[cmoc-bob]

Saw this in Engine Builder magazine, just happened
to see what they had for Pontiac.

Our 400 sized pistons are listed under the 455 PDF.

Coated, 2 forgings available, thin rings, etc.

https://www.us.mahle.com/media/usa/m...bp-webpage.pdf

[cmoc-bob]

From Mahle
POWERPAK feature includes:

Forged piston for performance applications
Fully-machined crown
GRAFAL anti-Friction coating on skirts*
Phosphate-coated to reduce micro-welding and pin galling**
Pin bores finished on CNC boring equipment
Hand deburred
High-strength steel pins
Race-proven round wire locks
Low-drag ring pack
Light weight slipper skirt forgings
* MAHLE’s GRAFAL skirt coating reduces drag, scuffing, friction and cylinder bore wear and piston noise.

** Phosphate coating provides the grey appearance to the MAHLE piston. This dry lubricant coating (not to be confused with a thermal film coating) provides a lubricant film in the pin bores and ring grooves until the oiling system of the engine reaches operating pressure; particularly useful during the initial start-up or break-in of engines to protect against galling and microwelding. The piston crown is still machineable.

[steve25]

I question why it looks like there are only 4 oil drain holes in oil ring land.

[cmoc-bob]

If the pics on Summit's website are accurate, looks like 6 or 8.

Which, can be a stretch considering how Summit sells and keeping accurate pics of parts.

I'll email Mahle next week.

https://www.summitracing.com/parts/m...WO0-P#overview

[JLBIII]

The machine shop that did my recent engine rebuild used a set of the Mahle 930275085 F/T pistons. Engine made over 600h.p. with ported KRE D-port heads, Northwind manifold and 850 carb on the dyno stand.

[JLMounce]

They've been available at least since mid 2024. My engine builder wanted to use them, but as you can see the pin heights are only for stroker combinations with 6.8" rods.

[cmoc-bob]

I'm doing 6.8 rods, so they kinda were perfect for me.

Any idea why Mahle notes "not for 400 blocks with valve reliefs"........I wasn't aware any 400 Pontiac blocks had valve reliefs.

Just curious......

[performerrpm]

Originally Posted by cmoc-bob

I'm doing 6.8 rods, so they kinda were perfect for me.

Any idea why Mahle notes "not for 400 blocks with valve reliefs"........I wasn't aware any 400 Pontiac blocks had valve reliefs.

Just curious......

because the top ring sits higher .200 from the top of piston. the 67 blocks have the relief in bores, a 4.155 piston the top ring will end up just in the bottom of the relief. 4.185 bore puts the top of the ring just at the bottom of the relief..

i know this because when i went to buy my stroker kit from a guy, he insisted i take the block which was a fully machined 67 block with reliefs. i had to assemble it just to confirm.

[chiphead]

All the 400 blocks have valve chamfers, but the '67 400 block has the old 389 reliefs. Those are in a different spot and slightly deeper than the 68-newer. I had to check them on my '67 block and set the top ring .300 down on the custom pistons.

[cmoc-bob]

thanks, didn't know that !