440 piston identification

[Voss]

Pulled the pan from my 440 today. I do not know the history of the car or engine, but is it possible to say anything about the pistons from the pictures I took? The only markings I see is 1276 05 cast into the piston skirt. Maybe it is possible to tell more when I remove the heads, but I won't do that right now. At this stage I'm only replacing the 187 pan with a correct 402, pickup and windage tray.

[Challenger340]

Sorry to be the bearer of bad news......
but,
Really, really, REALLY low compression rebuilder piston.

Like about 7.8:1

[Voss]

Sorry to be the bearer of bad news......
but,
Really, really, REALLY low compression rebuilder piston.

Like about 7.8:1

Well sooner or later I must start working on improving this engine. I'm certainly not the piston expert here so could you educate me how you identified these as low compression pistons? Learning every day here! 👍

[fy469rtse]

yes i would like to know also,
picked that they were a cast piston , no forged line, lowly cast alloy stock replacement.
dont know how Bob picked the compression ratio from that though ? ,

[Challenger340]

Mostly by just plain "eyeball" recognition of the goofy 1/2 moon skirt bosses by the Pins, and the cross-hatch patterns under the tops, seen those way to often before... like literally hundreds of times !
I guess I am dating myself and what I've been doing for 40+ years.... oh well.

But,
for the numbers proof needed fella's........
you can also google Silvolite #1276P Piston, wherein you will end up here;
https://www.uempistons.com/index.php?main_page=product_silvolite_info&cPath=6_25_27&products_id=1457&zenid=b37b1e4ee440c2e0f08dab4b75e99edc

Those are the notorious and ridiculously low compression Pistons so hated by Performance Enthusiasts..... responsible for giving so many 440's a BAD NAME performance-wise when used by unknowing rebuilders.

They are indeed the 1.91" Compression distance.... or about .140" DOWN THE HOLE @ TDC Pistons !!!.
Like I said,
I don't wish to be the bearer of bad news, but just don't go expecting much from this 440 Engine power-wise ?
That Piston(similar spec), was used in the 230HP and LOWER 440 Engines.

If using any open chamber Head, and a composition style Head Gasket, in the "real world" this will be a mid 7's to 1 compression engine.
Nonetheless, if it runs well..... DRIVE it and ENJOY it, just don't go thinking it is any kind "440 Magnum" type representation.

Secondary caution,
since you mentioned "improvements" or working on the Engine someday ?
That "Piston" is what you will be fighting all the way, with very limited gains to any bolt-ons, making them pretty much a waste of time & money.
ya didn't ask....
but my BEST advice would be to just wait, save your money, and when the time comes re-do the Engine complete, with NEW proper Pistons.

You can do your own Calculations to see what you are up against using Silvolite's own Compression Ratio Calculator here;
https://www.uempistons.com/index.php?main_page=calculators&type=comp

Open Chamber Head = ~88 CC's
Bore at .030 over = 4.350
Stroke = 3.75
Composition Head Gasket thickness = .039
Head Gasket Bore Diameter = 4.41
Rod Length = 6.76
Deck Clearance is .168" (2.08" Piston for "0" Deck on an UN-milled Block, so 2.08" minus 1.912" = .168")

7.5:1 Compression Ratio

[Voss]

Thanks for all info, learning a lot here. The engine has 516 heads. Challenger340, I know you mentioned in a previous thread that this could be a way to bump the compression when low compression pistons were used.

http://www.dodgecharger.com/forum/index.php/topic,89100.0.html

I won't waste any money on fixing things right now. But I have started to save money and plan for a proper rebuild. What's important for me is to get it right when it's done.

With the risk of being a bit off topic now... I'm not the engine rebuild expert here for sure so I hope you're okay with some basic questions for education. Let's say your goal would be to do a rebuild of this 440 aiming for "stock performance" with stock 906 heads. Do you always start by determining the wanted compr ratio and take things from there? What would a realistic compression ratio be for a stock 440 running on todays pump gas?

[BSB67]

Thanks for all info, learning a lot here. The engine has 516 heads. Challenger340, I know you mentioned in a previous thread that this could be a way to bump the compression when low compression pistons were used.

http://www.dodgecharger.com/forum/index.php/topic,89100.0.html

I won't waste any money on fixing things right now. But I have started to save money and plan for a proper rebuild. What's important for me is to get it right when it's done.

