Bolt size for engine stand (FAQ)

[Brucelee41042]

Got a 67 327. Wondering what diameter/size bolts i'm going to need to get this thing on the stand. I'm thinking at least 6 inches in length, and i'll fill up the slack with some washers. I'm guessing 3/8 diameter. Any other ideas would be great

[Real McCoy]

If it's like every one I've ever seen it will take 4 each 3/8X16 bolts and how long they need to be will depend on the type stand you use. Just measure the lenght of the mount on the stand and add 1/2 inch for the block to thread it in.

[NEVER FINISHED64]

I learned this trick from this site:
To take up the slack in the large holes of the engine stand's bracket use a piece of rubber hose (fuel line) cut the length of the support tube on the bracket - then the bolt goes thru it.

Chuck

[walkerjay]

I'm picking up my short block 350 next week. I have a stand and need to get 4 mounting bolts. Can anyone advise me as to what diameter / pitch I should buy. I plan on getting some good heavy duty hardened bolts tomorrow. thanks

[the FLYER]

nothing "special" is needed, a std grade fastener is all that's needed... length depends on the arm depth of the stand but the bolt size is 3/8-16


hope i helped :D

[tsimpson]

Just pulled a bolt from a 350 on my engine stand. It's a 3/8 by 16 NC 2 1/2" long.
Hope that helps.

[walkerjay]

3/8 16. great! thanks! hey, what are you guys doing home on a saturday night? oh wait, it is a bit early yet.

[1quik69]

Just for safety sake I would get a grade 8 bolt or min grade 5.

[Mike Goble]

Grade 2 bolts are rated at 43,000 psi @ 75% yeild strength
Grade 5 bolts are rated at 69,000 psi @ 75% yield strength
Grade 8 bolts are rated at 98,000 psi @ 75% yield strength
The root diameter of a 3/8-16 bolt is 0.294", providing an area of .0679 square inches.

Grade 2 3/8-16 bolts would be rated at 2919# each @ 75% yield strength for a total of 11,676# for four of them.
Grade 5 3/8-16 bolts would be rated at 4684# each @ 75% yeild strength for a total of 18,376# for four of them.
Grade 8 3/8-16 bolts would be rated at 6653# each @ 75% yeild strength for a total of 26,612# for four of them.

I have yet to have an engine that weighs even 10% of the lowest figure. My concern would be on the welded tube that holds the head.

[63nova2]

Anyone know what the bolt / thread size is for a stock 6 cyl 194 engine to use on an engine stand?

I'll figure out the length .....

[Mike Goble]

Since the 6-cyl uses the same bellhousing as the V-8 I'll bet the bolts are the same.

[chevynuts88]

I used grade 8 also.Why take a chance with anything less?

[bowtie0069]

I used some old bronze bolts that were laying around--unless you plan on jumping up and down on the engine while it's sitting there, somehow I think bolt strength will be a non-issue. Hit up the hardware store for whatever will fit. And don't apply 200 ft.lbs. to the bolts either, a little over finger tight will hold just fine.

[novaBRO]

i use grade 10 bro but if i can't find it i use grade 8

[Mike Goble]

I used grade 8 also.Why take a chance with anything less?

What kind of an engine stand do you use?

[bowtie0069]

What kind of an engine stand do you use?

That grade 8 bolt would be the strongest part of the entire engine stand unless the stand is made from 3/8" steel plate!

[walkerjay]

thanks everybody. I'll get the best bolts NAPA has. I got lucky with my stand. I was driving down the street one day and passed a shop that had a brand new stand and cherry picker sitting outside the bay. As I drove a bit more i saw their old stand and cherry picker on the side of the shop. I just happened to have my dad's pickup that day cause I was working on it for him. The shop owner told me I could have the stand and hoist if I took it right there and then. Sometimes I get lucky, not often. Anyway, the stand is 4 legged, 4 wheeled and very heavy duty but was missing one of the 4 brackets that mount to the motor. I went to harbor freight and they wanted 50 bucks for 4 brackets MIC. I stopped by a local welding shop and the guy made me an exact duplicate for 40. i think I did pretty good.

