Spun Bearings

[Don Crandol]

1997 Sportcraft 232, 5.7, Alpha I Gen II thunderbolt V ignition.<br />Apologize in advance for the long post but would like to explain the whole situation.<br />Oil pan Started leaking at the end of the season last year. Decided to pull the motor this spring and replace the oil pan. Although the motor was running good, ran compression check before pulling the motor in case I had a problem that I should take care of while the motor was out. Motor has 800 hours in salt water. All cylinders between 165 and 180. Pulled motor, replaced oil pan, complete service on outdrive. Reinstall motor, tune up. Motor had a slight miss on the muffs. Put it in the water and under load would not run above idle. Thought I had crossed plug wires but was not it. Put on the old distributer cap, no change, old rotor button, miss gone. Turns out that the rotor button in the tune-up kit was for a V-6 not a V-8. Anyway took out for a test run and it started losing power. Water temp never got over 150. Back to the dock, pull plugs, electrode completely gone off # 5 plug, compressiuon check, no compression in the #5 cylinder, # 3 down to 70 psi. Pulled heads Both head gaskets blown and the #5 exhaust valve tuliped. Heads machined, reinstalled, fired up ran good at idle. water temp at 150, oil pressure at 40. Take out for a test run still not running right, get back to the no wake and throttle down and oil pressure drops off to 0. Pull motor, tear down, spun main bearings. Question is, is this all related to the wrong rotor button, or should I be looking for another problem. I'm fairly certain it was the problems with the heads but not so sure about the bearings. Any thoughts?

 

[lilmandavis]

Re: Spun Bearings

usually a tuliped valve means some water got in the cylinder id say. see what the experts say

 

[I/O WALDO]

Re: Spun Bearings

Lean or timing advanced too much I thought sucks valves.

 

[searay3]

Re: Spun Bearings

0 oil pressure and spun bearings mean the oil pump stopped pumping. Working on the distrib is definately related as the bottom of the dist shaft turns the oil pump. Somehow the distrib was not seated completey and the pump did not properly engage or the dist shaft has an issue or there is a problem with the drive gear on the cam (unlikely the cam had an issue). Also, if you went to 0 pressure and fried the mains, all the bearings are shot, rods, mains, wristpins etc.. etc..Look for a long block, probably cheaper than another rebuild.

 

[whywhyzed]

Re: Spun Bearings

I agree with searay3's last statement. 800 hours in salt. What's left to fix.<br /><br />However I disagree with the failure analysis. If oil pressure dropped off at idle as was stated... the pump didn't fail.<br />The bearing failure had begun. Oil pressure is caused by the restriction of flow by the bearing clearances. Too much clearance, no pressure.<br />That .pdf from Clevite on bearing failure analysis that someone posted in another thread is a good resource.<br />9 times out of 10, you can find pictures that look just like your failed bearings and will help you trace the road back to the root cause.

 

[Bondo]

Re: Spun Bearings

Anyway took out for a test run and it started losing power.

Please Explain,......<br /><br />For some reason I see a Fuel Issue that caused Detonation,+ Smoked the Motor,.......<br />Bad Fuel,... Water,.?? Clogged filter,.??<br /><br />Was Anything done to the Carb..??....<br />How much Silicone was used installing the New Oil Pan,..???...<br /><br />The Broken Parts could lead you to believe Detonation I Think,.............<br />I Think the Bearings were Already on their way Out by the time you did the Head work.......It just took Longer to manifest,......<br />Especially after you restored the Compression,+ Finished Hammering them Out..........<br /><br />I Don't Think the wrong Rotor Button had Anything to do with Any of it,.... Totally Unrelated......

 

[DHPMARINE]

Re: Spun Bearings

Well,a V6 rotor has 6 tabs that run thru the ignition sensor,while the V8 has 8 tabs.So you were firing the sensor 2 less times per revolution,giving ignition to who knows what cylinder (it can be done,but I had a long day),or at what time (or part of the piston stroke).<br /><br />May have been firing a cylinder before top dead center and at top dead center,and directly reversed on another cylinder.<br /><br />You can't push a piston in two directions at once (well actually you were)<br /><br />DHP

 

[Don Crandol]

Re: Spun Bearings

Thanks for the replies guys. New motor going in next week, was just curious if a $6 part could be the cause of all these problems. I can garantee I'll be making sure all my parts are right from now on.<br /><br />Don

 

[Bondo]

Re: Spun Bearings

I Hope you Diagnose what Caused the Issue in the 1st place,............<br /><br />'Cause your New motor Could end up Just Like the Old Motor,........<br /><br />I Don't Think the Rotor Did It...............

 

[searay3]

Re: Spun Bearings

DHP....good call, don't know how I missed it. Don, you mentioned that it didn't run right, but it must've been running terribly....if at all... can you post some pix of those bearings?