difference in heads 906 vs 915 vs 452?

[firefighter3931]

Bob hit the nail on the head....the machinist is building you an OEM 75-76 smog motor. 

This will be a step backwards from your current engine combination. 


Ron

[Challenger340]

NEW DESIGN Pistons coming !

This whole WRONG Piston issue arising again..... has pissed me off !

So, I have been on the phone.
It is going to cost me.... but I am having 20-30 sets of Factory CORRECT  Cast Pistons built.

2 offerings;
* 68-70 Cast Flat Top Slugs on the 2.025" Compression distance
and
* "Correct" '68 to 70 SIX-PACK Cast Pistons, same as the L2355, but cast on the 2.055" to 2.062" Compression Distance W/4 Valve reliefs.

Seems to be a HOLE in the marketplace for a quiet running, inexpensive, CAST "correct"  Compression Ratio Pistons for 440 Mopars.
Might be good for the restoration crowd so they can restore "correct" performance on these Engines ! .... rather than " thinking" they did with some of the terds I have seen and ridden in !

[ACUDANUT]

I always thought the prime years of 440's and 383's used the 906 heads ?

[BSB67]

he said he is ordering the tall pistons...giving me a compression of 9.5 -10

There are 2 sizes , short and tall....im getting the tall ones for higher compression

im confused now

your telling me this is not going to give me around 10:1?

its a stock rebuild guys, just to get me buy 3-4-5 years before i do a stroker motor....

help!

I think we have been helping you, you're just not listening.  You so want to believe your machinist.  Just look at the catalog and do the math yourself, and prove it to youself.  You don't have to believe anyone.

This is a budget build.  That is fine.  I get it.  You will need to make compromises.  I get it.  It's okay.  But you still need to make good decisions.  You really need to put a decent compression height piston in it.  You are buying pistons anyways.  It is a really bad decision to not buy the only right piston.

Think of it this way, if you go cheap on the heads, the cam, the intake, the carb, the exhaust, you can fix anyone of those in a weekend when your budget allows.  You put the wrong piston in that short block, it is a turd forever.  FOREVER!  

So here are the numbers.  
If you use the 1276 piston (i.e. the worst possible piston you could buy) - the compression ratio will be between 7.3:1 and 8.0:1, depending on head and gasket.  There is nothing that your machinist can reasonably do to change that.  To achieve the 8:1 ratio it will require extra head milling ($), block decking ($), and a 0.020 shim gasket.   Oh, and then your intake probably won't fit.

If you use the 1263 piston (probably the third worst piston you can buy) - the compression ratio will be between 8.0:1 and 8.9:1, depending on head and gasket.  The 8.9:1 ratio will require extra head milling ($), block decking ($), and a 0.020 shim gasket.   If your machinist tells you any different, he is simply wrong.  That begs the next question, should you really be using him?

Here is my opinion on your best budget short block buy/build:

1) Get the Sealed Power CSMHP 815 rebuild kit,
2) Find a good machine shop
3) Have the block decked to get to zero deck with the piston.

IMO, this is the best, and frankly the only budget built anyone should do.  It also provides the maximum flexibility for future upgrades.  If you cannot afford this, wait until you can.  This short block can be as a smooth and docile as an original Imperial, or can be a thumper and propel a street driven B-Body well into the 11s and make over 500 hp with simple performance bolt-ons.

You can use your factory open chamber heads on this motor and a stock cam, run pump gas, and have great performance.  You can then put on a set of closed chamber aluminum heads (several suppliers) and a rowdy cam and take your stock 300 hp 440 and turn it into 450+ hp in a weekend.

[BSB67]

NEW DESIGN Pistons coming !

This whole WRONG Piston issue arising again..... has pissed me off !

So, I have been on the phone.
It is going to cost me.... but I am having 20-30 sets of Factory CORRECT  Cast Pistons built.

2 offerings;
* 68-70 Cast Flat Top Slugs on the 2.025" Compression distance
and
* "Correct" '68 to 70 SIX-PACK Cast Pistons, same as the L2355, but cast on the 2.055" to 2.062" Compression Distance W/4 Valve reliefs.

Seems to be a HOLE in the marketplace for a quiet running, inexpensive, CAST "correct"  Compression Ratio Pistons for 440 Mopars.
Might be good for the restoration crowd so they can restore "correct" performance on these Engines ! .... rather than " thinking" they did with some of the terds I have seen and ridden in !

Bob, if you are making this happen, my hat is off to you.  You are truly passionate and committed to the hobby and its enthusiasts. 

In my opinion, I think that there is a market out there for this type of piston.  The challenge will be to get the bone-head machine shops, like the one we are talking about on this thread, to start specing such a product.  There are just too many wrong piston product choices on the market to sift through.

Good luck!

[69wannabe]

Stegs, listen to Bob and Ron!!! These fellow's truly know engine's inside and out!!!! I have built several 440's myself and I know the good piston number's by heart and the 2355's are my first go to pistons on any 440 that i'm putting together. I have used the keith black 237's but I really recommend the 2355's as everybody on here has highly recommended too!!! I have never even heard of them other part number's and for a good reason...

[Challenger340]

For the life of me, I simply can not fathom "why" any manufacturer is still building both the 1.91" C.D., nor the 1.969" C.D. Pistons for 440 Engines as factory replacement ANYTHING !
IMO, simply makes no sense.
So, I have been in contact with the manufacturer United Engine and Machine, Silvolite Tech. Dept.,
ongoing,
but very simply here, they have NO ONE still on staff who has any recollection of the old Engineering drawings of these ancient designs, etc.
or,
the reasoning "why" they are built the way they are.

