251 connecting rod bolts

[karl head]

Hello everyone I am finally getting my engine back together. I have a question with regards to the con rod bolts, I was reading here in one of the treads about washers under the nuts and was wondering if the 251 had these, there were none on this engine when I took it apart. I was hoping some one could clear this little mystery up for me. I have the ones off the 218 I stripped but am reluctant to add them if they are not required.

Thanks Karl:)

[Tom Skinner]

Karl,

I have had several 251 cu. in. rebuilds there is a lock washer for the connecting rod bolt/nut configuration. My Chrysler Service Manual shows them my Chrysler Passenger Parts List shows them as:

9-31-8 page 191 WASHER, Connecting Rod Bolt Lock (S.,.387 I.D. x 17/32" O.D., 5/64"inch thick) (bearing cap) Original Chrysler Part Number 668555

12 each

Tom Skinner

Huntersville NC

[Tom Skinner]

Karl,

The 3/8" cap screws/nuts torque at 45-50 ft. lbs. (page 311 Chrysler Service Manual for C28-C40 Automobiles)

Tom Skinner

Huntersville NC

[karl head]

Thanks Tom

That's a great help, I had read at tread here about it a very little while ago but could not find it today, and wanted to make very sure I did this right the first time. I'm glad I kept all the 218 parts separated even kept most of them in groups so I can just take them off the other conrods.

Karl

[Tom Skinner]

Karl,

I rebuilt my first 251 twice the ten years I owned it, I never replaced the lock washers at the connecting rod nuts. I had no problems, however, conventional wisdom now is to replace with new lock washers when rebuilding.

I read this along with replacing head bolts as well during a rebuild. Also to chase the threads in the block with a tap to ensure accurate torqueing.

The source was Vintage Power Wagon. wwwvintagepowerwagons.com

It seems to me that they are giving good sound advice. They are also selling these parts. as I am older now and a bit more well healed so to speak it would seem smart to me to do those things now. Back in the 70's and 80's when I did my flat head rebuilds though I used grease on the copper head gasket (not copper head gasket spray) used my old lock washers, never chased the threads, used my old head bolts and never had a bit of a problem there. Maybe I was just lucky or maybe all that advice is overkill you decide.

Tom Skinner

Huntersville, NC

[John-T-53]

I have a set of 230 rods with these lock washers. Not sure if they're really needed for locking purposes - back in the day the engineers were concerned about the con rods coming apart, in some engines the nuts were secured with a wire too. Now days we lube 'em up with moly.

In any case, if yours have the lock washers, keep 'em. There should be a recess where the washer sits under the nut, and the nut will not seat properly without.

[Dodgeb4ya]

Rod caps using the special sized factory lock washers have a slight counter bore the lock washers seat into.

Edited September 30, 2012 by Dodgeb4ya

[karl head]

Thanks again to everyone for their information and quick replies. I will be torquing the bolts up today and will look for a recess in the rod cap if there's no recess I will put them back as they were if there is I will install the lock washers off the 218.

Thanks Karl

[Don Coatney]

Look closely at the rod bolts and lock washers on my 251. As Dodgeb4ya stated these lock washers are specific to these engines and not off the shelf.

[John-T-53]

I just discovered one of my washers is broken in half on rod #1.

I'm gonna give VPW a call first thing tomorrow; if anybody knows of another source, please share.

Thanks,

[Tom Skinner]

John,

V.P.W. has them and perhaps Terrill Machine, Inc (254)893-2610

They are specialists in Chrysler Parts out of Texas:)

Tom

[karl head]

Its hard to tell from my fuzzy pics but I was hoping to show the different style rod caps. the one on the engine is the cap from the 251 it has no recess for the lock nut the one on the engine base is the cap from the 218 it has the recess. I rightly or wrongly went without the lock washer as there was not one on the engine when disassemble.

Thanks Karl

[Rusty O'Toole]

What about reusing the old lock washers with a drop of Loctite for insurance?

Tom not only are we a lot older so are the motors. More corrosion, more wear, metal fatigue etc.

It can't hurt to be meticulous about cleaning chasing threads checking for warped heads etc.

[karl head]

I did consider using the old washers off my 218, however the rod cap didn't have a recess for the washer and when I disassemble this engine it did not have any washers. I did chase all the threads and measured all the bolts for stretch so I am hoping it will be okay. I don't recall ever using or seeing lock washers on a connecting rod bolt on any other engine I have worked on.

Thanks Karl

[Dave72dt]

Sometimes changes are made in production runs without updates in the service manuals. I've seen engines with and without lock washers, castellated nuts with cotter pins, double nutted with pall nuts for the double and locking nuts, all on the same series of engines, different years of production.

Replacing one lock washer means you replace them all. If it fatigued and broke, the others have been through just as much service and should be replaced as well. Myself, I'd be inclined to get a set of new nuts from a newer engine that were self locking. 3/8 x 24 is common as well as the 40 to 45 #ft of torque your engine uses.