Crankshaft tightness

Technical Question and Answer - On topic to 71-74 Plymouth B-bodies only.

Moderator: Site Administrators

Post Reply
User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Crankshaft tightness

Post by Smellslike1974 » Wed Aug 18, 2010 11:11 am

How tight should a crankshaft be?

Put In new main bearings in the other day.When i torqued the mains down I was spinning It after every torque,making sure everything was spinning correctly.After i did the rear main the crank was really tight.The seals are installed properly and all but its really tight.I can still rotate it but it takes a lot of effort.I must have had the crank torqued 3 times so far making sure it wasn't my bearings and seals.I'm using lubrication.Cranks out right now until I get my cam bearings in. :roll: Is this normal?should i skim a tad bit off the bottom of the seals so its not so tight?
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

User avatar
BuckNeccid
Satellite Sebring (RH)
Posts: 70
Joined: Wed Jan 14, 2009 9:53 am

Re: Crankshaft tightness

Post by BuckNeccid » Thu Aug 19, 2010 9:51 am

Make sure the oil passages on the crank were chamfered. I had a crank turned locally and they didn't chamfer the holes. When I picked the crank up, I asked them about it, they said it wasn't needed, and they guaranteed it to be ok. I was MUCH younger. Installed the crank and noticed it was pretty tough to turn over, sounding about like what you're describing, fired it up for break in, and it ran about 5 minutes before it locked up, HARD. I pulled it down, found bearing material shaved off the crank going thru the passages and into the next bearing. When I took the crank back to make them replace it, what I got was "It's been installed, there's nothing we can do about it" :shock:

User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Re: Crankshaft tightness

Post by Smellslike1974 » Thu Aug 19, 2010 2:18 pm

Everything Is fine dealing with the crank and bearings, I made sure of that,honestly I was obsessed about that.The crank was in and out being torqued and then undone making sure nothing harmful was happening.Nothings catching,grinding,rubbing raw,en even or anything.Its just really tight when the rear main goes on with the seals.After my cam bearings are installed Ill put the crank back in and Ill record how tough It spins.Maybe Its normal I just need to know for sure
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

1bluegtx
GTX (RS)
Posts: 268
Joined: Fri May 06, 2005 1:05 am

Re: Crankshaft tightness

Post by 1bluegtx » Thu Aug 19, 2010 5:59 pm

Dont mess with the seals it will just lead to problems down the road.Heres what i would do first:Check every bearing with plastigauge to be sure the clearances are within specs,make sure everthing is perfectly clean and reassemble using motor assembly lube (on the seals too) not just oil.

BRIAN
Its not numbers matching
It doesn't run on pump gas
And it doesn't purr like a kitten
11.73 at 115mph

Elvad
GTX (RS)
Posts: 108
Joined: Thu Aug 06, 2009 5:40 pm

Re: Crankshaft tightness

Post by Elvad » Thu Aug 19, 2010 10:41 pm

Sorry, but one test for a bent crank or poorly machined assembly is a tightness in a part of the rotation of the crank. Make sure all bearings are seated correctly, including NO OIL under the bearing shells installed in the block. Re check everything the machine shop did yourself. Mic every journal, plastiguage every bearing assy. Don't run that assembly, you have a problem. I have seen an incorrect ring gap cause rotational problems (too tight) check everything twice, DON'T RUN IT, you have a problem.

User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Re: Crankshaft tightness

Post by Smellslike1974 » Thu Aug 19, 2010 11:47 pm

Well i never said anything about a shop doing anything regarding my crank or bearings,...

I have said before I have had a machinist(who is also a mopar guy) measured everything for me before I even ordered my bearings.

The bearings are fine,crank was straight.nothing is abnormal as far as they go.I have checked them many many times.And of course I'm using assembly lube...
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Re: Crankshaft tightness

Post by Smellslike1974 » Fri Aug 20, 2010 12:11 am

i read online that some builders measure the resistance of their crankshafts using a torque wrench not sure how to go about that though.And btw my pistons aren't installed yet.All i have Is the crank torqued down when this problem occurs.
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

User avatar
quapman
GTX (RS)
Posts: 217
Joined: Wed Mar 14, 2007 2:57 pm
Location: Asheboro, NC
Contact:

Re: Crankshaft tightness

Post by quapman » Fri Aug 20, 2010 6:28 am

Did you lube the seals, too?

