Bolt Size between Engine / Mount / Firewall
 

I'm looking for guidelines that you use for mounting engines to mounts and mounts to firewalls.

For the engine / mount my standard is to use 6-32 hex head bolts. I've used it for 46 size up through a Saito 100. A YS110 gets 8-32 bolts.

For the mount / firewall Iuse 6-32 hex bolts for 46 to 90's (2 &4 stroke). For engines above that I use 8-32 bolts.

Well, almost. Ijust noticed that my Saito 100 that's mounted to my Hog Bipe uses 6-32 bolts - not 8-32. Do you think the 6-32's will keep up with the vibration of the 100?

Thanks for tossing your personal guidelines into the mix.

TTFN

RE: Bolt Size between Engine / Mount / Firewall
 

You often have a choice of two different grades of bolts in most hardware stores. Some have more than two grades.

The regular grade is tough as steel. The will usually have stainless, but it's not necessarily tougher.

Ask the hardware guy for his highest grade and you'll get 6-32s that will be stronger than what you're using now. And what you're using is probably stronger than an ARF's two layers of liteply firewall.

RE: Bolt Size between Engine / Mount / Firewall
 

What I kinda hear you say is "don't use "manufacturer supplied" hardware" even if it is of the right size and type because it's made of low grade materials. And that your local ACE hardware is an excellent source for quality, stainless or standard materials.

What's your opinion of Dubro's "black steel construction" bolts?

RE: Bolt Size between Engine / Mount / Firewall
 

.............which these tables confirm:

http://www.boltdepot.com/fastener-in...ade-Chart.aspx

http://www.derose.net/steve/resource...les/bolts.html

RE: Bolt Size between Engine / Mount / Firewall
 

Good stuff. Attached is a file that I've found useful when it comes to bolt diameters (metric-n-standard) and wire gauges.

RE: Bolt Size between Engine / Mount / Firewall
 

That's not what I'm saying actually.

The mention of ARF firewalls was trying to put a perspective on the strength of any bolts and the practice of most ARFs nowadays. They usually have a firewall made of liteply, which is not a good choice for firewalls. And the fact many use only two pieces glued together. Liteply is not made of hardwood, uses only one layer of decent thickness, has only a veneer layer on either side of the one thick layer, and uses a somewhat grainy wood overall.

They often have very strong motor mounts. The iron bits usually are obviously good or obviously bad. Easy to tell if you want to use those bits.

But yes, hardware stores are an excellent source. AND can point you to bolts with a strength that should suffice for sure.

Dubro stuff has been around for a long time and has always been dependable. They certainly have the experience to sell appropriate stuff. If the bag says it's for X-size engine mounts, it's an excellent bet it'll hold that mount to the firewall until hell freezes over. Until I hear they've been sold or taken over, Dubro will always be a trusted name.

RE: Bolt Size between Engine / Mount / Firewall
 

Some tips to test the hardness of the steel in the bolts that we buy:

Copied from:
http://www.metalwebnews.com/machine-tools/ch2.pdf

Spark Test

This is a simple identification test used to observe the color, spacing, and quantity of sparks produced by grinding. It is a fast and convenient method of sorting mixed steels with known spark characteristics. This test is best conducted by holding the steel stationary and touching a high-speed portable grinder to the steel with sufficient pressure to throw a spark stream about 12 inches long. These spark patterns provide general information about the type of steel, cast iron, or alloy steel. In all cases, it is best to use standard samples of metal when comparing their sparks with that of the test sample.

File Test
One simple way to check for hardness in a piece of metal is to file a small portion of it. If it is soft enough to be machined with regular tooling, the file will cut it. If it is too hard to machine, the file will not cut it. This method will indicate whether the material being tested is softer or harder than the file, but it will not tell exactly how soft or hard it is. The file can also be used to determine the harder of two pieces of metal; the file will cut the softer metal faster and easier. The file method should only be used in situations when the exact hardness is not required. This test has the added advantage of needing very little in the way of time, equipment, and experience.

Some pictures of spark tests:

http://wearanswers.com/Instant-Answe...ification.html

Mild Steel
Identification: If it looks like steel, weighs like steel, but is magnetic, you're down to whether you have mild steel or a harder steel. On the spark test look for longer streamers from the wheel with fewer sparkles.

Hard Steels
Identification: If it looks like steel, weighs like steel, but is magnetic, you're down to whether you have mild steel or a harder steel. On the spark test, the sparks will tend to end closer to the wheel, and the more carbon (i.e. the harder the material), the more sparkles you'll see. A noticeably different spark, perhaps with unusual colors and shapes implies an alloy steel of some kind.