I'm in the process of rebuilding my 95 LT1 Camaro for daily driver status with frequent trips to the strip and revving to redline on a regular basis. I wanted to get stock type pistons and I'll be boring .030 over. I ruled out forged pistons because I heard they can be noisier at startup due to the greater bore/piston clearance. I ordered Mahle p/n 224-2810 in the .030 over size, but got p/n 224-3498. The packing slip says these supercede what I ordered. Mahle's catalog lists both of them as replacements for the LT1 and it looks like the 224-2810 is discontinued.

My concern is that the 224-2810 is listed as hypereutectic which is what I wanted, but the 224-3498 is just listed as aluminum. Should use the 224-3498's or order from someone else like Sealed Power in hypereutectic? The Mahles are listed on pages 142 and 143 in the catalog link below. Your help is greatly appreciated!

Mahle catalog link:
http://www.mahleclevite.com/publications/PI-20-09.pdf

 

Why are you boring it?

 

I should also add that this engine will be naturally aspirated and I have no plans to ever add nitrous. In fact, the only real modification is the infamous Crane 227 cam. I will be strictly using the stock RPM range. I plan to put 30K+ miles per year on this car.

 

The engine has 260K miles on it. The machine shop told me I had about .003" wear in the cylinders. I could have just went .020", but we just picked .030". We agreed that it would be a good idea just to start fresh. Since I got so many miles on it in stock form, I would like to keep it mostly stock. My original problem that started this rebuild was a rod knock.

 

Honestly for what you will spend for good pistons you could find a reasonable mileage Caprice/Roadmaster engine(same bottomend as the f-body() and use that shortblock and probably have something higher quality than a budget local rebuild. GM has a LOT better equipment than most shops.

I am not saying the stock engine is best, I am saying the stock engine is better than cheap rebuilds.

 

It's too late now to change plans with a junkyard shortblock. I insisted on getting top notch machine work which is why I chose the shop I did. They build many race engines and have an excellent reputation. I am choosing to not overspend on parts for what I'll be doing with the engine.

So I guess my question is, are the "aluminum" 224-3498 Mahle pistons shown in the catalog link in the first post cheap and why would Mahle even offer a regular aluminum version in the first place? What would be the benefit over a hypereutectic piston?

 

OK, I'm going to answer my own question. I talked to Mahle directly today about these pistons. For anyone looking to do a stock type rebuild with OEM quality pistons, use either Mahle p/n 224-3497 or 224-3498. The only difference is the compression height. The 3497's will give a little more compression (height = 1.559" vs 1.549" for the 3498's).

As far as the material grade, these pistons are a higher grade than hypereutectic. In fact, the 224-3497 is listed as hypereutectic in the Summit Racing catalog. Not sure why the 224-3498 is listed as economy. 224-3497 and 224-3498 share the same casting.

 

While Mahle make great products, some of that is sales-speak. 'Higher grade than Hypereutectic' is fairly meaningless as that refers to the composition of the material used in the piston. All of them, Mahle included, are alloys of aluminum. Hypereutectic means that the allow contains a large amount of silicon.

What is the weight given for these pistons? That's pretty important when thinking of the stresses applied to the con rod bolts.

 

I am not a piston expert but I have experience with these pistons

I used those exact pistons in my "stock type .030 over rebuild" and then got a little carried away with some LE2 heads, ARP rod bolts, custom cam, ported manifold, 58 MM TB, 36# injectors, 11.7:1 CR, etc etc.
Car dynoed 373 WHP at 13.3 AFR.
Unfortunately It did not last too long. After 3000 miles and six consecutive passes at the strip revving it up to 6200 RPM I broke ring lands on three pistons and had to do it all over again.



I did re use the same pistons the second time around. I think they are a great buy for the money and you dont have to worry about balancing the rotating assy. The .030 over even have a slighly lighter wrist pin to compensate the heavier piston.

Just use them for what they are intended:
A stock type engine rebuild

 

Well Ricardo, that makes you an expert on these pistons. So you went with these again? Did you build it closer to stock the second time around or did you just take it easier at the dragstrip?

For the record, I'm getting mine balanced - same as factory - internal front, external in the rear.

 

Thank you guys for posting what you have found about these, there are more questions posted than real answers.

Personally I don't think I would buy anything less than a Mahle PowerPak for a performance build. Yes they are forged but they are a non-typical material which expands less and therefore can be run tighter and quieter than many other forged pistons.

 

If you get piston slap with forged pistons these days you need to find a new machine shop that knows what they're doing.

 

Sorry to hear about your problems Richardo. Sounds like detonation, not wrong pistons, caused the ring land to break. Maybe your tune needed less timing.
To the OP, your question started a good thread.

 

I am sure this was the effect of detonation, cast pistons do not tolerate detonation as opposed to forged pistons.
Since I was not able to determine the exact reason for detonation I took several precautions:

1)Lowered compression ratio a bit with a thicker head gasket (Fel pro over Impala - .039 over .029)
2)Richened the A/F ratio half a point on the top end (12.8 compared to 13.3)
3) Backed off timing by 2 degrees from my previous tune on the 80-100 kpa range.
4)Returned to the OEM baffled valve covers. (I was running some fabricated aluminum with no baffle in the TB connection )

Fortuately the cylinder walls were untouched and was able to get away with just a minor hone to seat the rings again. I have returned to the strip, but just for fun. I now use the engine in my DD.