are out of stock now .
I used to compete with the same old stock engine for 5 years , whitout breaking something.

Speaking about broken ringlands , I don't know if the weakness is on the hole shape :
Each time I broke ringlands , it was between 1st and 2nd rings.

My machinist think about high revs in charge and for a long time .
Such as 1km flat out , big braking , and restarting for 1km flat out.
There is no sign of detonations on piston top , and bearings are in good conditions

[robokill]

Fillh,

have you worked the water and oil channels of the bottom end of the engine? There is alot to gain in flow which should help the cooling.

In you case I would buy a 20v bottom end buy toda pistons (wiseco's dome is really not that good with the pointy roof)

Use either sports thermostat or no thermostat (need enough cooling)

Don't shave the head. Always shave the block.(only shave the head to get it straight) I assume you have a bigger radiator etc? Where is your rev limiter? Is the crank and rods balanced?