Ok, I just purchased a 383 nodular iron crank for my 350 from ebay, there was no pic. still though, you dont know what your getting. The block is a 1 piece rear main block. I want to make sure that they sent me the right crank. Thats where you guys come in. this is my first engine build that i want to do myself, and im not to sure about all the different cranks.

first. how do i make sure that IT IS A ROLLER CRANK. I have some pics here, which one in the 1 piece crank?

Second. The cranks that I have dealed with in the past always had metal drilled out or added to the counter wieghts. I assume to be balanced. This 383 crank has untouched counter weights.
What does that mean?
does the crank have to be balanced at a shop?
or does the crank rod and pistons have to balanced all at once?
The 400 cranks are extrernal balanced, does it mean this one is too because it was a 400 crank? If it is external balance, does that explain the counter weights not being touched?
finally. Do i have the option to internal balance if i want to, and is it better to do so. I plan on running a torque motor to rev no higher than 6,000 rpm.

Although tthe crank in this picture is not my crank, it looks just like it. the rear of the crank is exactly the same. IS IT 1 OR 2 PIECE???? Its big rear main journal with a round end. I know I should know this stuff.

 

that is a one piece rear crank ...

 

do you have a part number on this crank??

 

Where would it be located? on the crank?

 

Possibly cast or stamped into one of the counterweights.

 

Dont worry about the balancing i just did the same build (well its not built yet).But when you change your rods or crank or pistons you have to get it rebalanced.This isnt exactly true in all cases but with the scat crank there notorious for being out to lunch right out of the box.Mine was anyway,just take all your goodies to a good<---emphasize machine shop and get them to balance for ya.If you dont know of a good machine shop or are unsure ask around the local speed shop or this board probably has some one in your area that knows of one.
Make sure the balancing work they do doesnt involve removing or adding weight to your flywheel or balancer to get the crank balanced which some shops will do (cheapo).Then if ya decide to switch your trans to an automatic you dont have to worry about the flexplate not being balanced accordingly.
the part # for my scat crank was 9-350375057L ST and it was for the newer roller block like you mentioned.

Oh i forgot to mention something the balancing cost me 300cdn and after doing some research i think it would of been cheaper to buy a complet kit already balanced.Just another option for you to look at

 

Thanks guys. What about the fact that its nodular iron? I heard that the 400ci stock cranks are very strong. More so than anyone gives them credit for. I have been told by some speed shop guys to not waste my money on a forged steel crank unless im doing all out racing. Mine is for street strip. Is that true?

 

There's no such thing as a "roller crank". Don't make yourself look like an idiot to a seller or a machine shop by repeating that.

400 cranks suck. I've broken enough of them to know. I would not take a stock 400 crank and make a 383 out of it in this day and time; and it won't fit your one-piece block anyway, without spending wxtra money on the adapter. You'd be better off to buy a purpose-built 383 crank with the right flange on it. But, you're right that a forged crank isn't really necessary for most street build. RPM is what kills cranks. If you keep the RPMs below 6000 or so on a regular basis, and no more than 6500 ever, then a nodular cast crank (what 383 street cranks usually are) will be fine. Your description of what you're doing with this motor is too vague to mean anything, so it's hard to predict; but if it's a TPI motor with no blower or nitrous for example, the TPI itself will protect the crank from stress.

It is not possible to balance a motor internally with stock 400 (short) rods. Which is another good reason not to use a stock 400 crank for a build like this. The piston is too close to the crank centerline at BDC to fit in large enough counterweights between the bottom of the piston and the crank centerline. If you use longer rods, then it's possible to internally balance it. You can look at a stock 400 crank and see the problem; the outer surface of a 350 crank is a cricel, whereas the outer surface of a 400 crank's counterweights is "flat cut" to clear the pistons.

The crank with the small flange that's completely round, i.e. the top pic, is for 1-piece (late model) blocks. The lower pic, with the larger flywheel bolt pattern and the counterweight on the flange, is a 2-piece rear main seal one. You need one that looks like the top one.

You need all the other internal parts a crank is going to be used with, particualrly the pistons and rods, to balance it. There's no such thing as buying a "pre-balanced" crank; unless it's supplied as part of an assembly by someone who knew what rods & pistons it was going to be used with, and balanced it accordingly. If you change any of those parts, it will have to be re-balanced. Most new cranks will have a spec for how they come balanced from the factory, which it is very unlikely that your other parts will add up to exactly that bob weight. So, if you just bought a crank by itself, you need to get it balanced. I agree that you DO NOT want to send your flywheel and balancer to the shop for balancing along with the crank and rods and pistons; you want the motor internals set up to the stock spec, and maybe get those other things individually neutral-balanced, if you're concerned that they might be out. You DO NOT want those parts to be part of a custom balance setup.

 

So - I take it you don't post very often on the TPI board.......

 

Thanks for your help

 

Actually, he wants to bring a brand new stock fresh flywheel and balancer, to ensure the assembly is balanced to stock spec.

Then he wants to have his flywheel (and possibly balancer) rebalanced to the same spec.

 

He doesn't need a stock flywheel or balancer to verify the stock spec. Balance shops know what those specs are.

Don't send a flywheel or balancer to be balanced with the motor internals; or vice-versa. Balance each independently, so that interchangeability is maintained.

 

You remember what they are offhand?

A lot of guys don't realize there is a counter balance on the 1pc crank flywheel.

The 1pc motors are NOT internally balanced. They use a neutral balance damper, but the flywheel has a counter weight.


-- Joe

 

 

Heehee....It really is a classic!!

Mind if I add it to my sig RB??

 

Ok,What kind of fly wheel and harmonic balancer do I use in the 383 stroker????? I AM GOING TO INTERNAL BALANCE.

I heard that IF the motor is internaly balanced, I am to us a 350 balancer with a 350 fly wheel, or a 400 balancer WITHOUT the counterwieght in it with th e 350 balancer.

BUT if its externaly balanced, it should be the 400 balancer (with the counter wieght in it) and the 400 fly wheel, or 400 balancer with a adapter on a 350 fly wheel. WHAT DO I USE?

Its a 383 1 piece rear main seal. I have the crank and block only.

 

If the crank is internally balanced, have the rotating assembly balanced to the stock 305/350 balance spec, and use a stock 305 or 350 balancer and flywheel / flex plate for 1-piece rear main seal.

If the crank requires external balance, have it set up to the stock 400 balance specs; use a 400 crank damper; and get a stock 305 or 350 flywheel / flex plate for 1-piece RMS and have it "unbalanced" to the stock 400 spec.

 

You still need to bolt a 1pc flywheel on, or at least a bob weight (50oz right?) when balancing the 1pc style crank.

-- Joe

 

Whatever the stock 305/350 1-pc spec is, yes. I don't know it off the top of my head.

The goal is, when you get finished, the assembly looks just like a stock one, to the "outside world". That way, you don't need a special, custom, one-of-a-kind, made-just-for-you balancer or flex plate, that whenever you need to replace it, you have to tear the motor down and haul its internals to a shop to get another one matched to it. You want it so that any correctly (NOT custom) balanced stock part will bolt up and work. That is why, under no circumstances should you allow your motor internals and your externals to be in the same shop at the same time; you don't want that to happen to you, even accidentally.

The 1-pc motors are NOT externally balanced, even though a small part of the rearmost balance weight appears to be "external" to the motor. That little bitty weight is the balance equivalent of the funky-shaped flange on a 2-pc motor. It's only on the flywheel because it's imossible to install a metal-clad lip seal over the other thing.

 

I know what your getting at, but its not 100% correct.

I have a flywheel that was neutral balanced for a motor. The weight was comply ground off so its at 0.

That motor got taken apart, and my buddy ended up with the flywheel.

My buddy had it on his S10 with a hot 350.. At 5k it almost sent the windshield out of the truck.. He immediately tore it down, replaced it with a fresh flywheel.

I've still got the flywheel on my porch. Not really world putting the weight back on it.

-- Joe

 

that doesn't make any damn sense, if the weight is removed it's not balanced. a 1 piece seal crank is internally balanced, but the weight is reqired to off set the mass of te old style fly wheel flange. without the weight it's no wonder you had problems.

 

When I had my 383 balanced , I wanted it internally balanced. He asked for everything including fly and balancer.

 

That's the sort of thing that happens when you send a flywheel to a shop along with the crank and rods and pistons. That's why you shouldn't send your damper and flywheel/flex plate to get balanced along with your motor's rotating assembly.

Like I said, get your motor set up to the stock balance spec; and use a stock 305/350 flywheel THAT HASN'T BEEN MOLESTED. That way, you can put any flywheel on the motor later on if you need to; or, for that matter, you can still use that flywheel with some other motor if you want, unlike the example given above, rather than getting stuck with a "matched pair" that can't be split up because they only match each other and not anything else. Any balance shop that has a clue (unlike that one that shafted the other guy) will know what that little weight is supposed to be, and will bolt it onto your crank during the process. It's not much, but it matters that it be there.

 

I don't think you read my post ede.

Someone along the lines had the weights removed and the flywheel set neutral.

When my buddy tried it in his 1pc rear 350 in an S10, the thing shook like CRAZY. Replaced it with a brand new oem flywheel and it worked just peachy.

I don't know what you mean by "offset the mass of the old style flywheel flange" ?

-- Joe

 

As long as they have a bobweight to make up for the lack of flywheel. Otherwise they're gonna reduce one side of the flywheel by about 50oz.

Quote:

Like I said, get your motor set up to the stock balance spec; and use a stock 305/350 flywheel THAT HASN'T BEEN MOLESTED. That way, you can put any flywheel on the motor later on if you need to; or, for that matter, you can still use that flywheel with some other motor if you want, unlike the example given above, rather than getting stuck with a "matched pair" that can't be split up because they only match each other and not anything else.

Yes, you don't want to modify the flywheel. You want to make sure your new crank, new rods, and new pistons are balanced to the stock flywheel.

Is the way I'm wording this getting lost in translationor something? It sounds like we're saying the same thing in a way.

Quote:

Any balance shop that has a clue (unlike that one that shafted the other guy) will know what that little weight is supposed to be, and will bolt it onto your crank during the process. It's not much, but it matters that it be there.

Exactly! Thats why I said use a bobweight (prefered) or just bolt a STOCK flywheel when balancing. I said that like 4 posts up man!

-- Joe

 

I still have the weight o my flywheel also. Stock balancer too.