I blew my 686 this past weekend climbing a hill the Cinders OHV area in Flagstaff AZ.

It put an 8" hole in front case. Not a good deal. The rod failed at the oil hole. It broke in 4 pieces. They just cant take any hop ups.

Hot Rods makes a crank kit. It comes with a crank and a hot rod. Will this hold up on a 686 or 727?

Thanks!

 

You might try PM'ing THEBOM.He builds some very big DS's.I think he's up to an 830.Surely he can point you in the right direction,or tell you someone who can.

 

Have you got pic's? That sounds like a massive failure....




Bob Craycraft could definetly help you out. I'm running a Barker rod with a falicon balenced crank. No issues, and the rod seems very durable. A fellow drag racer with a Barker 686 was running the same rod as mine when his piston let go and it bent the rod in a L shape but did not break it. Saved the cases.

 

Yup, those stock rods LOVE to snap when you've put engine work into it. You should of replaced it when you did the first 686 rebuild, who decided not to put the Carillo rod or any rod of equal strength in?! A strengthened rod is basicaly necessary for any built Rappy. Expect to spend well over 2 or maybe 3k to fix it, especially since you destroyed your cases. Did the rod swing down and snap your main axle in the Transmission, too? That happens alot when the rod goes out. Just a tip, while your in fixing the engine, it would be a great time to be sure everything that is a reliablity issue is replaced because the engine is always going to fail at the weak spot and build Rappys have alot of those [img]i/expressions/face-icon-small-wink.gif[/img] Sorry to hear about your engine, I'm sure it'll be back up and running in no time [img]i/expressions/face-icon-small-smile.gif[/img]

 

I will post pictures after work today. It's a BIG hole.

The rod swung out the front of the case, and the trans seems to work still. So, I doubt if there is damage there. (I hope)

I am worried about head and valve damage. I haven't pulled her down yet. You can see the piston at BDC thru the hole in the case. The rod went thru the skirt. So, I am hoping it didn't bounce off the valves, then end up at BDC.

I ordered the case. I am looking at the Hot Rods crank kit. I found one for $250. Are these any good?

I think I am going to do a 12:1 727 this time. Got to get something out of this for all that money I will be putting in.

 

Nobody seems to know about the Hot Rods kit. To some, the rod looks too much like the stocker at the small end. I've never heard of a Raptor crank breaking, it would be hard to screw that up. Buy one and let us know if it holds up [img]i/expressions/face-icon-small-wink.gif[/img]


Carillo makes a strong rod but it's heavy and I've heard that tolerances aren't as tight as they could be.

I run a Ti Barker rod and it's holding up fine in a 10K rpm 727. Barker also makes a Chrome Moly rod for a few hundred less. Craycraft usually keeps Barker rods in stock and has dealt with blown rods and busted cases before, it's worth a phone call.

 

The Hot Rod does look a lot like the stocker, but it is forged and shot peened. The stocker looks like it is just powder cast. It looks like crap metal in the breaks. It was half fatigue failure and half brittle fracture. A forged rod would have a ductile failure. This rod did not have a ductile failure.

The thing about the Hot Rod Crank kit is that the crank comes with the rod intalled. I just have to drop the crank assembly into the new case. Even I can do that.

 

my 686 just galled the small end of the rod too, i am gonna take the gamble and put in the hot rods crank and pray for the best lol

 

Who did your 686 build???

 

I did the assembly. Max-Power did the porting, cylinder work, valve work and piston coating.

Checkout my page for pictures of the hole in the crankcase. It may take a bit before it is available.