Main bearing bolts

G

Geo.T

Member
I will soon be replacing the main bearing bolts in my model A. I see that the grade 8 bolt set sold by Snyders comes with cushioned washers. Can I still torque up to 90 lb. without problems ? Any comments?
Thank you,
George
 
You can buy "Stat-o-seal" washers from aircraft hardware suppliers or your local Aircraft maintenance facility may have them.
 
There should not be any compressible parts in the main bearing bolts. All should be steel to maintain the bearing clearance.
 
The ones I've seen are steel with a rubber "seal" in the center.

They are not "cushioned" washers as the OP suggests.
 

Attachments

  • Washer.png
    Washer.png
    7.3 KB · Views: 631
Last edited:
A hard washer and a touch of modern sealant on the shaft works as well.Torque is torque,as long as 90 lbs pulls the stretch out of the main bearing bolt it will hold the correct compression on the main cap regardless of the compression washer.
 
The new grade 8 studs are advertised not to stretch . Eighty ft. lbs. of torque has worked for me and I mostly use higher compression heads on my engines .
 
The theory behind torquing fasteners is to place the fastener in tension,to actually stretch the fastener to yield. Grade 8 phosphate coated fasteners are the standard of the engine industry, and are used in varying dimensions and torqued to a specification predicated by the dimension.Grade 8 design is harder than grade 5,less tolerant of shear,but more tolerant of tension.
 
Railcarmover said:
The theory behind torquing fasteners is to place the fastener in tension,to actually stretch the fastener to yield. Grade 8 phosphate coated fasteners are the standard of the engine industry, and are used in varying dimensions and torqued to a specification predicated by the dimension.Grade 8 design is harder than grade 5,less tolerant of shear,but more tolerant of tension.
Click to expand...

Unless otherwise noted, best tension for size is achieved when the bolt is stretched just below yield - unless the fasteners are designed to go above yield.

My VW TDI had four bolts which hold the engine in place. Two of these must be removed in order to change the timing belt (gotta love VW engineering!) And they are stretch bolts (about $8 apiece) and IIRC, they need to be torqued from new to like 275ft-lbs.

The area is cramped and the beam type torque wrench gives out at 150 - so that is what the old bolts got.

I never had a problem.

Joe K
 
People, these are not high speed, high RPM, high HP engines. Don't overthink it. Fords bolts have worked for 100 years and more. Why change them?
 
I certainly agree with Rogers, however I don't use the stock castelleted nuts as they have only a few 'full' threads. I use grade 8 or ARP nuts and no cotter pins. I've even used Model A lug nuts, machined flat. They look cool! I torque to 90 lbs., even on my race engines.
 
Cotter pins are worthless to hold torque..in the torquing process,the nut locks by bolt tension,Thus as Jim states more the thread face the better.Loctite blue is an effective way to lock a torqued nut,the anaerobic (works in the absence of air) sealant works at the load applied,the load on the fastener has to fail before a cotter pin works.
 
No , Ruth, not the head . It was mentioned earlier in this thread that model A engines that were running higher compression heads needed to torque the main bearings to 90 ft. lbs . I torque the new main bearing bolt kit only to 80 ft. lbs. like I have done with original Ford studs . These studs wouldn't get by on model A's that would be under national judging . The ones that I've used are much easier to use than original and none that I have used have leaked so far .

Just to add , the new stud kits that I used don't use castellated nuts or cotter pins . They don,t use the square ends on the front and center main bolts like original . This setup was a breeze to install and torque . This is just my experience .
 
Last edited:
Be very cautious using these. I can only speak for my own engine and one other. The counterbore in the block is too deep for the sealing washer and the diameter is not large enough for the steel washer. I realized something was wrong when I couldn't quite "click" nearing the 100 # torque. The flat steel washer was contacting a portion of the block that was not counter bored and bending the steel washer. I don't understand the reasoning to change something that worked for 80 + years when the originals are available and I doubt the grade 8's are any stronger than used originals. This puts a bending load on the bolt and won't allow the "sealing" washer to seal, which it doesn't need to anyway.

John
 
Last edited:
You must log in or register to reply here.
Back
Top