Here we go again--spun bearing

[rustfarmer]

Those of you who have read my earlier posts already know the long sad story, but a brief re-hash in case you don't. Bought a "good" JDM turbo 7MGTE to replace tired NA engine. After finding the correct wiring harness, ECU ect. ran it 2000 miles, changed to full synthetic and spun #6 rod bearing.

Tore it down and did total rebuild with ARP rod and head bolts, new squirters, new oil pump, metal head gasket, polished stock size crank from old NA engine, replaced several rods for bad side clearance, ran about 2000 miles again and started knocking. Sounded like a top end noise so pulled the head and found the shop I paid $800 to re-do the head did not re-shim the valves! Several were loose by as much as 6 thou of a spec of 6 to 10. I replaced all springs with the BBC inners and set all shims to spec. Before reassembly I had son rotate the crank pulley back and forth and found #3 piston had loose motion and knock.

Pulled the engine and found spun bearing on #3, although rod bolts still torqued to spec. I had machine shop I have used for 30 years check and polish crank and re-size all rods for this build, but can not say I personally checked the specs. You can bet I will not make that mistake this time. So, plan to re-work crank (10 thou should do it) replace all bearings, and replace oil pump. Last time I remarked that I did not like the low oil pressure at hot idle which seems to be correct for a stock engine. A huge e-storm ensued discussing high volume systems vs. high pressure. Please note that at least one expert feels the stock specs are insufficient as he sells a modified pump reported to produce 18psi at hot idle with 10-30w oil. (Check Aaron at Drift Motion) My rule of thumb in 50 years of engine building is 10psi per 1000 rpm for performance engines. This is the first bottom end I have had fail in 40 years of building chevys big and small (including 6's) Austin, Toyota 4's, Alfas, Jeep, Buick Caddys and who knows what. Most embarrassing as this was built for my son. I will admit this is my first turbo engine which makes oil pressure/volume even more important. Engine was built using CCR assembly lube, pump pre lubed, broken in properly and 1st oil change at 400 miles.

All advice greatly appreciated. RF

 

[IndigoMKII]

If you're using the same block, have all the passages blown out so ensure good oil flow.

A good read for you.http://www.supramania.com/forums/showthread.php?5631-7M-assembly-tips.

 

[rustfarmer]

This block was was cleaned by machine shop prior to last build (2k miles ago) however, since I will have it down, I'll do it again. Got to say, it looks very clean but why take chances. Should of had a V-8!

 

[nathaninwa]

just some random questions. Is the car all stock? What boost level? What fuel is the car running? type of oil? and you said you didnt know engine bearing specs right? Was the oil cooler replaced? And its been a while since I played with any 7m stuff, but is the crank cross drilled and a ball bearing pressed in placed on the rod journals? Muck can build up between the ball bearing and the rods journal.

 

[rustfarmer]

Mostly stock, pistons +.020, turbo elbow and exhaust all modified, stock boost so far, best gas I can buy, castrol 10w-30. Just finished tear down and all bearings are bad. One rod bearing on #4 showing copper, all others show signs of even but excessive wear, mains look bad as well. All bearings are stock size and crank is stock, polished but not turned as was within spec. New oil pump with shimmed bypass as instructed elsewhere in forum, prelubed and entire system brought to pressure before started. When running, oil pressure with mechanical gauge showed 5 to 7 psi hot at dead idle, and about 30 psi at 3k rpm. Forum posters all said this is enough oil pressure. The crank was one I pulled from the old NA engine which had BHG at 200k miles. Several rods were replaced from the set in the turbo engine in order to get side clearance into specs.

it appears to me the engine must not have been oiling properly, as I have never seen bearings all bad in 2K MILES SINCE OVERHAUL. I did not replace the oil cooler, but did clean it out carefully. Engine did not run very hot--200 degrees at interstate speed- but engine did seem to push oil into top end excessively. I noticed some seepage at hoses going into valve covers, but thought I had found the issue as a collapsed large hose in the PCV system, where I had used a section of heater hose to replace a formed hose not available locally.

Lacking a good set of micrometers, I will take all to my machine show to check crank and rod specs. The #3 rod which had spun the bearing seems too snug at the piston pin now, but was normal at past assembly. I assume it got hot or the pounding from spun bearing caused some damage.

As said before, I have built at least 100 other engines and usually have a feel for bottom end issues. I rotate the crank as I tighten each main or rod bearing to insure smooth turning and really believe the entire bottom end was in spec when assembled. All crank plugs are still intact, new squirters were installed, everything was clean, so I think some portion of thee oil system must be at fault. Perhaps a chart of the oil system for a turbo engine might be helpful. All ideas most welcome, and I will post measurements once taken. Oh and crank is stock and not cross-drilled as my machine shop refuses to provide this service.

 

[IJ.]

Were the Crank plugs ever pulled so the galleries could be wire brushed out?

 

[nathaninwa]

i just went through this with my 2j. Spun bearings suck for sure. Mine came from some detonation from 1 injector failing, spraying more fuel than the rest indicating a good afr, but 5 cylinders were lean. This could be something going on with you, and the bearing material from the rods were processed through the main bearings, or its possible the oil cooler didnt get 100% cleaned.

ever since this, I cut my filters open and have been getting my oil analyzed.

 

[rustfarmer]

I don't think the crank plugs were ever pulled so I will do this myself and see how much crud is there. Engine does have unusual residue in the oil pan which I was thinking was left over assembly lube, but after one oil change at 400 miles and another at 1500, perhaps this is a sign of something else. The oil seems normal except for the shinny little particles of bearing metal, but the 1/8th inch of thicker goo is strange. About the consistency of assembly lube. I'll post more after pulling crank plugs.

