440 rebuild kit what pistions?

[BLK 68 R/T]

So a few years ago (before I got smart and joined this site) my brother had a 440 built for his 68 Coronet. It has never seemed to have the power that it should. When he dropped the motor off he told them that he wanted a 10.0 to 1 compression and a Mopar purple shaft 509 cam. This was back in 2009 that he had all this work done. Anyways, I was able to get the part # of the rebuild kit the shop used of the master kit which included the pistons. I have searched online for what the specs are but come up blank on what the pistons actually are. CR440MK is the kit # from his receipt. Does anyone here know what the specs are of this kit or where I can find them? I'm thinking the poor performance he is experiencing is due to the motor not being 10.0 to 1 compression, probably more like 8.1 to 1. And he also pulled the distributor out this past weekend to verify the cam was a purple shaft and he did not see any purple on the shaft, which makes me think he got a turd built for his car.  

[Challenger340]

Finding the actual Piston specs will be difficult, probably because they are not proud of them... but make NO mistake here, it is 99% assured to be the Cast Silvolite #1276 1.91" Compression Distance Piston.
meaning,
more like 7.8:1.

I say this because the numerous places the CR440MK is listed online, pretty much all specify EXCEPT HP and 3X2 BBL Engines., which really means terd motorhome smogger pistons.

To be absolutely sure (100% instead of 99%),phone one of the places that sells the Kit.. and ask the Piston Part number ?

[myk]

I'm in the same situation as your brother, 'OP.  Looks like we'll both be heading to the machine shop eventually...

[BLK 68 R/T]

Finding the actual Piston specs will be difficult, probably because they are not proud of them... but make NO mistake here, it is 99% assured to be the Cast Silvolite #1276 1.91" Compression Distance Piston.
meaning,
more like 7.8:1.

I say this because the numerous places the CR440MK is listed online, pretty much all specify EXCEPT HP and 3X2 BBL Engines., which really means terd motorhome smogger pistons.

To be absolutely sure (100% instead of 99%),phone one of the places that sells the Kit.. and ask the Piston Part number ?

I was afraid you would say that, but deep down knew you would probably say that 
I will pass the info along to my brother and he can make a decision on what he wants to do.

[BLK 68 R/T]

I'm in the same situation as your brother, 'OP.  Looks like we'll both be heading to the machine shop eventually...

I'm sorry to hear that. Nothing worse than having to do the same job twice as well as pay for it twice  Good luck with your eventual rebuild.

[BLK 68 R/T]

So I found out what pistons come in the rebuild kit that my brother got. Below is the info from Summit on what they are.

Brand: Sealed Power
Manufacturer's Part Number: 350NP30
Part Type: Pistons
Product Line: Sealed Power Cast Pistons
Summit Racing Part Number: SLP-350NP30
Bore (in): 4.350 in.
Piston Style: Flat top, with no valve reliefs
Piston Material: Cast aluminum
Compression Distance (in): 1.990 in.
Wrist Pin Style: Press-fit
Pin Diameter (in): 1.094 in.
Piston Ring Thickness: 5/64 in. x 5/64 in. x 3/16 in.

[justcruisin]

With those pistons you will be around 8.5:1 with a virgin deck, standard .039" felpro gasket and stock heads. They will be down the hole around .090". I have a set in .040" on the shelf that I pulled and replaced with a taller piston. The 350P piston are a cast replacement and are heavy, not great for a performance build.

[myk]

It's alright, live and learn.  I hope I can educate others on how to handle their cars and the people they give their hard earned money to, in the future....

[Challenger340]

It is unfortunate that this is still happening to unsuspecting customers trying to rebuild their 440 engines for performance applications in this day and age, but it is.
Especially when you consider that this has been happening for over 30 years, with a plethora of information/warnings being out there and commonplace for anyone wishing to check before jumping into their rebuild.

It seems pretty much that all O.E.M. piston manufacturers at one time or another, in an effort that I can only surmise was intended to streamline product line offerings for applications between 1966 right through 1978....... then cataloged Piston choices for the 440 engines on the common 1.99" Compression Distance.
The distinction between 1966 when closed chamber Heads were used, up until 1968 when the open chamber heads were introduced, NOT seeming to have been relevant in the decision making...... nor that the overwhelming majority of engines were produced (10 years worth '68 to '78) with the larger open chamber heads versus only 2 years for the closed heads('66 & '67).
Can't really fault them,
the typically resultant 8.5:1 for open chamber applications and 9.0:1 for the closed chambers is safe for regular unleaded fuels(and these are typically highside numbers).
Nonetheless, the above are all static Compression Ratio numbers ?
wherein,
It then becomes even more depressing to "performance" intentions, once people take a step further to understand the effect that their selected "performance" Camshaft events have on their already anemic "static" C.R., to what's called "Dynamic" or actual running Compression Ratio, which gets slaughtered as far as any low end Torque/power whatsoever by later ABDC Valve closing events on aftermarket Cams.
There are some good calculators out there:
http://wallaceracing.com/dynamic-cr.php

NOT a good combo for heavy and highway geared Cars now is it ? especially on wedge engines like the 440 that were legendary for very pleasing tire frying Torque ?
The low pop 440's  still "try hard" once the rpm's come up, but alas too little too late, time to shift by then..... leaving their bewildered Owner's with that "is THAT all their is" feeling ?

[justcruisin]

New pistons would be good, but that would necessitate a full tear-down, balance etc then you would need to upgrade the top end to take advantage of the extra squeeze. Failing that, a set of 75cc e-heads, rpm manifold, headers and a cam grind in the 225@50 range would wake it up no end. Pull a head and see what you have along with some measurements first.

[Challenger340]

New pistons would be good, but that would necessitate a full tear-down, balance etc then you would need to upgrade the top end to take advantage of the extra squeeze. Failing that, a set of 75cc e-heads, rpm manifold, headers and a cam grind in the 225@50 range would wake it up no end. Pull a head and see what you have along with some measurements first.

The e-heads @ 75 CC's will help, but still at the very lower end for any potential gains one would expect versus money spent ? especially in conjunction with Cam/Lifters/Gaskets, Timing Chain etc., ?
Not to mention you still have NO QUENCH with the Piston still .090" down the hole ? plus a .040" Gasket for a total over 1/8" quench distance ?
Then add in...
Aluminum's greater combustion heat dissipation abilities ? which are such that they typically don't like lower C.R. ratios... or more importantly "dynamic" pressures below around 150 psi where you start to see real Torque gains for the Cam, and below which, a guy's gotta throw alotta total timing at it, so add a Dizzy re-curve to the mix so it still cranks over fine ?
It will help.... but IMO,
just a temporary band-aid stepping stone of parts/money with limited gains..... to inevitably later building a real deal  anyways to re-use the e-heads properly?

Even just a 225 @ .050 duration Cam will exhibit around a 63* ABDC event, which on the 9.5:1 static C.R. "bump" with the e-heads.... only nets you about 7.2:1 Dynamic C.R., that is good for 140 psi at 2000 ft elevation(about 90% of N.A. depending where you live).
Just say' in.... in my experience anyways,
The Aluminum Heads don't work great down there(mid 9's static C.R.) versus money spent ? and the .130" quench ain't helping at all.