We are finally starting to do the build on the last of our 428's and much to our dismay, we did not have any piston sets left. Yep, my life time supply of TRW and Ross pistons just didn't seem to be a whole life time. Any way what is everyone's take on the KB pistons? I see where some people like them, some people don't. I've heard that they actually perform quite well do to the flame path, others think they stink. I'm not using nitrous, no puffers, just pump gas, built heads and a C4ae-B cam with a 4 speed. My calculations put them in around 9.6/9.75:1. Second choice is a no mileage (about 4 hours run time) set of the SVO Ross flat tops. All opinions welcomed and considered. P.S. It's been awhile for a utilitarian 428 build, and we DO have Ethanol in here in our north Texas fuel supply.
I wound up boring the 390 .060 over and the best alternative (given the application) was KB hypers. Of course the top ring end gap was opened up, especially because of the sustained higher rpm/load it operates under. The timing is a tad conservative and I run a bit more octane than I need to, but it runs quite well.
thats all i have ever ran until the stroker i just did, all my motors to this point have worked excellent with the KB pistons. timing set at 38 total on pump gas racing, curising and a good top end sprint now and again i have never had a problem. i even had some bad gas once at the track a detonated down the track pretty hard, no problems.
I've got a set in a 302 that have some abuse on them and one has broken ring lands - a set of forged not have failed in this application - I learned my lesson and will not be disappointed with "over building" an engine with durable innards again -- just my .02
and the given answer is that KB are not a whole lot better than any other cast pistons, prone to cracking if the top ring gets to tight and generally not a good way to save money on a possibly expensive-to-replace FE.
I have broken the lands out from between compression and oil rings, from a set of cast pistons, due to what was eventually diagnosed as a high speed detonation. It was not apparent to me until the engine started smoking bad. I've never had problems with basic TRW style forged pistons.
>>>*I have been in the factory in Carson City several times, this is how it was explained to me as best as I can recall.
The Keith Black piston is a Hypereutectic alloy, this just means the metal contains 18% silicon. Frankly, that is not an easy process to control, Silvolite seems to be the best at it by far.
The advantage is they reflect heat, and thus will make more power than any other design, all things being equal. Another advantage is clearences can be much less than any cast piston, and way less than any pure aluminum forged piston, thus even more power potential. This is because the alloy does not expand with heat like a pure aluminum or forged piston will.
The disadvantage is the material is brittle, even more so than cast aluminum. Plus the head of the piston will heat more from holding the heat in the chamber, this means the top piston ring will require more end gap or they will expand and butt. This will jerk chunks of the piston head loose, not a good thing. There is an instruction sheet in every box, best to read and follow it exactly, this nearly always means file to fit on the rings.
Note many suppliers are now using a eutectic material, which is 12% silicon or less, an easier and cheaper process. I do not use those at all.
For any naturally aspirated engine, I would choose the KB every single time if maximum power is the goal. They are worth a full H/P per cylinder on most applications. Supercharged or Turbo with mild boost, same thing. I have built 700-750 H/P plus competition engines for circle track and NHRA using them, no problems if the machinist knows what he is doing. All of our Transam engines under the 5.0L rule used the KB pistons. We also had 7 local track champions in NASCAR out at the old Portland facility, zero failures and a bunch of track records.
Dead serious engines with extreme pressures would give me pause, I would be thinking forged instead, especially with thin rings such as 1/16ths or less.
On light weight, well, that is always a plus.
There are literally millions of them in service, in fact, I have a set in my personal 4X4 I drive regularly. They tend to rattle a tad cold since I set mine up at .0011" skirt clearence, NBD and it goes away in 60 seconds.....*EB
The hyper does refer to silicon content. Anything over 11% can be described as hyper. The silicon adds hardness to the alloy - good for scuff resistance, ring groove life and the like.
The claimed advantages of reduced growth or heat reflection are a fevered marketing guy's dream. When I ran Speed-Pro we made as many aftermarket hypers as anybody - the growth difference is on the order of 2% - meaning about .0002 less clearance needed - that's it. Anything else is due to piston design and not alloy. The heat reflection is a completely unsupported theory based on piston head running temperatures - nobody really knows.
In any case, the hypers are both physically stronger and more fracture prone than plain cast (eutectic) alloys. OEMs liked the hypers 'cuz they are inexpensive and live well in computer controlled (knock sensor protected) environments. With Silvolite moving their production to Mexico, and Federal-Mogul aftermarket now in India I cannot recommend a hyper to anybody - no way to verify quality anymore. Cheap rules that game (costs at about $4 per piston) and cheap ain't always good.
I'd put a forged piston in anything I cared about - including my lawnmower. Forged pistons are demonstratably better in every measurable way except cost.
Some are so brittle they shatter like a china cup if you drop them
October 24 2007, 5:38 AM
I'll stick with my heavy old forged ones myself, even used ones.
