[machine shop tom]

A customer of mine sent a block to have splayed caps installed and be align-bored (400 SBC). He also had the shop handle the crank turning (they farm it out).

Upon return of the parts, we checked them out.

The crank was a couple of tenths under the low limit on the mains (the rods were ok, just needed polishing). However, the big problem is the mains have .002" run out on 2 of the center mains, .001" on the other center main. Too much.

The owner of the speed shop (big name, big dollar, big ego place) was informed about the crank. His reply was that he never had a problem with the cranks and that we are checking them wrong. (!)

We check them on a set of V-blocks with a dial indicator (on our balance machine). Just like it SHOULD be done.

But Mr.Attitude says we should check them between centers! Apparently nobody showed him how to check a crank.

What irks me is that instead of saying "Gee, if there is a problem with the crank, let me check it out and we'll get back to you. But no, his way is to blame the guy who DID check it. (Mr. Attitude didn't even bother to check it, anyway!).

Now, the block.

The main bores are between .001"-.002" out of round. I haven't informed the guy about this, yet. I'm probably checking it the wrong way (a dial bore indicator that reads to the .0001".)

ARRRRGGGGHHHHHH!!!!

tom

 

[NXS]

Yea, we always turn them spot on but after polishing the check loose

haha

anyways when the block is line bored it raises the crank in the block? possibly requiring the starter face to be machined also?-curious.

 

[machine shop tom]

Align-boring or honing a block will not remove enough metal to affect the starter.

tom

 

[NXS]

I once had a Nova with a 350 4bolt. It ate the starter up and on replaceing the starter my dad noticed the starter was too far away from the flexplate to engage properly. Instead of shimming it we had to take material from the starter mounting pad. Never figured that one out but I suspected it had been align bored, guess not?

 

[paulo]

But what is this method of checking between centers? Would it be front and back longitudinally as if in a lathe?

 

[TurboS10]

Sounds like the engine would not hold a bearing to save its life. Good thing you checked it out. I am curious what typically causes these problems? The crank runout I can understand, but it seems like the align bore would be hard to screw up. Is it possible that the bored it without the main caps torqued or something?

Chris

 

[machine shop tom]

But what is this method of checking between centers? Would it be front and back longitudinally as if in a lathe?

Yes, that's what between centers would be. However, the crank lies in the block supported by the main bearing journals, just as in would be as it is checked in V-blocks. Another way to check is by putting the front and rear upper main bearings in a block (as it is upside down on a stand or bench) then laying the crank in place (lightly oiled), then checking the run-out on the unsupported main journals with a dial indicator.

tom

Sounds like the engine would not hold a bearing to save its life. Good thing you checked it out. I am curious what typically causes these problems? The crank runout I can understand, but it seems like the align bore would be hard to screw up. Is it possible that the bored it without the main caps torqued or something?

Chris

Align honing requires that the caps be cut the same amount and that the bore centers are close to being in line to start with. The more these factors are out-of-whack, the more work it is to achieve a straight and true bore.

Another factor is the type of material the caps are made of compared to the block itself. Caps that are billet will machine differently than those of cast iron. Another variable is the difference that will occur after the honing process is done a the the workpiece cools off. That is why the machinist must check the job after a cool-down period (the same thing applies to honing cylinders).

tom

 

[RCastle]

Hey Tom,now you got us asking questions.I was wondering,exactly how hot does a piece get during the turning process?Same for the block.What heat would be generated while doing a bore? I have seen it in footage on TV before.Of course I have never seen it done firsthand. I assume it must get pretty warm to require a hot and a cold material check.Pretty cool.Educate us.-Ron-

 

[bracketeer]

line bore

Try installing the crank on the upper bearing halves. If it turns freely your probably ok. If its stiff to turn, its wrong.

If you did a torque plate hone. They cylinders will be out of round. When you bolt the heads on. The cylinders go to a perfect circle.

 

[paulo]

Ok Tom! Good to have a machinist's opinion.Especially from Motown.I have all the freedom I want at a local machine shop down here.But sometimes the technicians are doing things and not sure why.By what you explained and the other "not so polite machinist" said,a crankshaft should be checked supported on all mains.I assume this way the counterweights themselves would not slightly bend a true shaft... I remember a machinist here in Rio grinding a new core for a 4 Cyl Audi,and telling me that even the lathe speed can cause errors if too fast.And that was for a sturdy and compact 4 cyl unit,let alone a V8 with its 4 different planes and natural unbalanced condition.Please explain more.

