I just got my taxes back, and I have plenty for a 686...but you guys are freaking me out with the stock rod breaking, and the JE piston. I'm starting to have my doubts. I know there are tons of 686's running around with the stock rod, and they don't have problems. And I'm sure there is just as many running around with a JE piston and no problem....is there anything I should look for or do to prevent breaking the rod or piston????

I'm supposed to get a TRUE 11:1 JE, and I'm staying with the stock rod(if I get the kit). Is there a certain way to break it in, or anything that I could do to help prevent detonation? Usually I break the Raptor in like I usually ride it. Pretty aggressive, but I do give it the cooling periods for the first 3-5 tanks of gas. But is there anything at all that would help keep it together?

 

Craycraft is having some TRUE 10.75:1 Ross pistons made that should be able to run on 93 octane pump gas.

 

I will have to talk to Bob about it. I was going to get the TRUE 11:1 JE and run pump gas. But we'll see. SixSixt, I may refer back to you a couple times when I get my top end sent to Bob.

 

hmmmmmmmmmmm things are lnot ooking good at JE land, YFZ 450 slug with like 10 -12 hrs.............

Cracked up !

not pretty.......

underside...........

it has so much carbon on the crown because it was starting to burn oil......................

Who have you guys been dealing with at JE on the cracked piston deal ?

 

How good are the Ross piston's?

 

Depends on what your talking about. If I scored 1 out of every 10 times I tried I would be extremely happy!!![img]i/expressions/face-icon-small-shocked.gif[/img]

Your right, that doesn't sound so great. Ahhh hell now I am going to worry about my rod and piston.[img]i/expressions/face-icon-small-disgusted.gif[/img] Yeah right....run er' till she blows, then call Bob.[img]i/expressions/face-icon-small-cool.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img]


I didn't know they changed pins 3 times, until now I had only heard of two.

 

Just to play it safe I'm going to throw a Ross piston and CM rod. Balanced and might as well go with an updated tranny while I'm at it. I told myself if the tranny went I would do the rod, it's the opposite, so Craycraft Racing will do all the work[img]i/expressions/face-icon-small-smile.gif[/img]

 

Those engines were designed and built around that 11:1 or 12:1 piston.There timing advance curves may be less aggressive than the one made for a 9:1 raptor engine.When you add the 11:1, the factory timing curve for that setup might be too aggressive and detonation can and will occur if octane requirements are not fuffiled.

Detonation is a bad thing,it should never be tolerated or accepted,if your getting detonation,you need to address it.Looking for a piston that can endure prolonged detonation might be your answer,but I would rather address the problem the right way.

My advice would be to go with an aftermarket ignition box that has programable ignition mapping.That way you can bring the advance curve in slower and really dial in the ignition for the best performance and reliability.I know its about 400 bucks,but if your gonna do it,do it right.

 

Having a carbuerated engine in perfect tune at all times is not going to happen in the real world. We ride from 45* temps at night to 85* in the day, pressure and altitude changes can vary from one hour to the next. Unless you change jetting and timing from one moment to the next things are not going to be perfect. That's why a piston should be able to handle not so perfect conditions and even some detonation.

In a carbuerated V8 with a distributor there is no way every cylinder is running the same,temps timing and mixture vary in each cylinder. If the pistons you had in it were as intolerable as the JEs in the raptor you'd have a good chance a piston would crap out on you every time you went to the races. Or you could run it rich and retard the timing use a high octane fuel to compensate for the ever changing conditions and be slower than the person using a piston that allows him to run closer to the edge without failure.

 

I guess you have to pick your poison,Personally,I would rather have the engine that can finish the race,rather than the one that runs the fastest but can't finish the race.There is an issue of reliability,You need to run on the edge,but not go over.

I would be willing to say that timing,temp and fuel mixture are consistent enough in a V8.If the temp,mix and timing were that far off,that engine would run like poo and vibrate to all hell at 6,000+rpm,if oit could even rev that high.That is why distributors are "recurved" or ignition systems are "remapped".This allows you to run right on the edge without ever going over.

I don't know how much time you spend at the track,but I see guys making changes to there fuel and ignition systems between each run and compensating for temp,humidity etc.

It may be an inconvienience to you to make the neccessary changes to keep up with these variations,but if you want to run on the ragged edge ,its the only way.If your looking for a piston to withstand abuse(detonation)then I think your lookin in the wrong direction.

I ran cast pistons in my V8's with 10:5.1 and close to 11:1.Never melted a piston or broke one.Luck,I think not.A good setup,definately was.