Pete K

Well, I finally found the reason for my 406's immediate (100 mile) failure. Professionally prep block was not align honed properly. Bearing clearances were .002 on the mains. #1 was .0015 too tight. This reduced my clearance to .0005 on one point of the #1 bearing. . This did not blacken the bearing but shoved the crank over in the saddle. The machinest claims this is prefectly acceptable and did not cause the problem. I know better than that. He pizzed on my leg and claimed it was rain! Moral of the story is no more plastigage. Bore guage only. It is a shame we need professional tools to double check a machinist. Pretty happy to have found it. Would have been a crying shame to reassemble it and have another failure.

jburnett

What a feeb... Dial bore guage is the ONLY way to fly. .002 is a little tight; .0015 is WAAYY too tight. And if the bores aren't concentric you'll never know exactly what the clearances are.
-Jeb

tjwong

Boy that is a bummer, I hope the guy pays up or makes good of it.

0ski_dwn_it

That is why a good machinist is like a good women. Treat them well and keep them happy - and you will keep a smile on your face at the same time, and save yourself a whole lot of headaches.

Its amazing and should be noted that while some think that throwing a motor together is a given that everything should be perfect....that is NOT always the case - "good" machinist or NOT.

I know Pete is no dummy when it comes to motors, you can talk to someone about motors and know if they have a clue or not, and Pete knows his stuff.

Point is there are a TON of variables that can lead to a problem with a motor, and anyone will tell you that puts them together - even with the utmost care taken, the first 100 or so miles and first trips to the track they are holding their breath and watching the oil pressure like a hawk to make sure everything is ok.

Good followup and tracking down of the problem you had Pete. .0005" is about 16% of the width of the average human hair to put it into perspective! That is not enough to carry oil effectively. However most of the cam caps we make here for GM in overhead cam engines get machined to .001 clearance - hence the reason you have 60psi oil pressure on a car nowdays after 80K miles. But that is NOT good for a performance motor.

8388

Any body can have a bad day. That's why you mic everything twice. I will not assemble an engine without going thru everything, and verifying all the clearances.

BTW, washing the engine down after the machinist gets thru with it is another important factor.

Pete K

He offered a free align hone to make everything right. I must pick up the other expenses. Worst part is we were friendly. I will not be doing business with him anymore. I do not care so much that he made a mistake. We all do from time to time. But to tell me that it had NO chance of contributing to a killed set of bearings, a ruined thrust surface on crank, and loads of metal in the oil tells me his character may be in question. A blind man can see it at least strongly contributed to my situation. Trans and conveter are fine. We will check for squareness of the block in relation to the crank before reassembly. Everything else checks fine.

Pete K

I absolutely agree. It is a shame when a shadetree mechanic must own a bore guage to check a well respected machinest's work. I am afraid I will have to buy an alignment machine and wheel balancer for my garage to make sure they alingn the wheels right.
The scary thing is the other motor (still in the car) has the same failure and the same machinest. I am having an expensive month.

8388

That reminds me of my Trick Flow week, or should I say Trick Blow. I had two very expensive engines ruined in the same week. Both had Trick Flow heads with crappy guides. Sometimes everything you can do is not enough.

Pete K

Anything that does not kill us makes us stronger. I am bummed out regarding the labor more than anything. I also ordered a new bore guage. I just found out the crank can be repaired to better than new shape. Today is looking up.

Red Tornado

an example of that blind man would be me! i'm appalled that a known professional won't accept a slight dent out of his monumental income and do the right thing. he must have had a new trainee in there with no supervision. maybe he's taking on too much business, but then here we are 8 years later with a similar problem. the personal $$ expense is no joke, and many of us share in that misery. unfortunately that's no help to you as it doesn't pay the bills. BUT.....there are better days ahead! You're right, if one isn't killed it only makes us stronger

Pete K

Brad, the worst part is the 383 (with 100 miles)in the car now, has the same exact symptoms. Thrust went from .005 to .010. Oil is loaded with gold dust. This was my clue for the 406. Both blocks were machined at the same shop. I am worried. The good/ bad news is that the 406 made enough power to knock out the 3-4 clutches on the test ride. While the 406 is remachined and dyno'd ,I will build it (trans) up and add some tweaks. Scat has been having trouble with their crankshafts lately. They have been hardening them excessively and leaving a rough finish on the thrust flange. This, in effect, makes the thrust flange work like a file. I am almost hoping this is my problem. Then someone else will have a hand in the repair. The machinist feels his work is god like, even though the round stuff is oval. Today I will pull the trans and at least get the motor ready to pull. It is gonna be a busy few weeks. 2 trannies for friends, 1 for me and 2 motors to rebuild and 1 dyno session. I am gonna need my wheaties!

Red Tornado

Pete, 15 hours straight you'll need 15 bowls of wheaties! Now its SCAT cranks? It seems that alot of the parts suppliers are having q.a. problems these days, how can anyone get a project done without imminent distaster Lets hope that whatever turns out, there will be cash in your pocket

Pete K

Brad, NEVER have I had a legit problem caused by others result in money back. There is always a perfectly good reason to shift blame from the product to someone else. I am prepare for $0 to come my way. I am hoping to solve the problem and spend the minimal amount to do it right. I did not post the scat thing to bash them. They have always made a decent crank with quality machining as far as I am concerned. I simply have something extra to look at. I feel ilke someonr handed me a teaspoon and said"go dig a swimming pool". Lots of work ahead of me and I cannot seem to get my azz in gear. Might abort the plans for today and take the v-rod out for a beatin.

Red Tornado

Pete, good info. If your heart isn't in it for today, go out and lay into that V-Rod! Don't forget to wave to our veterans

loiq

When it was put together the crank feel tight after the mains were torqued?

Pete K

Nope. Felt ok. I was suprised.

loiq

No kidding. Weird.

Pete K

When we bore guaged the saddles it was only tight in the 3 o'clock position.

BillWelter

I've never had anybody else build my motors, and none have had any problems, either. You need to double-check anybody's work. Taking a motor out, rebuilding it, and putting back in is a LOT of work. Once I had an engine bored, and one of the pistons wouldn't even go in the bore!! Good luck.

jfb

His first hone job was no good. What will the next one be? He would not touch that engine again if it were mine.