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Username Post: When is it time for a new crank?        (Topic#347461)
Raven18940 
Member
Posts: 450
Raven18940
Reg: 09-22-04
10-02-17 11:27 AM - Post#2709499    

I bought a 350 shortblock off craigslist for $100. I'm slowly taking it apart and assessing things.

One of the areas of concern is the crank. So the shortblock had been rebuilt at some point before. It's already 30 over and at least the rod journals are ground 10 under. The number #1 main bearing looks pretty trashed, but the crank doesn't appear worse for the wear. The most troubling issue is the crank snout. It appears to have been drilled out from 7/16-20 to 9/16-12. The threads do not look great and the angle is not straight. There's also a noticeable lip where the harmonic balancer ended.

So the idea for this build is I want to build some torquey grunt to push our 85 caprice around, and to have fun assembling my first engine. The engine won't see more than 2500 for sustained periods, highway cruise will be about 1500. A new cast crank is only $200 plus the cost of balancing. Is there any hope of fixing the crank I have or should I just replace it?

Crank threads
#1 Main bearing



Edited by Raven18940 on 10-02-17 11:33 AM. Reason for edit: No reason given.

 




Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
10-02-17 01:09 PM - Post#2709508    
    In response to Raven18940

The threads don't look horrible, but that bearing certainly looks like it caught a chunk of metal in it. Is the crank itself still smooth on that journal? As far as the balancer goes, if you put one on does it just slide on or is it still a good tight fit? (I'd suggest testing that with a new balancer, not an old one. I've had old balancers literally fly off of cranks that were perfect when a new balancer was applied)

"8 cylinders of why the f&@% not" - me


 
Raven18940 
Member
Posts: 450
Raven18940
Reg: 09-22-04
10-02-17 02:00 PM - Post#2709516    
    In response to Junkyardwarrior

You really think those threads will be fine? I was counting this thing out because of it. If the threads will be OK (I'll clean them up with a tap) and the slight angle won't cause me problems when I'm torquing it down then I'll press on.

I concur about the #1 main, it looks like something went through the engine. There wasn't anything to grab a fingernail on though, so I think it'll be fine with a polish.

Thanks for the tip on checking the snout with a new balancer. I have a new 305 balancer I can check it with next time I have a chance.

If this crank is good and I don't find anymore suprises (only got as far as the #2 main cap and the first 2 cylinders) It looks like I'll be able to slap this together for just bearings and rings. The first 2 pistons were a tight fit on my 0.0015" feeler gauge so those are good to go.



Edited by Raven18940 on 10-02-17 02:01 PM. Reason for edit: No reason given.

 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
10-02-17 02:07 PM - Post#2709517    
    In response to Raven18940

I would agree on the clean up of the threads with a tap. As long as you have a good sized bolt and it doesn't pop the threads out when it torques down you should be fine. Just pre check that as well before putting it in to make sure you don't assemble an engine just to have the snout chuck threads. Also, check to see what the local machine shop would run you to turn the journals a bit. Just to get that fresh surface. You can then run a slightly oversized bearing to ensure you don't have a bearing eating demon.

"8 cylinders of why the f&@% not" - me


 
Raven18940 
Member
Posts: 450
Raven18940
Reg: 09-22-04
10-02-17 02:32 PM - Post#2709520    
    In response to Junkyardwarrior

In respect to getting the crank turned, does it need to be rebalanced after that? Sorry, just trying to keep a sharp eye on costs. Since I can get a whole new Vortec 350 for $2100, I want to make sure I don't make ill advised financial decisions with this project.



 
Junkyardwarrior 
Contributor
Posts: 331

Loc: Yuma AZ
Reg: 02-25-15
10-02-17 02:35 PM - Post#2709521    
    In response to Raven18940

No, it should not need to be balanced after that.

"8 cylinders of why the f&@% not" - me


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17178
grumpyvette
Age: 70
Loc: FLORIDA USA
Reg: 03-16-01
10-03-17 07:36 AM - Post#2709619    
    In response to Junkyardwarrior

why take the chance on a crank that both non-standard and has been subjected to who knows how much stress,
cranks are fairly cheap, and its certainly going to be a whole lot cheaper to purchase and install a new crank now ,
vs repair the damage if that suspect crank breaks or throws a rod .
and because your in the engine re-build process, you have the choice and the motivation too upgrade to a 3.75: stroke version to build a 383.
that extra 1/4" is worth an easy 35-40 additional ft lbs of torque and 35-45 hp.
read the links it will save you a great deal of problems,


http://garage.grumpysperformance.com/index.php?thr...

http://www.scatcrankshafts.com/rotating-assembies/...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...


http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...



IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


Edited by grumpyvette on 10-03-17 07:41 AM. Reason for edit: No reason given.

 
models916 
Valued Contributor
Posts: 4781

Age: 67
Loc: Addison, IL
Reg: 05-28-10
10-03-17 07:40 AM - Post#2709621    
    In response to grumpyvette

past 30 and you are near the end depth of the hardening on the journals. Get a used std and have it worked. Should be millions of them out there after all the 383 conversions.



 
rumrumm 
"17th Year" Silver Supporting Member
Posts: 2075
rumrumm
Loc: Macomb, IL
Reg: 10-18-01
10-03-17 07:54 AM - Post#2709623    
    In response to models916

I agree with Grumpy on this. You don't know what this crankshaft has been subjected to by previous owners, and a new stroker crankshaft is money well-spent, especially when you are pushing a heavy car like your Caprice around.

