Piston & Cam upgrade...should I?

[Kaliv]

While my engine is apart, I have the opportunity to put in some recommended upgrades. The car I have now is pretty much stock as far as the engine is concerned with a 3.2L 9.5:1 compression ratio. I have available to purchase some Mahle Euro pistons at 10.3:1. As they say, displacement is everything. Also, I have available to upgrade is Dougherty Cams DC20 camshafts...whatever that is.

So, questions that I have. If I go with the Euro pistons, how much hp increase would I be looking at? And if I did that replacement, would I have to also do the new camshaft? This is going to be a daily driver, and as I understand it, changing the camshaft will change the rpm range of my car. Even if the new cam gives me more hp, if the rpms are in the wrong range, it's not worth it to me. I need my power between 3k and 5k as that is where I'll be passing most people on the highway. Above 5k does very little for me.

What says the populous? Upgrade the pistons? Upgrade both? Keep it stock?

Thanks!

[Steve@Rennsport]

Hi,

Two thoughts,....

1) If you need maximum performance between 3K & 5K, I would retain the stock cams.

2) At your current 9.5:1, you are at the limit for pump gas using single ignition. If you install the 10.3:1 versions, you will most certainly need twin-ignition unless you use race gas.

[joetiii]

What Steve said....

Is this a street car, or track?

FYI, I've read that the 964 cam extends your power into the 6K+ RPM range. I think the 964 profile is similar to DC20 or DC19... Check the specs on Camgrinder's site. Just don't expect a big bump in power, just less fall off at 6k plus.

[JFairman]

The advice you've gotten on the cams and pistons is spot on.

If the ring lands or skirts are not worn too far on your pistons I'd reuse them with new rings.

If you're getting a great deal on the higher compression pistons then I'd be tempted to use them if it's possible to remove some material from the domes and/or combustion chambers safely and in equal balance to bring the compression down to 9.8 or maybe 10:1 on premium pump gas.
If there is a sharp edge to the squish band in the combustion chambers you can round it off or bevel it to remove a hot spot that could cause detonation.
That would lower compression a small amount too.

Going from 9.5:1 to 9.8:1 or 10:1 will give very little increase in power but you may notice a little more pep, and a small increase in gas mileage.