Keith Black piston rod modification???

[Barry_R]

I simply answered the question. 
We used to do that - narrow the small end of an FE rod - all the time.
But since you want to force the issue of KB experience....I can add some data.

As far as KB hypereutectic pistons - I can explain the reputation issues in three paragraphs.  There were three intersecting root causes. 

First was the designer's desire to push the top ring groove up as high as physically possible.  Reduces crevice volume.  Good from a performance/power/emissions perspective.  But requires that the top piston ring and the upper ring land be able to handle higher heat during high load operation.  Also causes you to have a smaller cross section area behind the inner ring groove and the valve pocket in the piston.  This might have been OK with today's 1.0mm or reduced radial thickness steel rings, but was challenging in an era of ductile iron 1/16" D-wall packaging.

Second was the Silvolite piston (KB's manufacturer) metallurgy.  When we were developing our own aftermarket hypereutectic pistons at F-M we put samples of the KB parts through the lab to understand why they were having issues that were not experienced at the OEM manufacturers such as Goertze, or Mahle.  Their iteration of hypereutectic alloy had a comparatively large silicon nodule size, and comparatively poor homogenous distribution of the nodules.  This made the castings more notch & fracture sensitive than those of the other suppliers.  Couple the alloy difference with the use of electronic aids (EFI and knock sensors) in the OEM parts and you are able to run those OEM pistons in a higher load situation without an issue.

Third and most important was the Silvolite/KB focus on marketing.  At the time of their release, Silvolite did not have a forged piston offering, so they touted the hyper as the answer to everything.  This put the pistons into an environment population where detonation and extreme loads under uncontrolled conditions was not just possible - but likely.  Combine the top ring location, the alloy characteristics, and the improper application focus and you have a recipe for problems.  After a decade of excuses and explanations - including a request for absurdly large ring gaps in an effort to prevent the overheated top rings from butting - Silvolite released a forged piston program which they eventually renamed "Icon" to address the damage done to the KB name.  A clear admission from the manufacturer themselves that they had screwed up in marketing what was otherwise a pretty good part by putting it into the wrong market segment.

[67xr7cat]

Thank you Barry for the useful information. I remember when the kb pistons first came out. Remember when the hyper pistons first became popular and the engine failures with pistons failing, shattering into pieces.
Was a long time would not consider them. I'd say between setting the gaps right and time something changed as when I went back to work at a friends shop he was using them did not have failure issues in general. Now mind you normally did not put them or any hyper in something prone to detonation or race, but even then worst seen was a holed piston not total destruction.

GT500 really? Thanks for you concern. Steve

[My427stang]

I will add a couple of less technical points, but I think applicable anyway

- As Barry said, narrowing the rod was common in the "olden days"  LOL.... in fact many performance pistons did that in the old days to take advantage of BBC forging, also allowed a smaller step in boring with off the shelf dimensions. 

- Cast pistons have their place, and can be happy for a very long time, be they hyper or traditional. They fit well, run quiet, etc.  If the engine is built that way and run like a factory car, you could get plenty of fun out of it. I would say that most do not do that with 427s on this forum, but there are plenty of 390s and 428s getting flogged and run daily that do.

Triple the money you spend, (which is pretty cheap nowadays) and you get custom stuff that is REAL nice and runs almost as tight a clearances as a cast with a huge buffer in strength, but if the car really is never going to get there, nothing wrong with those pistons

The things that I like about custom forgings like Randy offers, is of course the insurance of a 4032 (or 2618) forging, but on top of that,  I can hit a quench distance with a 8554 gasket, that offsets a little cost; next, depending on the ring choice, rings are more readily available and cheap too, with some single digit power benefits; third, I can pick the exact compression I want;  and finally, the valve reliefs give a lot of radial and depth clearance.

With that being said, if it's a weekend cruiser, long haul highway toy, maybe you don't need ANY of those, so why spend the dough?

[Falcon67]

Why - because you want to make sure it lasts. 

I've built a lot of engines and IMHO cast pistons are for lawn mowers.  Even the street car 302 engine here uses TRW forged flat top pistons.  They work, they don't crack skirts and they would survive most "accidents" short of a dropped valve.  And may even survive that, seen that too.  Break a spring and/or hang an exhaust valve open enough to receive a tap from the piston top can shatter a hyper or cast piston.  Carb issue leans out motor and it maybe detonates - same deal.  If I've already got $$$$ in any engine build I'm not saving $250 by running a cast piston.  False economy.

[67xr7cat]

It is a changing world for sure. Back years ago most everything was cast and trw forged pistons were expensive, heavy, and low tech.

I know of a 68 302 factory cast piston engine stock rods with upgraded bolt that was raced for a season turned 8800 rpm every pass and did no break. When taken out to be freshened had some broken piston skirts but those engine did that anyway.

I know of a sbc dirt modified engine had top end forged pistons, rods, crank came apart. Totally destroyed cylinder. Not enough piston left to piece it all back together.

There were reasons the 302 lived and the sbc did not.

Alot has to do with the machine work, tune, and who uses it. In my case I have control of all that. Put a hyper in a 427 guess offends some here, but do not assume it wont work or last. There are people who can break anything and usually the failure is blamed on the builder and the parts, but usually is fault of the guy using it doing the wrong things.

So next lets talk about my using a stock factory rod. Again false economy right.

Btw a lawn mower is hard on pistons... Air cooled, crappy gas and oil control, prone to detonation so may want a forged piston for that...lol

[blykins]

So next lets talk about my using a stock factory rod. Again false economy right.

Well, there is a little bit of difference between a brand new cast/hyper piston and a 50 year fatigue stressed rod.  I'd use a hypereutectic piston way before I'd reuse a factory rod in any performance application. 

[gt350hr]

Guess I should have known better then ask if anyone had experience with this piston. Clearly nobody has any actual hands on experience with this piston.

As to the why I will have all of $240 invested in a new set including moly rings. As for machining the rods I can do that myself so will just be my labor. So in this case I am $$$ ahead and if I decide to go another direction am sure I can find someone who would want then.

Regarding the application it is a street car. Keith black hyper pistons are a well known quantity. The bad rap they got is by people who do not know what they are doing. For the record I am not a fan of hypers, but for what I am doing they will work well.

There is a trend in this hobby towards overkill. I have seen h beam rods and forged pistons fail because of poor work and/or tune up. I've seen stock rods and pistons pushed way further than any sane person would and live.

Anyway I appeaciate the answers, but really don't need the condesending bs, this not my first rodeo. You really never know what someone knows or why they are doing something. This kind of bs is what drives guys away.

     Maybe a different way of looking at this is since no one has experience with them , there might be a reason ( like the rod machining deal) why no one does.
    I agree with you that MANY engines are overbuilt these days and some of that is due to the costs involved with getting ''old" parts rebuilt. For example take a set of "nut and bolt" rods to the machine shop and get a bill for $400 after they are cleaned , re bushed and have aftermarket bolts and the required resizing. they still have years of "cycle time". Look at a set of "imported" H beams that are "overkill" in many applications BUT are new and only a little more money.  Cranks are similar. A "performance grind" that includes indexing , stroke correction and adding a radius to the sides can easily be $200 or more. A new "overkill" crank could be double that but you could still sell the old crank and reduce cost.
    I completely agree that there are plenty of 100,000+ mile "stock" engines and a fair amount of 1,000 (or less) mile , blown up race engines that use the best parts money can buy. Every engine doesn't need a Bryant crank , Carrillo rods and forged pistons but some HAVE to have them . Perspective as you mentioned is what it's all about. People that buy things "for insurance" always make me laugh. In defense of engine builders that build higher quality engines than the customer needs , this is often "required" as the customer has never experienced this performance level and abuses the engine beyond what he  told the builder. Been there done that. 
   Randy
    Randy

[Falcon67]

I know of a 68 302 factory cast piston engine stock rods with upgraded bolt that was raced for a season turned 8800 rpm every pass and did no break. When taken out to be freshened had some broken piston skirts but those engine did that anyway.

Yep.  I know of 8" rears that ran low 11s pulling the wheels every pass - until they didn't.  And plenty of 302s that split in half at 450 HP shifting at 6500.  You pays yer money and you takes yer chances.  I just prefer the better part when it's available.  I'm on a budget too, which means that if I get one shot at it I'll wait until I can buy the better part.  As hard as these older engines - FE, 351C, even pushrod 302s - are getting to find, any shortcut may result in a pile of parts needing a hard to find replacement whatever.  I can buy aftermarket "302" type blocks plenty reasonable.  351C and FE aftermarket are big $$$$ so I take all precautions possible when running a stock block.

[gt350hr]

 +1 Chris no matter how many times you stick you finger in the fire , you WILL get burned. Adding that last straw to the camel's back always breaks it. Guys that push stuff beyond a parts practical limit are only fooling themselves. Under building is just as common as over building these days.
    Randy

[67428GT500]

By the way I ordered a set of the Eagle rods with the ARP 2000 bolts for 440 to the door.  Great price in comparison to Summit, Jegs and the Molnar rods mentioned.  I am just going to have them magged and checked for roundness on the big end when he re-balances the bottom end with the rod and piston change.

[67xr7cat]

By the way I ordered a set of the Eagle rods with the ARP 2000 bolts for 440 to the door.  Great price in comparison to Summit, Jegs and the Molnar rods mentioned.  I am just going to have them magged and checked for roundness on the big end when he re-balances the bottom end with the rod and piston change.

You sure that rod is made by Eagle? Post up some pics when you get them.

[67xr7cat]

I said when I got the pistons I'd report on what found regarding the pin boss as may be someone one day wanting to know. So comparing to some 390 pistons the KB199 pin boss is wider on each side by about 1/8" so is actually more material there to support the pin.

If you machined the piston to have the same clearance the pin boss would be the same width. Of course is better leave the piston alone as it can use all the support in that area it can get and narrow the rod small end which is wider than needs to be anyway and is what I will be doing. Looks like really only need be narrowed an 1/8" to work.


Btw for all who have a problem with a KB hyper piston in a 427 well please save it as is not your build and think that horse has been beat to death and of course thank you all for your concern...