Technical Crankshaft problems-Chevy 261

Hello All,
I've got an issue with the crankshaft for my Chevy 261 build. After getting the crank back from the machine shop a buddy and I went to work installing it in the block. We did the plastiguage and got the following measurements:
Main #1-.002
Main #2-.001
Main #3-.001
Rear Main-.002 (before rope seal)

Tech manual stated that anything between .005-.0005 would be acceptable, but recommended shims for anything less than .001.

At the time we installed the rope seal, lubed up the bearings and began installation only to find the crankshaft won't turn if we got all the bolts passed finger tight. I installed the shims this morning on the # 2 and #3 mains which only helped slightly. I even tried shimming the #1 main to see if it made any difference, but not much. Also, if I start to tighten the rear main by itself it'll lock up the crank. Should I order another set of shims or does anyone know of any tricks with this situation? Any advice or input would be highly appreciated.

 

I had a similar problem when The 235 in my Hard Top was machined for a rebuild. The block had to go back to the machine shop for a line bore. That did it.

 

Watching. I've got a 235 with main oiling issue's. Only history I know prior to purchase of vehicle is engine was rebuilt at a collage. Maybe they missed something?

 

I hear ya. I'm beginning to think about doing the same thing. In that case, would it be okay to remove the rope seal and then reinstall it after the line bore?

 

What was the explanation as to why it worked before first machining was done but not after?

 

I'm not sure I understand your question. Are you asking how the crank was able to turn before machining? If so it didn't...two of the cylinders were rusted so I disassembled everything then took it to the machine shop.

 

And I just realized you were responding to the other post in this thread, not mine specifically. My mistake.

 

I was actually asking this of 52 Hard Top

 

It's all good. I have the same issue when reading but worse.

 

Hey guys, I see you're asking me. To be honest, I don't know why! When I dis assembled the engine, I found no shims when removing the main caps. I do remember the machine shop asking me that. You would had thought that there may have been and I should have kept them to replace them? The engine had to be original as the pistons I removed had no markings saying they were oversized. The block was bored and I do believe the mains were also machined. All new bearings were installed and when the crank was installed and the mains tightened, the crank wouldn't spin. It was thought the thrust bearing was the issue. It was not. The machine shop recommended the engine should be line bored. so I returned it, and when it was done the re assembly went along fine. I've been driving her since 2004 with the rebuilt engine and no troubles.

 

Being 52 I understand the need to ask but is it 52 engine? OP's 261's are 1954 and up and do not use shims.

 

I'd pull the rope seal back out and see if makes a difference.

 

Hi Johnny, no it's a 54, 235.

 

All 4 main Chev 6 engines have shimmed main caps - that's how the bearing clearance is adjusted.

 

Years ago I was told different and your right, they do need shims after some reading. Sorry guy's.

 

Here's another forum I just found with related issue. https://www.chevytalk.org/fusionbb/showtopic.php?tid/247887/

 

If you could turn it with everything torqued without the rope seal I’d say you put in the rope seal correct. Mine are hard to move at first but once it turns it’s ok. Bring them down one at a time adding 20 psi to the torque on the bolt and keep turning it, if it always turns all the way until all 4 are torqued it is with in spec. I personally have my crank guy, Marine Crankshafts in OC give .001 to .0015 extra clearance. I’ve never used shims on a 235-261 after 1955.

 

Thanks for putting this link up, it was very helpful! I'll be meeting with a buddy on Friday to pull the crank, remove the rope seal, reinstall, and see if it turns. I'm hoping that's all it is. Appreciate the input!

 

Will do! If it is the rope seal do you have any recommendations on installation to make sure it's not locking up the crankshaft anymore?

 

I did a lot of reading yesterday. These stovebolts have a lot of lost history and fact's that do not transfer from year to the next.

 

Rope seals are a art but if you pull the cap and the seal is mushroomed out then there was probably too much left standing proud of the groove or packed too tight.

 

Did you use something to roll the rope seal into the groove? Like a reasonably large diameter socket that you rolled back and forth to press the seal into the groove before you used a razor blade to trim the ends?

 

What year 261 @inline_sixer ?

 

What seal did you use? Try a seal from BEST GASKET, they have very good instructions on how to install.
I find its best to lay the seal in the block, install the crankshaft and press the seal down with the cranks weight and rubber hammer. Pull the crank back out then trim the seal according to instructions. Once trimmed, pull the seal out of the block and install it in the cap, then repeat the first steps for the block half. Add just a touch of smaller to the cap face where it meats the block, put nothing on the seal. A light coating of oil around the crankshaft seal area will help.

 

^^^^^ That's why asked about year. There's a dividing line at 56 as to what to use.

 

Just an idea. If you have to align bore it, think about having a crank seal from a Ford diesel installed. There is a video of the work done on You Tube. The work done was at R and D machine in Costa Mesa.

 

Alignboring a Chev 6 better be done by someone who knows his shit. 4 different sizes. Evans Machine here in So Cal has the setup. I remember them in Santa Ana but they moved...

 

That's awesome. Only 4 miles from girlfriends home and 56 235. Thanks!
Evans Speed Equipment
2550 Seaman Avenue El Monte, CA 91733 (626) 444-2838

 

It's a '61.

 

I believe it's a Fel Pro. I got it off Rockauto as part of the full gasket set. Here's the link...
https://www.rockauto.com/en/moreinfo.php?pk=123770&cc=3438713&jsn=2221

I'll try your tip about using the crankshaft's weight to install the seal, thanks! I'm guessing once the crank is laying in the block I can just tap it around the circumference of the rear journal with the rubber mallet?