more 427 piston questions....

[Greg L.]

Well I finally made it back from Carlisle(had a bit of a detour) and met some very nice people. Even had the pleasure of meeting the good ole Doc and Debbie as well as Dick Whittington.

Anyways now that I'm back I need to get the ball rolling on this engine of mine (it's a 69 L36 std bore). I'm going bone stock with it and as per previous suggestions I'll be going with Hypereutectic .020 oversize pistons with a target C/R of 10:1. The block has not been decked, I'm using standard Fel-Pro head gaskets and the combustion chamber sizes are pretty much all 105 cc's. My question is, would this be a good choice of piston?

http://www.cnc-motorsports.com/product.asp?Action=recalculate&Path=&CtgID=12532&ProdID=12534&AProdID=&Qty=1&OGroup2390=3809

How about this one?

http://kb-silvolite.com/performance.php?action=details&P_id=108

This might be a dumb question but are they not both the same piston? How can I tell if they have pressed pins or if they are full floating? They mention pin locks which makes me think that they are full floating which I don't want... Just want them to press in like the old ones and be done with it.

If these are the ones that I should get is there anything else to consider before ordering them or should they just replace the originals with no problems other than the wider specs for the top ring gap?

If these are not what I want can someone help me pick a set that will replace my OEM ones?

Thanks.

Greg Linton
#45455

[Joe L.]

Re: more 427 piston questions....

Greg------

The links you provided are for the same pistons-----one link is to a supplier that RETAILS the Keith Black/Silvolite pistons and the other is a link to the Keith Black/Silvolite MANUFACTURER'S website.

These pistons would be an excellent choice for your rebuild. They are exactly what I would use, and they are considerably stronger than the original pistons.

These pistons, as is the case with many Keith Black pistons, can be used with either pressed or floating pins. The rods determine whether the pistons are used in the pressed or floating configuration. However, the KB pistons have provisions for the installation of Spirolock pin retainers in the event that floating pin rods are used. The retainers are also provided with the piston set. In your case, they will be "surplus".

[Duke W.]

Re: more 427 piston questions....

United Engine & Machine Co., the manufacturer of Keith Black pistons, does not sell them direct, so just find a retailer that gives you the best price on that KB part number.

Whether or not the pins are "floating" or "pressed" is dependent on the connecting rod design, not the piston. In either case the pins always float in the piston. KB supplies spiral retainers with all piston sets. They should be used if the rods are designed for floating pins. If the rods are designed for pressed pins, discard the retainers. Do not use them.

There are various reports on the Web of KB pistons breaking - usually on fresh engines. I am convinced that these failures are caused by failure to follow the specific wider that OE top ring gap requirement. This is clearly explained on their web site, and I believe the packaging also includes the instructions.

The primary cause of these failures are likely a manifestation of "Stapp's Law":

"The universal aptitude for ineptitude makes any human accomplishment an incredible miracle".

Colonel (Doctor) John Paul Stapp, MD, USAF, (1910-1999) was the guy with the big cajones who rode rocket sleds back in the fifties looking for the human g-load endurance limit using himself (and others) as guinea pigs. That was back in the day when little kids had REAL heros to look up to.

Colonel Stapp's seminal work led to improved occupant safety in both airplanes and automobiles. He is a legend. On his best sled ride he briefly endured over 46g.

One of Col. Stapp's associates was Major Murphy - yes, the guy who is credited with coining "Murphy's Law".

Duke

[Greg L.]

Re: more 427 piston questions....

Thanks guys. I just needed a little reassurance on this one so now I'll order them ASAP.