Rocker arm lock nut backed off???
#660189
04/03/10 10:03 PM
04/03/10 10:03 PM
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Joined: Aug 2009
Posts: 2,054 Mooresburg, Tn
'72CudaRacer
OP
top fuel
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OP
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Joined: Aug 2009
Posts: 2,054
Mooresburg, Tn
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Fired up my new engine today and while warming it up and seating the rings, after running about 8 minutes (water temp about 165*), it started to sound noisy, like valve adj loose, oil press good, brought RPMs up to about 2500, and it popped back through the carb. I thought it may have closed up a plug, but pulled Valve cover, the #5 ex rocker adj screw lock nut had backed off and fell onto the head, push rod eat up the alum rocker arm. What the He**??!! After I set the valve lash cold, I went over the nuts with a torque wrench, so I know it was tight. But to loosen and fall off after only running for just a few minutes, it would seem that it was left loose. Anyone got any other sugestions? Why would a nut loosen? All the rest were tight. Anyone know where to buy 1 MP alum roller rocker arm?? Thanks guys, Brian Dunnigan
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Re: Rocker arm lock nut backed off???
[Re: '72CudaRacer]
#660193
04/04/10 12:50 AM
04/04/10 12:50 AM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,303
Bend,OR USA
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What procedure did you use to set the valves? What are the specs. on the cam at .050 and lobe seperation angle?
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Rocker arm lock nut backed off???
[Re: Cab_Burge]
#660194
04/04/10 01:13 AM
04/04/10 01:13 AM
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Joined: Aug 2009
Posts: 2,054 Mooresburg, Tn
'72CudaRacer
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OP
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Joined: Aug 2009
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Mooresburg, Tn
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Cab, The cam is a MP .590 solid that I had in my other engine. The cam, lifters and push rods are the only internal parts that are out of the other engine. Different stock 440 block & crank, Stealth heads, Ross pistons and Ohio Crankshaft rods. I really need to find an explanation for this before I just feed it some more parts. I adjusted the valves using the old Direct Connection chart (sticker on firewall). The cam card calls for .028" intake & .032" exhaust. I actually set them at .026" and .030" cold and was warming the engine to rest them hot. I'm amazed that it back completely off in that short of time, even if it was left loose. I'm a Diesel truck mechanic (we're "techs" now) and we had 25 2000 model Macks that would be fine, sometime for 50K miles, no one touched them, then would back off a adj screw lock nut, kick the push rod out and sound like it had "blown up". Always exhaust. Mack couldn't tell us why.
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Re: Rocker arm lock nut backed off???
[Re: 70AARcuda]
#660195
04/04/10 01:16 AM
04/04/10 01:16 AM
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Joined: Aug 2009
Posts: 2,054 Mooresburg, Tn
'72CudaRacer
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OP
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Joined: Aug 2009
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Mooresburg, Tn
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Quote:
it says w2/w5 exhaust..but it is the same rocker as the standard heads take intake or exhaust.
I have big block engine.
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Re: Rocker arm lock nut backed off???
[Re: '72CudaRacer]
#660198
04/04/10 08:30 AM
04/04/10 08:30 AM
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Joined: Jan 2003
Posts: 16,932 NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,932
NC
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Quote:
After I set the valve lash cold, I went over the nuts with a torque wrench,
That is my routine also. I don't know, sorry to hear it when you took the right precautions.
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Re: Rocker arm lock nut backed off???
[Re: 440Jim]
#660199
04/04/10 09:14 AM
04/04/10 09:14 AM
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Joined: Nov 2004
Posts: 3,544 Syracuse,NY
CompWedgeEngines
master
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master
Joined: Nov 2004
Posts: 3,544
Syracuse,NY
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Brian,
Its probably one of two things with used Cranes. Not knowing their actual "prior" life, hard to say, but most often it is as stated, a ( stretched or soft) adjuster screw, or perhaps a bad rocker. The Crane Golds after time would also tend to stretch ( normal wear and tear) the threads in the rocker boby. Basically just thread fatigue in the body). Those rockers would take a lot of abuse for what they are, but like anything, can wear . Check the threads real close on that rocker. Also as stated, make sure the rocker is getting proper oil ( check that pushrod length and rocker oil hole.
All that said, probably still a streched or soft adjuster and or rocker threads.
I should have some new spare rocker bodys in stock if its a 1.5 ratio.( Mopar Performance blue)
There may be some new " Crane style" rockers coming to the market, but I am not sure of exact schedule yet, hoping to know soon.
RIP Monte Smith
Your work is a reflection of yourself, autograph it with quality.
WD for Diamond Pistons,Sidewinder cylinder heads, Wiseco, K1 rods and cranks,BAM lifters, Morel lifters, Molnar Technologies, Harland Sharp, Pro Gear, Cometic, King Engine Bearings and many others.
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