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SBC Flywheel Swap. 350 to 383

Old 02-24-2019, 07:28 PM
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Default SBC Flywheel Swap. 350 to 383

Hi Guys,

Please see the attached pictures. Can I take this 350 SBC flywheel and install it on a 383 SBC? Will that work correctly?

Thanks,

Pat


Old 02-24-2019, 08:37 PM
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Should be the same. A 383 is just a bored out 350 cu in.
There were some crankshafts that had to have a balance weight but I think it was only on the 400 cu in.
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Old 02-24-2019, 08:47 PM
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Originally Posted by Stim View Post
Should be the same. A 383 is just a bored out 350 cu in.
There were some crankshafts that had to have a balance weight but I think it was only on the 400 cu in.
And there's the tricky part! A 383 is a bored out 350 with a 400 crank.

I can't answer this for you with 100% certainty, so I won't even throw out what I think.

EDIT TO ADD:


Start by checking the diameter and count the number of teeth. Also note that the counter-balance (raised part on first pic) on the 383 wheel is much larger than the 350 wheel. Get it right. It's not something you want to screw up!

Last edited by ChrisW21; 02-24-2019 at 08:53 PM.
Old 02-24-2019, 08:49 PM
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Originally Posted by Stim View Post
Should be the same. A 383 is just a bored out 350 cu in.
There were some crankshafts that had to have a balance weight but I think it was only on the 400 cu in.
The 383 is a 350 with a 400 crank not bored . So not the same it will vibrate . unless merc did something different .


Originally Posted by PatrickPresti View Post
Hi Guys,

Please see the attached pictures. Can I take this 350 SBC flywheel and install it on a 383 SBC? Will that work correctly?

Thanks,

Pat
What is wrong with the flywheel ? if its just the gear its a cheap and easy fix

Last edited by prowlersfish; 02-24-2019 at 08:55 PM.
Old 02-24-2019, 08:59 PM
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Originally Posted by prowlersfish View Post
The 383 is a 350 with a 400 crank not bored . So not the same it will vibrate . unless merc did something different .




What is wrong with the flywheel ? if its just the gear its a cheap and easy fix
I'm converting the 383 from a Sterndrive setup to an Inboard setup so I need to change the flywheel because the ring gear needs to be to the rear of the flywheel...
Old 02-24-2019, 09:02 PM
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Any recomendations on where I can buy a correct flywheel?
Old 02-24-2019, 09:04 PM
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oh
Old 02-24-2019, 09:19 PM
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Based on the casting numbers and internet searches, they are both for 350 internally/neutral balanced engines. I also found that 383s came in internal or external balance. Looking at your pics, they are both internal balance, as the external balance had a very pronounced raised weight cast into it. If the 383 flywheel in the pic is from the actual engine you have, I think with flywheel will work.
Old 02-24-2019, 09:24 PM
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Originally Posted by getusummm View Post
Based on the casting numbers and internet searches, they are both for 350 internally/neutral balanced engines. I also found that 383s came in internal or external balance. Looking at your pics, they are both internal balance, as the external balance had a very pronounced raised weight cast into it. If the 383 flywheel in the pic is from the actual engine you have, I think with flywheel will work.
You mean like these?? Notice one is bigger than the other.


Last edited by ChrisW21; 02-24-2019 at 09:29 PM.
Old 02-24-2019, 09:35 PM
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No, more like the one on the right in this pic:

Old 02-24-2019, 09:44 PM
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So you think your pic has a more pronounced cast weight than the previous pics? The bigger weights are for internally balanced motors? What am I missing here?
Old 02-24-2019, 10:03 PM
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start with bolt pattern then go to counting # of teeth (diameter to fit the FW housing engine block) , you have to then determine if your 383 is internal or external balanced IE 400 ci or i think from my memory of research Mercruiser OEM crankshaft,.
one of the units you have there should be right , if not there are manufactures that make custom FW for race applications.

whatever you do be sure the correct FW is used.because it must be balanced to suit crankshaft.

post outcomes , i had a good source of info from people here on the forum and also posted my findings when i did my conversion.

Last edited by 1breakinit; 02-24-2019 at 10:20 PM.
Old 02-24-2019, 11:06 PM
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Also, don't forget 1 piece rear main vs. 2 piece. Different flywheels.

Not as easy as you thought, is it? I also searched the casting numbers and what I found said they were both for 350 Chevy. GM had so many different variations it's really hard to find parts sometimes. Throw in the fact that it's a 383, which could be a stroker 350 w/400 crank, or purpose built 6.2l, the rear main seal thing, ring gear variables, and the fact that older GM records suck............

Now you see why I won't say which (if any) will work. Too many variables.
Old 02-25-2019, 02:01 AM
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Originally Posted by 1breakinit View Post
start with bolt pattern then go to counting # of teeth (diameter to fit the FW housing engine block) , you have to then determine if your 383 is internal or external balanced IE 400 ci or i think from my memory of research Mercruiser OEM crankshaft,.
one of the units you have there should be right , if not there are manufactures that make custom FW for race applications.

whatever you do be sure the correct FW is used.because it must be balanced to suit crankshaft.

post outcomes , i had a good source of info from people here on the forum and also posted my findings when i did my conversion.
The one I wrote "383" came off of MerCruiser MPI 383 engine that was a Sterndrive setup. The one I wrote "350" came off of my MerCruiser MPI 350 Inboard setup. I am converting my 383 from a Sterndrive to an Inboard so That's why I am trying to see if that 350 flywheel will work on the 383...
Old 02-25-2019, 03:53 AM
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Originally Posted by prowlersfish View Post
The 383 is a 350 with a 400 crank not bored . So not the same it will vibrate . unless merc did something different .




What is wrong with the flywheel ? if its just the gear its a cheap and easy fix
383 is is bored thirty over.377 is standard bore.
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Old 02-25-2019, 04:02 AM
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Originally Posted by PatrickPresti View Post
The one I wrote "383" came off of MerCruiser MPI 383 engine that was a Sterndrive setup. The one I wrote "350" came off of my MerCruiser MPI 350 Inboard setup. I am converting my 383 from a Sterndrive to an Inboard so That's why I am trying to see if that 350 flywheel will work on the 383...
In the beginning,stroker kits used a turned down 400 crank that were externally balanced,350 was not.Your new style 383 has internal balance like a 350 so it should work.Diameter could be different,whats the tooth count of the two flywheels and bellhousing dia.?
Old 02-25-2019, 04:34 AM
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Originally Posted by mitchell master View Post
In the beginning,stroker kits used a turned down 400 crank that were externally balanced,350 was not.Your new style 383 has internal balance like a 350 so it should work.Diameter could be different,whats the tooth count of the two flywheels and bellhousing dia.?
I would have to count the teeth. The flywheels are both 14" diameter. The bellhousing from the 350 fits on the 383...
Old 02-25-2019, 05:44 AM
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Originally Posted by PatrickPresti View Post
I would have to count the teeth. The flywheels are both 14" diameter. The bellhousing from the 350 fits on the 383...
https://www.chevrolet.com/performanc...els-flexplates
Old 02-25-2019, 05:50 AM
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It's been over 30 years since I worked at a speed shop when a guy put the balance weight (add on weight) on indexed wrong on a 400.
That engine wanted to jump out of the boat at low rpm!
He had to pull the Mercruiser back out just to turn the weight over (IIRC).
Old 02-25-2019, 05:58 AM
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The cast in weight is the issue, and the problem. You can drill out the new flywheel to equal the external balance required. Bottom line..they are NOT interchangable!!

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