[63moredoor]

Okay stupid question time. I am ready to put my 283 on the engine stand to begin tearing it down but I don't know what size bolts to buy and don't have any to use as examples. The stand I have has 2" deep mount tubes so can some one tell me what size bolts to buy that will fully seat in the block?

[ProchargedchevyI]

I used 3" Grade 8 bolts from NAPA. You probably could get away with using Grade 5 bolts, but I'm neurotic and overkill everything. :D

[63moredoor]

what size and pitch?

[72Orange]

what size and pitch?

I think it's 3/8", maybe someone else can chime in here.

[ProchargedchevyI]

3/8 coarse threads are standard on SBC's

[63moredoor]

Thanks to all! So 3/8 corse 3" long right?

[ProchargedchevyI]

If you're doing a sbc 3/8 coarse is what you're looking for. However, the length depends on how long the slots on your stand are. The rule of thumb is you want the threads inside block at least 3/4" each. So measure before you buy them.

[Real McCoy]

3/8 coarse = 3/8X16 in technical terms if you need that info. Most bolt bins use the threads per inch term at stores here. You could buy 3 inch bolts and use a washer or two if they bottom out. Any grade will work but if you want go with a grade 5 or 8 if it makes you feel better. The bolt is 3/8 dia so any thread engagement past that is not going to make the bolt any stronger but helps the block from stripping out. JMO, RM

[Tommy]

I had some bolts break a few years ago when I let the weight off the cherry picker after bolting a 351W to a stand. Luckily the hoist was still attached so it kept it from hitting the ground. I thought I had bought quality bolts but they were less than grade 8. I was told they were adaquate... they weren't. I won't use anything but the best now. I have a BBC on a stand in the garage and I think the stand will buckle before the bolts give up.

Tommy :)

[rhorne12]

Beware of bolts that are not graded or less than grade 5. Common at home improvement stores and some hardware stores is ungraded and grade 2. These can break with your hands and can kill you if you are not careful!!!:mad:

[Mike Goble]

You have to be careful how much weight you put on your engine stand.

A typical full dressed all iron small block Chevy weighs about 600#.

A typical cheap engine stand from Harbor Freight is rated at 1000#.

A typical grade 2 bolt will support 3332# at 75% yield strength. If you use 4 of these bolts, the load rating would be 13,330#.

If you step up to Grade 5 bolts, the load per bolt increases to 5347#, or 21,390# for a set of 4.

If you're really squeamish and opt for the Grade 8 bolts, you're looking at 7595# per bolt, 30,380# for a set of 4.

I'll bet there are many weaker points in your mounting system. Many failures are caused by overtorquing the bolts, which puts tremendous stress on them.

[63moredoor]

Got it mounted just fine and finally I can start to work on the engine. Got some 3" grade 8s but should have probably gone with 2.5 or 2.75. Oh well just used some washers as spacers. Any way I can't wait to get started.

[Nox]

Hi! Where do I bolt the engine stand into the engine?

I'm guess it goes where the transmission bolts onto, but I don't want to guess.

I don't have the transmission / engine block bolts, so I'll have to go find some that fit... (If, that is where it really does bolt onto. )

[The Big Al]

Not a chevy engine but this help?

http://img530.imageshack.us/img530/4113/engineonstandzl6.jpg (http://imageshack.us)

[62civa]

Hi Al,
What kind of engine is that?

[burkej62]

Hi Al,
What kind of BOOSTED engine is that?

+2

asdfghjkl

[The Big Al]

Hi Al,
What kind of engine is that?

I was waiting on this question.

It's a Twin Turbo Mitsubishi V6 2.8L for a GT Rally car. Has dual overhead cams.

This was a practice engine that they ask me to check bearing. With the amount of boost and abuse it eats bearing and cranks. This one need a crank and bearings.

I was just amazed at how HD the crank and block area. everything was HD and precision fit.

