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Spun rod bearing on a 2K mile engine

After 2000 miles on a rebuilt engine and only one race weekend, I spun a rod bearing last weekend, while trying to get my SCCA license. Not sure which one, probably #2.
Right now, I may have a line on a local used engine. If it works out I'll probably replace rod bearings and rings and swap it out. Then re-rebuild the original engine. I hope I can make it to next weekend's race.
I would like to know what can I do to the original engine to prevent this. I have 2 theories of what happened. First a little history:
Engine had about 140K when I bought the car and spun the #3 about 3k later. I found out the rod caps were mismatched. I bought a used crank, used 951 rods, crank scraper and new ARP rod bolts. Trying to make the engine reliable, I took everything to the machine shop and had everything measured and balanced. Everything measured fine and they rebored the connecting rod bearing bores. I ended up not very confident on the machine shop as they had the engine for 2months, and did the actual work in 1 week. So theory #1 is the machine shop screwed up the rod bores.
Theory #2: Since my last race (April 1) I installed MSDS headers (jet coated). I am kinda uncomfortable of how close the headers are to the engine. It's probably 1" from the oil pan. Could the oil have overheated? I saved some of the old oil and will try to have it analyzed.

Now, what can do to prevent this? I know there's some crank work that can be done?
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Armando Diaz
85 911 Carrera - Track car
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87 944na - Old Daily Driver, now 944 CUP
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Old 06-11-2007, 04:50 AM
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I can't offer any real help, but I do have some questions and answering them may help others help you.

Did you do anything else to the motor? Lindsey baffle and pickup mod? Did you assemble the lower end yourself and/or double check the bearing clearances upon assembly with at least plastigauge?

Are you doing anything for oil cooling? How was you oil pressure and level right before this happened?

Also, are you certain it's a spun rod bearing? When you drained the oil, did you found evidence of a spun rod bearing (lot's of metal flakes and such in the oil)? The reason I ask is because the 944 rod knocks I've heard before sound different than most other motors I've heard them on. The 944 rod knock to me seemed to come more from the head area that down in the pan. This makes it easy to assume it a rod when it can be a head/cam tower issue. The reason I mention this is because I went through this recently and assumed a had a spun rod bearing when it ended up being a loose cam gear.

Out of curiousity, what crank scraper are you running? Is it the Ishihara-Johnson one?

I do have a standard crank and a set of forged 951 rods for sale if you end up needing them.

Thanks,
Rob
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Old 06-11-2007, 08:18 AM
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I may take you up on the offer. I have a line on a complete engine but I'll still want to rebuild this one to have a spare.

Getting back to the problem:

Yes the scrapper is from Johnson. Other mods where a 951 oil filter housing, an aftermarket oil cooler routed to the front of rad. I plastiguaged the main but didn't think of the rods. Now I can't remember why, either because I didn't see any specs in the manual for the rods or maybe I trusted the machine shop too much.

The oil pressure was fine throughout my run. I was running normal, then I felt the engine go flat. I looked at my guages oil pressure was great, temp was great, I would still gain revs and speed as I pressed the gas. So I took it easy but kepted going. Somebody behind me said they saw a cloud of smoke. As I pulled into the gurage and the engine started to idle the oil pressure started bouncing and I started hearing noise. I shut it off. First thing I did was check level and it was good.
Last night I had my wife start/stop the car while I was underneath, it seemed as if the connecting rod was going to go through the pan. I drained the oil and desha-veu, scrap metal on the plug.

Thanks for listening.
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87 944na - Old Daily Driver, now 944 CUP
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Old 06-11-2007, 08:43 AM
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Hopefully someone can fill in the details here as I am just going off memory, but ISTR that there was an oiling issue with the 944 cranks and that redrilling the oil passages differently would help the oiling to the rod and/or main bearings at high RPM (centrifugal force would be helping oil flow to the bearings rather than holding it back at high RPMs.) If you are actively racing the car it might be worthwhile to see if someone else remembers what I'm talking about, it might be a worthwhile mod for you to have your crank redrilled so this doesn't happen again.

nate
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Old 06-11-2007, 12:10 PM
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I've heard 2001 different theories on why the '44s spin bearings. Definately heard that during hard cornering the #2 rod bearnig is momentarily starved.

But it always seems to boil down to the little green o-ring in the oil cooler. (Oil/water seperator.) From what I've been told its the leading cause in spun 944 bearings. I say it cant hurt to put a baffle in the oil pan anyways.
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Old 06-11-2007, 12:15 PM
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Toolboy... your thinking of cross drilling the crank. I had it done when I rebuilt my motor. Definatly a good thing do. Also another thought is an accusump. Someone was selling one here a little while ago. It maintains oil pressure at all times, even at startup. A little extra insurance against worn bearings. Not legal for all types of racing though. It is in 944 spec, but may not be in CUP.
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Old 06-11-2007, 01:28 PM
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first you should have check the clearince of the rod bearings during assembley, ALWAYS CHECK. Like many have said there is a million different theory's of why it happens so Im not going to talk about it.

To fix, I would keep the crank scraper, add a lindsey Racing oil pan baffel and oil pickup ring, Cross drill #2 and #3 rod bearing journals ONLY ( I can find the artical that talks about it but the oil flow in the crank is funky, by just doing 2 and 3 it will improve flow. Doing all of them wont.) I would aslo add a external oil cooler. AFter all this Alwats check your oil after every run and make sure your using the correct wweigh.

