what grade should engine support bolts be ?
 

have to replace many of mine, 454-420 engines. What grade bolts should I use? I went to a marina today, they did not have any and told me to get some at places like home depot !!! Went there, no stainless bolts first, and second, what they had was all grade 5. How many kind of natch on bolt head should I see according to the right bolt grade?

Thanks!

This is where I get mine but usually purchase by the box.


http://www.dlilly.com/

Bolt grade identification http://shopswarf.orcon.net.nz/boltid.htm

I would go with stainless, make sure you put anti-sieze on the threads, or they may become self-locking bolts!!!:D If you couldn't get stainless, grade 8 would be the other choice. Grade 5 is a waste of time for motor mounts.

Lowes in my area of Houston have Stainless Grade 8 bolts..

My under standing has always been that you do not want to use stainless for motormounts because of the fact that stainless is more brittle and has a tendency to shear off.

As far as know, stainless does not come in grade 5 or 8.

I know whatever you put in there has a tendency to rust but stainless is weak, I wouldn't trust stainless lag bolts to hold my motor mounts.

Same here... I always use steel with nylock nuts and washers on both sides. I've seen people use stainless cause it looks cool but stainless is soft compared to steel.

NO STAINLESS.....I learned the hard way. Sheered them right off and motor was lying in bildge! Grade 8.....

Do not use stainless for engine mount bolts! The sheer strenght of stainless in fairly low, the will fail. Use Grade 8 carbon alloy steel, look for 6 hash marks at the points of the hex bold head.

I quick look at Mcmaster Carr only show steel for grade 8

this is interestin Arp does list there Sainless as having better properties then grade 8 by about 10%

http://www.arp-bolts.com/Tech/TechMetals.html

Quick Reference Guide to Fastener Materials
Material ARP Uses? Yield Strength Tensile Strength Used For
Grade 5 No 90,000 120,000 accessory bolts and studs
Grade 8 No 120,000 150,000 accessory bolts and studs
Stainless 300 Yes 140,000 170,000 accessory bolts & studs, head studs
Custom 450® Yes 150,000 180,000 head bolts, accessory bolts
8740 Chrome Moly Yes 160,000 190,000 rod bolts, head & main studs & bolts
A286 Yes 170,000 200,000 head bolts, accessory bolts
ARP2000 Yes 180,000 215-200,000 connecting rod bolts
L19 Yes 200-230,000 230-260,000 connecting rod bolts
Inconel 718 Yes 190-210,000 220-240,000 connecting rod bolts
Custom Age 625+ Yes 235-255,000 250-280,000 head studs, connecting rod bolts
ARP 3.5 Yes 220-250,000 250-280,000 connecting rod bolts
AerMet® 100 Yes 258,500 300,000 connecting rod bolts
Titanium Yes 160,000 180,000 head studs, accessory bolts

There are many grades of stainless. Get a very good grade of stainless and you'll be good to go. The best of both worlds, corrosion resist and strength.

from aquick search on stainless 300
PHYSICAL PROPERTIES(ANNEALED CONDITION)
Modulus of Elasticity in tension psi - 28.0 x 10(******)

so it looks like they could get some str=ong bolts out of it

never thought I'd have so many different opinions on that! I thought There was only one thing suggested / approved to go there!

Any boat manufacturer / racing shop on this board that has THE answer? What do you guys use in offshore racing?

Another thing everyone should be very concerned about is there are a lot of fake hardware manufacturers out there.
I'm in the military equipment business and virtually every fastener we use is grade 8. A number of years ago a lot of fake grade 8 stuff was being made in Taiwan.
ed

not sure on the thread size but assuming 1/2 inch the carbon steel grade 8 has a recommended torque of 119 ft lbs
http://www.engineershandbook.com/Tables/torque.htm

and from the Arp catalog look like they say there Stainles is good for 110 ft lbs you should be fine with the stainless just torque to spec and get the arps

Grade 8 only for motor mounts. I buy them from a local Fastenal store (Zinc-Chromate) plated to help with corrosion. This is the only way to go.

