Piston Rod movement
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From: Morgantown US
Piston Rod movement
I am putting together a 351M motor I obtained used. I discovered yesterday the there is some movement left to right along the crankshaft of the piston end caps. They are not loose "around" the crankshaft, just horizontally along it. The movement is very slight. I just wondered if I should be able to move them at all. Also, if needed, can I just purchase and install new crankshaft bearings, without pulling the shaft and having it machined. I only need about 10k out of this motor as over in the other corner of my garage I am building a super duper 2000 hp (lol) 400m to put in it eventually. But I do need to drive the truck occasionally in the meantime. Thanks for your help
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From: PacNW
Piston Rod movement
>I am putting together a 351M motor I obtained used. I
>discovered yesterday the there is some movement left to
>right along the crankshaft of the piston end caps. They are
>not loose "around" the crankshaft, just horizontally along
>it. The movement is very slight. I just wondered if I
>should be able to move them at all. Also, if needed, can I
>just purchase and install new crankshaft bearings, without
>pulling the shaft and having it machined. I only need about
>10k out of this motor as over in the other corner of my
>garage I am building a super duper 2000 hp (lol) 400m to put
>in it eventually. But I do need to drive the truck
>occasionally in the meantime. Thanks for your help
It's normal to have some "side to side" movement of the rods when they're installed on the crankshaft. What you don't want is any perceptible play along the perpendicular axis or "around" as you call it, so it sounds like you're fine. Yes you can install new main and rod bearings without having the crank machined, for a temporary motor it shouldn't be a problem.
>discovered yesterday the there is some movement left to
>right along the crankshaft of the piston end caps. They are
>not loose "around" the crankshaft, just horizontally along
>it. The movement is very slight. I just wondered if I
>should be able to move them at all. Also, if needed, can I
>just purchase and install new crankshaft bearings, without
>pulling the shaft and having it machined. I only need about
>10k out of this motor as over in the other corner of my
>garage I am building a super duper 2000 hp (lol) 400m to put
>in it eventually. But I do need to drive the truck
>occasionally in the meantime. Thanks for your help
It's normal to have some "side to side" movement of the rods when they're installed on the crankshaft. What you don't want is any perceptible play along the perpendicular axis or "around" as you call it, so it sounds like you're fine. Yes you can install new main and rod bearings without having the crank machined, for a temporary motor it shouldn't be a problem.
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Senior User
Joined: Apr 2002
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From: Morgantown US
Piston Rod movement
Thanks guys, I feel better now. I will measure and plasti gauge. I am trying to avoid "machine work" with this motor and just build it in my garage..I have 400 lying in the corner ready for phase two..I'm going for 1000 hp with it so I can beat Shazam ! 
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Joined: Dec 2001
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From: space city
Piston Rod movement
there is actually a spec for the rod big-end side clearance - i don't know if it's a total clearance per crank pin (seems like it would be) or what, or even how much the clearance should be, but the info is out there somewhere. i think i have it in a book at home...
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Joined: Feb 2001
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From: Porterfield
Piston Rod movement
>Thanks guys, I feel better now. I will measure and plasti
>gauge. I am trying to avoid "machine work" with this motor
>and just build it in my garage..I have 400 lying in the
>corner ready for phase two..I'm going for 1000 hp with it so
>I can beat Shazam !
Rod Clearances should be .015 to .020
So did I hear Competition out there for a bigger and badder 400.....
Well just so you know I'm thinking about having a 4.500 stroke crank built that will give me 466 Cid. and 1150 H.p.....
This ones got me thinking just how tough the bottom end is going to be ..
ShaZam
>gauge. I am trying to avoid "machine work" with this motor
>and just build it in my garage..I have 400 lying in the
>corner ready for phase two..I'm going for 1000 hp with it so
>I can beat Shazam !
Rod Clearances should be .015 to .020
So did I hear Competition out there for a bigger and badder 400.....
Well just so you know I'm thinking about having a 4.500 stroke crank built that will give me 466 Cid. and 1150 H.p.....
This ones got me thinking just how tough the bottom end is going to be ..
ShaZam
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Posts: 829
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From: Porterfield
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Senior User
Joined: Apr 2002
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From: Morgantown US
Piston Rod movement
Geez Shazaam, let me catch up first!! When you go rob the bank to build that sucker can I come? 
I found the below post. I dont plan on exceeding 500 hp with my new motor but should I still look for this type block?
MCC castings before march 19 1977 (i think) crack in the lifter valley
DIF well i have seen of 3 so far, no issues on mine.
there was a block change in 1977 that made the webs stronger, also a 1973 block that has the fmx bellhousing.
bill_beyer
Club FTE Member 2. "RE: Casting codes"
16-Sep-02, 10:10 AM (EST)
What GT40 said is absolutely correct. As far as the actual codes go I'd look for a D7TE or D8x block to build.
FTE Moderator
Thanks for the rod clearance data...I found it last night in my manual too. Hopefully by next monday I will be ready to order rings, and bearings and gaskets to try and put it all back together..
I found the below post. I dont plan on exceeding 500 hp with my new motor but should I still look for this type block?
MCC castings before march 19 1977 (i think) crack in the lifter valley
DIF well i have seen of 3 so far, no issues on mine.
there was a block change in 1977 that made the webs stronger, also a 1973 block that has the fmx bellhousing.
bill_beyer
Club FTE Member 2. "RE: Casting codes"
16-Sep-02, 10:10 AM (EST)
What GT40 said is absolutely correct. As far as the actual codes go I'd look for a D7TE or D8x block to build.
FTE Moderator
Thanks for the rod clearance data...I found it last night in my manual too. Hopefully by next monday I will be ready to order rings, and bearings and gaskets to try and put it all back together..
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Posting Guru
Joined: Aug 2000
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From: PacNW
Piston Rod movement
>Geez Shazaam, let me catch up first!! When you go rob the
>bank to build that sucker can I come?
>
>I found the below post. I dont plan on exceeding 500 hp with
>my new motor but should I still look for this type block?
>
>MCC castings before march 19 1977 (i think) crack in the
>lifter valley
>DIF well i have seen of 3 so far, no issues on mine.
>there was a block change in 1977 that made the webs
>stronger, also a 1973 block that has the fmx bellhousing.
>bill_beyer
>Club FTE Member 2. "RE: Casting codes"
>16-Sep-02, 10:10 AM (EST)
>What GT40 said is absolutely correct. As far as the actual
>codes go I'd look for a D7TE or D8x block to build.
>FTE Moderator
I would definitely look for a CF (or DIF) D7TE or D8x block if I were going to put any serious $$$ into building a strong 400. I'd also try to stay with the bare minimum on the overbore. You'll have to either do the measuring yourself or talk to your machinist about being conservative on the bore specs.
>bank to build that sucker can I come?
>
>I found the below post. I dont plan on exceeding 500 hp with
>my new motor but should I still look for this type block?
>
>MCC castings before march 19 1977 (i think) crack in the
>lifter valley
>DIF well i have seen of 3 so far, no issues on mine.
>there was a block change in 1977 that made the webs
>stronger, also a 1973 block that has the fmx bellhousing.
>bill_beyer
>Club FTE Member 2. "RE: Casting codes"
>16-Sep-02, 10:10 AM (EST)
>What GT40 said is absolutely correct. As far as the actual
>codes go I'd look for a D7TE or D8x block to build.
>FTE Moderator
I would definitely look for a CF (or DIF) D7TE or D8x block if I were going to put any serious $$$ into building a strong 400. I'd also try to stay with the bare minimum on the overbore. You'll have to either do the measuring yourself or talk to your machinist about being conservative on the bore specs.
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