im thinking about making my 350 a 383 but ive been told that i have to get a flywheel and a harmonic balancer out of a chevy 400 to make the kit work. my question is why and will they fit on my 81 vette? thanks for the help,
Randall Graves :chevy

 

Yes and no. If you go the traditional and historically less expensive route, you get a 400 crank and drop it in. This is an externally balanced crank (needs an offset weight outside on the damper and on the flywheel.) A lot of people get an aftermarket crank that is internally balanced. Then use a “normal” damper and flywheel on it. Internal is considered better.

Internal or external is relative to inside or outside the block.

Will work on an '81.

Welcome to the forummaximus :)

George

 

Ditto what George said.

I just started a 383 project for my own car and I am going with the aftermarket crank, even though I have two other cranks sitting on the shelf.
I assume you are aware of the block etc clearance issues with a 383... some grinding is necessary unless your block has already been prepped.
Unless you buy a "kit", you also have to mastermind the correct combo of parts so that the pistons end up at the proper height from the deck.
The length of the rods & pistons have to add up correctly with the new stroke, and if the block has been decked, you have to be careful there also.

Tom

 

Just contacted Eagle...

Their cast 383 cranks are all externally balanced. Only the forged cranks are internally balanced.

They have a kit which is worth looking at if you don't mind the ext/int balance issues (I do).

Rotating assembly balanced, new 5140 lightweight rods, cast crank, KB Hyper Pistons, rod & main bearings (Clevite or Fed Mogul), plasma moly cast iron rings (faced), new balancer & flexplate (not flywheel)... $899.

Adding it all up-
New Rods $280 (non lightweight, refurbished/used, other sources, $150)
New Crank $289 (cast
Pistons $200 ($160-$240 depending)
Bearings $40 (cost varies significantly)
Rings $60 (price varies greatly depending on type of ring)
Balancer $100 (? guess)
Flexplate $75 (? guess)
Balancing $100

$1144
- 899
--------
$245 Kit savings

My price estimates are quick & dirty, so please don't flame me on them.

Looks like the kit could save a few bucks as opposed to buying it all piecemeal.

I shy away from the external balancing though.
Instead of spending the extra money to buy the 400 balancer & flexplate, I think I would rather spend $400 more to get a forged crank (internal balance + better part) and use my existing balancer & flywheel (manual trans).

I build engines, I don't buy pre-assembled (crate) engines. They never have all of the parts that I want inside (particularly the rings), and it is not cost effective to tear down a crate engine to add back in what I want. Plus, my tolerances are usually tighter than crate engines.

 

Scat makes a kit using their 9000 series cast steel cranks that is internally balanced. I think too much emphasis on internal balancing is often made though. Keep in mind the small block chevy has been externally balanced for many years now. I dont know the exact date but it started sometime in the 90's. I believe the new vette motors are externally balanced.

If attention to detail is paid during the assembly I doubt there is any reliability/durability differences between the two, there certainly isnt any power differences.

 

Actually, there are reliabilty /durabilty issues. The stress on an externally balanced crank tends to be higher because the balancer & flywheel are constantly tryng to counteract torsional (twist) of the crank. This constant push/pull between the crank and its friends on the outside gives the crank a headache. The same thing occurs with internal balanced engines, but internal balancing reduces this problem as long as the balancer & flexplate/flywheel are properly zero balanced.

Significant? Never did my own test... don't know. My 70 LS5 454 is also external balanced... so GM has been doing this for quite some time.

As far as GM doing it for years, that doesn't carry any weight with me. GM is run by "bean counters" not, engineers.
GM also allowed .008 on the rear spindle bearings.... at .003 you can feel the camber change. I stick to .0015.
They were wrong.

How much is scats 383 cast crank? (just the crank, not the kit) I don't have a price on that one. I might be interested.




[Modified by Tom454, 10:35 AM 1/16/2002]

 

Just checked my sources on the Scat crank... they list several cast 383... but....

They also say "Requires 400 Flywheel and Balancer", which means they are externally balanced.

What is the part number for the Scat crank that is internally balanced.... I can't seem to find it..
They have a web site?

Tom

 

:eek: :D :D
http://forums.corvetteforum.com/zerothread?id=218884 Thanx!

 

Tom,are you sure about the Eagle info......i have a new 4340 crank,part #M 992274.......JOHN :chevy

 

I have an internally balanced Eagle cast steel crank in my 383 that was internally balanced by a machine shop.


[Modified by 79MakoL82, 8:35 PM 1/16/2002]

 

Tom,

Here is a link to Sallee Chevrolet's Scat page:
http://www.sallee-chevrolet.com/Scat...mbly_Kits.html

 

Okay... we're going in a bunch of different directions here...

First, a 4130 or or 4340 crank from Eagle is not a "cast" steel crank... they are both forged, both expensive, and both internal balance.
Unless you are building a very high HP engine, or are going to use N2O, a forged crank is overkill. Nice, but overkill.

