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383 Install

Well I can't see the pictures, I'm not a full member. I'll have to take your word on it they are the same, you seem to know what you are doing. I just can't believe how a stock 350 would have an externally balanced flexplate on it without shakin' like a wet dog. That just doesn't make any sense. Makes me want to know how that's possible.
 
folkenheath said:
Well I can't see the pictures, I'm not a full member. I'll have to take your word on it they are the same, you seem to know what you are doing. I just can't believe how a stock 350 would have an externally balanced flexplate on it without shakin' like a wet dog. That just doesn't make any sense. Makes me want to know how that's possible.
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Send me an email to catalinaskirace at hotmail dot com and I'll send you a link. I can't PM, guess because you're not a member.

Trust me, if I thought it was wrong, I'd more then gladly spend the $200 bucks for a new flex plate. At this point that's nothing.
 
The HT383 is an externally balanced engine. GM performance offers three ext/bal flexplates. 14088761 is a 14" with dual patterns for the convertor. Measure the 4l80 convertor diameter. The small convertor pattern is 10.75" and the big is 11.50". The heavy duty 14" flywheel is also the big pattern only it is part #12554824. It is also externally balanced.

Hope you find what you need.
 
84zz4ss said:
The HT383 is an externally balanced engine. GM performance offers three ext/bal flexplates. 14088761 is a 14" with dual patterns for the convertor. Measure the 4l80 convertor diameter. The small convertor pattern is 10.75" and the big is 11.50". The heavy duty 14" flywheel is also the big pattern only it is part #12554824. It is also externally balanced.

Hope you find what you need.
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I know it's an externally balanced motor.

I'm trying to figure out what your suggestion is here.
 
I suggest you do not use the original flexplate. That is why I listed the dimensions of the convertor mounting circle and part #'s. I don't have a 4l80 flex here to measure.
 
84zz4ss said:
I suggest you do not use the original flexplate. That is why I listed the dimensions of the convertor mounting circle and part #'s. I don't have a 4l80 flex here to measure.
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Why do you suggest not using the old one?

It has the same size weight in the same location as the dual pattern one that shipped with the motor. It is the same tooth count and size as well.
 
Success!!!

I found a listing of flex plates for the HT 383.

Requires a counterweighted flywheel or flexplate, (GM Part#'s 10105832, 14088646, 14088650, 14088765, or 14088767).

My factory flex plate(from the 350) is the counterweighted 14088767!!


Thanks for the bearing with me on this one guys. I do appreciate it.

Also of note, the normal 400 crank is 3.75 stroke with a bore of 4.125. The HT383 uses a 3.80 stroke and a 4.000 bore so it's not normal garage build 383. I'm sure that changes a few things in the clearance department.

I'm hoping to get the key turned tomorrow!
 
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So you have confirmed your thoughts where right that they are both counterweighted the same. But the big question still remains, why was that counterweighted flexplate on your 350? And how was it not shaking like a wet dog while it was running? That's what I am wondering. :confused:

In the meantime, enjoy starting up your new engine, that's always exciting.
 
Hate to ask the obvious but: Are you sure that it is a 350 that you removed from your Sub?
 
Keitha said:
Hate to ask the obvious but: Are you sure that it is a 350 that you removed from your Sub?
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The casting number is 14093638 = 350 2 or 4 bolt main, mine happen to be the 4 bolt with a factory windage tray.


I'm pretty sure the PO never did anything to the motor, nor does is have a counterweight harmonic balancer.

The engine ran smooth other then a small vacuum leak that I have now traced to a rotted vacuum line.
 
You do know that 1 pc rear main 350's are externally balanced, hence the flexplates are the same. A '638 block is exactly what you said 87-95 1 pc hydraulic cam with roller provisions, and 2 or 4 bolt main. The HT383 and a 1 pc 350 use the same flywheel or flexplate.

Here you go, from the GM website itself:

IMPORTANT! ​
​
​
​
​
All Chevy small-block and big-block
engines with one-piece crankshaft seal require an
externally balanced flywheel or flexplate.

​

 
I guess that clears up why my old one will work. I never knew all one piece rear main motors where externally balanced.Thanks for the post.
 
Yep, threw me for a loop in the same situation you are in currently. Little piece of info to remember.

-Alex
 
WRENCH-HEAD said:
Yep, threw me for a loop in the same situation you are in currently. Little piece of info to remember.

-Alex
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Strange also that no one else seem to know about the externally balanced 350 one piece rear mains. Even with the fact that a lot of people are doing swaps with newer motors.

Thanks Alex.
 
cuervo said:
Strange also that no one else seem to know about the externally balanced 350 one piece rear mains. Even with the fact that a lot of people are doing swaps with newer motors.

Thanks Alex.
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I looked into this because I was curious, you guys are correct, all the one piece seal engines are indeed externally balanced, I am surprised, good to know. Even the balancer is, but the weight is on the ID of the back of the balancer, so it's not very obvious.
I was also thinking, and I think this is not common knowledge for a simple reason. Because they changed the flexplate bolt pattern at the same time, there are no internally balanced flexplates with the new bolt pattern. So unless someone removes the weight or makes a custom one, it's near impossible to put the wrong flexplate on there since if it fits, (and it hasn't been modified) it has to be the correct one. So unless it's a custom internally balanced crank, there are no interchangeability issues to worry about on the flexplate with the newer engines. Thank you for the info.
 
folkenheath said:
I looked into this because I was curious, you guys are correct, all the one piece seal engines are indeed externally balanced, I am surprised, good to know. Even the balancer is, but the weight is on the ID of the back of the balancer, so it's not very obvious.
I was also thinking, and I think this is not common knowledge for a simple reason. Because they changed the flexplate bolt pattern at the same time, there are no internally balanced flexplates with the new bolt pattern. So unless someone removes the weight or makes a custom one, it's near impossible to put the wrong flexplate on there since if it fits, (and it hasn't been modified) it has to be the correct one. So unless it's a custom internally balanced crank, there are no interchangeability issues to worry about on the flexplate with the newer engines. Thank you for the info.
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I've look at the back of the balancer, there is no weight like you see on the new one or like the after market bolt on weights. It just isn't there.

I never found the info on Chevy's sight about the external balancing of one piece crank seal motors but I was pretty confident once I read the part number on flex plates that could be used on the motor. Mr Head (lawl) made it clear as to why this was.

Now! Everyone start putting out the news so we don't have a thread like this again!
 
cuervo said:
Got it done this morning. Take a look before I put the tank back up.
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Well, for some reason the new pump doesn't work and my fuel gauge pegs 2 inches past full.

I guess tomorrow I'll pull the tank back down and have another go at it.
 
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