400 small block questions
Thread Starter
Team Owner
Joined: Jun 2002
Posts: 21,510
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From: On a Wisconsin Death Trip
400 small block questions
Maybe someone here can help me. I know the 400 sb is externally balanced and there are other harmonic balancers available that clear the crossmember, but what about the flywheel? I have an 87 with the one-piece rear main and 4+3 trans. Will the flywheel off an 85 work? Will I have to add weight to it?
What is the consensus on this motor? I have heard good and bad, mostly surrounding the siamesed bores.
Any input would be appreciated! :seeya
What is the consensus on this motor? I have heard good and bad, mostly surrounding the siamesed bores.
Any input would be appreciated! :seeya
Melting Slicks
Joined: Mar 2003
Posts: 2,744
Likes: 9
From: FL
Cruise-In VI Veteran
Re: 400 small block questions (loiq)
The 85 flywheel will bolt up, BUT it will NOT the right balance. It's set up for an internal balance motor. You "might" be able to have someone add the weight to it, or possibly purchase an aftermarket unit.
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: 400 small block questions (loiq)
Maybe someone here can help me. I know the 400 sb is externally balanced and there are other harmonic balancers available that clear the crossmember, but what about the flywheel? I have an 87 with the one-piece rear main and 4+3 trans. Will the flywheel off an 85 work? Will I have to add weight to it?
What is the consensus on this motor? I have heard good and bad, mostly surrounding the siamesed bores.
Any input would be appreciated! :seeya
What is the consensus on this motor? I have heard good and bad, mostly surrounding the siamesed bores.
Any input would be appreciated! :seeya
In retrospect, I would have bought a balanced rotating assembly and had them balance the back of the crank with the flywheel and clutch attatched.
Or you can indent your cross memeber to allow for the use of the 8" 400 SBC damper.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: 400 small block questions (loiq)
Unless you have a special aftermarket crank, your flywheel will NOT work. The one piece seal cranks and the two piece seal cranks, (all production 400s) have different flywheel bolt patterns. And as you know, the 400, unless expensively, internally, balanced requires an unbalanced flywheel. A stock 153 toothed 400 flywheel, solves both these problems. Good luck, and...
RACE ON!!!
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RACE ON!!!
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Member NHRA
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: 400 small block questions (CFI-EFI)
I used my stock 1985,,, 153 tooth flywheel on a standard 400 crank., 2- piece seal
So yes you can use your flywheel with a flex plate adapter and external rear balance of the clutch and flywheel.
[Modified by ld85, 10:27 PM 6/4/2003]
So yes you can use your flywheel with a flex plate adapter and external rear balance of the clutch and flywheel.
[Modified by ld85, 10:27 PM 6/4/2003]
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: 400 small block questions (ld85)
I read that he had an '87 and failed to note that the question refered to an '85 flywheel. As you well know, your method works.
The point of 1 piece and 2 piece seal crank bolt patterns, is still valid. Just not applicable to the question.
RACE ON!!!
The point of 1 piece and 2 piece seal crank bolt patterns, is still valid. Just not applicable to the question.
RACE ON!!!
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Drifting
Joined: Apr 2001
Posts: 1,926
Likes: 279
From: Portugal
Re: 400 small block questions (loiq)
Make sure you buy a 2-bolt main block, not a 4-bolt main block. Believe it or not, the factory 4-bolt main 400 blocks are weaker than the factory 2-bolt main 400 blocks. :crazy:
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: 400 small block questions (DiabolicalDave)
I do remember finding a flywheel that is 153 tooth that is made for a 400 crank, found it searching the web. I would do this if I were to do it over again.
Melting Slicks
Joined: May 2001
Posts: 3,270
Likes: 26
From: Winchester VA
Cruise-In V Veteran
Re: 400 small block questions (ld85)
A couple of things I would have done different,
1. If possible, start with an aftermarket block with larger cooling jackets and more metal between the bores. Check out World Products.
2. Make sure your piston/rod combo is on the light side. There are aftermarket cranks for the 400 block designed for internal balancing. I have an Eagle designed for this, unfortunately my rod/piston combo was too heavy for the counterweights. With the correct piston/rod weight, no mallory metal ($$$$$) will be needed to internal balance.
If you decide to external balance, get in touch, I have an unused ATI Superdamper and a Hays Flywheel for externally balanced 400's
1. If possible, start with an aftermarket block with larger cooling jackets and more metal between the bores. Check out World Products.
2. Make sure your piston/rod combo is on the light side. There are aftermarket cranks for the 400 block designed for internal balancing. I have an Eagle designed for this, unfortunately my rod/piston combo was too heavy for the counterweights. With the correct piston/rod weight, no mallory metal ($$$$$) will be needed to internal balance.
If you decide to external balance, get in touch, I have an unused ATI Superdamper and a Hays Flywheel for externally balanced 400's
Burning Brakes
Joined: Feb 2002
Posts: 804
Likes: 5
From: Fresno CA
Re: 400 small block questions (loiq)
I used at CAT 5140 Forged 400 Crank and the CAT 4340 6" rods with Ross Pistons and there was no problem internally balancing this combo without adding mallory to the crank. I used a 7 1/4" Fluidamper and a new flexplate which turned out to be 168 tooth so I had to use a different flexplate cover from GM..no big deal though.
