Update on the broken 383 stroker. What happened here? - Team Camaro Tech
Engine General Engine Discussion.

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post #1 of 17 (permalink) Old Aug 25th, 02, 04:40 PM Thread Starter
 
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I spun 3 main bearings, the darn thing is broke. The good news is that Ive decided not to sell. Its not nearly as bad as I thought. We are not positive about the cause of the problem but thats where you guys come in. When we got the oil pan off, the first thing we noticed was that a few stud nuts backed off the mains(very not good I know). The other problem is that the machine shop that did the mainline honing said they didnt know it was a race engine so they made the main clearances tight. We told them it was for racing! They suck!

So, is it a combination of the studs not being torked right and the tight clearances? The engine had way too much oil pressure which we didnt understand in the first place. Another thing is the torque wrench we used may have been off because alot of the bolts on the heads were off. So heres my questions for you guys as to why this happened
1) What is most likely the cause of the nuts backing off the studs?
2)DO I have to have the engine line honed again?
3)Could tight clearances alone have caused the bearings to spin? Where should the clearances be for a 6500rpm stroker that sees a fair amount of street use?
4) what should I look for before we put it back together so that this doesnt happen again?

On my second pass at the strip I felt it go right at the finish but I thought it was the carb or something(denial). I ran my next pass at 102mph with 3 spun main bearings!! My first and second run were both 84mph @1/8 [email protected]/4 but my 3rd was 81-102. I think she went on the 2nd, or maybe it already had a spun bearing or 2 when I got there! I just dont know.
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post #2 of 17 (permalink) Old Aug 25th, 02, 07:34 PM
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I don't remeber the exact setup...how about a refresher? How do the piston tops/spark plugs look? I am thinking you might have run into some top end detonation, and pounded the bearings out. Of course, too tight of bearing clearances is definately a possibility too.

[This message has been edited by travis (edited 08-25-2002).]
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post #3 of 17 (permalink) Old Aug 25th, 02, 07:57 PM Thread Starter
 
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Well,heres my combo

11.17/1 compression @.041 quench
Studded high 4 bolt main nickel block
internaly balanced 3.750 forged steel crank
4340 H-Beams 6" bushed
Wiseco F/T forged pistons/plasma moly rings
Federal Mogul comp series bearings
292H comp magnum

Everything in the engine looks great other than the spun bearings, it pinged a few times with 44 total timing. We ran at the track with 8 intial 32 total timing, the carb was running lean. I dont think it pinged at all, it runs great on 92 octane. The pistons wiped clean to a new shine with brake cleaner. The chambers,vavles and raings were fine. I have to find out what happend so I cant prevent it from happening again. Everyone was amazed that everything held together with 3 spun bearings and I drove it 15 miles home from the track like that WITHOUT the fan and it stayed at 190. The stroker is down but its not out,thanks for any help guys.
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post #4 of 17 (permalink) Old Aug 25th, 02, 09:23 PM
 
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First of all. I would demand that the machine shop redo everything for free, pay to have another shop of your choice do it(just labor) unless this engine is over a year old. I don't see how a main stud/nut would come off without being installed improperly, also 6500 is kinda high for a stroker motor, and how in the world did the shop not know it was for racing with all those RACE parts in the motor???? for seven grand you better be able to race the motor, I think it maybe wasn't balanced, alignhoned, or torqued right, or put together correctly, probably not from pinging, to my knowledge pinging ususally wipes out the rod bearings, not the mains.
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post #5 of 17 (permalink) Old Aug 26th, 02, 02:11 AM
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Answers to your questions:

1. Remove of the faulty torque wrench! Might also check with stud manufacturer about using oil or not when torquing fasteners.
2. Machine shop will determine re-align-bore for block. You can check by removing crank and torquing down bearing caps and placing a straightedge through the bores and try to slide a .001 inch feeler gauge between the edge and bearing saddle. If you can, then align-bore time.
3. Tight clearances - maybe. No [email protected] - definiately! Stock capacity oil pan, stock oil pump, and hi-revs, oil is pumped upstairs and pump starved for oil. It can happen so fast, you and the oil gauge will never know it until its too late. Good clearance I think is .002-.0025 inches.
4. Throttle limiter or rpm limiter to shut off sooner.

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Everett 68/350/PG/11.90/115mph
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post #6 of 17 (permalink) Old Aug 26th, 02, 02:57 AM
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Allright guys...I have to chime in,
Who assembled this engine ????? If the machine shop did, then they "might" be resoponsible. If anyone else did, then the person who assembled the engine is responsible. All the machine shop can do is finish the main bearing bores to a size within the factory specs. If they finished them on the tight side of the spec, and the crankshaft was finish ground on the large side of the specs, then the clearances "might" have been too tight. BUT....it is the engine builders responsibility to check them !!! If you did not check the bearing clearances, then shame on you...you should not be assembling engines. If you did check them and they were what you wanted them to be, then how can you blame the machine shop ???
By the way, we prefer the main bearing bores, and connecting rod bores, to be on the tight side of the spec...it helps hold the bearings in place a little tighter, making certain of good heat transfer, and less chance of bearing movement. Have never had a bearing problem due to this practice.
I dont think the machine shop owes you anything, you might owe them an apology if they happen to read this.


