Main bearing bolts

[Geo.T]

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

[Bruce of MN]

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

[daren007]

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

[daren007]

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

[Joe K]

Originally Posted by daren007

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

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

[Bob Bidonde]

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

[Ruth]

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

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

[Purdy Swoft]

I use them and they have worked excellent for me .

[daren007]

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

[Railcarmover]

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.

[Purdy Swoft]

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 .

[Railcarmover]

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.

[Joe K]

Originally Posted by Railcarmover

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.

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

[James Rogers]

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?

[Jim Brierley]

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.

[Ruth]

Originally Posted by Purdy Swoft

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 .

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

[Railcarmover]

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.

[Purdy Swoft]

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 .

[aermotor]

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

[SteveB31]

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

[50Trucking]

My main bolts are square and I can’t get 90 lbs of torque before the edges of the bolt head shear off with a 16 point socket.

[oldspert]

Originally Posted by 50Trucking

My main bolts are square and I can’t get 90 lbs of torque before the edges of the bolt head shear off with a 16 point socket.

Buy a 9/16 square point socket.

[Bruce of MN]

I can’t remember, can you get a crowfoot wrench on it?

[Flathead]

The original bolts were a snug fit in the block. You would tighten up the nut, after positioning the cotter pin hole in the bolt for best installation. This snugness is what centers the main cap on the block, there are no dowel pins or other methods to keep the cap in position. The popular grade 8 bolts are looser in the block and do not center the cap. Just something to think about.

[Bob Bidonde]

Torque of a structural joint should be to 75% of the bolt / stud yield strength. This reduces the alternating stress range (varying tension) induced by the reciprocating parts in the engine. Reducing the alternating stress range significantly improves the joints fatigue life.

There should be nothing in the joint that compresses before the bolt / stud reaches its maximum loading. If there is, the joint looses its preload and the strength and fatigue life of the joint is threatened.
I strongly suggest that the original joint design should not be altered by the addition of any none stock parts.
Oil leakage from the exposed nuts is rare in my experience, but can be easily sealed by coating the nuts with an epoxy paint like POR15.

[nkaminar]

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On my Burtz block I used some O rings that had a small (thin) cross section. They were completely compressed into the hole so that the fastening was metal to metal.

All steel has very much the same coefficient of elasticity up to the yield point. It is 30,000,000 psi. The grade 8 bolts have a higher yield point than grade 5 or lesser grade.

[Dan McEachern]

Are you guys really pulling main bolts to 100 ft-lbs ???????????

[Flathead]

No.

[Gene F]

What Bob said goes for me too. I have a center pressurized main in my engine, and the microscopic amount of oil that may get past the shank of the bolt is insignificant. In fact, I have never even noticed such a thing on my car. I used to fix things (and equipment) for a living. We used to say tinkeridus has ruined a lot of equipment.

Just put the engine together, do a good job, and go on. No magic washers needed.