Caddy 500 thrust bearing problem

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augur
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Caddy 500 thrust bearing problem

Postby augur » Sun Apr 24, 2016 8:18 am

Ever noticed how a drill bit cuts metal better at slow speed vs high speed? This is my theory of why I wasted my new thrust bearing within a few hours of light running. My prop pitch was limiting my engine rpms to 2200. Too much thrust at low engine rpms? I'm new to airboats and not sure exactly where to set my pitch vs engine rpms. I have read that this engine should be limited to around 2800 rpms. Should I set the pitch so the engines power can't overcome 2800 rpms, or pitch it less and use the throttle stop? Any Ideas would be greatly appreciated.

Striker543
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Re: Caddy 500 thrust bearing problem

Postby Striker543 » Sun Apr 24, 2016 8:50 am

Don't think the prop speed was the cause. Many caddys spend years at an average cruising speed of +/- 2000rpms. Was this a newly rebuilt engine or a junkyard engine? What oil were you running in it?

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BluByU2
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Re: Caddy 500 thrust bearing problem

Postby BluByU2 » Sun Apr 24, 2016 8:53 am

The thrust bearing surface is smaller than the area on big block Chevys, and according to Buddy Branch, the one thing which will eat up the bearing on a Caddy is running narrow blades instead of the wider ones. The type lubricant used is another factor. Rotella 15-40 with a quart of Lucas, and 4 oz. of Comp Cams additive is a proven combination for longevity in a petroleum product, and Amzoil Zrod with Lucas is a good choice for a synthetic.

augur
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Re: Caddy 500 thrust bearing problem

Postby augur » Sun Apr 24, 2016 9:50 am

It was a complete rebuild. The break in oil was rotella 15-40 with a bottle of additive the machine shop recommended. I have changed the oil since with STP 10-40 twice in fairly quick succession before I noticed the end play. I just did another change with the same but haven't run it yet. guess I'll drain it back out and put in a better mix. The blades {two) don't have the dimensions printed on them but at the widest point they are about 13 inches and eight inches at the tips.

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Deano
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Re: Caddy 500 thrust bearing problem

Postby Deano » Sun Apr 24, 2016 9:55 am

augur wrote:Ever noticed how a drill bit cuts metal better at slow speed vs high speed? This is my theory of why I wasted my new thrust bearing within a few hours of light running. . .
That is not the root cause of your issue. The big Caddy produces big torque which can and will accelerate the evidence of things gone bad when they are not right. As Al pointed out, our thrust surface is not as proportionately big as is found in other big blocks and these do NOT produce LESS torque. Hence, the problem is magnified.

To use your analogy . . . did you ever notice that the a drill bit with a flat end will never drill a hole at any speed? It's pretty much the same thing.

How much crank end play did you have upon assembly? I would be willing to guess, far to much. If a man is not aware of what is going to happen, this is something that is easy to overlook when and if the journals look good.

The problem can be twofold: First, with the proper amount of bearing clearance, there is a film of oil maintained between the surfaces that prevents them from making contact and at the same time is small enough to allow the oil to be replenished as it runs out. A perfect balance, when clearances are ideal. With to much clearance (end play in this case), the oil runs out quicker than it is replaced and the bearing runs dry. :shock: Secondly, when the #3 main bearing was replaced it had nice smooth running and thrust surfaces but the thrust surface on the crank likely did not. Because of the thrust produced, the excessive clearance, lack of oil, and the rough thrust surface on the crank, the new thrust bearing face had no choice but to get chewed. :wink:

OEM spec calls for between .002 and .012, with worn service limit being at .015. Depending on which Caddy vendor you talk to, they will generally shoot for around .003 and .008 on a fresh build. Once the wear gets to about .022 or .025 it will move VERY QUICKLY to around .34 -.36 and much beyond that that crank is approaching hitting the webbing in the block and he will be done quicker than right now.

If you search, you will find a thread by another brother that documented a very similar occurrence that he had.
You can also search for "Caddy crank end play" and probably find more info. You certainly are not the first.

I doubt yours was this bad, but here is a pictured of one that was "chewed and screwed":
Image

If you have a good crank shop, that thrust surface can be welded and re-ground.
Although some folks prefer not to go that route, it is in fact done all the time in other
applications where the time and expense simply preclude installing a new crank.
You just need to make sure that you have the right guy doing it.
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan

augur
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Re: Caddy 500 thrust bearing problem

Postby augur » Sun Apr 24, 2016 11:44 am

The crank was machined before I re-assembled the engine and I didn't know enough to specifically check that surface, but Kevin at deland auto parts went so far as to add an oil jet to squirt oil right through the face of the thrust bearing. I can only assume that if the crank was shot he would have advised me to get a new one. I do have a slight amount of crank damage now. Not as bad as the pic shown but enough. I bought a couple sets of bearings and hope they will get me by for a while. Is this a catastrophic error in judgement?

