What piston do i have?

[66FBCharger]

With my Charger I got some receipts. I have a receipt from a NAPA in Wisc. listing engine parts. The receipt was from July 1981.
I have listed, Qty.:8  P278 Pistons $217.52
My questions is what size overbore is it? What approx. compression ratio is it supposed to be? For some odd reason I thought I found something that said the part number was a Badger piston. Are all Badger pistons cast?
I can post the receipt if that would help.

[66FBCharger]

Here is a copy of the rebuild receipt.
What do I have (assuming the engine hasn't been rebuilt since '81)?

[Challenger340]

With my Charger I got some receipts. I have a receipt from a NAPA in Wisc. listing engine parts. The receipt was from July 1981.
I have listed, Qty.:8  P278 Pistons $217.52
My questions is what size overbore is it? What approx. compression ratio is it supposed to be? For some odd reason I thought I found something that said the part number was a Badger piston. Are all Badger pistons cast?
I can post the receipt if that would help.

As far as I know, all Badger Pistons were "Cast".
and Yes,
it certainly looks to be the old Badger Piston numerical parts listing     

I have no clue on the P278 Number, but yes..... Badger did in fact list a 440 Piston under the P218 part number.

Could you be mis-reading the "1" as a "7" ?  
Could it be a typo on the 1981 Invoice ?

[66FBCharger]

What is the description of the P218 piston? Would the part number tell you what oversize it is and what advertised compression ratio it is supposed to be?
P278 could be written wrong on the invoice. It does look at like a "7". See the invoice I posted.

[Challenger340]

What is the description of the P218 piston? Would the part number tell you what oversize it is and what advertised compression ratio it is supposed to be?
P278 could be written wrong on the invoice. It does look at like a "7". See the invoice I posted.

Yep, sure looks like a "7" to me as well ?
But Badger never made a P278 as far as I could find, NO listing for "278" anything in any manu's books I could find ?
So,
I am still guessing a typo ? and you may indeed have the Badger P218 ?
The Invoice has PLENTY of other typo's... CB527 bearings are RODS.... not "mains"

The P218 Badger is another of the common notoriously LOW Compression "rebuilder" Pistons, that plagued BB Mopars when rebuilt back in the day. They were offered in .030, .040, and .060 oversizes.... but no way to tell from your Invoice that I can see ?

Badger listed them as "replacement" Pistons for the 72-81 Smog Engines, you can take it from there compression-wise, but not very much.
The only way to tell for sure,
would be to pull a Head and "see" if the Piston sits about 1/8" down the hole @ TDC. That's them !
and then look for/measure the oversize ?

[66FBCharger]

What is the description of the P218 piston? Would the part number tell you what oversize it is and what advertised compression ratio it is supposed to be?
P278 could be written wrong on the invoice. It does look at like a "7". See the invoice I posted.

Yep, sure looks like a "7" to me as well ?
But Badger never made a P278 as far as I could find, NO listing for "278" anything in any manu's books I could find ?
So,
I am still guessing a typo ? and you may indeed have the Badger P218 ?
The Invoice has PLENTY of other typo's... CB527 bearings are RODS.... not "mains"

The P218 Badger is another of the common notoriously LOW Compression "rebuilder" Pistons, that plagued BB Mopars when rebuilt back in the day. They were offered in .030, .040, and .060 oversizes.... but no way to tell from your Invoice that I can see ?

Badger listed them as "replacement" Pistons for the 72-81 Smog Engines, you can take it from there compression-wise, but not very much.
The only way to tell for sure,
would be to pull a Head and "see" if the Piston sits about 1/8" down the hole @ TDC. That's them !
and then look for/measure the oversize ?

I probably won't be pulling the heads any time soon. Do you think I would be able to see anything by using a borescope through a spark plug hole?
Are the Badger pistons dished versus flattop?

[Challenger340]

Almost ALL "Rebuilder" type cast Pistons for 440's are Flat-Tops...... yes, even the really low compression versions, Badger included.  

They just build the "Flat-Top" lower, so far down the hole in fact @ TDC, it is measurable with a ruler, usually about 1/8" or more.

I don't think you would be able to tell Piston(Flat-Top) Compression Height with a borescope, but you may see a oversize stamping like ".020" or ".030" etc. ?