Here is the email I sent/received from Eagle...

To: eaglerod@netten.net
Sent: Tuesday, January 15, 2002 10:33 AM
Subject: 103503750

My question:
The ESP #103503750 cast 3.750 stroke crankshaft on page 2 of the yellow catalog-

1) Is this an "internal balance" crank?
2) Who manufacturers it?
3) Where are they located?

Their answer:
1. External balance, our 4130 and 4340 steel cranks are internal.
2. It is manufactured by factories contracted by Eagle in China.
3. Eagle Specialty Products is located in Southaven, MS

Second, any crank can be internally balanced if you want to pay the bucks for the work. Since "heavy metal" (mallory) *usually* (that means not always) must be used to do this job, the cost can be close to the cost of a forged crank. So you might just as well have bought the forged crank and not mess around with the cast.

What typically happens, is that people will buy the cast crank before understanding the balance issues, and then take it to a crank shop to convert it to an internally balanced crank. In my opinion, messing around with heavy metal (and a machinists labor), or messing around with a 400 balancer and flywheel (more expensive for a flywheel instead of a flexplate), is counter-productive. Might just as well get a forged crank and be done with it.
And it doesn't end there... Fluidampr for internal balanced SB: $230, external balanced: $340.

In either case, (cast or forged) a complete balance job is advisable, but converting an external cast to internal balance is an additional cost. If you spend $300 for a cast crank, then spend 150 to 200 to get it balanced internally, you might as well go $700 for the forged.

I checked out the Sallee site.... as usual, the 383 kit does not have what I would need in it. But, it indicates that there may be a Scat crank which is internally balanced.... I need to find Scats catalog or website. Sallee may have already done the conversion by already adding the mallory metal. This would be reflected (buried) in the Sallee price which is a few bucks above the similar Eagle kit. The final balancing could then be done conventionally. This is a guess on my part.

Added note: I already have rods, dampers, flywheels etc that I will be using.... I don't want to pay for parts that I already have. I have never purchased a "kit" because the kits have never matched my requirements. I'm always starting with an existing engine with re-useable parts. When you modify a kit by adding in the parts you really want, the cost approaches the same as picking the parts one at a time from a supplier, because the kit vendor usually has higher prices for the single items than a high volume catalog dealer.

Now.... where is that Scat website....

 

Tom,

Check out these guys, they have quite a few 383 cranks, maybe something will suit you. They Carry callies aswell as skat brands. http://www.flatlanderracing.com/ I'll give you a call today. Good luck, ttyl!

Great to hear that the engine is in good shape! The more you can reuse, the better off you are.
Question: a 383 is a 350 w/ 3.75 stroke and +30 over. How advisable is it to Go +40 over? Does it affect the structure of the block at all, reason being, i noticed they make +40 over SBC pistons, just wanted your opinion.

 

J-

There is more than 1 way to build a 383... that is one.

Using basic math, .030 => 382.667 (383), .040 => 384.569 (385), .060 => 388.386 (388).

The bore increase doesn't buy you much. It's the stroke that counts in this case.

You can have pistons custom manufactured to any size you want... but you will pay dearly for the service.
They have to "re-tool" for custom piston sizes.... albeit much easier with new equipment & CNC machines.
Standard size pistons are cheaper because they can do large runs all at once.

RE: boring a GM 350 to .040... it is done all of the time. So is .060.
Here's the catch...

Some GM blocks will have a lot of meat in the cylinder walls, and some will not. Even if you find a good casting number block, there is always a chance that when it was cast, that one or more of the walls is a little thinner than the others. .030 and below, it is generally accepted that a GM 350 can take it. Above .030, this is considered a slight gamble. The way around it is to have the boring shop "sone" the block BEFORE they bore it. This is an indicator of how thick the walls are. They can tell you what your odds are for a good .040 or .060. I never sone for .030. For .060, I always sone. For .040, depends on which side of the bed I got up on.

It is standard procedure to first scope out a block. Based on what you find, you then buy pistons. The boring dude needs to have one piston in his hands to properly bore your block... pistons have a RANGE of size, the final honing of the block is done to match the manufacturers choice in OD. Edit: and whether you are using cast/hypereutectic or forged pistons. Classic forged pistons have a higher coeficient of expansion than cast, and so they require more initial clearance. In effect, you start out with 60,000 miles of wear with .005 (.0025 x 2, or more) initial clearance for forged pistons.

On all blocks, part of my prep is to use lacquer thinner to remove the heavy oil before I media blast the casting. Otherwise, the blasting process is futile. During that step, I put on a pair of Granny Glasses so I can see the block up close & personal. Thinner will evaporate off the metal quickly, but will hang around in any crack or crevice. I catch a few cracks now & then (mostly on cylinder heads) by doing this... saves me the hassle of media blasting and magna-fluxing when a crack is obvious via the thinner method.