Lynn

"There's no 12-step program for stupid."


383 sbc, Eagle, AFR, SRP, CompCams, Edelbrock, FiTECH. Dyno #'s: 450 hp @ 5700, 468 ft. lbs. torque @ 4300.

http://photo.net/photos/Lynn%20Johanso n


 
Raven18940 
Member
Posts: 450
Raven18940
Reg: 09-22-04
10-03-17 03:50 PM - Post#2709673    
    In response to rumrumm

The only reason I'm hesitating on stroker is that it will add probably close to $1000 to the rebuild as I'd need new rods and pistons with it. Unless I can sneak in a set of reconditioned 400 rods, and I've heard that may make the pistons hit the crank.



 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17178
grumpyvette
Age: 70
Loc: FLORIDA USA
Reg: 03-16-01
10-03-17 05:07 PM - Post#2709682    
    In response to Raven18940

a couple 383 sbc parts

http://www.ebay.com/itm/SCAT-SBC-CHEVY-35 0-383-5-7...
rods $260

http://www.jegs.com/i/Scat/942/9103750/10 002/-1
crank $210

http://garage.grumpysperformance.com/index.php?thr...

http://www.jegs.com/i/United-Engine-Machi ne/648/99...

pistons $217


keep in mind youll need to replace the rings, bearings and damper on any rebuild and youll more than likely need new pistons in any case,
if the bores are not in great shape , so the difference between a full refresh on a 350 vs building a 383,
with better connecting rods and a new crank,
will most likely be about $700 -$800
, once the machine work like balancing clearancing, etc, is completed.
it helps a great deal if you take the time and effort to find a trust worthy and reasonably priced local machine shop , and trust me when I say this is critical, and yes, the machinist will seem to point out endless things that should be done to increase durability, or just allow proper component function,and a good machinist will try to guide you in component selection to help avoid mis-matched parts and low quality parts being used, yes quality parts and machine work, ALWAYS COST more than you may expect them too!

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


Edited by grumpyvette on 10-04-17 06:33 AM. Reason for edit: No reason given.

 
models916 
Valued Contributor
Posts: 4781

Age: 67
Loc: Addison, IL
Reg: 05-28-10
10-04-17 08:44 AM - Post#2709739    
    In response to grumpyvette

http://www.ebay.com/itm/Chevy-383-Stroker -Kit-RECE...



 
Raven18940 
Member
Posts: 450
Raven18940
Reg: 09-22-04
10-04-17 01:44 PM - Post#2709765    
    In response to grumpyvette

Excellent food for thought. I need to finish the tear down before I make any moves. I'm going to carefully measure things (looking at expensive micrometers and dial gauges now) and if everything checks out I might not even go to a machine shop. I'm not really worried about the unknowns of the crank and the rods because I'm building a low RPM cruiser. The guy I bought it from had it in an S10 that was setup as a street rod/drag racer. So that short block has seen things worse than I'll do and didn't fly apart. It was a running engine, and I should be able to make it a running engine once more.



 
MikeB 
Ultra Senior Member
Posts: 10058
MikeB
Loc: Plano, TX
Reg: 08-28-03
10-06-17 01:40 PM - Post#2709945    
    In response to Raven18940

You can get an entire balanced assembly from Eagle for around $700, or a better one from SCAT for around $1,100.

My truck's 355 has the entry level Eagle kit, which 2-3 years ago cost less than $700 at Jeg's including shipping. It came with rings, bearings, and even a flexplate. I don't see any issues with it when used in a street-only vehicle.

If I had a do-over, I'd probably get a 383 kit from SCAT, with their 9000-series crank, bushed rods, and D-dish K-B pistons, but at the time I was trying to build a $1,500 engine.


1982 C10 SWB pickup: Unmolested base truck, original paint. Originally had 250 six and 3-on-the-tree
Now has 355 with Vortec heads, RamJet roller cam, LS6 beehive springs, TH350
Retired, but working part-time on 50s-70s cars & trucks.


 
Bad56Sedan 
"11th Year" Gold Supporting Member
Posts: 931
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
10-09-17 08:50 PM - Post#2710360    
    In response to Raven18940

Take the crank to a reputable shop.
Access the costs of the crank snout bolt issue repair and verifying the crank is not cracked.
Costs of mains and rod bearing checked, polished or turned.
If these costs are lower than a new crank and you don't mind a 20/20 crank go this route.
The condition of the rod bearing is not good.
Not just the scratches but the appearance of disperportionant wear on one side.
The additional cost of having the rods resized is as important
as using new bearings.



VC56S 2 door Sedan, 38 Years



Edited by Bad56Sedan on 10-09-17 08:51 PM. Reason for edit: I am not a electro mechanical engineer

 
models916 
Valued Contributor
Posts: 4781

Age: 67
Loc: Addison, IL
Reg: 05-28-10
10-10-17 05:18 AM - Post#2710378    
    In response to Bad56Sedan

Check the thrust plate to rear main play. Lots of mile could have taken its toll on that part.



 




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