FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Jim Comet on October 29, 2017, 08:59:54 PM
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I took the bottom end of my 390 apart tonight and noticed odd "chatter" marks on the main bearings. The rod bearings all looked great. This is a 390 with main studs and had the mains aligned honed on the last build. This block does not have the extra webbing in the mains. I am adding a set of Blair's pro ports and a roller cam and this wear pattern has me wondering if I may need to go with a different block with the extra webbing? Any thoughts or comments are appreciated. Thanks, Jim
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Hey Jim, if I am seeing that right, the center main isn't marked that way.......if that is true, check the crank for straightness. Also, sometimes journals are not round. Lastly, check the balance. My thought is that one of those three things could be wrong. Just things that come to mind.....
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Broach bounce in the manufacturing process.
Worn bearing in the machinery leaves artifacts in the parts so small you cannot measure them with normal handheld shop equipment. But they show up as polished striations in the used parts, Somebody at the plant should be on top of that...
FWIW I am not a fan of that big ol' hole in the middle of the load bearing area on those bearings.
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That's interesting. I have seen those same kinds of marks in crankshafts when super-polishing the journals. I could see how worn bearings in a crank grinder might do the same thing to a crank journal. Worn spindle bearings in a milling machine do that also. I'd say that is a good call, and interesting. The stuff that makes stuff has to be in good shape......
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More info and opinions wanted. All the rod bearings looked very good. This engine always ran 5W20 Mobil 1 after initial break in. It used a high volume, high pressure pump. The main saddle oil feeds have been enlarged to 5/16. The oil pressure was always good. So with does everyone think about using this block for a 500hp build? I have another block with the extra web supports that is standard bore I could have machined. I just hate to put this block to pasture as it has align honed mains (maybe faulty), zero decked parallel to the mains, torque plate honed for my pistons and the trans mounting face was trued to the crank as well. Thanks, Jim
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I'm not too keen on the main feeds being drilled out, that's a no-no in my book, but otherwise, I don't see any reason why you couldn't reuse the block, especially since it's got a lot of the good machine work completed.
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More info and opinions wanted. All the rod bearings looked very good. This engine always ran 5W20 Mobil 1 after initial break in. It used a high volume, high pressure pump. The main saddle oil feeds have been enlarged to 5/16. The oil pressure was always good. So with does everyone think about using this block for a 500hp build? I have another block with the extra web supports that is standard bore I could have machined. I just hate to put this block to pasture as it has align honed mains (maybe faulty), zero decked parallel to the mains, torque plate honed for my pistons and the trans mounting face was trued to the crank as well. Thanks, Jim
It sounds like your real question here, beyond all the rest is simply: will this or another block support 500hp? Sure as many here have proven over the years.
Btw, I agree with the diagnosis on those odd main bearing chatter marks (bad tooling). Bet merely slapping in new bearings is the fix.
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I think that block would be fine to 500 hp. I think that cam and your new heads are going to send you closer to 600 than 500. I did a 390 with like that with the last version of the Street Pro Ports that made 580 with a worked Street Dom on it. Your heads are 15 to 20 cfm better than those at most lift points that matter. The three webs would help, but the 3.78 stroke will not be as hard on the mains as a long stroker would. I have seen those marks in the bearings like that on cross-bolted 427s, so I don't think that situation is caused by the block giving up. If the parting lines are not showing metal transfer from cap walk, your clamping was sufficient. The extra web is better for the long term, no doubt.
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I am taking a risk posting after Blair and Barry but doesn't the application also play into this? For example, 4-speed car racing on slicks will test the integrity of this block more than an automatic on the street. I have had 428 blocks cracked through that main bearing oil feed passage which was thought to be caused by hard launches.
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I am hoping that me being a foot brake bracket racer will allow this setup to live until I can step up to a better short block. Jim
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Any thought on these main caps. Does it look like there was some metal transfer on the face around the stud hole?
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Yep
Caps are fretting - moving around.
More clamp load or dowels might help some
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That is a lot of fretting. Just how much power did the engine have?
Between the main bearings and the cap fretting, I wonder if you've encounter severe detonation. How do the rings, piston tops and ring lands look?
