I got THE answer !
Thread Starter
Drifting
Joined: Dec 2004
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From: Edgewater (20 miles south of Daytona) Florida
I got THE answer !
Well, I finally got the word back from SRP (the piston makers) about mine. They did a Rockwell test on them and found the two that had cracked off a ring land were at 50 on the rockwell scale! The urgently advised NOT to use the ones that were still in the block (they had been removed already anyway). They claim the pistons had been subjected to EXTREME heat thus the reduction in the hardness. Looks like I'll be buying 8 new ones from another manufacturer. I just never seem to get a break. I'm out of money and the wife is out of patience and now I tell her I need to spend another $1,000 for MORE pistons, rings, thermal coating etc. Needless to say this weekend I did a lot on her 'honey do' list. Thanks for letting me vent. 
Glenn
Glenn
Intermediate
Joined: Aug 2006
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From: Michigan
For what it's worth, I've always used Speed-Pro or TRW pistons with good results. The only piston failure I ever experienced was with a rebuilt engine I purchased, equipped with SRP pistons. The skirts on three of them became brittle and litterally shattered.
It was a generic 350, so it simply got hauled to the curb and replaced!
It was a generic 350, so it simply got hauled to the curb and replaced!
Le Mans Master
Joined: Jan 2006
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Originally Posted by Glenn"Mr.Blue"Smith
Well, I finally got the word back from SRP (the piston makers) about mine. They did a Rockwell test on them and found the two that had cracked off a ring land were at 50 on the rockwell scale! The urgently advised NOT to use the ones that were still in the block (they had been removed already anyway). They claim the pistons had been subjected to EXTREME heat thus the reduction in the hardness. Looks like I'll be buying 8 new ones from another manufacturer. I just never seem to get a break. I'm out of money and the wife is out of patience and now I tell her I need to spend another $1,000 for MORE pistons, rings, thermal coating etc. Needless to say this weekend I did a lot on her 'honey do' list. Thanks for letting me vent. Glenn
Glennand what were the conditions aorund the extreme heat issue?
IU clearly recall the thread on this, but an curious how your damage occured
thx
tim
Le Mans Master
Joined: Jul 2005
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From: Austin Texas
In my 383 build, I used SRP forged pistons. In the paperwork with the pistons was a tag that said basicallly "these pistons are o.k. for light nitrous and low boost blower applications, for more aggressive use use a more rugged piston". It appears that the piston top is not very thick.
Thread Starter
Drifting
Joined: Dec 2004
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From: Edgewater (20 miles south of Daytona) Florida
Tim,
The ROCKWELL test, as I understand it in simple terms, measures the hardness of a substance. Obviously, something as low as a 50 is VERY soft, especially for the top of a piston in a supercharged engine.
As for the heat, I am of the opinion that the car overheating caused this problem, since there were NO signs of detonation when examend by us AND the piston manufaturer. Though I monitor all the temps duing that problem and none got THAT hot in my book, the exhaust gas temps were in the 950, to 1100 degree range, and anything under 1250 should be safe. I did have a short temp of 1400* (which was above a safe limit) but that was back in 2004 and I thought I had gotten away with that, but obviously it must have done the damage and took this long to break. I will never really know.
I don't have all the answers and I'm looking still for them. Hope this helps you understand what I was talking about. Glenn
The ROCKWELL test, as I understand it in simple terms, measures the hardness of a substance. Obviously, something as low as a 50 is VERY soft, especially for the top of a piston in a supercharged engine.
As for the heat, I am of the opinion that the car overheating caused this problem, since there were NO signs of detonation when examend by us AND the piston manufaturer. Though I monitor all the temps duing that problem and none got THAT hot in my book, the exhaust gas temps were in the 950, to 1100 degree range, and anything under 1250 should be safe. I did have a short temp of 1400* (which was above a safe limit) but that was back in 2004 and I thought I had gotten away with that, but obviously it must have done the damage and took this long to break. I will never really know.
I don't have all the answers and I'm looking still for them. Hope this helps you understand what I was talking about. Glenn
Safety Car
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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
I think they have you a little confused, or you miss heard what they said. 50 on a Rockwell scale is VERY hard. I am not a metalurgists (sp) but I am 99.99999% sure you can not get aluminum to 50. Most of the chromemoly rifle barrels we did were a 28, and the stainless ones were usually around 32.
Depending on a variety of circumstances extreme heat introduced to metal will usually soften it (anneal) this is the problem guys run into at the Pro-mod level when using extremly high nitrous loads. If they do not melt the pistons during the run they will check the Rockwell bewteen rounds and even if nothing major goes wrong, the pistons are servised out after approx. 25 runs. The extreme heat of the nitrous softens the pistons so much they are in danger of coming apart.
If you can get JE (makers of SRP) to admit any fault in the matter you may get a set of their top of the line JE pistons for a better deal. They have treated me pretty good in the past. I would not run anything less than a top of the line forged piston in a blower car. I run JE's in my nitrous race car and they have have lasted very well.