[66FBCharger]

I was thinking that maybe the rebuilder piston was a dished top.
So a good guess is, my compression might be in the 7's?
What is the stock compression ratio for the '69 440 HP (10:1?)? Would the stock compression ratio be too much for today's gasoline?
Would a compression check give any indication of compression ratio? Would a lower compression piston give a lower reading when checking compression?
Thanks for all the responses Challenger340!
John

[Challenger340]

I was thinking that maybe the rebuilder piston was a dished top.
So a good guess is, my compression might be in the 7's?
What is the stock compression ratio for the '69 440 HP (10:1?)? Would the stock compression ratio be too much for today's gasoline?
Would a compression check give any indication of compression ratio? Would a lower compression piston give a lower reading when checking compression?
Thanks for all the responses Challenger340!
John

No problem John, glad if I can help

Depends upon the Cylinder Head, but any of the "open" Chamber Heads(906, 452, 346, etc) and a composition style Head Gasket, typically yield in the mid to high 7's "static" Compression Ratio.

Factory targeted Compression Ratio was 10 or 10.1  I believe ?
Which,
by itself using the stock "hp" 440 Magnum Camshaft will exhibit some detonation on Today's Fuel at factory timing specs @ sea level.
You can work around the 10:1 factory Compression Ratio, with a custom Camshaft( still same specs but changed events), and altered Cylinder Head prep, but far too involved to get into here.
Safest way is to just build at the 9.5:1 static C.R. if using the resto "HP" Cam and stock type Head rebuilding.

Yep, you can get a pretty close "guesstimate" of static C.R. off a compression test, but only if the Camshaft IVC point is known.(IVC= Intake Valve Closing)

Bob 

[BSB67]

I was thinking that maybe the rebuilder piston was a dished top.
So a good guess is, my compression might be in the 7's?
What is the stock compression ratio for the '69 440 HP (10:1?)? Would the stock compression ratio be too much for today's gasoline?
Would a compression check give any indication of compression ratio? Would a lower compression piston give a lower reading when checking compression?
Thanks for all the responses Challenger340!
John

Here are some additional specifics to what Challenger340 said.

Like Bob said the factory rated the 68 to 70 440 at 10:1 or 10.1:1.  They were not that compression ratio, but actually closer to 9.7:1.  Back in the day, when there were still original untouched hp 440 cars still on the road and gasoline went to 92 - 94 octane, they would detonate, at least where I lived (altitude makes a big difference).  Also, the factory hp cam had the intake valve closing fairly late, like 67° ABDC.   Going from memory, they were ground on a 115°, and installed at 113°.

So ,if you build an actual 9.5:1 motor, with a factory open chamber head, and put a small cam in it, like a Comp Cam XE w/268° duration (i.e. early intake valve closing point), and have a performance ignition curve, you will be very close to the edge, and I would guess might have a detonation problem.  Simply changing to a bigger cam (or one with a later intake closing point) could make the difference.

When you are close to the edge on compression ratio, the finer details will add up to determine success.  Things like cooling water temperature, spark plug, cold/hot intake, altitude, quality of local gas, ignition curve, and even things like car weight, gear, and converter.......not to make it complicated.

As far as cylinder pressure testing and determining compression ratio, it can be estimated if you know the cam specifics.  But, it really is not that important once the motor is together.  160 to 170 psi cranking pressure is about the limit with an iron head.

[Cooter]

Do not install "Six Pack" piston and steel shim gaskets with iron closed chamber heads. 180  psi.
cranks like it's gonna knock the starter off block when hot.

[c00nhunterjoe]

Do not install "Six Pack" piston and steel shim gaskets with iron closed chamber heads. 180  psi.
cranks like it's gonna knock the starter off block when hot.

I will have to take mine again. I know im well over 180 in my car with closed chamber irons, 28 initial/40 total with 0 problems in 100' summer days. I dont know what im doing different then everyone else.

[BSB67]

Do not install "Six Pack" piston and steel shim gaskets with iron closed chamber heads. 180  psi.
cranks like it's gonna knock the starter off block when hot.

I will have to take mine again. I know im well over 180 in my car with closed chamber irons, 28 initial/40 total with 0 problems in 100' summer days. I dont know what im doing different then everyone else.

Certainly quench helps, but I had one like that too.  915 heads and it would blow about 180 - 185.  It would rattle backing out of the driveway. Well not exactly, but under just about any part throttle load in any gear.  It to like 40°.

Maybe its my gauge.

[c00nhunterjoe]

Do not install "Six Pack" piston and steel shim gaskets with iron closed chamber heads. 180  psi.
cranks like it's gonna knock the starter off block when hot.

I will have to take mine again. I know im well over 180 in my car with closed chamber irons, 28 initial/40 total with 0 problems in 100' summer days. I dont know what im doing different then everyone else.

Certainly quench helps, but I had one like that too.  915 heads and it would blow about 180 - 185.  It would rattle backing out of the driveway. Well not exactly, but under just about any part throttle load in any gear.  It to like 40°.

Maybe its my gauge.

So yours did detonate? Im saying mine does not. Plugs always look good. I will take my gauge out and check it this coming weekend. I recall 185-190 on mine.