1971 440 HP Pistons

[BSB67]

My intent, first and foremost is to get educated here, thus as a novice, please bear with me. I have a '73 stock 440 HP. I want to leave it stock in external appearance but would like to get more power out of it, similar to a stock '71 440, thus without going to a different head, my most effective options would be pistons and cam (I think). I am thinking about replacing the thermo-quad with a Holley Sniper EFI and eventually going to an overdive automatic trans. My intent is to have a great highway crusier not a drag car and I could probably just rebuild the engine in stock '73 form and get that. However, it is a 440 and without getting to radical I'd like to get more out of it than the stock '73 version offered. I know they changed how they rated horsepower starting in 1972 thus I don't know how far apart a '71 vs. '73 are if they rated horsepower the same way on both engines. I do know the compression ratio is different amoung other things. Thanks for any feedback.

Here is the problem, we don’t know what you know, and don’t know.

It’s not clear to me if you know what it means to change pistons. Some experienced folks can probably do a piston swap on the cheap in certain conditions, but that’s not you.

You take your motor to a shop and ask for new pistons you’ll probably have a $6000 bill when it’s all said and done, you’ll still have junk heads, and little performance improvement, IMO.

Conversely, the right set of well prepared heads will cost half as much and give a noticeable performance boost.

Let’s start with: What is your budget?

 

[Curiousyellow71]

Yes, Kb, Icon and Silvolite are all made/offered by UAM.

But not Icon from the shelf on stock stroke for 440… not at least on their website.

Silvolite offers them thought… 1.912 and 1.969 CR for flat tops and 2.023 for dished

Below are the icons from their list. There is one stepped piston available.. but has a dish. I have not yet seen a forged stepped piston flat top like the kb pistons. But we have a stepped icon flat top in our 542.
The op needs to be aware that any piston with a bb chevy .990 wrist pin will need aftermarket rods or the stock rods will need to be bushed. Also pistons can have different size rings. Thinner rings typically free up a couple hp. Also plan to balance the crank with lighter pistons.
There several companies that make pistons.
CHRYSLER 7.2L/440 Mopar big block RB Pistons - 3.750 in. Stroke - Free Shipping on Orders Over $109 at Summit Racing

 

[Nacho-RT74]

Hence why I said, not at least on their website LOL. OR I couldn’t find them at least.

Anyway, aside the price for them, if the pin is not the stock one, adds more money. Sooooo I guess the KBs still are the best bang on the buck on market… and still considering the stock replacements speed pro and similars.

Also I know there are even better prices than Summit.

 

[Charger Fan]

For reference, does anyone have compression height and how far in the hole the stock 1971 440 HP motor piston had?Also the cam specs?

 

[66 Cornpicker]

I did use the KB quench dome on my 440 build for my 63 Savoy grocery getter that runs on premium pump gas here in Ohio. Had to go +.040, used 452 heads off a motorhome and installed larger intake with some bowl work. Small roller cam and topped it off with an A&A max wedge intake. This car is way to much fun ! Just an old school throwback..

 

[Nacho-RT74]

For reference, does anyone have compression height and how far in the hole the stock 1971 440 HP motor piston had?Also the cam specs?

The cam specs…

Is the basic Purpleshaft camshaft PN P4452783

Although those specs are aprox and the real values measured by experts are here:

Chrysler High Performance Cam Data


Now, the pistons… supodselly SpeedPro are made within stock specs, being the straight replacement for the factory ones

Mopar TRW Forged Pistons Speed Pro Forged Piston Hypereutectic Sets

Now, how much deep into the hole… I guess thats a machinery deal and that changes a lot between engines, since it was never a precise cut.

 

[BSB67]

The 1.99” piston will be about 0.090” - 0.100” in the hole on an uncut block.

 

[Charger Fan]

The cam specs…

Is the basic Purpleshaft camshaft PN P4452783

View attachment 1748586

Although those specs are aprox and the real values measured by experts are here:

Chrysler High Performance Cam Data


Now, the pistons… supodselly SpeedPro are made within stock specs, being the straight replacement for the factory ones

Mopar TRW Forged Pistons Speed Pro Forged Piston Hypereutectic Sets

Now, how much deep into the hole… I guess thats a machinery deal and that changes a lot between engines, since it was never a precise cut.

Nacho, do you have the cam specs for a stock '73 440 HP for comparison?

 

[Nacho-RT74]

Is that one… the MP P4452783 camshaft was a factory production camshaft for all magnum engines. It got several supersedes numbers along the years but that was the last PN asigned and included on the MP catalog being the factory replacement.

The real specs are posted onto the victory library link I posted on same reply

 

[Charger Fan]

Thanks. Did all “U” code 440’s come with a forged or cast crankshaft in ‘73.

 

[Curiousyellow71]

Thanks. Did all “U” code 440’s come with a forged or cast crankshaft in ‘73.

We have a 73 440hp and is has a steel crank. I don't know what car it came out of.

 

[Nacho-RT74]

THEORICALLY since 72 just 4 speeds got forged cranks. But on 73 no 440 4 speeds were offered, so probably some 73s 440s got leftovers forged cranks.