User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Re: Crankshaft tightness

Post by Smellslike1974 » Fri Aug 20, 2010 11:36 am

Yesss
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Re: Crankshaft tightness

Post by Smellslike1974 » Fri Aug 20, 2010 2:13 pm

I think I have some good news.I torqued all the caps down again.And this time its not that tight,tight but not crazy tight like before.I did nothing differently,everything's the same.Like I have before I checked all of my bearings and they are all fine.Could It be the the seals were just so hard from sitting in the box and they softened up a bit from the torquing and the oil?When i first found out how tight it was I have had my crankshaft sitting in my engine coverd up not torqued.I last messed with It a week ago.I guess seals need to be broken In also.haha

Anyway for a typical crankshaft how tight should It be?I can wrap my pinky finger in one of the holes on a counterweight and rotate it that way,couldn't do that before,now i can.Id say that's a good thing.
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

Elvad
GTX (RS)
Posts: 108
Joined: Thu Aug 06, 2009 5:40 pm

Re: Crankshaft tightness

Post by Elvad » Fri Aug 20, 2010 4:54 pm

Maybe the rear main bearing you have is mispackaged and is an undersized bearing, like a ".010 under that could certainly cause that problem. I am guessing you have a stock piece and just refreshing the motor? Install the bearing, without the crank, and mic the inside diameter, then measure the crank journal, that should give you the answer.

User avatar
Smellslike1974
GTX (RS)
Posts: 2024
Joined: Wed Nov 14, 2007 9:12 am
Location: south new jersey

Re: Crankshaft tightness

Post by Smellslike1974 » Fri Aug 20, 2010 10:52 pm

Like I said before the bearings are fine.2 people i know who have built engines are gonna be here over the week Ill see what they say.Like my last post i think the problems solved.that seal isn't so hard now.
"Sunny D"-1974 Plymouth Satellite Sebring With Sundance Packaging

User avatar
JosephGiannini
GTX (RS)
Posts: 130
Joined: Tue Oct 21, 2003 9:40 am
My Cars: 1972 roadrunner 340 4 barrel with 727
Location: washington dc

Re: Crankshaft tightness

Post by JosephGiannini » Fri Mar 11, 2011 11:27 am

one word plastigauge?
if the plastigauge says your good your good.
I own a 340 850hp Dick landy industries spec engine god rest his soul.
A Mopar god Is dead.
1972 roadrunner.

User avatar
72 U Boat
Satellite Coupe (RL)
Posts: 16
Joined: Sun Jan 30, 2011 1:59 pm
My Cars: 1972 RR/GTX, 1972 SSP 400 4-Barrel
Location: North Seattle, Washington

Re: Crankshaft tightness

Post by 72 U Boat » Fri Mar 11, 2011 12:10 pm

Try pulling the rear main seals out and then re-torqueing the mains and see if that makes a difference, if it does then it the seals and not to worry, if it doesn't ... then you've got problems!
Well, I don't know if your like me, but I know I am!
67 Belvedere 1, 440/727 05 Jeep Wrangler 99 Ram 4X4 Cummins
72 RR/GTX, 440/727 08 Mazdaspeed3
72 SSP, 400/727 96 CBR 1000F
I definitely need more space!

SureGrip
GTX (RS)
Posts: 143
Joined: Sat Mar 20, 2004 11:04 pm
My Cars: 71 SSP....lots of parts
Location: Central Md.

Re: Crankshaft tightness

Post by SureGrip » Mon Mar 14, 2011 12:33 pm

JosephGiannini wrote:one word plastigauge?
if the plastigauge says your good your good.
What he said.

But, if you can spin it with your pinky , you should be good...it's not going to free-spin like a bike wheel, but I would deff check all clearances with plastigauge...it's dirt-cheap insurance.

Good luck
One day - 1971 Road Runner clone

Post Reply