383 Flywheel 400 motor

[23T]

Will a 383 Flywheel work on a 72 400 motor? Are do I need to have it balanced to the new motor? Thanks for any and all help/ideas!

[ajmopar]

383's are internally balanced and 400's are externally balanced, so you will have to get the flywheel, crank and balancer balanced to get it to work. Or you could find a 400 flywheel, but they are not that common.

[6 packin]

You could replace the 400 cast crank (external balanced) with the 383 Nuetral balanced (internal baqlanced). The 400 with the 383 crank has many advantages over the cast crank. There identical except the 383 is steel and the 400 is cast iron. If you use the same flywheel and harmonic balancer as a package from the 383. there will be no reason to balance it. Factory balance is ok for daily driver/street engines.

[dirty dan]

Originally posted by 6 packin
You could replace the 400 cast crank (external balanced) with the 383 Nuetral balanced (internal baqlanced). The 400 with the 383 crank has many advantages over the cast crank. There identical except the 383 is steel and the 400 is cast iron. If you use the same flywheel and harmonic balancer as a package from the 383. there will be no reason to balance it. Factory balance is ok for daily driver/street engines.

Hey 6packin
You are right about the fit and useing the harmonic ballance with the right crank.
But I would be sceptical when it comes to the ballanceing.
Simply because the 383 and the 400 had differant piston weights.
This would have an effect on the amount of bob weight required for ballanceing.
There for it would have an effect on the factory ballance.
The bob weight required for a 400 is 258 grams.
I don`t know what it is for a 383..
If someone could find out the differance between the two,then we all would know if ballanceing is needed or not.

[dirty dan]

Originally posted by 23T
Will a 383 Flywheel work on a 72 400 motor? Are do I need to have it balanced to the new motor? Thanks for any and all help/ideas!

You r best bet would be to have the fly wheel ballanced to the 400 crank. I had one done for $100 .
I took an old 400 crank and ballance from another 400 and had it ballanced to it.
That way I didn`t have to tear into the engine I planed on
useing.
The machine shop will want to know what the bob weight is for a 400. it is 258 grams
There is a bearing available from mopar performance to replace the need for a pilot bushing.
Part #53009180.
In 1972 the 400 was introduced in a very limeted amont of these were steel cranks.((very limited amount))
This was when the factory was useing up the remaining 383 cranks.
If you have one of these you have a very rare peice.
After that all 400`s were cast crank and externaly balanced.

[6 packin]

If your going to get balancing done go with the steel crank of the 383. It makes sence to go with the superior crank of the 383. The in the future if deside to go automatic you wont be running into the same problems. My brother has replaced a 400 crank with the 383 parts as an package. The engine has been togather for 3 years run only 1/4 mile. Runs low 12's. This winter we fresh up the engine with new rings rod and main bearings. They looked good considering the 4000 RPM launches it has been through.

[23T]

I will not ever run anything but a 4 sp in this 23T and do not really want to unbutton the bottom end. If I am luckly and have the steel crank in this motor is it still internally balanced? and is there a way to tell without pulling the pan and checking the casting #?

[6 packin]

The 400 never had a steel crank. about all 383 had them too. The balancer will look big and have a odd lookin weight on it if is cast crank. The 383 will be much small and look alkot like a 318 balancer if you have one to check out. Any 318 will have it.

[dave571]

To install the 383 crank, you're balancing the entire rotating assembly. The 400 pistons are much bigger(They are the biggest bore mopar) so the weights are way different. Complete tear down, not just replaceing the crank.

If you're not in the process of rebuilding the motor, then this is a complete waste of time and money.

The 383 flywheel just needs a weight added to it. I had a weight added to a 383 converter(to use in my 400) at a transmission supply store. I cost me a whopping 20 canadian($13.00 us funds) and took 7 minutes.

[Ausydad]

I would say find the 400 flywheel and sell the 383 one to me (lol)....

[6 packin]

The engine is question is not a automatic and is stick shift. Balancing will cost way more than that. The will be weight took from the flywheel not added to it. Being a standard shift a cast crank will be a waste of money for this. By the time you pay to have the flywheel balanced and ready to go. The 383 will be had for the same price. Why bother all that money to a cast crank engine.

