Thrill of victory and the Agony of Defeat Cam bearings destroyed. (NOT the lobes) - Page 2 - Vintage Mustang Forums
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post #16 of 87 (permalink) Old 07-16-2019, 07:05 AM
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Nothing sort of blowing a motor is worse than taking apart a new motor. Been there, done that - It SUCKS! Sorry you have to go through all this. The block I had problems with I finally found a bent rod but I decided to sell the block and get a different one as it had bad juju...
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post #17 of 87 (permalink) Old 07-16-2019, 08:44 AM
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A different direction than the others....

Cam lift, valve springs and locks etc. Is there a possibility that you are running a valve train combo that doesn't have enough clearance and when the valves open they are binding and putting more downward force on the cam. I have seen similar issues with guys putting big cams in engines that don't have the valvetrain to handle it and then if the lifters were adjusted too tight it can exacerbate the problem.
It could also be rockers binding at full lift as well.
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post #18 of 87 (permalink) Old 07-16-2019, 08:58 AM
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It looks like the majority of the damage on the bearings is on the bottom of the bearings? If so I would think its a valve train binding issue.

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post #19 of 87 (permalink) Old 07-16-2019, 10:42 AM Thread Starter
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Cam bearings look out of round with a flat zone on the bottoms. Since your engine rotated easily it is probably minute but then the cam bearing tolerance is minute. They still need that molecule of oil protection all the way around though. So just asking but are you sure you put the right cam bearing in the right hole because they are 5 different dimensions or did you possibly put them in backwards?
I will double check once the bearings come out, but I can say I am positive the cam bearings went in properly form back to front. I appreciate the reply and suggestion. I actually think it would be hard to put them in wrong as if you put one in the wrong place, as you would end up with at least one that is too loose to press. I believe each bearing is .015 smaller front to back.

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post #20 of 87 (permalink) Old 07-16-2019, 11:08 AM
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Sorry.....I just couldn't resist.....



"....The agony of defeat...."......lol...


)

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post #21 of 87 (permalink) Old 07-16-2019, 11:24 AM Thread Starter
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Originally Posted by elcam84 View Post
A different direction than the others....

Cam lift, valve springs and locks etc. Is there a possibility that you are running a valve train combo that doesn't have enough clearance and when the valves open they are binding and putting more downward force on the cam. I have seen similar issues with guys putting big cams in engines that don't have the valvetrain to handle it and then if the lifters were adjusted too tight it can exacerbate the problem.
It could also be rockers binding at full lift as well.

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Originally Posted by Redneckgearhead View Post
It looks like the majority of the damage on the bearings is on the bottom of the bearings? If so I would think its a valve train binding issue.
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Originally Posted by Tallguy View Post
I will double check once the bearings come out, but I can say I am positive the cam bearings went in properly form back to front. I appreciate the reply and suggestion. I actually think it would be hard to put them in wrong as if you put one in the wrong place, as you would end up with at least one that is too loose to press. I believe each bearing is .015 smaller front to back.
Thanks to both of you for this suggestion of binding valve train. This would make sense for how the bearings failed, as all look to have failed exactly at the highest pressure point and "swept" molten babbit clockwise. That said, my heads are Edelbrock 5023 with a Comp Cams 256H cam. Lift is "only" .477 I/.484 E. When I measured for pushrod length I used a lifter I converted to be solid (stacked washers in to replace the spring). I ended up with about .125 longer than stock at 6.95". The cam lift I have is well within the cylinder head specs where they allow up to .55" lift.

I do see that Durabond offers 3 types of bearings and I have the lowest model (OE replacement). Still with my set-up, yes not stock, but still a mild street build.

Maybe this is my second mistake: 1) not measuring cam bearing bore and cam journals for clearance, 2) not specifically checking the valve train for binding. It was not on my risk radar as I was well within the specs of the heads.

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post #22 of 87 (permalink) Old 07-16-2019, 11:47 AM
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If it is indeed a binding issue, you will also need to check every pushrod to ensure they have not bent (if you plan on reusing them)

Rolling them on a piece of glass is a quick way to check for any wobbles.
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post #23 of 87 (permalink) Old 07-16-2019, 11:51 AM
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Man, this scares me. I just dropped a fresh 289 that I built in the car. I only got about 5 mins into the break-in run when I had to shut it down to an intake leak. I hope to crank it again tonight but now I will have anxiety the rest of the day.....