RE: The website- I am on a dial up- I went there a few days ago and had to STOP the transfer because it was hanging up my machine. The site has way too much blinky fuzzy cutesy stuff... but I managed to wait it out today at your suggestion, and it looks like scat has a cast 383 crank that is internally balanced.... more to come on that. Time to investigate.

T-



[Modified by Tom454, 7:48 PM 1/17/2002]

 

This raises an interesting question. I just had a 383 built using a 400 crank, damper and flexplate. The builder suggested also balancing the reciprocating assembly while the machine work was being performed. I took his advise, but wonder how the internal balance will coincide with the external balance of the damper and flexplate. Will they work in concert with the internal components? Will I have a smooth engine? The engine is inthe car, but not yet fired. thanx Bob Myers NC

 

External balance is somewhat a misnomer as only a small part of the balancing is external. All 400 SB & 454 BB came from the factory externally balanced. Many very fast cars have been built from these. When the 400 crank is used to make a 383 external, then the reciprocating assembly is balanced as your builder said.

:cool:

 

Ditto what Ganey said.

The reference to external is due to the fact that the balancer and the flexplate are not "zero" balanced... that is, they contain weights which are used to offset crank imbalance. The balancer & flexplate are "external" to the block, but are part of the internal balancing. Some balancers have "add-on" weights specifically for this purpose... they bolt on to the balancer. Others have welded on weights.

On an "internal" balanced engine, the balancer etc are zero balanced, and all crank imbalance is taken care of solely by adding/subtracting weight from the crank counterweights inside of the block.

To completely balance an engine, all rod, rod bearing, rod cap screws/nuts, and pistons are brought to the same weight as the lightest combination. This is done for both external & internal balanced engines.

This is why the builder has to have all of the parts at his disposal to balance an engine properly.

Also... the clutch can/should be balanced separately if you are going to spin the engine at high rpm for any length of time such as in drag racing or oval/circle track.

I don't recommend balancing for non-high performance daily drivers, but everything else gets balanced.

 

IMO

First of all there is no reason to build a 383. Because it costs the same to build a 391 or 396.

Second - I believe in purchasing the best crank. Because they are a long term investment. I've had the same forged crank in different blocks. My advice is to buy the lightest (44 lbs or less) internally balanced 4340 forging with all the tricks.

This is a picture of my 3.750 stroke 40ish pound, nitrided, micro polished, and coated with oil repellant crank. The only reason I bought it was. 1. This style in 3.875 or 3.800 was not available and I was in a hurry. 2. I also had some concerns about the longer strokes and 7500+ rpm. Now I know that it is not a problem out to 4.00 inch strokers.

Note how tiny the throws are and no heavy metal was used to balance with 685 gram H beam 6 inch rods and lite weight JE pistons This is a work of art!




[Modified by gkull, 9:33 AM 1/18/2002]


[Modified by gkull, 9:37 AM 1/18/2002]

 

I need to clear something up that Ganey brought to my attention... (Thanks Ganey)

RE: Balancing daily drivers...

It is a good idea to balance ALL engines.

However, millions (billions?) of engines have come out of Detroit that were not balanced from the factory... and ran for triple digit mileage. I build Ford, Chrysler, Toyota engines as well as Chevys... 4 cylinders, 6 cylinders, 8 cylinders, and most of them are not balanced from the factory. When I rebuild them, if they are just grocery getters, I feel it is not cost effective to spend money on balancing. My customers agree. This rule of thumb has worked for me for 36 years... I have built a lot of engines (most) that were not balanced. In fact, I just overhauled my own 305 Silverado and I did not balance it. It runs fine. No vibration what-so-ever.

A "daily driver" Corvette should be balanced.... I don't consider it a "grocery getter". A 1980 Pinto Wagon 2.3 4 banger does not need to be balanced, especially if the owner is on food stamps and the rest of the car has 250,000 miles on it.... fenders a flappin. It just simply is not cost effective.

RE: The forged crank... (gkull) I agree it is the best choice. But... some people have to scrimp, save, and shine shoes for their money, and a $400 diff in price is very often the determining factor as to whether they can even build a stroker. That's life. We have to deal with it. If the car is not going to be punished badly, then a cast crank will suffice, given a budget constraint. If you can afford it, then surely go forged.

 

Hmm well if i could afford a $2500 superlight crank, i'd get one,

But i think cranks in general, forged or cast, will be the strong link in the engine, you'd sooner snap a rod, or drop one of the mains before the crank would even start to complain. I'm probably gonna go for a budget forged, with some nice rods and pistons.

Are balancers universal? It would seem to me that a 400 balancer would be a mismatch in a 383?


[Modified by Jenny, 7:52 PM 1/18/2002]