Forged pistons, silicon content and sidewall clearance

Tait Parkin
Tue, 5 Aug 2003 09:15:58 -0500


I have no doubt there was some serious expansion going on with the first
engine, when warm it did fine (untill a host of other problems showed up).
Also, this engine's piston were coated by Swain Tech- I doubt it had
anything to do with the final destruction of the engine.  With the Sunbelt
engine I am a little in the dark.  They used no coatings that I am aware of
internally.  Jim did state they spec'ed the pistons and I have no idea what
the clearences are (I will find out for you- I also made perfectly clear to
Jim that the engine was to be daily driven and wanted some life out of it).
The Sunbelt engine is great so far.  Talk about a bunch of professionals.
The base-line run of the engine at the wheels was ~200 hp and ~227 torque at
10psi.  I had to have some plumbing related issues cleared up (leaky
intercooler pipes and a too-short intake pipe) before the tunning went any
further.  To date I have not turned the boost above 10 psi and I should try
and call today and hope I can catch Jim at the shop.  Those guys are all
over the country supporting those Mazda engines.  Bace to the point at hand.
Jim recomended forged pistons (and at the cost of his labor I do not believe
I was being stroked) but stated the connecting rods (DET) would work with
just shot-peening.  I did ask about Swain coating the piston in this engine
and he replied that it was not necessary (he didn't expound further).  I am
happy with the engine and can not wait to get it back on the dyno, then go
and break some third gears!!!

Word to the wise- if you do not have complete faith in your builder
(personal experience or one hell of a reputation), do it yourself or do not
do it at all.