Depending on a variety of circumstances extreme heat introduced to metal will usually soften it (anneal) this is the problem guys run into at the Pro-mod level when using extremly high nitrous loads. If they do not melt the pistons during the run they will check the Rockwell bewteen rounds and even if nothing major goes wrong, the pistons are servised out after approx. 25 runs. The extreme heat of the nitrous softens the pistons so much they are in danger of coming apart.
If you can get JE (makers of SRP) to admit any fault in the matter you may get a set of their top of the line JE pistons for a better deal. They have treated me pretty good in the past. I would not run anything less than a top of the line forged piston in a blower car. I run JE's in my nitrous race car and they have have lasted very well.
Last edited by 69 N.O.X. RATT; Aug 7, 2006 at 09:55 AM.
Thread Starter
Drifting
Joined: Dec 2004
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From: Edgewater (20 miles south of Daytona) Florida
Like I said, I'm not sure about all this Rockwell stuff, but these were forged pistons, and I was told the Rockwell should have been up around 80 on thses pistons. I'm even more confused than wehen I started with this problem. They (SRP) will NOT stand behind these pistons saying that they were exposed to extreme heat and it isn't in their product. I'have ordered a new set of forged pistons from Keith Black and they will be drop shipped here by the end of the week at least. Because I have custom length Carillo steel rods and the pin hole is up further into the piston than normal, I can't get 'off the shelf' pistons, though KB does have a combination that will work for my proper CC and other requirements, and they will 'ONLY' be another $450 instead of the $110 I was quoted from SRP. Now, I still have to send them out and have them thermal coated, but it's a less expensive starting point. 
Glenn
Glenn
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Le Mans Master
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From: I can walk to MA
Originally Posted by noonie
So did you ever come up with a definite diagnosis of the heat problem causing all this?
Bummer Glenn ... is this what was giving you the overheating issues
a month or two ago when the power tour was on ?
Race Director
Joined: Mar 2006
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From: Florida
Originally Posted by NHvette
See post #5 above.
Bummer Glenn ... is this what was giving you the overheating issues
a month or two ago when the power tour was on ?
Bummer Glenn ... is this what was giving you the overheating issues
a month or two ago when the power tour was on ?
Thread Starter
Drifting
Joined: Dec 2004
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From: Edgewater (20 miles south of Daytona) Florida
Hot under the collar
Originally Posted by noonie
I'm asking why it overheated in the first place to cause the piston problem.
It all makes sense, so hope it's the right move. It's not like it's a 'standard' system, so standard items don't always apply. Basic principals however, do still apply. You have to have water moving and air flowing over the radiators to expell the heat from the block and heads. Time will tell. Glenn
Drifting
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From: Flanders NJ
A Rockwell Hardness number needs to have scale denoted. There are A, B, C, & etc. Rockwell scales. Each Letter is a different type test designed for different typs of metals. Without this the number is useless. A Rockwell 65C is very hard, like drill bits, tool steels. In this range & above it gets brittle. The B scale is for medium hardness like low & medium carbon steels in annealed condition. The C scale is for materials harder than B-100. On the C scale there is no way you could have a Rockwell 85. So unless everyone is talking about the same scale there is no way you can make comparisons. It's not a cut & dry thing.
Thread Starter
Drifting
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From: Edgewater (20 miles south of Daytona) Florida
Originally Posted by mooneyd
A Rockwell Hardness number needs to have scale denoted. There are A, B, C, & etc. Rockwell scales. Each Letter is a different type test designed for different typs of metals. Without this the number is useless. A Rockwell 65C is very hard, like drill bits, tool steels. In this range & above it gets brittle. The B scale is for medium hardness like low & medium carbon steels in annealed condition. The C scale is for materials harder than B-100. On the C scale there is no way you could have a Rockwell 85. So unless everyone is talking about the same scale there is no way you can make comparisons. It's not a cut & dry thing.
Race Director
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if you overheat the pistons (crowns) they do get more brittle and the ring land tends to break off like yours did. It'll be next to impossible to prove if they were bad from the get go or because of overheating/detonation/high cyl temps... You had thermal coating on the piston tops? That should keep the heat out of them, who did the coating? Maybe someone messed up the process with the sinter oven.
HR (rockwell hardness) = E - e
E = constant dependant on indentor either 100 for a diamond120 degree tipped indentor and 130 for a round steel ball indentor.
e = permanent increase in depth from major load (total indentation after releasing major load - initial minor load indentation) in units of 0.002 mm
Softer metals like aluminium are usually measured in the B scale. The B scale uses a 1/16" steel ball indentor with an E of 130. This means your 50 harness would mean a permanent indentation of .16mm
(RH = 50 = 130 - e) -> e = 80. 80 units of 0.002 = .16mm indentation.
From this you can see that the rockwell hardness scale gives a LOWER number for a harder material since it's a measure of indentation.