 

[camaroman7d]

Tom,
I know how that is. Look at how they treated you and you are a machinist (professional). Now the poor average Joe home builder (that may be VERY good) doesn't even stand a chance. This is why it is good to have work done some what locally and get a relationship with your machine shop. I don't know how these "top dollar" "big ego" shops stay in business. I have been through a similar situation, not much you can do about it. The court costs out weigh the price of just fixing the problem.

I am sure you will make it right Tom, just be sure everyone in the area knows about that shop.

Making a mistake is perfectly natural and nothing to be ashamed of, when you make a mistake you need to step up and fix it. Those shops are "too good" to ever make a mistake, Right?

Royce

 

[paulo]

Not about the crank subject.Royce,is that color on the Camaro the Le Mans Blue? I need the PPG formula for a friend's '74 down here.

 

[arch]

Before I give my suggestion, Apperently this guy/company has no intention of fixing the problem... are you going to mention the other wrong measurements to him or just forget about it? If he offers to fix it... great.. if not, then my suggestion:
If you're in agreement about court costs not being worth-while, then, next step... Better Business Bureau

 

[machine shop tom]

The problem I have is that a good friend of mine to the block to the other shop because HE is a good friend of the shop's owner. I'm irked because the owner didn't deal with MY friend in good faith.


We are checking the block twice to be fair. It has ARP main studs so we are checking it with both types of lube (moly paste and SAE 30 oil) and at the respective torque specs.

Here's the rub. We don't check to "look for a problem". We are simply making sure the job is within specs. If it's not, then let the other guy know there is a problem. We are actually doing them a favor by not letting the problem get any further. Yet we get smoke blown up OUR ***! As far as the crank goes, they didn't even turn it. I would think that the guy turning their cranks for them would be interested in knowing that he may have a machine problem. BUT Mr. Attitude apparently doesn't care about that, only that HE knows more about checking cranks than I do (!).

This isn't the first time I got an attitude from these guys and a while ago we had a guy take his block back to get the main bores corrected after a slayed cap/align hone job. But, as I said, a good friend is caught in the middle. I don't want him to get a bunch of crap cause I won't let the Big Boys slide on this one.

tom

 

[crazy larry]

you know what i say.:mwink:

 

[machine shop tom]

Here's an update.

We checked the block again, the studs lubed with oil and torqued accordingly. The main bores check within .0005" or so of the mid-point of the tolerance range except for the center main which is closer to .0008' out-of-round. Not perfect, but usable.

I had my friend call the shop and talk to the machinist (NOT the owner) and expain the crank run-out problem. The machinist agreed with our method of checking and that the run-out was too much.

So my friend is taking the crank back this week to be fixed.

If only the owner would stay away from his shop!!

tom

 

[camaroman7d]

paulo,
No, that is not Lemans blue sorry.

Tom,
Looks like they are going to try to "make it right". My question is this: Why didn't your friend just have them do all the work? (or have you do all the work). That almost always results in a problem. I personally would have told him to take everything back to that other shop and have them assemble it, that way when the problem popped up it would be on them and not you. I understand you are trying to help out a friend but, sometimes that comes back to bite you. Hopefully everything will work out in the end.

Royce

 

[machine shop tom]

We are actually the second shop that has gotten involved with this engine. The first shop did an okay job, but the guy had some problems and contacted my friend. We can do all of the work except for the align-honing and crank work and my friend trusts us implicitly.

tom

P.S. MY 69 Camaro is LeMans blue!

 

[paulo]

Le Mans Blue! Ok Tom,paint jobs have nothing to do with metal machining.Anyhow could you get the PPG formula for a crying Camaro down here.I want to do away with the VW color its got now.By the way I had it cut 30" over,flat top Badger pistons,Z28 cam from Fed Mogul,valve job etc.Car is an original Saginaw 4 spd with Posi 3:42.Not bad for our standards.

 

[4 Jaw Chuck]

What is wrong with checking a part between centers? Thats how I do it and it gives you a better idea of the shape of the round.

Checking parts on v-blocks distorts the measured shape of the curved surface if you were to lay the measurements out on a chart.

Sounds like the crank is a trochoid shape (triangular) and is a result of hard spots in the crank exacerbated by a worn out grinding machine. I have many worn out crank grinding machines in my time, they do eventually wear out but it seems they keep getting recycled (from shop to shop) and never replaced.

Kinda like valve grinding machines with worn out chucks, don't even get me started on those.