When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Yeah, it definitely looked like detonation to me and should have guessed it was sudden by the looks of things vs. over the long haul. However, I recently saw something very similar with KB cast Hypereutectic pistons and it was definitely over a long period of time. I'll see if I can find the pics I took. The denotation wasn't coming so much from timing as it was running the motor WAY to fat for a long time, years. Too fat/rich will cause the same type of issue by washing the cylinders and unseating the rings which can cause gaulding as well. Un-burned fuel trapped between the rings as the piston comes back up will ignite and try and push the piston back down, thus hammering the lower rod bearing. Those types of catastrophic piston failures can be rather expensive for sure. Like I said earlier and like others. Using a Hypereutectic piston is NOT the way to go if you are building a performance motor and certainly not for a 383 or higher build just to save a dollar. Like the trans commercial from back in the day said, "you can pay me now or you can pay me later" for not doing it right the first time. Thanks for the pics.
Found the pic of KB Hypereutectic piston that was fuel fat and didn't like it after a while. Another reason NOT to use them and not to run too fat on your tune.
Fuel Detonation over time
Last edited by Buccaneer; Jul 19, 2017 at 04:01 PM.
How does CF feel about forged 4032 alloy vs. 2618 alloy today?
Personally, I'd much prefer the 4032 alloy to have tighter clearances, less noise, less scuffing, no "piston slap" and I've heard that they can even tolerate small doses of NOS without issue.
2618 for racing, superchargers, turbos, and big NOS doses is a no brainer, but I'm not sure it makes sense for a rebuild done in 2017 for a street or street and occasional strip motor.
-Thoughts?
It also seems like forged pistons can be essentially the same price as hyper pistons, which kinda shocked me. The difference between cast and forged cranks is still pretty significant, but for pistons, I really can't fathom anyone going with cast given the tiny price differences right now...
Adam
Last edited by NewbVetteGuy; Jul 19, 2017 at 03:37 PM.
Un-burned fuel trapped between the rings as the piston comes back up will ignite and try and push the piston back down, thus hammering the lower rod bearing.
Are you describing pre-ignition here. Ignition of the fuel independent of the spark plug too early in the stroke.
Pre-ignition is devastating to every engine.
I got a question for you GOSFAST, how much HP was this engine producing and how high was it being revved? Any power adders? A 350 or a 383 or was it some other stroker motor?
Bone stock bottom ends. I can find a link when I get home. You don't read Hot Rod????
I don't read anything except the general performance stats for any of the new cars. I might glance thru one on the mag rack, but I stopped my subscriptions for like Hot Rod and Car Craft at the turn of the Century.
How does CF feel about forged 4032 alloy vs. 2618 alloy today?
Personally, I'd much prefer the 4032 alloy to have tighter clearances, less noise, less scuffing, no "piston slap" and I've heard that they can even tolerate small doses of NOS without issue.
2618 for racing, superchargers, turbos, and big NOS doses is a no brainer, but I'm not sure it makes sense for a rebuild done in 2017 for a street or street and occasional strip motor.
-Thoughts?
It also seems like forged pistons can be essentially the same price as hyper pistons, which kinda shocked me. The difference between cast and forged cranks is still pretty significant, but for pistons, I really can't fathom anyone going with cast given the tiny price differences right now...
Adam
Forged pistons are typically made from one of two alloys: SAE 4032 or SAE 2618. The 4032 alloy is most often used for pistons in street engines, drag engines, naturally aspirated engines and many sportsman class circle track engines. The 4032 alloy contains more silicon (11 to 13.5 percent) than 2618 (less than 0.25 percent), which reduces thermal expansion, improves lubricity and scuff resistance. The 2618 alloy, by comparison, is a low silicon alloy so it has a higher coefficient of thermal expansion and much more tendency to scuff. But it is about a 10-15 percent stronger material and is typically the alloy of choice for serious racing, marine engines, and boosted and bottle-fed engines that produce a lot of heat in the combustion chamber. However, these pistons are not to be used for street or mild racing applications where they won’t be replaced routinely.
I don't read anything except the general performance stats for any of the new cars. I might glance thru one on the mag rack, but I stopped my subscriptions for like Hot Rod and Car Craft at the turn of the Century.
4032 works well. I ran basic SRP 4032's for years in my 540 at 800+ HP and 7500+ RPM. No issues. Nice and quiet even though I ran them looser than recommended at around .0045". Skirt design has a lot to do with noise.
