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Brockoli · Posted: Thu May 10, 2012 2:07 pm Post subject: bad noise from rebuilt engine

Finally got my rebuilt engine in the car an it was running strong. Pulled hard sounded great. Put about 1400kms on it (odometer was broken for some of the kms so was going by fuel used). Ran it to redline a couple times the night before my first auto x of the season. Everything was fine. My dad drove it and I followed him and there wasnt any smoke and I believe he ran it to redline or atleast close to it.

Did five parade laps at the autocross the next day and it was running great. On my second timed run i noticed the oil light was coming on when braking hard in a decreasing slalom section. Figured I might be a touch low of oil but I checked it the night before. The light would turn off quickly.

On my third run I was mid corner in 2nd gear at about 5500-6k rpm and lifted for the rest of the corner. I noticed a lot of engine braking compared to the original engine in that car (makes sense with (9.3:1 pistons). I was video taping from the rear of my car and there was a lot of smoke shortly after I lifted. I accelerated out of the corner and shifted to third. Came to the decreasing slalom again and the oil light came on and I noticed a slight noise coming from the engine. The oil light didnt turn off so I slowed down and pulled of the track.

Parked and turned off the engine. checked the oil and it was full. Tried to start the engine a couple minutes later and it would turn over very freely. I have noticed this when my engine was hot during break in but thought it was just my starter. eventually it fired after half a dozen attempts.

I then heard a loud clacking noise from the enigne. it was worse when revved up a bit to about 3000rpm. At idle its not there. So I towed the car home

Tonight I took of the valve cover and checked the valve lash/adjustment. Some were out slightly. Set the valve clearances and started the enigne without the valve cover (with the help of some cardboard to catch the splashing oil. The clacking noise sounds deeper than the valve train

Used a stethoscope and the clack noise is the loudest when Im listening to the oil pan by cylinder 2 and when Im listening to the oil pump. Doesnt make much noise at idle but reving to 3000 it clacks a lot.

Im thinking this is a spun rod bearing, but that doesnt explain the smoke (mostly white/blue, looks like burning oil), but does explain the oil light. Havent cut open the oil filter yet.

Any suggestions??? Broken valve spring???

I had the all the machining done at a reputable shop, had 1st O/S 'king' main and con rod bearings, aligned honed crank, resized the con rods, new con rod bushings, balanced everything, new 9.3:1 pistons, new rings (I think chromoly), valve grind, new valve guides oil seals, machine shop assembled the head, I installed the cam shaft, align honed the head, ARP head studs, cometic head gasket.

Let me know what you think...

_________________
'80 924 M471,Wideband O2, Full coilover susp,23/19 sways,Bilstiens,KLA Strut Brace,Roll Bar,Test Pipe,BBS RS, Willwood BBK

25% of a '87 944 Chumpcar http://straightpipe.ca/forums/showthread.php?t=2454

'79 924 Sebring Edition(Sitting)

Cedric · Joined: 27 Aug 2004 Posts: 2809 Location: Sweden

This might sound stupid, but on my n/a the rubber stop on the oil dipstick had moved a bit, so even though i thought i was full of oil it wasnt. Discovered it in time so engine was saved, but could have ended badly.

To bad about the engine, if everything seems to be correct there must have been something during the assembly/machining that wasnt done right, otherwise it shouldn break so shortly afterwards.
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1980 924 Turbo
www.instagram.com/garagecedric/

leadfoot · Posted: Thu May 10, 2012 6:20 pm Post subject:

oil is know to travel up the side of the pan during hard cornering to the left, most people who do track work either baffle or dry sump to prevent this...
sorry but it sounds like you may have starved the engine of oil and spun a bearing...
if this is the case you've probably got white metal shards sitting in the bottom of the pan or in the oil galleys now...

now having taken the oil pan off the car from underneath you're not going to save yourself much more time by doing this as opposed to pulling the engine out completely...
considering the cost it takes to replace bearings and get the block cleaned of metal and possible damage to the crank etc you might consider engine replacement with something a bit more modern...
Stu
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

peterld · Posted: Fri May 11, 2012 12:37 am Post subject:

Sadly, you have almost certainly run the bearings. Which will necessitate engine out, strip down, crank grind (if you are lucky) and oversize bearings.
924 motor is already on a horrible lean and autocrossing only exacerbates the situation - hard cornering throws the oil further up the wall of the block away from the bearings and oil pickup.
Some people swear by running the sump a litre overfull, however this just means the crank is fighting through oil on the straight bits, and can lead to broken cranks (at worst).
A crank scraper is of some help, but far better still is a comprehensive windage tray. Available from Ideola or possible to fab your own. The best of course, is a full dry sump system, but that is very expensive and an overkill for DE and autocrossing.
Unfortunately you have a motor rebuild on your hands. Possibly you may have also now incurred a broken ring land as well - only a full strip down will tell.
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80/81 932/8 ROW

mikebola · Joined: 07 Sep 2009 Posts: 361 Location: Parkside, PA

I've done this exact thing to an engine before. I took a turn too hard in a race and the bottom end was starved for oil for a few seconds, and it started clattering. what made it worse was I tried to continue the race.. the entire bottom end was junked, metal somehow made it past the sump filter and filled the top end with shavings. sounds like you have just a spun bearing or two. you should be okay with an oil flush and a bottom end rebuild. and a scraper and a windage tray.

my question though, would a dry sump help to avoid a situation like this?
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proud owner of a 1979 924 Sebring Edition with a 931 trans that looks horrible but somehow runs...

Brockoli · Posted: Fri May 11, 2012 2:48 pm Post subject:

The strange thing is is that I ran this same track and event 3 times last year with the original engine. My dad ran two of the events too last year. So that makes five events on the original engine last year with no problems. That engine had 85000kms. That would be 30 timed laps and multiple parade laps with no issues. The oil light used to come on in the same turns but go out immediately.

I started running 20w50 this year with the new engine but oil pressure didn't seem to change much compared to the original engine with 10w40.

Chrenan and another guy run there 951 at the same event for years with no issues. And a 944s2 has run the event for even longer.

Maybe a combination of a tight new engine, 20w50, hard engine braking, and oil starvation caused the problem.
_________________
'80 924 M471,Wideband O2, Full coilover susp,23/19 sways,Bilstiens,KLA Strut Brace,Roll Bar,Test Pipe,BBS RS, Willwood BBK

25% of a '87 944 Chumpcar http://straightpipe.ca/forums/showthread.php?t=2454

'79 924 Sebring Edition(Sitting)

!tom · Posted: Fri May 11, 2012 2:51 pm Post subject:

Given these anecdotes, I was wondering if a freshly rebuilt engine is more susceptible to oil starvation damage. The film in the bearings is likely thinner due to fresh parts, and the surfaces haven't bedded in fully.

Is there any truth to this?
_________________
78 924 NA
5-lug

Cedric · Joined: 27 Aug 2004 Posts: 2809 Location: Sweden

Ive run many many track days (and auto X days) in both ny n/a and turbo (on stickyRcompund tyres) and have never ever seen the oil light come un, so if it do there must be something wrong since it shouldnt do that. Maybe I would think about baffling if I ran on slick tyres but on R compund it has worked for me and for many race cars that I have seen around here.
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1980 924 Turbo
www.instagram.com/garagecedric/

daniel · Joined: 18 Jun 2009 Posts: 686 Location: Sydney, Australia

I would be looking at a clearance problem or blockage in an oil gallery due to excesive sealant.

I also have raced and old 30 yr old engine with my baffeling and no problems.
_________________
Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet

924RACR · Posted: Fri May 11, 2012 9:58 pm Post subject:

Dan brings up a good point.

No, I don't think a fresh engine might be more susceptible to damage on-track. That's usually where I break my race motors in.

Accusump and windage tray or crank scraper do help a great deal in dealing with controlling the oil flow, preventing this problem. We have both the former and the latter on our racecar. Of course, that means it's a 2-gallon/8qt oil change, which gets expensive with race oil!! But after a number of oil analyses, everything's still in excellent shape...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Fifty50Plus · Posted: Sat May 12, 2012 2:10 am Post subject:

I second what Vaughan said. I experienced the same conditions/noises a few times with my BMW 2002 race cars until I installed an AccuSump. Hard cornering pulls the oil away from the pickup and the oil pump cavitates momentarily until the oil gets back to the pickup. Cavitation causes momentary loss of oil pressure in the system (oil light flickers) and the rods receive their oil last. Actually, none gets there for a period of time while they are spinning at 5000+ RPM. At the end of the cavitation process, oil pressure is returned to the engine and eventually gets back to the rod bearings. This can happen many times and damage is incremental or it can happen once for a long period of time. In either case, the bearings heat up, turn blue then start melting and squish out the sides of the rod. The bearing clearance gets very large and you see a loss of oil pressure on a guage. If you are fortunate, you turn off the engine before an explosion (rod bolt breaking causing max internal damage). After the oil and engine cools, if you try to restart the engine, you will hear the rod clanging around the crank (rod knock) and you know for certain that it's time for a rebuild. You will find bearing material throughout the engine but it is still salvageable after a thorough cleaning, regrind and refresh of bad parts.
After we started using AccuSumps on our race cars, we've had no cavitation problems and no engine failures ( many 12 and 24 hour endurance races).
On a street car, momentary cavitation is never a problem (the factory did install sump baffling in the pan for street conditions) but autocrossing and racing require a better solution. Dry Sump is the ultimate but expensive and not always allowed under some rules (SCCA doesn't allow Dry Sump). For hard cornering, additional baffling and oil scrapers can be installed to help keep more of the oil in the pan near the pick up. But in a long hard corner at high revs, the pump eventually sucks up the available oil. Thats when the cavitation starts. An AccuSump is a two or three quart chamber connected in the oil pressure stream (adapted at the oil filter) with a check valve that prevents reverse flow back towards the pump. The pump pressurizes the engine and AccuSump until it sucks air from the pickup. The check valve closes, the AccuSump starts evacuating its pressurized oil into the oiling system and all is good - for a while. As the Accusump bleeds oil into the system, its pressure is falling but there are several quarts of oil available. This bleeding process takes several seconds and hopefully, the oil pump pick up is again bathed in oil. When the pump starts pulling oil, it overcomes the check valve and begins to supply oil to the engine and recharges the AccuSump for the next long hard corner. As an aside, if you ever want to find out if the AccuSump works, feel it after a session on track. If the Accusump is cold, it hasn't activated. If it is warm/hot, oil has been flowing in and out of the AccuSump. Nice to know.
Hmm...Sorry. I got carried away but I hope that helps anyone in the future that likes to push their car.
Chuck
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1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

924RACR · Posted: Sat May 12, 2012 3:23 am Post subject:

Wow, you sure did get carried away!

Our Accusump is ALWAYS warm after a track session, plenty warm... enough that it's not too comfortable to sit on for victory laps...

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Slam · Posted: Mon May 14, 2012 2:01 am Post subject:

Brock, it really hurts to read your post! I know how much work went into that car. What you describe sounds like (as posted already) at least one spun bearing. Did you plastigage all the crank journals on assembly? I agree with the cavitation theory (not that I'm any kind of authority on the subject) and with that in mind, are you sure your oil pickup isn't cracked or was installed correctly? What were the symptoms on the oil pressure gauge? Did you see a lot of swinging?

I was going to take Chrenan's spare engine off his hands but you may need it more than I at this point. Let me know.
_________________
'84 944 - kid blew motor
'83 944 - resting comfortably. For 12 years
'87 944 - sideswiped by trucker
'80 924 - gone
'78 924 - gone
'77 924 - rusting comfortably

Brockoli · Posted: Mon May 14, 2012 2:50 pm Post subject:

Ineresting read about the accusump. I will look into that for the next rebuild. And the crankscraper too.

When I got the car home and ran it for a bit to pin point where the noise was I still have good oil Pressure. Even on the track with the oil light on I still had good oil pressure levels on the gauge. That's why I didn't pull over immediately.

I won't need the block or crank as I still have one spare from the '79 Sebring. I actually have 4 engines in total for 2 cars. A '77, 2x '79 and a '80. 3 of the engines are complete and I scavenged some valves from the last one for my build.

I didn't plastigauge the bearings during assembly. I gave everything to the machine shop and the did all the machining and said the clearances would be checked. Hopefully they did. I believe I installed the oil pickup properly but it may be damaged, I won't be able to comment until I open it up.

I just hope my block isnt ruined as I had the crank journals align honed. Hopefully it's just connecting rods since I has lots of those sitting around.

I'll let everyone know how it turns out once I tear it open...
_________________
'80 924 M471,Wideband O2, Full coilover susp,23/19 sways,Bilstiens,KLA Strut Brace,Roll Bar,Test Pipe,BBS RS, Willwood BBK

25% of a '87 944 Chumpcar http://straightpipe.ca/forums/showthread.php?t=2454

'79 924 Sebring Edition(Sitting)

daniel · Joined: 18 Jun 2009 Posts: 686 Location: Sydney, Australia

hmmm if the motor still starts and runs and has oil pressure I would pull the sump off in the car and have a look, also cut the oil filter open and see what (if anything) is in it
_________________
Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet