My shop has advised that my new Eagle forged crank has main that measure .001 under! He said I can buy bearings that will match. Thats all well and good but I am kinda pis&%$d!
I am going to call them today and see what happens.

So what should the tolerances be for this anyway, + - .0005, or less?

 

Above not uncommon with any of the bargain hotrod cranks of asian heritage ... so are hacked up counterweights that can make balancing more of a chore & more $ ... so is out-of spec index aka phase ... and out-of-spec stroke length ... and out-of-spec journal width ... and out-of-spec thrust ... better get a crank machinist to check it all over real close.

 

I'm not going to get too far indepth on this because I don't want to say someone "might" be a little off. IMO .001 on a mic is a pretty big gap to mess up by being a little to tight on your mic clutch or feel or what ever. Still every one has a different feel on a mic. You can take the same crank and have it mic'd by 10 different people and you will get 10 different measurements (even if they all used the same mic), by a few tenths.

First I would suggest your machinest put some standard brgs in the block, set his dial bore gauge off the mic reading he got and correctly measure the actual clearance. Because saying for instance a rod journal is 2.099 when it should measure 2.10 dosen't mean your going to really have .001 extra clearance in the real world. Measuring things with nothing to correleate that measurement to but a spec in a book is asking for trouble. Espc when everything in the rotating assy is aftermarket manafacture and new.

I know everybod is so posed to build to that spec but in the real work they really don't. Different brands of brgs will measure different on the clearance sometimes by quite a bit more than .001. Federal Mongrel are slightly tighter on the clearance than say King in my experience (hence why I won't use FM brgs). Also Clevite has been tighting up their clearance in the past few yrs causing race engine builders alot of headaches with their brgs in reguard to clearance (espc in Alum rod engine).

Who knows Eagle may have been compensating for that as most people use Clevite brgs they got from Summit or Autozone and just slap stuff together using plastigauge or worse with out measuring it all. Eagle may by rights be off that day, I know it happens. I got a billet Bryant crank in the shop a few moths ago that was about .005 too BIG and I had to polish it to get the correct clearance. Not something you expect when you pay almost $3500.00 for a crankshaft.

Also every engine builder has their own idea about how much clearance to run on a street engine or a race engine, steel rods or alum rods, ect, ect, ect.

Just as an example as for how close it should be tollerance wise - an Eagle 4340 crank I measured the other day for an oval track engine I am building was within .00015 from journal to journal but measured about .0005 on the small side from the book spec (on both the rods and mains). As spec'd it came out to .0025 clearance on the rods and .0035 on the mains with King Pro Series brgs when I measured actual clearance with a dial bore gauge in the Mains and Rods.

Jackson
As for its Asian heritage that is true, it was forged in China. The rest of it is just BS. I have gotten cranks from GM, BRC, Callies, Crower, Bryant and Kings that were all "off spec" at time or the other in my life. Anybody can make a mistake and I know for a fact Eagle sells way more that are right than F'd up. They would be out of businees if they couldn't sell a good prouduct most of the time and deal with the bad ones when they happen the best they can.

To the OP
If your Machinest figures his clearence is wrong with the crank as shipped then call Eagle and I am sure they will take care of you.
Will

 

Since the above poster commented on bearing differences, as an FYI, Eagle recommends and provides Clevite 77 bearing with their 4340 crank kits. Rod bearings (part number CB663H) and main bearings (part number MS909H). I had picked up a used Eagle LW 4340 very cheap and sent it to Henry Velasco (Velasco Crankshaft) for some work and I asked Henry to verify all specs, index, throw, pilot hole size etc prior to work since I had heard numerous horror stories. He called to say it was dead on and proceded with the custom work.

 

The third poster is right in many ways. When you start measuring bores and cranks, you get a little different reading everytime you do it.

My eagle crank measured out as far as i recall.

 

Nothing wrong with a .001 under. Much better to be here than the opposite. Use 30W oil. Some of my shafts measured more than that {Moldex Tool} but we use 70W oil and spin the hell out of them. Bearings are available to compensate them anyway.

 

My machinist said it's a good crank but it's not a high end crank so it can happen. He said I can return it but who knows what I will get in return. He recommends getting the .001 bearings to match and move on. Because at that point it is essentially the same thing. Maybe he is right. Maybe I shouldn't be upset that the crank is uniformly under by .001 but I should be happy that my machine shop is good enough to know, and cares enough to tell me to slightly alter the bearings I buy to match. In short my engine is in good hands.

 

seems you've may've gone beyond that.If you think that's BS that's your choice ... but I think it's wrong to portray bargain asian cranks as having similar rate of nonconformity as better stuff. Thing here is ... none of us KNOWS ... none of us have any meaningful data for an accurate comparison ... only what we, our colleagues & machinists are seeing.

I have worked on red chinese military radial aircraft engine (internal) ... it is very well made & quite durable ... the finish on its parts & pieces are great & bear no resemblance to bargain asian cranks. So, my intent is not to bash asian ... but to finger bargain ... afaik all of today's bargain cranks have asian heritage. Asian mfgs are quite capable of producing 1'st quality ... US importers can choose to have their asian suppliers up their quality ... preventing that is US importers' greed.

As for managing over or undersize journals ... I fit bearing halfs ... a few months back built a ct motor with new GM crank had Oversize main journals ... I did polish it but not to remove O/S ... I used O/S half shell. Same goes for undersize ... I use whatever combo of half shells I need. I use good gaging too; not pg.

Best to thoroughly check out any crank, regardless of brand/$. Everyone makes mistakes; some more than others.

Call it BS if you wish, but on whole ... I'd expect a month's production of bargain cranks to have higher nonconformity rate AND a wider tolerance than a month of pricier cranks such as bryant, crower, moldex & the like.

 

No engine builder worth his salt would ever assume clearances to be within the desired tolerance range without actually measuring, regardless of the pedigree of the crank in question. It's part of the blueprinted build process to verify everything, identifying whatever is out of spec and addressing those issues.

Your builder surely understands that, but then some people like to dramatize such matters so that others may marvel at their expertise. Don't loose any sleep over anything like this unless he tells you something is out of spec and he didn't do anything to correct it.

Of course, having gone behind a "highly reputable" builder or two and found things out of spec, I've long insisted on doing all of my own final assembly work, with the machinists knowing full well I measure everything and that I'll be back if anything isn't up to snuff.


BTW, I've got an Eagle crank and rods for my 496, as they are literally just minutes from my house, so I'm not too worried about customer service if I chance to find something wrong.

 

This is 100% correct. I have first hand knowledge that with, and without a little help, Chinese manufacturers can make first quality product. If we in this country are going to rest on our laurels and think they may be cheaper but not better, we have a rude awakening. Problem is we may not wake up until it is too late. They make what we ask them to make.

I appreciate my machine shop and will take their advice and buy bearings to match the crank. Cause I'm not going to spend another nickel on another ungrade!!

 

IMHO if the crank is .001" under everywhere and i could buy correct bearings then not a problem. Now if was +/- .001" all over the place may be a concern.
For your peace of mind Pontiac would send out thier RAM AIR Hi-Po big blocks in the late 60's with over .015" loose clearance from the factory. Thats what i recall and I may be wrong but i will look that up again if u request. I wouldn't blink an eye over installing with an extra .001" clearance - it will only aid in break-in. U may loose 1K or 2K of engine life though.

Good luck,
cardo0

 

A couple of years ago a friend of mine paid big bucks for a rebuild of his SBC in a 91 'vette. He had me go along to the machine shop during the build to talk to the owner. I am not an engine builder, merely a backyard gearhead; however I started off life as a mechanic, even did some machine work. Then managed to get a few degrees in engineering, I now work as an engineer drilling offshore and building drilling rigs for an oil company. Hence I know enough to be dangerous!

Any how I asked this guy aobut the crank. He used only US forged pieces, such as Crower. Dennis Farmen (spelling?) of Farmen racing engines in Houston was so excited about the work he put into this 388 that he flipped the engine over and pulled the pan to show me. We talked cranks, pistons and rods. However he uses Eagle rods as many others do; appareently they are a great rod; period.

My question is: I thought Eagle was Chinese forged adn US machined? Hence with the final machine work done in the US you more likely to get a quality product, correcct?

By the way I am writing this from Korea; Samsung Shipyard where we are building a drillship to drill in 10,000' in the North Sea. I can assure you that the Korean yard can produce a fine product. I even stay at the Samsung Hotel, which is 5star and better than most in the US. Its a nice place to work!

carbster

PS the only problem is that nobody here even knows what a Corvette is! I have seen one Boxster!

 

Memphis, TN has a significant history in the crank and cam industries, so it's no surprise that a company such as Eagle is in our backyard. I haven't yet toured the Eagle facilities in Southaven, MS (a suburb just south of Memphis), but I understand that they receive semi-finished cores and complete the machining here.

The shop I buy from is almost literally a stone's throw from Eagle's location nearly on the Mississippi River, and only a few minutes drive from my home. Needless to say, with no additional shipping expenses I can buy Eagle components at very low prices.

 

Cardo,
It is .001 under on all. I think your right because my machine shop said something similar. He said he prefers I get the .001 bearings and tighten it up a little. I guess that means it would work as is. That's why I will buy the .001's and call it good. Thanks for the post.

 

The crank has a tolerance measured in the 10 thousands of an inch. For example a 400ci crank the mains should measure between 2.6484" and 2.6493" a spread of only .0009", less than .001" that your engine builder says you crank is out.

Now usually these cranks from Eagle and Scat are within these tolerances but sometimes very near the limits. Now if the main crank bores in the motor are within tolerance everything should be OK to go with standard bearings. But even then you need to measure properly because the crank bores could be on the upper limit and now you might need .001" bearings anyway.

My new Eagle crank is way down to 2.6485" but they are all the same so that helps.

Now I haven't got to this part yet but I would question anyone that builds a motor before doing this. This is how you get your mains/oil clearance.

First you figure out what oil clearance you want , for street / strip I try and get between .0025 and .0035" the higher the RPM's and power the more clearance you want.

Now you put your standard bearings in ( if you are within tolerances on the crank and main bores ) and you torque the main caps down. With a bore gauge you measure the inside bearing diameter at 90 degrees from the parting line. You take this measurement and you subtract the crank journal measurement for this main and you have your mains/oil clearance.

It is only at this point do you determine whether you need .001" bearings or more

 

Agree with MotorHead (nice post). For anyone doing this themselves, if you don't have a bore gauge, snaps will do. Measure more than once and average out your findings. If you don't have mics there's Plastigauge, which will show if you're in the ball park, but you really ought to get your hands on some instruments.

And, if the clearance isn't where you want it, break open another set of bearings, up or down a thou, and try again. Should you be about 0.0005" either side of where you want to be, use halves from each set with the thinner shells in the caps.

Now, I know a lot of guys don't want to end up with an extra set or a couple of broken sets of unused bearings laying around after a one off build, considering that a money down the drain. But, if you want to do it right (and you do, don't you?) sometimes that's just part of the price of admission.

One thing that might be noted, it would be pretty easy to make a 0.0002" measuring error which seems to put your crank just outside the normal range of tolerances where it might be just within...



BTW, AWilson, I do not agree with a general view to tighten up clearances a thou. What does your builder know that the General doesn't about this? Stay within the specs. If you're building for power and/or top end, that would be on the looser end of the scale (larger clearances). Should your builder put your engine up "tight", you will likely be disappointed with performance if that's your goal.

 

Great posts. It's appreciated.
I will ask my builder but I believe he is actually right in line with what you guys are saying. Thats why he wants the -.001 to tighten it up to. He says the journals in the block are ok. I will give him a call tomorrow.

 

If he took alll the measurements like he should ( believe me not all do ) and told you that you needed .001" bearings then he is doing his job properly.

Ask him what he measured the mains / oil clearance to be, if he doesn't give you a straight answer then ask him how he determined you needed .001" bearings

 

All good advice from the usual suspects, as usual

This has unfortunately been my experience with the Eagle cast cranks, but for a forged crank there's absolutely no excuse for that type of variance. Hopefully they've also had a good look at taper, etc. IMHO, it goes back - period.

I have NOT seen this issue with SCAT cranks.