Hey all,

For some reason I have the opinion that 92mm pistons are a bad idea in a performance engine and 94s would be better.

somthing about thin walls and going oval when they get hot?

I mate a picked a scat engine kit with AA 92's and wants to circuit race it so im a bit worried for him.

Can anyone with actual case machining and or engine building knowledge give me some info about this scenario please?

He is convinced the 92s are a better way to go because he is scared of getting too close to the head studes when machining for 94's????
cheers

There's plenty of guys running 94s circuit and drags.
For what it costs for machining i'd go 94s. In saying that I've had an 1835 and never had an issue but I didn't race it.
My advice would be to unconvince him.

I wouldn't touch the thin wall 92's. One look at the two side by side and it's very obvious, the 92's cylinders are way thinner. Cylinder stability (staying round), head to barrel seal and ring sealing suffer. There are thick wall 92's available but they use the same size hole as 94.

Top engine builders use an even thicker cylinder than the std 94 when possible

Is he worried about the case or the head? Doesn't really matter as his concerns are unfounded. It is a tricky machining proceedure as sometimes the original barrel spiggot location needs to be tweeked to be centred to the studs but nothing an experienced VW machinist isn't used to. Best to get someone like DB (Dangerous) to do the machining.

He could always put 90.5's in - the case and heads are cut the same as 92's
Yes - it will only be 1776

The 90.5's will be thicker walled at the heads than the 92's

Or just run the 92's and reasses when/if you develop power loss or problems later