With the risk of being a bit off topic now... I'm not the engine rebuild expert here for sure so I hope you're okay with some basic questions for education. Let's say your goal would be to do a rebuild of this 440 aiming for "stock performance" with stock 906 heads. Do you always start by determining the wanted compr ratio and take things from there? What would a realistic compression ratio be for a stock 440 running on todays pump gas?

You have to pick the piston and head together.  If you are starting from scratch, the Mopar open chamber ( i.e. 906) is about as poor of a choice as you can make. You can pick a decent piston for just about any other cylinder head out there.  For what it will cost to make the 906 a decent head, you'll have a bunch of money in them, and it will still be a crumby open chamber head.  There is just no logic to it if you are wanting a performance motor. and that is coming from a guy that uses exhaust manifolds instead of headers.

If you want to keep it simple, by a piston with a 2.06" ish compression height, and a closed chamber head.  You can either use a true flat top and a 84 cc head, or a 75 cc head and a dish piston.

[Challenger340]

Thanks for all info, learning a lot here. The engine has 516 heads. Challenger340, I know you mentioned in a previous thread that this could be a way to bump the compression when low compression pistons were used.

http://www.dodgecharger.com/forum/index.php/topic,89100.0.html

I won't waste any money on fixing things right now. But I have started to save money and plan for a proper rebuild. What's important for me is to get it right when it's done.

With the risk of being a bit off topic now... I'm not the engine rebuild expert here for sure so I hope you're okay with some basic questions for education. Let's say your goal would be to do a rebuild of this 440 aiming for "stock performance" with stock 906 heads. Do you always start by determining the wanted compr ratio and take things from there? What would a realistic compression ratio be for a stock 440 running on todays pump gas?

Thanks for all info, learning a lot here. The engine has 516 heads. Challenger340, I know you mentioned in a previous thread that this could be a way to bump the compression when low compression pistons were used.

Yep I did,
and I although I didn't go back and re-read what I posted, ANY of the Closed Chamber Heads were usually installed after the initial "mistake" of using the low-pop Pistons was made..... as a way to try and increase what's called Dynamic Compression, or the "effective pressure" the Engine is working with.

With the risk of being a bit off topic now... I'm not the engine rebuild expert here for sure so I hope you're okay with some basic questions for education. Let's say your goal would be to do a rebuild of this 440 aiming for "stock performance" with stock 906 heads. Do you always start by determining the wanted compr ratio and take things from there? What would a realistic compression ratio be for a stock 440 running on todays pump gas?

This could be a very extended topic, suffice to say, far more going on with what's known as "quench" and "Effective Combustion Pressures" or DYNAMIC Compression Ratio(google it) modified by Camshaft events
as it relates.....
to then duplicating the Original 440 Magnum's performance with the factory 2843906 Iron Heads, using Today's lower Octane Benzene rings.
than I could ever get into here....

It CAN be done, I have done it, even with NO quench on the "open" 906, and even exceeded the factory advertised numbers with 906 Irons on pump gas with NO detonation whatsoever ! usually for High-Dollar resto guys though, who absolutely HAD to have their 906 Heads for originality.
Just say'in...
I can't go enlightening enough of 40+ years of experience Machining, Building and Racing these Engines here, up to and including taking FlowBench data and then custom grinding Camshafts, using swirl on cylinder flucuts(put any BB Head Gasket on a stock Block to "see" what I mean here), and on, and on,
just far too many pitfalls for laymen.... for me to just say "DO THIS"

But, that said....
and also recognizing the NEED for some decent "performance" out of 440's for laymen, without breaking the Bank PAYING me(I get paid very well BTW), that's why I posted those "lowly 440" engine builds on here ?
They look "stock", (albeit with the "stealth" Aluminum Heads when painted), are CHEAP to do, and should be repeatable pretty much anywhere geographically using local Shops ?


What would a realistic compression ratio be for a stock 440 running on todays pump gas?
"Published" is about 9.5:1 "static" with Iron Heads..... but waaaaay more going on with an internal combustion engine, nonetheless 9.5 is the "safe' number for conversation.
Sorry, I know I am NOT answering your basic question here....
but basically it boils down to there is no GOOD answer as it relates to strictly "static" Compression Ratio ?

I can show you 2 IDENTICAL Engines, BOTH 10:1 static Compression Ratio, BOTH with 906 open Chamber Iron Heads, even BOTH using the SAME Camshaft.

one will DETONATE like a motherfawker and eventually kill itself...
and,
the other will run absolutely fine, and make way better power.
What's the difference....
it all depends upon Cylinder Head prep(how it flows the Air & Fuel) and Machining.