Link to baffel
http://www.lindseyracing.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=LR&Category_Code=PANBAF

One oil cooler link, there are many others
http://www.lindseyracing.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=LR&Category_Code=944ENGINETRANSOILCOOLER
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]87 924S Gaurds red- SOLD after 11 years of ownership
Old 06-11-2007, 01:28 PM
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ALWAYS CHECK CLEARANCE (lesson learned).

thanks for the advise that's the kind of stuff I'm looking for. I did see that baffle but figured with the 87s it already had baffling from the factory. What ring are you talking about.

I did intall a 951 filter housing and have this cooler mounted in front of rad:

http://store.summitracing.com/partdetail.asp?autofilter=1&part=EAR%2D42512ERL&N=700+400041+115&autoview=sku

I'd be very interested in reading any articals you have.
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85 911 Carrera - Track car
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87 944na - Old Daily Driver, now 944 CUP
03 Chevy Avalanche- Support Vehicle
70 Olds 442 W30 Conv- Gone but not forgotten
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Old 06-11-2007, 01:37 PM
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The 87 pan does have a baffel/windage tray But not one that stops the oil from pulling away from the pickup when turning hard, The baffel kit comes with a "collar" that you weld onto the pickup making it suck lower in the pan to try and limit oil starvation. Also if you want to spend some time and fab something up, You might want to try and redesign the oil return tube, For some odd reason Porsche put it RIGHT next to the oil pickup so All the hot/dirty/foamy oil gets sucked right Back in, The collar will help this to a point but if you could make it dump the return oil away from the pickup Im sure it would help more
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Old 06-11-2007, 01:43 PM
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good read on the whole cross drill thing

http://forums.rennlist.com/rennforums/showthread.php?t=343714&highlight=cross+drill+crank

Here too
http://www.nasaforums.com/viewtopic.php?t=4398
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Last edited by fast924S; 06-11-2007 at 01:53 PM..
Old 06-11-2007, 01:51 PM
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That Nasa forum has some of the best info I've seen Thanks.

So as I see it I would:
cross-drill #2,#3
Get an S2 baffle
coat the bearings
add the Lindsey baffle
come up with a way to point the return tube away from the screen.

I'm clear on everything except the last 2:

What kind of welding is need for the Lindsey baffle? I have a mig welder. Will I have to weld aluminum? I have tryed welding aluminum yet.
Also does anyone have any pics of the return tube mod?
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85 911 Carrera - Track car
01 996 Carrera - For Sale http://forums.pelicanparts.com/showthread.php?s=&threadid=327823&highlight=996
87 944na - Old Daily Driver, now 944 CUP
03 Chevy Avalanche- Support Vehicle
70 Olds 442 W30 Conv- Gone but not forgotten
http://www.diazracing.com
adiaz@diazracing.com
Old 06-12-2007, 03:55 AM
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The Lindsey baffle requires welding aluminum. I took the baffle with my oil pan and pickup to a local machine shop and they charged me one hour ($60) to weld both pieces. I am also the person who was selling the accusump (sold). I experienced two catastophic #2 bearing failures with it and don't believe it offers any benefit other than preoiling the engine before starting. It may actually make things worse when racing as it can overfill the sump and cause the oil to foam. The current engine in my car had less than 50k miles on it when I bought it. The previous owner had driven a few DE's, but it was basically a street car. I replaced the bearings before I installed the engine and the #2 bearing was badly scarred. I put the Lindsey baffle in this past winter and will replace the bearings next winter. After I see the bearings, I'll make a decision on crossdrilling.
Old 06-12-2007, 04:33 AM
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Sounds like you got it right armando. The last 2 things on the list

1. baffel kit- does requir welding a flap door into the oil pan so yes you will need to weld aluminum, The ring is just a steal ring that you weld to the pickup. The kit comes with good instructions and your local machine shop should be able to do it.

2. The return tube mod is just a idea That I had, Not sure if anyone has tried it yet, I might soon while my motor is out being rebuilt. If your good at fabing things up then give it a try, if not then just leave it where it is
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Old 06-12-2007, 02:22 PM
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Just don't understand how these engines ever made it over 100K? Was Miss Daisy driving them?
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Armando Diaz
85 911 Carrera - Track car
01 996 Carrera - For Sale http://forums.pelicanparts.com/showthread.php?s=&threadid=327823&highlight=996
87 944na - Old Daily Driver, now 944 CUP
03 Chevy Avalanche- Support Vehicle
70 Olds 442 W30 Conv- Gone but not forgotten
http://www.diazracing.com
adiaz@diazracing.com
Old 06-12-2007, 04:26 PM
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Thanks to Erau944 (Mike) I picked up an 83 engine yesterday. Engine looks great inside. Rod bearings all show even wear. I spent the day dissassembling, inspecting and degreasing. Now, I'm ready to start reinstalling everything. I'm going for a basic and fast rebuild: rod bearings, rod bolts, rings and engine reseal. I have a deadline of next Friday (22) to get her on the road. I should have the engine put together by end of week. The old engine is disconnected and sitting on the cross-member, so during the weekend I will be swapping out engines and also swapping parts from the old to the new engine. I'm hoping to have it running my Mon.

BTW: Also picked up a manual steering assem. and he donated an extra set of 83 rods and pistons for the original engine. Way to go Mike
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85 911 Carrera - Track car
01 996 Carrera - For Sale http://forums.pelicanparts.com/showthread.php?s=&threadid=327823&highlight=996
87 944na - Old Daily Driver, now 944 CUP
03 Chevy Avalanche- Support Vehicle
70 Olds 442 W30 Conv- Gone but not forgotten
http://www.diazracing.com
adiaz@diazracing.com
Old 06-14-2007, 04:11 AM
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good luck armando! have fun at the track!
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