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Discussion Starter #1
Rod and main bearings. Worth the extra money? Really any better coated?

Engine BBC, Eagle crank/H beam rods with L19 bolts, forged Wiseco pistons, 12.5 to 1 turning 7400 with an occassional 8000 rpm. Drag race only in a hydro.

Thanks
Tim
 
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Discussion Starter #3
Well so far as my first experience with them has saved my crank. They are beat up but the crank looks good. I'm taking it to a different machine shop and hopefully I can find out why. I'm thinking the last one messed the crank up. Don't know how things can measure right and the wear on the bearings show they are all wrong. Going to measure tomorrow and see what I get.

Tim
 

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steelcomp was here
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In your case yes, well worth the money.
X2
Tim, there can be all sorts of different things going on that aren't necessarily clearance related. Also, clearance differences as small just a few tenths cn be significant...if you can't accurately mesure to .000X, try to find someone in your area that can. Check things like crank runout and main bore alignment. Turning that kind of r's requires some good attention to detail.
Maybe post a pic of your bearings if you can. That's always fun. :D
 
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I'm going to check the clearances and compare them to the machinsts. When I took this engine apart in spring the bearings all were good but #3 rod. The crank was turned and now everything is wrong. I beleive it's in the crank. The crack has been turned .010. How far would you guys go on turning it if it needs that to fix it? Or would it be better to replace the crack and start over?

Tim
 

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WON'T LEAVE HOME WITHOUT THEM! This pic was taken by WANNABE at out last race. Notice there is no oil pressure and the tach is at 6000. Our races are shore start with a dead engine. Fire and go. Do they help? Have no idea! But we haven't failed a bearing in 4 years. As Steel stated, .000X means alot! And it doesn't have to be in the crank or bores. It can be in misaligned main bores. And the tighter you try to run your clearences, the closer the alignment has to be. Sometimes I am amazed at have perfect the mains come out of one motor, and the wear on another. We have one block that must be absolutely dead nuts on, because it has never even left a mark on a bearing.



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steelcomp was here
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I'm going to check the clearances and compare them to the machinsts. When I took this engine apart in spring the bearings all were good but #3 rod. The crank was turned and now everything is wrong. I beleive it's in the crank. The crack has been turned .010. How far would you guys go on turning it if it needs that to fix it? Or would it be better to replace the crack and start over?

Tim
I always look at the fillet raduis on the crank...a .020/.020 crank can be stronger than a new crank if the fillet radius is better.
JMO
 

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I always look at the fillet raduis on the crank...a .020/.020 crank can be stronger than a new crank if the fillet radius is better.
JMO
On a GM crank how far do you feel you can go under without worrying about the Nitrate depth??

Can you also elaborate on why the .020/.020 crank would be stronger??
 

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On a GM crank how far do you feel you can go under without worrying about the Nitrate depth??

Can you also elaborate on why the .020/.020 crank would be stronger??
I believe he's saying it "could" be stronger, but only if the fillet is increased from standard.

I couldn't imagine an undersized crank would be weaker to any perceivable degree all by itself. The down side I believe is the added thickness of the bearings required. I may be wrong(if so prove me wrong in less than 42 pages please).

Question, at what point does the bearing thickness become an issue? A thicker bearing reduce heat transfer, Correct? or something like that? And hows does the coated bearing effect same.
 

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steelcomp was here
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On a GM crank how far do you feel you can go under without worrying about the Nitrate depth??

Can you also elaborate on why the .020/.020 crank would be stronger??
.020 pretty much wipes out any factory treatmenet, but tha'ts easily fixed.

I always look at the fillet raduis on the crank...a .020/.020 crank can be stronger than a new crank if the fillet radius is better.
JMO
 

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steelcomp was here
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I assume this is because if the radius is smaller that area is more prone to breaking where as if it has a larger radius it strengthens that transition?
eggzackley. Smaller or poorly machined. I reject more new cranks because of poor fillet radii than for any other reason. If a customer has to grind his crank anyway, and the fillet sucks, I may advise him to go .020 instead of .010 (from standard) so we can clean up the radius. He'll have a stronger crank, and IMO the amount you're removing from the journal is negligible. The crank's weakness isn't in the dia. of the journal, it's in the stress risers that can form in the fillet. Reduce that potential, and the crank is in essence stronger (in that it will have more resistance to breaking) than if you don't.
 

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steelcomp was here
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I believe he's saying it "could" be stronger, but only if the fillet is increased from standard.

