My buddy is pulling his 383 to drop in a sc 383, and I bought his old 383 off him. I went ahead and ordered the parts I need since I'm not getting everything off the block, and figured I'd go ahead and buy some main studs. I was told the other day that if I went ahead and used the main studs, I'd need to go get the engine machined?

 

This is more of a tech question than motor swap, but...

You were told wrong.

I also don't see any reason to do this. Unless you're disassembling this engine on a regular basis, studs don't really buy you anything. Some type of stud is needed for a baffle/windage tray, but that's a different story.

 

Sorry, I forgot to mention I bought a windage tray, so needed something. The guy I'm buying the engine off said since studs are stronger, it may no longer make the crank balance..

 

Ask him what the weight of the rotating assembly has to do with the fastener used on the main caps. You might want to look at the rest of the engine too.

Studs are generally stronger because they don't have a twisting force applied to them with tension force. Less preload stress gives more strength to the part.

 

What do you mean?

 

If he's saying that the main cap bolts were included in the rotating assembly balance maybe he also thought that valve seats were the man just overcharging him. I dont' know. Just sounds kind of scarry if that was his reason for not using studs. Sounds like he's building engines without all of his wrenches if you know what I mean.

 

Edit: Never mind, Monk got back first....

 

Not tring to say I am correct or start a war, but I thought you had to have the main line honed if you put in studs? Or is that only if you check oil clearances and they are not good after installing the studs? I may have misunderstood this so a little clearification would be nice. I've never really figured out how a stud would change the main cap position but I don't know.

 

82 Trans man....I've heard the same thing about the studs...
I plan on changing to studs and will be line boring the block.

 

You don't necessarily have to have the block aligned honed to use studs. Studs are a great way to add stability to the lower end however. In many ways a studded 2-bolt block is better than a 4-bolt bolted block as far as strength goes. Don't forget to check and recheck the clearances between the tray you use and all the rod bolts/nuts, crankshaft counterweights, etc. before you put the pan on; it's no fun pulling the motor back out because the rotating assembly is tapping the tray.

 

So, it's in your best interrest to get the block honed if you change over to studs? I'm lost with the replys. I'm going to put in the studs and windage tray, even know it's not needed, I'd like to install them. I'm just not sure if the block should be honed or not afterwards.

 

I have no idea why it would need to be honed. All of the stresses on the caps and main webs are the same. Sometimes you just need to use common sense. When you torque the nuts on the studs make sure the crank spins freely, the same way you would with bolts. If you torque them down and the crank spins what was the difference?

BTW line honing only works if you get the block decked and bored at the same time. The whole goal is to get everything square. My '74 4 bolt that needed to go 60 over to clean it up didn't need to be line honed.

 

Studs will require more clamping force. Hence the higher torque numbers for a stud vs. a bolt. This higher compressive force on the mains can cause the main cap to distort a little more. But I believe that we are talking only half a thousands here.

Plastigauge the engine after you add the studs to check for clearance and you should be fine if all checks out.

 

Studs do not "require" more clamping force. They might "provide" more clamping force than cap screws, if they were torqued down more. But a certain torque on a fastener will produce a certain amount of force; the fastener does not care whether it's turning in cast iron, or whether half of it is stuck in cast iron and the other half is spinning around on threads at the end of it.

Main studs are a total waste of $$$ on a street motor until you reach the 500 HP / 6500 RPM kind of area, except as necessary to hold on a windage tray. But if you actually look at the ones for a tray, you'll see that they're often really just a cap screw with a big long thing sticking off the head.

Align boring a block is not usually necessary. That involves cutting some metal off of the mating surfaces of the caps, and re-boring the main journal bore a few thousandths higher up into the block. This can cause starter problems, timing chain issues, and sometimes even rod-to-cam clearance problems. It's a last-resort repair of a severaly defective block. I would not do it to a block that wasn't measurably warped, or unless replacing main caps (putting 4-bolt splayed caps on a 2-bolt block for example). Usually when doing the cap thing though, they take very little metal off of the block side, since that half of the corcle is usually already in perfectly good shape. Align honing is a different matter; that just runs a hone through the bore, which enlarges it slightly (half a thousandth or so when done properly) which has the bad side effect of opening up the main bearing oil clearance by that amount, but also guarantees that the bores are straight, round, and concentric.

None of this has anything to do with crank balance.

I agree with the former observation: if those comments are any indication of this person's understanding of how to build a motor, you definitely want to undo every single thign they touched, and check it carefully for other results of ignorance.

 

Thanks for the help guys =)

 

You are splitting hairs with semantics here.

Studs are made of a harder material (larger Modulus of Elasticity) than factory main cap bolts. Therefore to reach 75% elastic yield of the fastener, it is required that the installer torque the stud/nut tighter. This will exert more clamping force.