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I'm guessing 400-450hp as my 3800lb car (w/me in it) ran 110-112 through the traps. I used ARP main studs. The rod bearings looked great and I cannot see any piston/ring issues. Is there anything that will help a regular 390 no cross bolted block live? Should I start over with a block with the extra webbing? Does that help stop the cap movement? Jim
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I'd be curious how much register the caps have. Do they move around if the bolts are loose? Do you have to tap them into place? Can you pull them out of their register easily by hand? Detonation is a likely cause of what you have, but loose register can also do that.
A three web block with loose register could still suffer from movement at the parting line. Crossbolts would also be something to consider if the rest of the block is cherry. We sometimes machine a key slot and put 3/16 key stock in the registers and machine for .002 to .003 press if they come in "loose".
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With only 400-450 horsepower, I too would look for another cause other than power. Detonation would possibly show up on rod bearings and piston crowns. Cap fitment would be a good spot to look.
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My thoughts as well Brent. Perhaps the main studs weren't torqued correctly. Check your wrench or borrow another to test both on say engine stand bolts or another bolt by comparison. At that level of hp, something else is amiss, which is why I asked about piston, ring, ring land condition.
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are the ends of the bearings curling in at the end , were the main caps mating surface machined after the align hone ? bearings not having any crush with the caps tightened down .
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The rod bearings look good to me. Here is a pic of a rod bearing and piston top. I don't think it was detonation. Also, I pulled the studs and installed a main cap. I had to tap it into place with my fist and wiggle it out as it seemed to fit fairly snug. Jim
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Did the rod bearings fall out of the rods or do they still fit snugly?
Does that area that looks pitted at the center of the piston feel rough?
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Bearings were snug. They stayed in the cap and rods as I removed them from the block. No pitting on the piston, it is actually carbon, I just went out and scotch brighted it with a little brake clean and there is no pitting. cleaned up smooth. I am going to have a machinist look at and fix up the register area. But as of right now they only thing that may be suspect is my torque wrench. Now that I think of it the only main bearing without the odd wear pattern is the center thrust. I will look tonight and see if that one has metal transfer also. Jim
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Side view of pistons and rings with close up please.
Is the second ring free to spin in the groove or does it feel snug?
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I can get photos tonight. The second rings are Total seal 2 piece gapless. They do move and rotate freely. Jim
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But as of right now they only thing that may be suspect is my torque wrench. Now that I think of it the only main bearing without the odd wear pattern is the center thrust. I will look tonight and see if that one has metal transfer also. Jim
What did you torque them too?
I think ARP recommends 110 on FE mains
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I wish I could remember 20 years ago. I am sure I would have torqued them to what the instructions that came in the box with them said. At this point I think I need to have the registers checked and also my torque wrench calibration. I live in the Twin Cities, are there any places a guy can take his torque wrench to to get it checked. It is a early 90's era Craftsman clicker. My dad taught me to always release the tension on it when not in use to help maintain accuracy. Jim
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Jim: look here.....
https://www.thomasnet.com/minnesota/calibration-services-10021202-1.html
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Here's how I do it:
http://fepower.net/simplemachinesforum/index.php?topic=352.msg2846#msg2846
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I just tore down an engine with similar but lesser witness marks, and found that the flywheel bolts had been hitting the rear main seal area and actually gouged a groove in a circle on a different Ford engine family. The main thrust bearing was worn on the sides, but the rod bearings looked good. Just an extra item to check on assembly that the flywheel bolts didn't hit the block. Joe-JDC
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I would recommend a line hone on the main.
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But as of right now they only thing that may be suspect is my torque wrench. Now that I think of it the only main bearing without the odd wear pattern is the center thrust. I will look tonight and see if that one has metal transfer also. Jim
What did you torque them too?
I think ARP recommends 110 on FE mains
Those recomendations was not with my studs. But i milled down the 5th cap and spotfaced all caps when i changed from bolts
to stud and nut. The bolt have the Bufo ring under the head and after the engine have been apart a few times the ring have often
dug in to the caps and the flanged nut dont get the correct support. So after a while when things have moved around the torque loosens upp. The first set of studs was bottoming out i the holes so i put a steel ball in there to pre load the treads even The other set bottomed out in top of the threads so there was not room for a ball big enough to meet the stud