I couldn't imagine an undersized crank would be weaker to any perceivable degree all by itself. The down side I believe is the added thickness of the bearings required. I may be wrong(if so prove me wrong in less than 42 pages please).

Question, at what point does the bearing thickness become an issue? A thicker bearing reduce heat transfer, Correct? or something like that? And hows does the coated bearing effect same.
I haven't seen or heard any evidence that at .020 heat transfer is a problem. Theoretically, heat may be reduced some because of reduced surface speed.
Is it measurable? Who knows.
 

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IMO, from what I've seen, is IF the bearings were sent out to a reputable
coater, like Calico, or Swain, etc. for a real coating, it is Definately worth
doing! have seen motors , that when taken apart after years of hard
running, had virtually no wear on the bearings! and were put right back
together! on the otherhand, have seen some of the "FACTORY" coated
bearings, and you could literally wipe the silkscreened coating right off
with a rag and some thinner! X2 on the fillet radius! would rather see
.020 under with a generous fillet than standard with practically a 90*
cut! (have seen factory bbc standard cast cranks that actually have
what looks like a "chattered trough" where the radious should be!)






i
 

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Question, at what point does the bearing thickness become an issue? A thicker bearing reduce heat transfer, Correct? or something like that? And hows does the coated bearing effect same.
Vast majority of the heat is carried away by the oil. If there was that much heat transfer by the bearing they would have put a water jacket in the journal bulkhead. There is a ton of heat carried away by the exhaust seat, and that it is why it is surrounded by a water jacket.



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WON'T LEAVE HOME WITHOUT THEM! This pic was taken by WANNABE at out last race. Notice there is no oil pressure and the tach is at 6000. Our races are shore start with a dead engine. Fire and go. Do they help? Have no idea! But we haven't failed a bearing in 4 years. As Steel stated, .000X means alot! And it doesn't have to be in the crank or bores. It can be in misaligned main bores. And the tighter you try to run your clearences, the closer the alignment has to be. Sometimes I am amazed at have perfect the mains come out of one motor, and the wear on another. We have one block that must be absolutely dead nuts on, because it has never even left a mark on a bearing.
GN, I just figured the OP gauge was broke!! We have trouble with OP during shut down after a run so we added an accusump. So far, it seems to work as advertised One cool feature is being able to have OP just prior to start up. We use a manual valve to open the accusump and have about 15 seconds of 50-80 PSI oil pressure. I know you said bearings are fine, but it would freak me out seeing that. An accusump might be an option to pre-oil the engine just before you start the engine.

I believe he's saying it "could" be stronger, but only if the fillet is increased from standard.

I couldn't imagine an undersized crank would be weaker to any perceivable degree all by itself. The down side I believe is the added thickness of the bearings required. I may be wrong(if so prove me wrong in less than 42 pages please).

Question, at what point does the bearing thickness become an issue? A thicker bearing reduce heat transfer, Correct? or something like that? And hows does the coated bearing effect same.
Bearings are the sacrificial part of the journal. Babbit has a relatively low melting point so you don't want much heat transfer through the bearing. Like GN stated, the oil is what carries the heat away.
 

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GN, I just figured the OP gauge was broke!! We have trouble with OP during shut down after a run so we added an accusump. So far, it seems to work as advertised One cool feature is being able to have OP just prior to start up. We use a manual valve to open the accusump and have about 15 seconds of 50-80 PSI oil pressure. I know you said bearings are fine, but it would freak me out seeing that. An accusump might be an option to pre-oil the engine just before you start the engine.
.
Yeah I agree. We ahve had an accumulator in it of and on. And we are going to put it back in. It was on a switch that he would flip when the flag went up. Less 20 seconds to start. Plus the extra safety if the pickup should become uncovered.



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GN, I just figured the OP gauge was broke!! We have trouble with OP during shut down after a run so we added an accusump. So far, it seems to work as advertised One cool feature is being able to have OP just prior to start up. We use a manual valve to open the accusump and have about 15 seconds of 50-80 PSI oil pressure. I know you said bearings are fine, but it would freak me out seeing that. An accusump might be an option to pre-oil the engine just before you start the engine.



Bearings are the sacrificial part of the journal. Babbit has a relatively low melting point so you don't want much heat transfer through the bearing. Like GN stated, the oil is what carries the heat away.
Hey David,

Any idea's on how long the sump will support a starved motor??

I was going to run a dry sump on the new stuff to help with starvation. Cost & room is tough building a new boat. May have to do a accusump.
 
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