Later I installed some Mahle 4032's in it when I made it a 555". Also no issues and hammering it hard.
I've got 2618 Diamond's in it now for the turbos. A little noisier cold....but it's a very tight engine as far as blowby and oil control. Not a drip or a puff anywhere even under boost.
I got a question for you GOSFAST, how much HP was this engine producing and how high was it being revved? Any power adders? A 350 or a 383 or was it some other stroker motor?
It was probably making about 420 HP when all hell broke loose?? It definitely was on the chip which was set to 5800.
No power adders, only injected.
(Add) It was a 383" hyd-roller platform, 9.5:1 comp.
I do have a bunch of personal issues with this unit. One being the cost ($6000.00+) and getting some "welded-ball" pushrods, among other "cheap" pieces in here, for the money?? I have literally hundreds of these on the shelf from around the early '80's, that I ended up never selling. They cost us about .50/per back then! I never expected to find these in this "performance" unit??
Thanks, Gary in N.Y.
P.S. Here's a shot of the pushrods. Just my take here, but I would steer clear of ANY "crate engines" regardless of the mfr. I would want an itemized list including the brands of EVERY piece used in the build.
Last edited by GOSFAST; Jul 20, 2017 at 05:26 PM.
Reason: Add info
It was probably making about 420 HP when all hell broke loose?? It definitely was on the chip which was set to 5800.
No power adders, only injected.
(Add) It was a 383" hyd-roller platform, 9.5:1 comp.
Thanks for the info GOSFAST.
None of those numbers look to be in excess of what a cast hypereutectic piston should be able to handle. In fact I would say well below the HP level and just a little below the RPM for the 383.
Maybe it was just a poorly built and or tuned engine, and detonation was not just a contributing factor but the real cause of the destruction. Too much squish distance maybe along with open dish piston tops? Quality of the brand of piston? Poor engine cooling, using under hood hot air, Running lean, all kind of stuff that could contribute to deto destruction.
No personal experience but have read of folks running a lot more HP and nitrous to hypers and them surviving. I think it's all about tune and avoiding the dreaded detonation destruction.
I personally run hypers at 440ish HP with an RPM limit of 6,400 on a 350 @ 10.6 CR and they have survived 10,000 miles so far. However never any detonation and I use D-dish pistons vs open dish type with a squish of .038".
Good post go fast. If a shop charged even modestly for decent parts and great machine wrok they would beout of business....same goes for guys who run dynos, flow benches etc. 3rd world mentality it seems
If one couldnt afford a real nice build, get a cheapo GM crate from summit, a SFT cam used Weiand blower or a chitload of nitrous on it and hammer away. If it breaks spend another 1300 and do it all over again.
Learned my lesson not once but twice buying those P.A.W shortblocks! Wasnt bad parts so much as horrible machine work.
May have overspent this time on a lousy 383 but its good stuff at least.
Some times its possible to make not so great parts last (and good tuning)with awesome machine work, that old timer, ie 1 man shop that knows his stuff. Joe Sherman comes to mind..mine retired last yr.
This line explains why that engine lived: "The sole modification to the short-block (at the advice of Jerry Stetler from Ace Machine) was to increase the gap of the top rings from 0.015 inch to 0.028-0.030 inch (we reused the original rings). The second (factory gapped at 0.028 inch) and oil rings were left untouched."
That and the 118 octane race fuel that prevented any detonation.
Most hyper failures are from either too tight of a ring gap or detonation. Most of the guys blowing up boosted stock LS engines do so because of one or both of these things.
Mike
Last edited by v2racing; Jul 21, 2017 at 04:40 PM.
Yeah, it tells you how the wristpins were inserted into the rods.
I've fitted hundreds of pistons to rods with a a few different brand heaters, I have never seen a rod blue.
Dark blue mean the temp has been at least 575 deg F
Far to hot for molecular integrity of the rod.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Originally Posted by v2racing
"The sole modification to the short-block (at the advice of Jerry Stetler from Ace Machine) was to increase the gap of the top rings from 0.015 inch to 0.028-0.030 inch (we reused the original rings). The second (factory gapped at 0.028 inch) and oil rings were left untouched."
Most hyper failures are from either too tight of a ring gap or detonation.
I have the KB hypers in my build for some 20 years and 40000 miles without issue. I did pay attention to the KB instructions on increasing ring end gap.
