Main bearing bolts
 

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

Re: Main bearing bolts
 

Snyders thinks they can http://www.snydersantiqueauto.com/Pr...shaft-camshaft

Re: Main bearing bolts
 

Can someone tell me the theory behind "Pressure sealing washers".

Re: Main bearing bolts
 

You can buy "Stat-o-seal" washers from aircraft hardware suppliers or your local Aircraft maintenance facility may have them.

Re: Main bearing bolts
 

Prevent oil leak UP the center main bolts and run down the side of your motor? A known defect of the cotter pinned setup.



Joe K

Re: Main bearing bolts
 

There should not be any compressible parts in the main bearing bolts. All should be steel to maintain the bearing clearance.

Re: Main bearing bolts
 

The ones I've seen are steel with a rubber "seal" in the center.

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

Re: Main bearing bolts
 

I use them and they have worked excellent for me .

Re: Main bearing bolts
 

That's what I thought although I don't have that problem.

Re: Main bearing bolts
 

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.

Re: Main bearing bolts
 

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 .

Re: Main bearing bolts
 

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.

Re: Main bearing bolts
 

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

Re: Main bearing bolts
 

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?

Re: Main bearing bolts
 

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.

Re: Main bearing bolts
 

80lbs on a head? Or am I reading this wrong?

Re: Main bearing bolts
 

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.

Re: Main bearing bolts
 

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 .

Re: Main bearing bolts
 

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

Re: Main bearing bolts
 

He asked about main bearing bolts. Somehow this evolved to discuss head studs.