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post #24 of 87 (permalink) Old 07-16-2019, 12:12 PM
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Kudos to your approach to the problem, definatly see the engineer shining through. Looks like there might be enough good bearing surface left to at least try measuring clearance, probably not. I'm sure you have a mic and if you don't have an inside mic a snap gauge would suffice. I would speculate that maybe the block didn't get the cam journals line bored and they are out of round which allowed for oil leakage at the bearings. Rod bearing starvation would have been next if it managed to rack up some miles. I wouldn't be afraid of putting another set of bearings in and trying again after line boring if needed and making sure the clearances are good. Would be nice to conquer the beast, I think you have done an excellent job on your build in spite of the problem!
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post #25 of 87 (permalink) Old 07-16-2019, 12:43 PM
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Tallguy,
Was the timing chain very tight? I had one that was and took out four sets of cam bearings ( two engine builders before me) and I installed the fifth set but the timing chain was SO tight that it would not fit onto the cam stub with"screwing" it on with the cam bolt. I ended up going with a used chain that had "some" play and 7 years later the engine is still running flawlessly.
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post #26 of 87 (permalink) Old 07-16-2019, 02:06 PM
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All oil galley plugs (3 front 3 rear) are installed and still in place after tear down, including the single 3/4" plug on the top rear. Yes, I did check distributor shaft to driveshaft compatibility and engagement. When I primed I got 60 PSI cold and then the same 60 PSI cold and 25 PSI or so hot at 1250 RPM. I know I had oil pressure the entire break-in, but did not monitor the 2nd day other than at start-up.
25 PSI hot at 1250 RPM? That sounds low for a fresh windsor motor- what oil were you using?

I know the whole "10 psi per 1000 RPM blah blah", but my experience tells me that a fresh, or even fairly used windsor block should be higher than that. FE's are another story, I won't go into that .


Very sorry to hear about your misfortunes. Just keep in mind, machine shops aren't perfect- odds are you put more attention to detail in your motor than they would. Do you have a part # for the bearings you used?

FWIW, I've tried using a solid lifter for measuring pushrod length only to find out that it made the pushrod sit slightly higher than hydraulic lifter. I usually use a checker spring on the heads and pump up the lifter with oil.

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Last edited by happystang; 07-16-2019 at 02:09 PM.
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post #27 of 87 (permalink) Old 07-16-2019, 02:10 PM Thread Starter
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Tallguy,
Was the timing chain very tight? I had one that was and took out four sets of cam bearings ( two engine builders before me) and I installed the fifth set but the timing chain was SO tight that it would not fit onto the cam stub with"screwing" it on with the cam bolt. I ended up going with a used chain that had "some" play and 7 years later the engine is still running flawlessly.
Randy
So tight is of course relative. I was able to install the timing without tools other than some tapping with a dead blow hammer. When I removed it it would not just pull right off. I had to apply some force with a small pry bar to work the sprockets off a little at a time. Not much force, just moved it 1/8-1/4" top, then bottom, etc. I feel the timing chain was not overly tensioned but thanks for the idea as it is a good one.

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post #28 of 87 (permalink) Old 07-16-2019, 02:35 PM
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Side to side "play" must be there or the chain is too tight. "slight deflection" is not enough. The gear being tight on the cam is no big deal. I like to see a full chain width of play. Cam timing change is less than 1/2 of a degree with that play. If your valve train was going solid , the cam would fail. Valve spring pressure will not cause what you are seeing.
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post #29 of 87 (permalink) Old 07-16-2019, 02:37 PM Thread Starter
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Originally Posted by happystang View Post
25 PSI hot at 1250 RPM? That sounds low for a fresh windsor motor- what oil were you using?

I know the whole "10 psi per 1000 RPM blah blah", but my experience tells me that a fresh, or even fairly used windsor block should be higher than that. FE's are another story, I won't go into that .


Very sorry to hear about your misfortunes. Just keep in mind, machine shops aren't perfect- odds are you put more attention to detail in your motor than they would. Do you have a part # for the bearings you used?

FWIW, I've tried using a solid lifter for measuring pushrod length only to find out that it made the pushrod sit slightly higher than hydraulic lifter. I usually use a checker spring on the heads and pump up the lifter with oil.
Thanks for the reply. Oil pressure cold was almost 60 PSI, and then 25ish hot. Standard oil pump.

As for the pushrod length, I did use a solid lifter and I also did use checking springs. I did not account for any valve lash which should make my pushrod shorter than needed if anything (as it will sit down lower on the hydraulic lifter). My lash was 5/8 turn past no up/down movement of the pushrod and with 3/8-24 thread that is .026" of lash.

I don't know why but I never did the simple math on the difference of .488 (cam) and .550 (head max). When I saw this my brain was thinking 1/2" difference which is ridiculous. It is only .062" so my .075" longer pushrods than stock put me really close to this limit

.488 lift (plus) .075 longer than stock pushrod (minus) .026 valve lash = .537 lift, way closer than I ever thought it would be. I would be surprised if I had a bind but still needs to be checked as my reference to stock pushrod length is not really valid with aftermarket parts.

(Note, I may have stated earlier that the pushrods were 1/8" longer than stock but it was actually .075" longer)

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post #30 of 87 (permalink) Old 07-16-2019, 02:52 PM
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The longer pushrod doesn't give you more actual lift, it just ensures that the operating angles of the rocker are correct. You still set the lash, to get more lift you would have to be holding the valve off the seat.

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