660 Engine Failure

Went riding Saturday to Elkhurst with some friends, (got rained on twice including hail) and one with a 06 Rhino Sport had massive engine
failure. He had put I think a Mudbuster cam with the stiffer center intake valve spring, and a clutch kit all with over 200 miles. From the looks
the center intake valve head sheared off punching a hole in the piston, and destroying the other valves and an exhaust rocker. He was lucky
but the case and all the gears, shafts, and bearings seem fine. He was wanting to know if that stiffer spring that came with the cam might have
put to much strain on the valve and sheared the head. So if anybody has had a similar failure please give me clue so it won't happen again.
Here are some pics.

The keepers may have got him. Or retainers as some call them. If you don't make sure they are seated correctly by tapping the valve and spring, with a hammer, lightly, of course the can come off, yes they can hang in there for 200 miles plus before they come-off.
Could have just been a bad valve, too tight of adjustment, or several other things.
I would flush that motor with mineral-spirits fourty times tho. It has shrapnel in the bottom-end, which if you don't wash it out good, will get the rod-bearing sooner or later. I assue you that. Flush it until you get nothing in a clear bowl. It will take several times.

After looking at the pics some more. It does look like the valve broke. If the retainers had failed the stem would be bent, it looks perfectly straight. Just a bad casting??
686 it from here why not.

Thats his plan right now (686). We did take the case apart to get all the little pieces of piston, and just to check if anything else broke
with pieces flying around. All looked good he just wants to know if the spring caused it, cause if it did he said he would go back to the stock cam
and spring.

nitefab wrote:

Thats his plan right now (686). We did take the case apart to get all the little pieces of piston, and just to check if anything else broke
with pieces flying around. All looked good he just wants to know if the spring caused it, cause if it did he said he would go back to the stock cam
and spring.

I can't believe it was the spring. I'm running the same Raptor center spring, with the blue on it, as thousands of others have. With that much damage, it must have been wfo, it's really hard, if not impossable, to know. Could have jumped-time and the piston broke the valve-head off. Was all the valve-drive still intact?? Cam-chain, sprocket bolts, ect?? I'd check the tensioner close too.

I vote 686.....

Hell maybe a 720.....

I don't think there is a good reason it happened, it just happens sometimes. Just got thru building one that happen to and it was totally stock.

I like others don't think the raptor spring is the issue, by the way it is not stiffer it has smaller coils or less coils to prevent coil bind with the larger cam.

Todd

Thanks for the info. He was wondering now if that mudbuster cam will work with the 686 or 720 stroker. Our motor guy said he could fix the head,
just have to get him the parts. They told us to bring him the crank and rod so he could check to make sure it is not bent. Also, if he goes with a 720 stroker
do you have to have dual exhausts or will a single aftermarket or stock exhaust work. He does not like some of the loud dual exhausts.

Thanks

Your kidding about reusing that head aren't you?

I would highly recommend staying away from stroking it, you asking for more trouble like cracked cases due to harmonics.

......I hope he's joking about using that head!!!!!! Use it as a sinker on a fishing line ....maybe!

That heads done, no doubt.

Update the head is not finished and can be rebuilt. Our buddy got new plus 1 valves, guides, springs, retainers, seats and rockers. Should have the head back this week hopefully, and when I do I will post a pic. Here are three shots of the case rebuilt. You can see the Hot Rods stroker crank and rod, plus the new 11:1 piston.

How are you going to get the compression ratio back to stock, with the repaired/machined head?

Are you going to "CC" it and shim the head accordingly? Can you even shim the head on a Rhino engine, since it is water cooled? You can shim air-cooled engines...

I would highly recommend you loose the stock-studs. With 11:1, the stockers will stretch and the head-gasket WILL blow. KMS makes some. Money well spent.