[23T]

OK Team, Hope you are still reading the thread, My machinist for the last 25+ years died. I called a new " Speed Shop" The man? said he could balance my 383 flywheel if he had another 400 to "spin" from. I told him if I ahad a 400 flywheel I would not be calling him. Then he said he could balance the 383 flywheel off a 400 flex plate and he wants $90.00 per head to mill my heads .060 and cut the intakesides.

My first instinct was to run far and fast, Can you use just a flex plate to match a flywheel?

ps: Ausdad I will trade a 383 flywheel for a 400 even, might even pay the shipping.

[dirty dan]

Originally posted by 6 packin
The 400 never had a steel crank. about all 383 had them too. The balancer will look big and have a odd lookin weight on it if is cast crank. The 383 will be much small and look alkot like a 318 balancer if you have one to check out. Any 318 will have it.

Hey 6packin
You know what they say.
Never say never.
Go back and regroup .
they did have some ((note some)) as in very few steel crank 400`s ,only in 72.
I don`t wish to about it.
with you but thems the facts

[dirttrackracer]

None of the stock flex plates were balanced. To balance that 383 flywheel for a cast crank 400 try to find an old direct conection engine book it has the information on how to balance your flywheel.Its a matter of removing the correct amount of metal at the proper distance from centerline and the correct angle from the offset hole in the flywheel. If you can't come up with the book I have one just have to dig it up. could scan the info and attatch for you.Let me Know.

[dave571]

I don't understand you're math on the cost's involved here, 6packin.

Dan has already said he had a flywheel balanced for $100.

How is 23t going to buy a steel crank, a balancer, bearings, timing cover gasket and seals, a rear main seal, an oil pan gasket, oil, and a filter, for only $100

Besides that, 23T has said he doesn't want to tear down his bottom end. It's a lot of work, in or out of the vehicle.

I see the benefits of a steel crank, but it would seem to be unnecessary here. A rebalanced flywheel, or finding the right flywheel, would seem to be a much easier solution.

[Tarrbabe]

Maybe I don't know anything about it but the 383 and 400 should have a different bob wt. than the other. The 400 piston is heavier than the 383. The piston is bigger that the 383. If you are planning on a MILD street engine the 383 crank will work with just the stock balance. If you plan on running this engine hard at all, you will get much better performance and longevity if you balance the whole thing. The idea is to build it and live with it and it with you. Yes you can put the 400 balance on a 383 and it will live for an acceptable time, but if you want it to hold up until the time expected, you will get it balanced. If you expect it to last and perform as expected, you will spend the little extra to get it balanced correctly. Engines put out more hp if they are in balanced and put out more hp if they aren't fighting the internal weight problems. Do you want it to live? Do you want it to run right? It aint that much money. $100? Talk to someone who is an expert, like cuda66273, he will tell you the same thing. I hope!

Just thinking out loud.

[23T]

Dirttrackracer, if you could post the info you have I will be very greatful, This motor is going in a 23T 1900#, just a cruser and toy no track time intended just the occasional rice, chevy, ford fry.

[John Kunkel]

Here's a page with the info on how to modify the flywheel for cast crank big blocks:
http://www.moparts.com/ub/ubb/Forum4/HTML/000009.html

[6 packin]

Ok
My bad! I thought He said he had a 383 crank and a flywheel. I had to go back and read some threads. To even balance the 400 flywheel to the cast crank without balancing the rest of the rotating assembly would at best be poor. Mopar did not to a great job from the factory at there engine balancing. I just figured he was going to disaseemble it to balance the the crank and rods etc. with the flywheel. At that point it would be best to use the 383 crank, being it would not cost you no more money. I had a 360 engine built ready to go but could not find a 360 flywheel. at least on for a car, had one for a truck. I ended up balancing a 318 flywheel. I had the chassis manual with the weight to remove and the location of the 3 holes to drill. Well it worked ok, but I think it was still not correct. It is best to balance everything as one unit for the best results.

Merry Christmas to all,
and all
A good night!

Bob

[dirttrackracer]

Can't seem to get the attachments to work I'll try your E-mail

[23T]

Thanks dirttrackracer