HR (rockwell hardness) = E - e
E = constant dependant on indentor either 100 for a diamond120 degree tipped indentor and 130 for a round steel ball indentor.
e = permanent increase in depth from major load (total indentation after releasing major load - initial minor load indentation) in units of 0.002 mm
Softer metals like aluminium are usually measured in the B scale. The B scale uses a 1/16" steel ball indentor with an E of 130. This means your 50 harness would mean a permanent indentation of .16mm
(RH = 50 = 130 - e) -> e = 80. 80 units of 0.002 = .16mm indentation.
From this you can see that the rockwell hardness scale gives a LOWER number for a harder material since it's a measure of indentation.
Last edited by Twin_Turbo; Aug 7, 2006 at 01:51 PM.
Thread Starter
Drifting
Joined: Dec 2004
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From: Edgewater (20 miles south of Daytona) Florida
Coatings..
Originally Posted by Twin_Turbo
if you overheat the pistons (crowns) they do get more brittle and the ring land tends to break off like yours did. It'll be next to impossible to prove if they were bad from the get go or because of overheating/detonation/high cyl temps... You had thermal coating on the piston tops? That should keep the heat out of them, who did the coating? Maybe someone messed up the process with the sinter oven.
A local company here in Edgewater did the thermal coating to the top of the pistons, as they will do to the new forged KB's I just ordered today. A full set for $450.
I don't feel the problem was in the coating, but the 'materil' the SRP's were made from. I STILL think it was a bad 'run' of pistons. It DOES happen, just ask Firestone tires! Especially with all this 'off shore' foundry work going on. Glenn
Race Director
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another thing to consider is what type of pistons did you buy, low or higher silicon constent? Forgings are usually made from either 4032 or 2618. The 2618 has a lower silicon content and therefore more thermal expansion but also more scuff and pin and ring groove wear. They are stronger than the others (but have more wear). The 4032 is usually used in the cheaper pistons and since you have SRPs
(being sportsman type pistons) I think yours fall in that category.
If you have high cyl. temps requiring thermal coatings...have you thought about drilling the main webs and grinding a slot to the oil feed hole in the mains and inserting squirters? A little oil spray on the bottom of the piston would help tremendously in cooling.
(being sportsman type pistons) I think yours fall in that category.
If you have high cyl. temps requiring thermal coatings...have you thought about drilling the main webs and grinding a slot to the oil feed hole in the mains and inserting squirters? A little oil spray on the bottom of the piston would help tremendously in cooling.
Race Director
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From: Plano TX
Originally Posted by Twin_Turbo
From this you can see that the rockwell hardness scale gives a LOWER number for a harder material since it's a measure of indentation.
The B-scale is used for softer materials (such as aluminum, brass, and softer steels). It employs a hardened steel ball as the indenter and a 100kg weight to obtain a value expressed as "HRB".
The C-scale, for harder materials, uses a diamond cone, known as a Brale indenter and a 150kg weight to obtain a value expressed as "HRC".
The depth of penetration is converted to a scale in which the harder the material the higher the number.
Common values
* Very hard steel (e.g. a good knife blade) HRC 55 to HRC 62 or so
* Axes, chisels, etc. HRC 40 - 45
Thread Starter
Drifting
Joined: Dec 2004
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From: Edgewater (20 miles south of Daytona) Florida
Rockwell Smockwell
Wow, I'm just an old grease monkey from the 60's. I appreciate you taking time to explain all this to me, but honestly, I'm still as lost about MY pistons as before. Without having asked the right questions of the company when they called and left that message, I still don't know if they are too soft due to heat like they said or not. I need to ask them what type of metal they were forged from and what they consider a 'normal' Rockwell rating for their pistons. I also need to ask my engine builder if he know what he's talking about, cause I sure don't on this subject. He's the one who told me they should be around 80 Rockwell.
Thanks guys for trying to help.
Glenn
Thanks guys for trying to help.
Glenn
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Originally Posted by zwede
I was with you until this last statement. From wikipedia:
The B-scale is used for softer materials (such as aluminum, brass, and softer steels). It employs a hardened steel ball as the indenter and a 100kg weight to obtain a value expressed as "HRB".
The C-scale, for harder materials, uses a diamond cone, known as a Brale indenter and a 150kg weight to obtain a value expressed as "HRC".
The depth of penetration is converted to a scale in which the harder the material the higher the number.
Common values
* Very hard steel (e.g. a good knife blade) HRC 55 to HRC 62 or so
* Axes, chisels, etc. HRC 40 - 45
The B-scale is used for softer materials (such as aluminum, brass, and softer steels). It employs a hardened steel ball as the indenter and a 100kg weight to obtain a value expressed as "HRB".
The C-scale, for harder materials, uses a diamond cone, known as a Brale indenter and a 150kg weight to obtain a value expressed as "HRC".
The depth of penetration is converted to a scale in which the harder the material the higher the number.
Common values
* Very hard steel (e.g. a good knife blade) HRC 55 to HRC 62 or so
* Axes, chisels, etc. HRC 40 - 45
You're right...I messed up my own description d'oh!!! Of course it's a higher number, it had to say for a harder material the indentation is less, so e is a lower number and therefore E- e is a higher number..oops
thanks for the heads up 