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Re: Caddy 500 thrust bearing problem

Postby augur » Sun Apr 24, 2016 12:27 pm

freehand measurement with a harbor freight caliper looks like I have about .030 end play with the new thrust bearing installed.

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Re: Caddy 500 thrust bearing problem

Postby terrible ted » Sun Apr 24, 2016 4:24 pm

the best thing is to get a gear box like a 1 to 1.5 and a longer prop. after you fix your motor.

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Re: Caddy 500 thrust bearing problem

Postby rjfjr » Mon Apr 25, 2016 8:33 am

That seems excessive do they make over size thrust bearings

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Re: Caddy 500 thrust bearing problem

Postby Bdriller » Mon Apr 25, 2016 9:26 am

augur wrote:freehand measurement with a harbor freight caliper looks like I have about .030 end play with the new thrust bearing installed.

if you have .030 with the new bearing in place I would bet that you had a very similar reading upon rebuild completion, new bearings wont wipe a crank flange out that quick, you can drop the crank without disassembling any more than timing cover and oil pan, fix crank and reassemble.

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Re: Caddy 500 thrust bearing problem

Postby One Eyed Gator » Mon Apr 25, 2016 4:10 pm

I had a rebuild do the exact same thing. Crank was checked prior to rebuild and after being polished. Endplay was at .007. Ran it with light pitch for about 2 hours. had to much pitch in prop should have gone right back to the ramp but I wanted to ride. End of ride it was .012 endplay repitched prop went back out when I was done it was at .024.

Got another crank started over again end play was .005 spent 8 hrs running it with just enough pitch to keep it cool on the trailer. then pitched it to what I wanted and never had another problem. it settled at around .008 after over 50 hrs and was still there when I sold it. Love those caddy's but went LS and a gearbox and won't be back.

It was an expensive lesson. Like Bdriller said nothing will make it better, save yourself tearing up the motor and just start over, now.

Just my experience.

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Re: Caddy 500 thrust bearing problem

Postby Bdriller » Tue Apr 26, 2016 12:17 am

A good specked out caddy crank will last 10-15 years in a normal environment, now if you have a cad crank with 10-20 years of abuse and rebuild motor with out of spec crank, you will probably wind up with results similar to what you just experienced.

augur
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Re: Caddy 500 thrust bearing problem

Postby augur » Tue Apr 26, 2016 5:36 am

I've thought about starting over with a new crank, but my fear is the same thing will happen again. Dang, I sure wish I would have checked that end play after the rebuild. Thanks for sharing your experience. Anyone interested in trading a bass boat for a really expensive automotive self pace class :)

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Re: Caddy 500 thrust bearing problem

Postby Bdriller » Tue Apr 26, 2016 8:03 am

augur wrote:I've thought about starting over with a new crank, but my fear is the same thing will happen again. Dang, I sure wish I would have checked that end play after the rebuild. Thanks for sharing your experience. Anyone interested in trading a bass boat for a really expensive automotive self pace class :)

Got a buddy that would buy the right boat pm me what u got.

augur
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Re: Caddy 500 thrust bearing problem

Postby augur » Wed Nov 09, 2016 5:12 am

Update- I pulled the crank and sent it to Steve's custom Crankshafts. He welded and polished it back up. The motor is re-assembled and running. The end play almost imperceptible with new mains and thrust bearings. I read some post on here that couldn't overstate how important the right lube is, so I filled it with 4qts Rotella 15-40, 1qt Lucas additive, and 4 oz comp cams 159 (that's a slimy mix!!) Ran it on trailer a few times enough to warm it up and check for fluid leaks, so far so good. So now what? I not quite sure how to proceed. I need to figure out where to set my timing, and pitch my prop, and most of all (not fry my thrust bearing and crank again).

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Re: Caddy 500 thrust bearing problem

Postby Waterthunder » Wed Nov 09, 2016 2:19 pm

If you have to go thru this again give us a call I know a trick to do on the thrust bearings. THIS IS A COMMON PROBLEM ON DIRECT DRIVES!
THE PROOF IS IN THE PROP!

"If you copy someone you will only achieve what has already been done."

http://waterthunder.com/
321-508-5316

augur
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Re: Caddy 500 thrust bearing problem

Postby augur » Wed Nov 09, 2016 3:22 pm

Oh yea, I forgot to mention there is an extra oil jet drilled into the block that goes thru a small hole drilled into the thrust bearing face.

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Re: Caddy 500 thrust bearing problem

Postby jeepinocala1111 » Thu Nov 10, 2016 7:07 am

Get a gear box you will be very happy. Car engines are not designed to have their crank pushed or pulled. I have never seen an application where a car motor has it's crank pushed or pulled only AC engines are designed for that. :dontknow: It will save you a lot of money and headaches down the road.


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