 

[rustfarmer]

Just removed all crank plugs and found some gunk under each plug (worst at rear two plugs) not blocking the passages, but a total amount of stuff the size of a small marble perhaps. Material was like soft clay and built up against back side of plugs. Not nice, but I don't think this is the complete cause of my bearing failure. Closer inspection of the goo in the oil pan reveals it is coating the baffle top 1/8th inch thick and the bottom of the pan. I've seen oil that was over heated and foamed (think VW engines) and it doesn't look like that, but might be good to get oil analysis done on this stuff. Where can I get this done and how pricey?

 

[IJ.]

If the machine shop set it up at factory specs it takes very little debris washed out of the crank to get stuck in a bearing and begin the process of destroying it, Spun bearings are usually more a case of insufficient clearance or Oil starvation..

 

[nathaninwa]

Just removed all crank plugs and found some gunk under each plug (worst at rear two plugs) not blocking the passages, but a total amount of stuff the size of a small marble perhaps. Material was like soft clay and built up against back side of plugs. Not nice, but I don't think this is the complete cause of my bearing failure. Closer inspection of the goo in the oil pan reveals it is coating the baffle top 1/8th inch thick and the bottom of the pan. I've seen oil that was over heated and foamed (think VW engines) and it doesn't look like that, but might be good to get oil analysis done on this stuff. Where can I get this done and how pricey?

I agree with IJ. Oil starvation or to tight of tolerance. Combine that with the gunk in the crank and cooler.

What bearings were used?

You said this was for your Son? Is it his first turbo car? Does he maybe get on it a bit when the oil is still cold?

Blackstone is kind of a place everyone uses. I use them and like the person bits he puts in the analysis. Cost is 25 bucks and he can provide you the cups. I can email my report if you would like to see one.

 

[rustfarmer]

Thanks for all the replies. Nathaninwa it would be great if you could send me a sample oil report with Blackstone's contact info. I really think the clearances were OK, but agree with oil starvation being the likely cause. Also wonder if possible fuel injector leak may have contaminated the oil as the gunk in the pan looks unusual to me. Oil analysis should tell the tale if this is so. Son is 26 and a good kid, but this is his first turbo car. We have talked about warm up and letting the turbo wind down before shut off, but when your showing off sometimes you forget these issues.

 

[nathaninwa]

PM me your email address.

 

[super51fan]

I saw that you replaced rods to get correct side clearance. However did you replace the rods that had spun bearings. If you spin a bearing you need to replace the rod.

You can use plastigauge to get a rough idea of clearance. Now days they sell some ok mics at reasonable prices and get some snap gauges for internal measuring.

 

[rustfarmer]

I was unaware that one must always replace a rod that has had a spun bearing. I always have my machine shop resize and check all rods, but I'm not sure they always tell me to replace them. Sure if a rod has no bearing material left when you take it apart it is likely beyond repair, but if each bearing half still has 1/16th or so of material remaining isn't it possible the rod is not damaged?

Anyway, in my case #6 was in bad shape when last built so it and one other were replaced. I set up my usual balance bar= a 3 foot piece of all thread, and after fashioning some hooks from wire I hang a pair of rods from each end and find the lightest. Then balance all rods to equal the lightest one by removing material from the balancing pad.

This time I will replace the rod which had spun bearing as the piston pin seems tight which makes me think the rod either got hot or deformed a bit. Luckily I have a few extras.

I guess it is time to get some snap gauges. My cheap mic shows crank should clean up fine at ten thou.

Thanks for you response. RF

 

[nathaninwa]

Ill get that report emailed today. Resizng the rod is just fine. When mine went (aftermarket H beam) it was a quick 20 dollar cleanup and all is back in order. Mine was so bad that my crank journal was trashed and the crank had .020 runout! The crank got replaced for sure on that one.

 

[rustfarmer]

Machine shop has turned crank rods .030, mains .010, straightened crank run out, resized two rods (# 3 + 4) and cleaned up block and crank(with plugs removed this time) rods and pistons and say all is good.

Reassembly will include driftmotion blue printed oil pump, braided cross over pipe, remote oil filter using Canton adapter, Earls thermostat, Canton cooler and CVS billet filter mount. Also adding new larger intercooler and pipes and gauges including A/F mix, boost, oil temp and oil press.

I'll post pics and maybe video soon as we get it running. Thanks to all for your help, and Aaron at driftmotion for the better pump.

 

[suprarx7nut]

Machine shop has turned crank rods .030, mains .010, straightened crank run out, resized two rods (# 3 + 4) and cleaned up block and crank(with plugs removed this time) rods and pistons and say all is good.

Reassembly will include driftmotion blue printed oil pump, braided cross over pipe, remote oil filter using Canton adapter, Earls thermostat, Canton cooler and CVS billet filter mount. Also adding new larger intercooler and pipes and gauges including A/F mix, boost, oil temp and oil press.

I'll post pics and maybe video soon as we get it running. Thanks to all for your help, and Aaron at driftmotion for the better pump.

Keep us updated on the results! I'm curious if the moly coated gears really up the idle pressure a noticeable amount. Of course, the oil cooler and adapter will increase your oil pressure as well so it'll be hard to tell exactly how much the pump is contributing.

Good luck!

 

[IJ.]

30 under?

If so Crank is now junk as the Toyota Hardening is only at best 15 thou deep....

 

[rustfarmer]

Any one else want to confirm this crank can not take more than 15 thou cut on rod throws? This comes as quite a surprise to me. I have not known of any crank since studebaker that had such a thin hard surface. I really need to know if this is true before I pour more $ into this engine.