I recall that!
We had to do a stock sweep of all bolts. We ditched everything and reordered thousands of bolts.

Iggy,
We replaced every bolt on every M1 & M1A1 tank cannon in the fleet at contractor expense.
Funny thing happened afterwards. The USG decided to get rid of cadium plated hardware so we replaced them again.
ed

In all my years doing this, 99% of all the motor mount bolts I've ever seen are steel. The zinc chromate plated helps with the corrosion. Also, most of the offshore mount thru bolts have always been fine thread steel, not coarse.

Fine thread, grade 8 especially for motor mounts, use the stainless for cosmetic stuff not to hold down your powerplants.........

If I remember right it was the mid '80's... We had to change out hardware on about 50 F-15 & 16's due to that.:eek:

I've heard that grade 8 shears more easily than grade 5, even though it has a higher tensile strength. I don't know for sure. I do know that grade 8 doesn't rust as quickly as lower grade bolts.

Isn't tensile strength and shear different? I would think the highest shear strength is what your after for Motor mounts. And I don't think that SS?

There should be businesses that specialize in fasteners in any decent size city. Here in the Detroit area I can think of about 6 right off the top of my head. They are much cheaper than ARP. Get the grade 8 and you'll be fine.

Yes! If stainless was strong enough I'm sure mercury would use it for their engine couplers, fly wheels and drive shaft couplers. :drink:

Bingo!

So, without any warning, you sheared of 6 or twelve 1/2" diameter bolts allowing you motor to drop? Damn.

Something I have noticed on aftermarket truck suspensions they use Grade 5 bolts. But they are very large diameter, 7/8ths etc.

+1

If JC built your motors i guess a couple of 10-24's and some wing nuts ought'a do it :D

High school graduates or GED equivalent?...:evilb:

Yup

Guy's reading this thread are you talking....
L-ANGLES TO CRADLE MOUNTS
CRADLE MOUNTS TO ENG. BLOCK
L-ANGLES TO STRINGERS
or all of the above? I used Grade 8 on just the cradle mounts to the Eng. Block and SS for L-Angles to Cradle Mounts and Stingers, But I only have Small Blocks not the Big 630cu in like you big dogs run. Am I ok that way?

Cuda is right. Grade 5 is a better choice in this case. Grade 8s are stronger if all surfaces are machined and the bolt is in pure tension. If the surfaces are painted and possibly not 100% square, grade 5 would be stronger/tougher. It is more ductile and forgiving of uneveness of surfaces like you would see in generic motor mount applications. Grade 8s are for perfect clamping situations like a head to block.

Many years ago I was an engineer at John Deere Tractor Assembly in waterloo Iowa. The plant was highly automated and most handling systems were underhung from the trusses of the superstructure of the building. The engineer that installed the overhead cranes and such used grade 8 bolts to toe clamp the bottom chord of the trusses. The bottom chord of trusses are somewhat angled. After a few years of operation we started to find broken bolts on the shop floor. The grade 8 bolts were snapping!! Not good with engines and transmission moving over people!!. Anyway, all the bolts holding the cranes up in the 2 million square foot factory had to be changes out to grade 5 bolts. Grade fives can take the load and be forgiving of uneven surfaces. Many an engineer has made this mistake.

BT :cool:

My boat was rigged with SS from the L-angles to the stringers. There are 6 (3/4") thru bolts in the center and 3 (3/4") on the outsides. Steel on the offshore mounts to the engine block and steel from the offshore mounts to the L-angles.

That's exactly how you want to do it

I use Gr8 in all the high- stress applications and coat them with KGI Gunkote. If you do, you must use a lockwasher and torque them. The Gunkote has moly in it.

Applications-

Mount thru-stringer, plate to mount, plate to motor, accessories, bellhousing, starter, accessories, etc.

My local Lowe's has a big selection of Gr8 but the one down the road doesn't. The quickest way to get them is McMaster-Carr. www.mcmaster.com

Most farm/tractor supply stores carry a good assortment of grade 8