Re: [FWDLK] 413 pistons
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Re: [FWDLK] 413 pistons



Not to say they were cheap, but I paid under $400 for my set of Sealed Power cast. All I can say is it pays to shop around as most people wanted $50 a piece for them.
 
Dave Casey
----- Original Message -----
Sent: Thursday, October 23, 2003 11:23 AM
Subject: Re: [FWDLK] 413 pistons

The RockAuto pistons are Sealed Power cast pistons.  They cost almost twice as much as 440 cast pistons, about $150 more than standard weight 440 forged pistons, and almost as much as lightweight forged 440 pistons.
 
The 9.7 CR rating means nothing.  The compression height for these pistons is an even 2.0 inches.  Plug that into a calculator and the deck clearance calculates to be -.082.
See
 
 
This is for a 3.75 stroke, 6.786 rod, and 10.725 crank centerline to deck (common dimensions for 413's and 440's, only the bore size is different).
 
With that deck clearance and small chamber head with FelPro gaskets, you end up with an actual CR of 8.98.  That's assuming the heads are 78 CC, which is about what the early small chamber heads are supposed to be.  If they are actually 80 cc's, the CR drops to 8.84.  If you put a set of later large chamber heads (i.e., 906, 452, 346 etc) because they flow better or to get hardened seats, the CR drops to 8.3, and that's assuming the large chamber heads are only 88 cc, which is probably on the low side.  With 90 cc. heads, the CR drops to 8.17.
 
You can play with these numbers on this compression ratio calculator:
 
 
Remember that any head gaskets you buy for a 413 are going to have large enough opening to fit a .060 over 440, which means the gasket opening is going to be at least 4.38, and is probably a bit larger.
 
The FelPro blue head gaskets are .039 thick, while the replacement type steel shim are about .021.  The steel shim gaskets will bump the CR up about three tenths, but don't seal as well if the surface isn't absolutely true and generally aren't used on a rebuild, although I have them on my 413 just to get all the CR help I could.
 
The only way to really know what the actual CR is, is to CC the heads and check the actual deck clearance, which can vary from one 413 to another or even one cylinder to another due to slight variations in rod length and deck height.  (Typically, the deck is not machined true to the crank centerline, and can be taller on the intake side than the exhaust, or on the front than the rear, and vice versa).
 
All boils down to this: the only readily available, off the shelf pistons for a 413 are going to be .080 from the deck at TDC.  Want better than that and you are going to have to have them custom made.
 
Curtis
59 Coronet
56 Belvedere 
----- Original Message -----
Sent: Thursday, October 23, 2003 8:34 AM
Subject: [FWDLK] 413 pistons

The 300 listserver had a bit of mail recently regarding 413 pistons.  Here's what I found.
The Rockauto site is a catalog you have to download, but it had the cheapest pistons at about $68 each if I remember rightly. 9.7:1 cr they say.
What happened to Badger?  Have they departed the planet?  I have a new set of .030 413's cast Badger pistons, 10:1 cr I bought about 1995 for $300.  Moly rings were another $70, they were Hastings rings and I bought them from Hastings themselves.
           Dave........

 
 
 
 
 
 
 
 
 



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