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Author Topic:   Broken Crank and Bent Push rods
chief4car
Dirt Full Roller

Total posts: 56
posted June 30, 2002 09:08 PM
This past friday the snout of our crankshaft broke off. Is there anything that would have caused this other than fatigue. Secondly, it appears that 13 of 16 pushrod are severly bent also, what could have caused this. My opinion is that when the crank broke the cam and crank were no longer in time with each other and pistons contacted the valves bending everything. I am assuming I'll need new valves also. Lastly while inspecting the bottom end for other damage it appears that our cam has developed a sizable groove in each some lobes near the nose of the lobe (this is a mechanical roller) Is this just wear or lifters going bad, or was it caused by the crank breaking. We build our own motors.

I am just looking for some insight into the hows and whys of these various problems. Advice would be greatly appreciated.


Jim Cleaver
Cleaver Racing Inc.

chief4car
Dirt Full Roller

Total posts: 56
posted July 01, 2002 11:19 AM
No i didnt use a big ol hammer, I used an installation tool.

Thanks

JIm

marty
Dirt Maniac

Total posts: 111
posted July 01, 2002 01:03 PM
Hi chief,
How did the main bearings look? Had any of them spun? If the block has survived then it might be worth getting it line bored & then fitting some good race bearing (they cost a little more but are much stronger under high loads), by the way they come without that coating of white metal-that old case in racing of paying more for less.
As for the heads i would just try inverting them on stands and then ,after leveling them i would put some liquid in the chambers (maybe grease eater fluid) one at a time and see if any leaks past the valves.
Hope this helps a little.
marty.

CUZZ45
Dirt Roller

Total posts: 15
posted July 01, 2002 02:12 PM
CHEIF YOUR PROBABLY RIGHT ABOUT YOUR VALVES AND PUSH RODS .MOST LIKLY YOUR CRANK BROKE BECAUSE OF YOUR BALANCER IT EITHER GOT LOSE OR IF YOU USE STOCK IT TURNED ON THE ISOLATION RING. OR WAS JUST OUT OF BALANCE .YOUR CAM SOUNDS LIKE TO SOFT SPRINGS OR TO MUCH VALVE CLEARANCE. AND LASTLY IT COULD ALL BE FROM AN OILING PROBLEM(IE)OIL GALLEY PLUGED

chief4car
Dirt Full Roller

Total posts: 56
posted July 01, 2002 02:55 PM
Have not completely tore the motor down yet, will look for spun bearings. The block appears fine the crank broke just behind the lower timing gear and just in front of the first main. I intend to thoroughly clean the entire block. On the cam the springs are roller springs that came with DART Iron Eagles (are they to soft) these springs were new at beggining of the year. I had not noticed any problems when setting the lash throughout the season. I was going to change them mid year any way.

Jim Cleaver

sdhnc29
Dirt Freak

Total posts: 467
posted July 01, 2002 10:30 PM
Sounds like your cam is torn up from severe valve float . The spring's that come on the Dart Iron Eagles will not run on any modern circle track roller cam grind , at least not for any extended period of time . As for the broken snout , be sure to mag your main web's in the block , especially the front main web . Then switch to a big block snout on your next crank .

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

chief4car
Dirt Full Roller

Total posts: 56
posted July 02, 2002 03:54 PM
Steve,

I had no idea that these springs were no good for roller cams. I would have thought that springs advertised as roller springs would work. I am a bit disapointed since I purchased these heads through your shop.

What springs would you recomend.

Thanks
Jim Cleaver

sdhnc29
Dirt Freak

Total posts: 467
posted July 03, 2002 12:44 AM
Hey Jim ,

The spring's that come standard on the Dart Iron Eagles are advertised as roller spring's , and they are , but I do not use them because they will not work with any cam that I use in the engines that I build . Most of my roller cam's require titanium valves , retainers , keeper's , and either the 1043 or 1044 PSI spring . In other word's , I use very aggressive profiles that require a ton of valve spring pressure , and very light weight valve train . To pick the proper valve spring , I would need to know what cam you are using (grind number , lift , etc.) , and what your intended RPM range will be ?? If you can answer these question's , then I can give you a part number for an appropriate spring . Or just give me a call at work , and I'll give you a part number over the phone .

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

chief4car
Dirt Full Roller

Total posts: 56
posted July 03, 2002 08:10 AM
hey steve,

I hope you didnt take my previous post the wrong way I am having a bad week. The cam in question was from herbert performance (This was recomended to us by some one I trust and has helped us a ton.) The part # is cc6kf. The specs are lift: int .598 ex. .635
duration at .050 int. 253 ex. 261

I use 1.60 rockers for the int. and 1.50 rockers for the exhaust.

I believed this to be a fairly "mild" roller cam profile.

Also the springs we used last year were comparably lighter than the ones on the Iron Eagles. The iron eagles come with Comp# 954
190 seat pressure and 515 over the nose. Compare that to the springs used last season on a different set of heads 175# seat pressure and 400 over the nose. During freshening over the winter I noticed no wear or grooving of the lobes after using the lighter springs.Also the driver has never reported any valve float. If it was severe enough to groove up the cam this way I would think he would notice.
Could the cam have just plain wore out. I have ran it for about a year and a half.


Thanks
Jim Cleaver

chief4car
Dirt Full Roller

Total posts: 56
posted July 03, 2002 08:15 AM
Steve,

also upon further inspection of the cam. This groove if you will seems to begin as the roller is traveling up the ramp and beginning to open the valve, and continues across the nose (it is more pronounced hear) and down the closing ramp. I have never seen how valve float affects a cam but I would think the damage would be less uniform.

Jim Cleaver

sdhnc29
Dirt Freak

Total posts: 467
posted July 04, 2002 12:05 AM
Hey Jim ,

No don't worry ,I didn't take anything the wrong way . I just want to help you figure out the problem . Your right , this cam is a very mild roller and valve float should be pretty difficult to get into , provided the spring's have not gone bad . But what your describing about the groove , sound's to me now like a soft billet . Perhaps the additional spring pressure that your running now ,vs. last years spring's ,is why these grooves are just now showing up . I'm leaning toward a defective billet as being your problem . Generally when you see a valve float problem , the opening ramp is damaged , but the closing side in usually in good shape . But since you describe the most damage being on the nose of the cam , and it sounds like the opening and closing sides are damaged about the same , then I must believe you have a soft billet (defective). Hope this helps !!

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

chief4car
Dirt Full Roller

Total posts: 56
posted July 04, 2002 08:36 AM
Steve,

Thanks for all of you insight. I to am of the opinion that the cam was defective. Because as you said the groove is uniform around the lobe of the cam. However thanks for all the input you gave now I know what to look for, for valve float.

Thanks
Jim Cleaver
Cleaver Racing Inc.

sdhnc29
Dirt Freak

Total posts: 467
posted July 04, 2002 01:25 PM
No problem Jim . Good luck !

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

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