Your description on align honing is incorrect. Machinist WILL remove a few thousands off the main cap parting line and hone out the main bore. I suppose a machinist could do as you described, but there would not be any point to it. If all main bore holes are within 0.0005", he is just taking your money for an align hone job.

 

I think you are mistaken. There should be NO clamping force applied to the crank. If that is happening then you've screwed something up somewhere. If the threads are self overhauling(which they are) then you don't need to take it to 75% yield. Of course that doesn't hurt anything.

 

The "clamping" force being referenced is that of the cap to block, not cap to crank.

And, just for the record, modulus of elasticity is a function of the material, not hardness (or strength).

Higher strength does allow for additional torque, which translates to higher clamping force - which is desirable to keep the caps from "walking".

 

Well, since we are picking on semantics here...

"Studs are made of a harder material (larger Modulus of Elasticity) than factory main cap bolts. Therefore to reach 75% elastic yield of the fastener, it is required that the installer torque the stud/nut tighter. This will exert more clamping force."

Granted studs arent factory bolts, but aftermarket performance type bolts and studs are no different from one another. Taking a look in my 99 ARP catalog, both the main studs and good main bolts share the same tensile strength, 190,000psi. Now as an example, same book, 7/16" studs should be torqued to 85 and 7/16" bolts to 90. Hmmmm. Actually, I know why but it doesnt really matter for our comparison. Now, my Chiltons manual (I know, I dont feel like getting the real one) calls for 70-85 depending on year, application. Most are 75-85. Lets go with 85... and guess what? No difference. Even if I pick 75, the difference in clamping force isnt enough to make a considerable difference in the compression of the main cap to worry about. I could sit here and calculate it, but there are better things to do in life.

"If the threads are self overhauling(which they are) then you don't need to take it to 75% yield."

This has nothing to do with the threads being "self-overhauling" (which is a term I've never heard in my life) but rather the fastener is supposed to be elongated a certain amount for proper clamping force. Again I dont feel like doing any math, but 75% is a number I have seen and heard before, and IMO reasonable. Ever heard of torque to yield fasteners? Thats 100% yield in theory... 75% yield is a fine number to deal with. As a guess from what I know about bolts, I'd say any less is probably not a good thing.

"And, just for the record, modulus of elasticity is a function of the material, not hardness (or strength)."

True and false. True, the modulus of elasticity is a function of material. Hardness and strength arent the same thing. Hardness wouldnt be termed with modulus of elasticity, but the modulus of elasticity has everything to do with strength... strength being either yield strength or ultimate strength. Think Hooke's law. I'm kinda picking straws because I see what youre saying, but strength and the modulus of elasticity are related.

And to the question...
Dont bother with main studs if you dont have to. If you do, then dont worry about align honing or align boring. Why? Well, the cap is located by the block, not the bolts. There should be no misalignment problems with swapping main bolts, or studs as it may be. Clamping force differences will be minimally different at best, not enough to worry about unless you just worry in general. Now if you were talking about rods, thats a different story. Rods use the bolts to align the cap and IMO its a good idea if you replace rod bolts to have the rods resized. Main caps arent like that, it'll be fine the way it is.

No offense meant to any of the quite knowledgeable gentlemen mentioned and quoted here.

Oh yea.. just for the hell of it: CE, emphasis in structural and materials.

 

Throwing degrees around 'eh?

ME emphasis on everything (or nothing depends on how you look at it.)

Where'd you go to shcool? I graduated Rose-Hulman Institute of Technology.

 

Fresno State!

Yea I got 2 degrees, a degree in BS and a degree in CE. The BS part seems to be more important at work too, strangely enough.

 

As far as machine work is concerned I dont know a whole bunch about it. All I can do is state what I have been told by my machine shop, 38 years in the business, and also what ARP puts on their stud kit directions.

I will have about 425-450 flywheel hp, and not spin above 6000rpm.

Machine shop: Dont align hone or bore a block unless it is needed. Return the stud kit and buy ARP bolts.

ARP directions attached.

 

Anyway, I couldnt get the jpeg of the directions to post. Here is what they say about align honing.

ARP: When changing from factory fastners to high strength fastners, clamping forces and tolerances will change. The main bore should be align honed using the fastners which will be installed at the recomended preload.

 

I built a 383 4-bolt with studs and no align hone and it runs quite well. I'll let you know in another 30,000 miles though.

 

wow.......

I could write a BOOK on the do's and donts of main studs, and or head studs..... etc
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Reminder..... most kits are fairly reasonably priced...

Main Studs

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Id be spending my time on the horn with summit ordering my new ARP main studs, and head studs... and know ive got some cheap and STRONG INSURANCE on the way.....

 

 

That is one buff looking engine up there, hehehe