Friday's conversations were put over until next week, where I will pursue it further with their Engineers, but thus far in a nutshell, it seems the supporting data for their design criterion was the old N.H.R.A. published "minimum" CC Head Chamber specifications, for both the closed and open Chamber Cylinder Heads.....Waaaaaaaaaaaaaaaaay back in the 1970's for FAWKS sakes !

Now, as background to what seems to have happened 40 odd years ago... when these garbage compression height 440 "replacement" Pistons were designed,
at about the same time....
N.H.R.A. "published" their minimum Chamber sizes as 79.5 CC's for the Open Chamber BB Mopar Heads
       and,   "            "      minimum           "      "  73.5 CC's for the Closed Chamber BB Mopar Heads

Anybody see what happened ?

Nobody bothered to make the distinction between a minimum acceptable CC Chamber Size that a racing sanctioning body(NHRA), would accept before dis-qualification
and,
the "Real World" CC Chamber sizes in production.
So it would seem,
these pistons were designed/built according to Compression Ratios that would result, but from those "inaccurate" CC sizings.

As we all know 40+ years later, most, if not all....
"open" Chamber Heads fall between 86 CC's to as high as 90 CC's as cast.
and
"closed" chambers between fall between 78 CC's to 82 CC's as cast.
Which basically makes these 1.91" and 1.96"C.D. Piston designs, very solid mid 7's to 1,  and mid 8's to 1 offerings(the so-called HIGH piston)

First step:
is to present enough valid "real world" data so the Engineers can come to the same conclusion
2.) make it substantial enough on such a low numerical old engine design, that they see the cost benefit to "updating" for whatever market sales are left (not many). Lets face it here.... just how many "stock" 440 Engines are being rebuilt these days ?

I don't think it is a big deal ? at least on one piston, the 1968 to 1970 440 piston.
"Adjusting" a CNC Piston program a little higher.... piece of Piss !
So should be fairly easy to get the old factory advertised "10:1" Compression Ratio Piston(actually around 9.6 to 9.8 with a .022" Steel Shim head gasket) which was 2.025" Compression Distance.... made by merely adjusting the 1.96" C.D. program upward about .050" to the 2.025" C.D.

A little harder....
is convincing them to make a "Cast" version of the actual 440- 6 Pack Piston(yes they were "cast" stock), basically a copy of the Forged L2355 Piston on the higher 2.062" C.D. W/4 valve reliefs.
The "carrot" for them... is that the L2355 is still a decent numerical seller, from which they could draw sales as a much lower priced alternative.

Normally, I would not recommend "cast" pistons for performance useage.... but for anyone who has held a stock BB 440 Mopar cast piston in their hand ?.... you know why they are fine for 5,500 rpm !
With the added benefit for many... is they are far more forgiving to lesser Bore & Hone Jobs accomplished devoid of a Torque Plate(seems most), and can be fit at .003" with no noise, and at 1034 grams Piston & Pin, they require no re-balancing with stock parts.

I will keep you posted..... but strange days indeed,
when it seems that it may be easier to tackle an actual "Manufacturing Company" and their "Engineers".... and convince them their "product" is flawed
than to,
try and convince one individual, after hundreds have been burned through decades, that the "product" itself is poo !

[Stegs]

sorry guys, thats not what he is going with

I was talking to him on the phone while driving

He said thats what his book called for

He is going with a different number piston, to get me right up there to 9.5-10 compression

that part number i wrote down would be 8.5 to 1 "motor home" pistons (what his book called for as a standard replacement, and we are NOT going with these

[ACUDANUT]

I always thought the prime years of 440's and 383's used the 906 heads ?

No response ?

[BSB67]

I always thought the prime years of 440's and 383's used the 906 heads ?

No response ?

yes

[BSB67]

sorry guys, thats not what he is going with

I was talking to him on the phone while driving

He said thats what his book called for

He is going with a different number piston, to get me right up there to 9.5-10 compression

that part number i wrote down would be 8.5 to 1 "motor home" pistons (what his book called for as a standard replacement, and we are NOT going with these

What is the part number?

[Challenger340]

sorry guys, thats not what he is going with

I was talking to him on the phone while driving

He said thats what his book called for

He is going with a different number piston, to get me right up there to 9.5-10 compression

that part number i wrote down would be 8.5 to 1 "motor home" pistons (what his book called for as a standard replacement, and we are NOT going with these

So Stegs
Could you please tell us what Piston number he is going to use ?... to get you "right up there to 9.5-10.0 compression"
Federal Mogul/Speed Pro # L2355 ?
Keith Black Hypereutectic # KB237 ?

[ACUDANUT]

I always thought the prime years of 440's and 383's used the 906 heads ?

No response ?

yes

I have not seen one ? 

[oestermarken]

NEW DESIGN Pistons coming !

This whole WRONG Piston issue arising again..... has pissed me off !

So, I have been on the phone.
It is going to cost me.... but I am having 20-30 sets of Factory CORRECT  Cast Pistons built.

2 offerings;
* 68-70 Cast Flat Top Slugs on the 2.025" Compression distance
and
* "Correct" '68 to 70 SIX-PACK Cast Pistons, same as the L2355, but cast on the 2.055" to 2.062" Compression Distance W/4 Valve reliefs.

Seems to be a HOLE in the marketplace for a quiet running, inexpensive, CAST "correct"  Compression Ratio Pistons for 440 Mopars.
Might be good for the restoration crowd so they can restore "correct" performance on these Engines ! .... rather than " thinking" they did with some of the terds I have seen and ridden in !