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Bill Koustenis
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post #7 of 17 (permalink) Old Aug 26th, 02, 03:21 AM
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Any idea why your oil pressure was so high? BTW how high was it exactly? I wonder if you could have had something blocking an oil galley causing the pressure to go high and starve the mains. That would definately cause them to spin - so would loose main bearing caps.

Just a thought.
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post #8 of 17 (permalink) Old Aug 26th, 02, 09:59 AM
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The thing that stands out most to me is the loose bolts. I think this is the source of your problems. How loose were they? Get a known good torque wrench for the re-assembly. As Bill said when you are building and engine is is always good to measure everything. Machinists are human too. Unless the clearance was really tight I don't think this is your cause. Might want to have the machine shop check. One other thing, don't expect to get the work done for free, it happened while racing. How many miles were on this engine before you took it to the track?

Royce

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69 Camaro (soon to be 6" rod 355 backed by a T56)
2000 GMC Z71

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post #9 of 17 (permalink) Old Aug 26th, 02, 12:58 PM
 
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I believe that he posted that this engine only has 500 miles on it in another post, also i happen to believe that if an engine shop assembles your bottom end, and if you finish everything according to plans, and if done correctly, that a machine shop should warranty their work after only 500 miles, even if he was racing it, also remember this was the first time to the track, and he only ran twice, it's not like the engine was severly abused, and with the expensive parts in the motor why shouldn't you be able to drag every now and then. loose stud nuts to me shows that the shop did not do a good job at all, that is almost the most likely case why your bearings went out, but not having enough oil to supply the pump could also go along with it. THis is all assuming the shop put the bottom end together? if you did it, it's your fault for using a faulty torque wrench, or improper instalation procedure.

[This message has been edited by cody (edited 08-26-2002).]
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post #10 of 17 (permalink) Old Aug 26th, 02, 02:45 PM Thread Starter
 
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Ok, I sadly have to admit it was ME who assembled the engine NOT the machine shop. They did however do the mainline(align bore,check clearances), I guess I trusted them and didnt double check. I dont even know for sure if that was even the cause, because I didnt even torque the studs right. I went 70 on the inners and 65 on the outers, but Im pretty sure now that my dads torque wrench was not accurate.

My engine has excellent oil contrtol but I think I got a little carried away with the 7000rpm shift points. It only has a 292 cam but it went to 7k easy! The engine has a 7qt pan with trap door and windage tray with high volume pump. The thing Im thinking is that since my oil pressure was so high during street driving, when I went 7k RPM it may have ran out. I cant be so certain thats the case because Im using electric gauges and I dont trust them(I was going to change soon).

The GOOD news is that machine shop has offered to help get mym engine goin again for a huge discount. They felt very sorry about it and they are aware of the nut backing off but said thats probably not the cause. They do believe they had the main clearances too tight. Thanks for all the help guys, Ive got some ideas of what may have happened now. I think its important to know for sure before I assemble it again.
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post #11 of 17 (permalink) Old Aug 26th, 02, 06:22 PM
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Install a mechanical guage and keep an eye on it. Pressure over 100 PSI can "wash" bearing off shell. Use a good clicker type of torque wrench. In general, use 5-10 ft. lbs. higher when torquing with lubes. Check with fastener manufacturor if in doubt. Don't rebuild without teardown and cleaning. Good time to chamfer oil holes! Better luck this time!

------------------
Steve
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post #12 of 17 (permalink) Old Aug 27th, 02, 05:44 PM
 
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That's OK, nitrous383!

It takes a big man ta admit he "F--k-- -Up"!

You will do better next time, just hang in there! pdq67



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post #13 of 17 (permalink) Old Aug 28th, 02, 02:02 AM
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You've earned my respect, you stepped up to the plate and admitted to your faults.

As pdq67 said, Takes a big(ger) man, regardless of physical size, to admit he has done wrong.

Respect is always earned, not given.

Sears is having a Tool Sale starting this Thursday, go buy that new torque wrench and put Dad's wrench back into his box.

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post #14 of 17 (permalink) Old Aug 28th, 02, 03:45 PM
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While we are on the subject, I wanted to know where people go to get there torque wrenches calibrated?
Sorry to hear about your 383.
good luck on your rebuild.
jeff
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post #15 of 17 (permalink) Old Aug 28th, 02, 05:19 PM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by JefeOsterhead:
While we are on the subject, I wanted to know where people go to get there torque wrenches calibrated?
Sorry to hear about your 383.
good luck on your rebuild.
jeff
<HR></BLOCKQUOTE>

If you have a Craftsman TQ wrench, just take it to the Sears parts department (where you get lawnmower or power tool parts). Its usually a small office by the pick-up door. They charge a fortune though - they wanted like $50 to do my 3/8" drive clicker type.
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