"There's One In Every Crowd"
1965 Galaxie 2dr HT 352/ Cruiso, soon to be a hot 390
1965 F250 4X4, 390 4-speed, getting a little rusty
2007 Focus Black and beautiful
White cane, keeps me from breaking my bones walking into things.
LOL Bill you better be dang carefull with that race cam they to shatter like a china cup
October 24 2007, 3:11 PM
if you drop them. Years ago I witnessed a friend drop a used race cam on the floor and it broke into 5-6 chunks. Like an idiot I took a stock 390 cam and eventually ended up hurling it down on the road over and over again and the dam thing just bounced. There are plenty of OEM motor co's using Hypers today.
You best not take a hammer to the Mrs wedding ring it to will shatter but that is not indicative of hardness, LOL I'm not sure about a piston being able to get knocked by a valve and getting only minor damage is that great an asset where as I'd think piston skirts and dimensions that last for years and years is good in a moderately stout engine.
I agree Forged are tops but are often miles tougher and heavier then needed. I paid mega bucks for highly lightened forgings for my 427 from Wiseco
If I can't beat a grizzly to death with it, it fails the durability test n/m
October 24 2007, 6:33 PM
LOL
"There's One In Every Crowd"
1965 Galaxie 2dr HT 352/ Cruiso, soon to be a hot 390
1965 F250 4X4, 390 4-speed, getting a little rusty
2007 Focus Black and beautiful
White cane, keeps me from breaking my bones walking into things.
>>>*I defer to your expertise on the subject of terminology and silicon percentages, all I really know is from my visits to the factory. They described "Hyper" as 18%, less as eutectic alloy.
Now I didn't know they had moved operations to Mexico, but I wouldn't have a problem with that since the Mexicans I know in this industry are often darn fine techs and I suspect they can produce quality there as well as here. I found that brand to be extremely consistant as to size, weight and finish. My son runs our engine shop now and he uses them still, same success.
Maybe since I have been retired for some 8 years now I am slipping, but I do know this...Set the KB piston ring gap at stock and the rings will likely butt and damage the piston in any high load situation. This means more heat up there to me, heat is power. I couldn't prove gains on a dyno and tried, too many variables and within the error factor but the engines sounded sweet and worked.
Perhaps I was fooling myself, but I had very good success with those pistons, won a lot of events, and I like them.....*EB
I really have no issue (other than the obvious loss of jobs) with the parts being made in Mexico or India - - but I get afraid because they let go of anybody stateside that gave a rip about the parts or cared about the market/customers - the beancounters are running the show - which means taht the cheapest part wins.
The gap issue with KB has two sources - first is that Erb - the designer - decided to position the top ring really high. Racers do that to get the last ounce of power, and OEs do it to reduce crevice volume - the unburnt fuel trapped there increases emissions - particularly at cold start. A high top ring will obviously increase its heat absorption.
The second cause is that the Silvolite metallurgy used a rather large silicon nodule size with marginal distribution - increasing the potential for crack propagation - hence the use of a large gap and a huge second land to reduce damage. Compare this to Federal-Mogul's Sealed Power/Speed-Pro/AE (OE brand), Zollner OE, or Mahle hypers - all of which have a smaller nodule size, smoother dispersion, and conventional gap requirements.
All that duly noted - a good tuner and engine man can make any of these parts run and run well. Others can break a bowling ball in a sandbox with their bare hands...
This go around on this subject seemed to offer a wider variety of experienced input than the past. The general consensus seems to be that for the LOOOONG Haul, stay with the one that brung us... the forged. The issue of extra gap on the top ring concerns me due to those of us that use Max Seal ring sets, this compounded by the fact that all my engines get the Ceramic coating on piston tops, all of this changes the dynamic of the end gap due to extra heat in the equation. Sounds like a whole new learning curve, I'll probably stick with what has worked for the last 25 years and run forged. OMG! I've turned into an inflexible Old Fart! Funny how you tend to become what you critized an an intolerent youth.
I've been into FE's a long time, used to be if i wanted a 4.25" stroke it was gonna cost over two grand for a crank. Now i could buy a pallet load for that. I spent $700 on LeMans rods, aftermarket would have been much more. The TRW forged pistons were the least expensive but still cost what i thought was a bunch so i've used cast on everything, only my 427 has forged.
At $4 per piston somebody it still making good money at the cheapest resale rates i've seen, i know the Chinese cranks and rods wholesale for ridiculously low prices. How come this hasn't filtered down to $200 per set forged pistons yet?
is for the plain cast parts that they sell to all the rebuilders. It may be crazy - but they actually sell guys like Jasper those pistons at under $5 each. US made forged pistons were costing us around $16 for the cheapest SB Chev parts.
....be attributed to higher thermal conductivity of this hypereutectic material as compared to a standard cast aluminum alloy used to manufacture regular cast pistons? If these hypereutectics truly "reflected" heat better, why do they run noticeably hotter than other types of pistons? This "reflected" heat, if measureable, should correlate to more combustion energy being used to do work on the piston instead of being lost as heat absorbed by the piston or other surrounding components/radiation of heat to the surroundings.
