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Discussion Starter #1
I have run hypereutectic pistons in several engines, they work fine PROVIDED you stay out of detonation range,and keep the rpm levels under 6000rpm, let me put that another way, hypereutectic pistons are only slightly stronger than cast pistons, (there are MILLIONS of cars running CAST and HYPEREUTECTIC pistons, with no problems) BUT they are not nearly as strong as forged pistons, and keep this in mind,if you do get the engine into detonation by running it lean or over advanceing the ignition timing , or you do get into valve float, and a piston touches a valve, they have a bad habit if breaking off bits of the upper ring land, now no piston,even a forged piston is going to withstand abuse like detonation , or valve float for very long, but forged pistons do hold up longer and don,t tend to fail as dramatically when they do get dammaged, and forged pistons don,t tend to shatter if they get into minor contact with a valve, I think Id ask myself , just how often and how hard I was going to run that engine, and how carefully I was going to keep it tuned,and how close to the valve trains rpm limit I intend to run that engine, if your just going to build what most guys do, a hot street/strip car that you may run seriously at the track only a few times a year they should be fine, but if theres a resonable chance that you might try nitrous in the future or your seriously thinking about running the car hard on a frequent basis I think Id spend the extra money and get forged pistons, now forged pistons are not a big cure for every problem, but they are stronger, they tend to be both lighter in weight and more closely machined, plus your more likely to get them in a compression ratio that can work well with that cam. but whatever choice you make its a good idea to get them ballanced to the rest of the rotateing assembly, and make sure the ring end gaps are correctly set up.AND do yourself a big favor and check the piston to valve clearances carefully, Ive seen several pistons with valve notches machined in such a way that the valve edges did not fit correctly into the relief cuts,check carefully now personally, I won,t run them any more in performance engine if that engine is ever likely to be run at over 6000rpm MAXIMUM, because Ive had, and seen other people have, a few failures that I feel would just not have happened if the pistons were forged. be sure you check clearances carefully, a mistake can and will damage the engine, DON,T GUESS<KNOW WHAT THE CLEARANCES ARE, ESPECIALLY SPRING BIND,VALVE TO PISTON,ROCKER TO ROCKER STUD, and retainer to valve guide clearances I still use the strips of modeling clay about 1" square and .2" (two tenths thick) but one thing everyone forgot to mention so far is that you need to spray the piston and valve and clay strips with WD-40 to ensure the clay does not stick to any parts, otherwise the clay will tend to stick to the valve and piston allowing them to push the clay between them durring the compression of its surface by the valve (exactly what its there for) and PULL ON THE SURFACE of the clay as the valve moves away durring seperation (because the clay tends to stick ever so slightly as the parts pull away from each other if you don,t)which tends to give a false slightly greater than correct clearance measurement
most people tend to tell me Im wrong about that untill they try it both ways :grin: yeah the differance is usually minor but five to 10 thousands differance is not rare if the parts are clean and dry versus sprayed with an oil mist
first check to make sure that you are measureing correctly, many times the valve actual has more clearance in the flycut clearance notches,or only the very edge of the valves head and the edge of the notch are close and very minor cutting with a tool fitted in a valve guide will clear the problem and the valve has more clearance than measurements taken from the pistons upper surfaces, and that the head gasket thickness and valve train geometry are correct,
check if changing the cam retard/advance or installed possition can be changed to increase the clearance to 0.100 minimum on both the intake and exhaust valves (MOST LIKELY TO WORK WITH THE LEAST PROBLEMS)
 

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Paragraph: A distinct division of a written work or composition that expresses some thought or point relevant to the whole but is complete in itself and may consist of a single sentence or several sentences.

They make reading easier, especially an essay on a technical subject.

:D

Ray
 

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DC Crew
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RT66Z06 said:
Paragraph: A distinct division of a written work or composition that expresses some thought or point relevant to the whole but is complete in itself and may consist of a single sentence or several sentences.

They make reading easier, especially an essay on a technical subject.

:D

Ray
:laughing: But, we still love him.:thumbsup:
 

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DC Crew
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Is it also true that with hypereutectic pistons that if you get the ring gap wrong that it will break the top edge of the piston?
 

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RT66Z06 said:
Paragraph: A distinct division of a written work or composition that expresses some thought or point relevant to the whole but is complete in itself and may consist of a single sentence or several sentences.

They make reading easier, especially an essay on a technical subject.

:D

Ray

:surprised
 

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Super Moderator
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Discussion Starter #7
spring bind
What is Valve Spring Coil Bind and How Does it Relate to Spring Travel and Valve Lift?

When the valve spring is compressed until its coils touch one another and can travel no further, it is said to be in coil bind. To measure this you must install the retainer in the valve spring, then compress the spring until it coil binds. Now measure from the bottom side of the retainer to the bottom of the spring. This measurement is the coil bind height. This can be done on the cylinder head with a spring compression tool (part number 99417-1), in a bench vise, or in a professional valve spring tester.

Using Figure 5, subtract the coil bind height “B” from the valve spring installed height “A”. The difference “C” is the maximum spring travel. The spring travel must always be at least .060” greater than the full lift of the valve. This safety margin of .060” (or more) is necessary to avoid the dangers of coil bind and over-stressing the spring.
A common cause of interference and consequent cam and valve train damage is valve spring coil bind. Coil bind is when the coils of the spring stack solid at or before full lift. The spring becomes solid and will not allow the valve to move any further. The shock and load on the valve train when coil bind occurs will demolish the cam. Coil bind usually occurs when people attempt to assemble hybrid kits or use stock springs with high lift cams.

Another common area for interference is between the valve spring retainer and the valve guide, or where fitted Teflon guide seals – the type that clip onto the valve guide.

Since the average valve seal is nearly 4.5mm thick, the valve guide height must be reduced by this much in most cases to provide clearance between the retainer and the seal at full lift. This is easily checked by installing the retainer that is to be used on the valve, without the springs. Depress the valve and retainer, without the valve spring, by hand to the valve lift figure given on the timing tag. At this point, there should be at least .150" clearance between the bottom of the retainer and the top of the seal. If there is not enough clearance, the seals will have to be removed and the guides machined for more clearance
things to read

http://www.babcox.com/editorial/ar/eb50232.htm

http://www.rpmoutlet.com/camfac.htm

http://www.amotion.com/tech/caminst.html


http://www.grapeaperacing.com/GrapeApeRacing/tech/valvesprings.cfm

http://www.lunaticams.com/Springs/SpringProRevH11.html
 

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Patrick96LT4 said:
Helping is the prelude to all problems! I remember this every time a friend asks me to help them move.:nuts:
You have a point, sir. The corollary to that is "no good deed goes unpunished".

I'll save my literary critiques for the English Lit forum.:stick:

Everyone can now return to the discussion of forged pistons (that's forged as in counterfeit, yes? Probably knock-offs from China) and please pardon my untimely and OT interruption.

Grumpy's essay was good , but I was getting vertigo trying to read it.

Sono spiacente!

Ray
 

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i am no grammer expert for sure,but if grumpy can spell...i can read.i just took a break a re-filled my coffee mug/barrel...:laughing: :smokin:
 
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