Felt bad bolting it to a 75.00 engine stand.:o

AL

[Nox]

What size bolts do I need to go from my 350 block to my transmission? I'm trying to mount my engine on a stand, but I don't have these bolts...:rolleyes:

Do you need to know anything specific about my engine? If not, can I please get some measurements? Thank you.:)

[Paul Wright]

I merged these FIVE posts into one. This is now an official FAQ.

[stock z/28]

Grade 2 bolts are rated at 43,000 psi @ 75% yeild strength
Grade 5 bolts are rated at 69,000 psi @ 75% yield strength
Grade 8 bolts are rated at 98,000 psi @ 75% yield strength
The root diameter of a 3/8-16 bolt is 0.294", providing an area of .0679 square inches.

Grade 2 3/8-16 bolts would be rated at 2919# each @ 75% yield strength for a total of 11,676# for four of them.
Grade 5 3/8-16 bolts would be rated at 4684# each @ 75% yeild strength for a total of 18,376# for four of them.
Grade 8 3/8-16 bolts would be rated at 6653# each @ 75% yeild strength for a total of 26,612# for four of them.

I have yet to have an engine that weighs even 10% of the lowest figure. My concern would be on the welded tube that holds the head.

Hi Mike,

I agree with you that the stand welds are probably the weakest point, but dont you think the length of the weight supported by the bolts would be an important park of a calculation on bolt load?

[Mike Goble]

An engine is a pretty regular shaped piece, so it is relatively easy to calculate the stress on the bolts. The stress that is on the engine bolts is also on the arms, the bolts holding the arms to the head, and it is all concentrated on the junction of the head and the tube.

[stock z/28]

Do you think the load on the engine mounting bolts would just be equal to the weight of the engine?

[Mike Goble]

No. It would be more than the weight on the top bolts.

[Nox]

Ahh, nevermind my last question.

I eyeballed it, and it took three trips to my hardware store, harrassing the kind old folks that helped me out to get them.

Oh, and sorry about not searching more before i posted.:shh:

[stock z/28]

I wonder what the load actually is on the bolts, figuring the weight and length on a typical iron head small block and the bolt spread on the bellhousing?

It would be interesting to me.

[Paul Wright]

Coincidently, we are studying this in Physics. I'm pretty sure the load difference between the top and bottom bolts is a Vector problem. Might also require calculating center of mass.
I think the spacers help resist bending forces and the bolts just provide clamping force. The weight applied plus the bolt torque has to be considered when calculating total strain.
While the load may not be super high, I wouldn't chance a $7,000 engine with grade 2 bolts, especially with all the poor quality, Chinese bolts at hardware stores.
It would be interesting to see what the actual loads would be. I'll have to find the equations and submit a report.

[Mike Goble]

Here's an introductory course on the importance of stress analysis:

http://www.gendertree.com/a_stress_analysis_of_a_strapless.htm

A rough calculation on the stress put on the bolts would be a ratio of the distance of the engine's c/g from the mounting flange to the distance between the bolts. Let's say the c/g of the motor is 16" from the flange and the bolts are 8" apart. If it's 2/1, the stress on the upper bolts is about double the weight of the engine.
The same rough calculation would apply to the estimate of the stress on the mounting head, the ratio of the diameter of the tube to the distance from the end of the tube to the c/g of the motor. If the tube is 2.5" in diameter and the c/g is 20" from the weld, it's about an 8:1 ratio.

It's interesting that so much time is spent gnashing teeth over the rating of the engine mounting bolts, yet so little time is spent calculating the forces on the cheap Chinese engine hoist and the low-priced chain that comes with it.

[The Big Al]

Now y'all done it!

After 35 years of using any bolt I could find that would fit.
The engine will now fall off and crash to the floor because now I know the bolts are not rated for the stress of holding up the engine.

They worked perfect until someone pointed this out.:eek:

[Real McCoy]

I'm with Al on this. All my life I've used whatever bolt fit and all those iron headed BBC completely assembled pushed around the shops have never failed. Even the aftermarket block and stoker cranks with my new motor was attached with whatever bolts I found and that motor added 100 lbs to the front of my car.....LOL. Now I'll have to find better bolts and a 5 minute task will take all week.....LOL. I'm filing this under the More info than necessary section. RM.