351M vs 400M
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Elder User
Joined: Sep 2000
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From: Bay area
351M vs 400M
When the day comes and I need to replace the 351M I am thinking going to a 400M. The only question I have is will the 400 emit more pollution @ the smog station than the 351 does?
The 400 will be stock except for a high quality aftermarket oil pump. I just would not have the space to do a complete engine build up, so my best bet is a remanufactured engine.
The 400 will be stock except for a high quality aftermarket oil pump. I just would not have the space to do a complete engine build up, so my best bet is a remanufactured engine.
Lead Driver
Joined: Nov 2000
Posts: 6,624
Likes: 342
From: Albuquerque
351M vs 400M
I would think the 400 would do just as good if not better. It's a percentage thing and not volume I believe.
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
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Elder User
Joined: Sep 2000
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From: Bay area
351M vs 400M
Will the 400 offer much of a power increase?
I do know it has a longer stroke. and more cubes equal more torque.
but will I feel it in the seat of my pants type?
Thanks for the info!
I do know it has a longer stroke. and more cubes equal more torque.
but will I feel it in the seat of my pants type?
Thanks for the info!
Posting Guru
Joined: Dec 1999
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From: Benton County, MN
351M vs 400M
It depends on how you build it. From my personal experiences and opinion is that the 400 is a better engine than the 351M, especially for trucks. I have seen some of these engines putting out some nice power.
People who say it can't be done should not interrupt the person doing it.
People who say it can't be done should not interrupt the person doing it.
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Elder User
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From: Bay area
351M vs 400M
I will not rebuild it myself. No time to do so. but swapping the motor out will be done by me.
I would like to replace the pan wiht something with more capaticity, and a better quaility oil pump. Also maybe some nice looking chrome valve covers, 4 barrel intake. but I would have to swap these to pass emmissions here in CA
I would like to replace the pan wiht something with more capaticity, and a better quaility oil pump. Also maybe some nice looking chrome valve covers, 4 barrel intake. but I would have to swap these to pass emmissions here in CA
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Elder User
Joined: Sep 2000
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From: Bay area
351M vs 400M
Would the 400 get pretty much the same MPG as the 351M?
Everything else is the same correct? all the ignition parts will bolt up and work just fine?
I seen in another post someone said the 400 had a bigger clutch than the 351? will my fly wheel work on the 400?
I do know I need a new harmonic balancer!
Everything else is the same correct? all the ignition parts will bolt up and work just fine?
I seen in another post someone said the 400 had a bigger clutch than the 351? will my fly wheel work on the 400?
I do know I need a new harmonic balancer!
Posting Guru
Joined: Dec 1999
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From: Benton County, MN
351M vs 400M
The 400 has a 12" clutch and the 351M has an 11". All ignition parts and external components are identical, or at least compatable. I don't know if your flywheel will work, but I know that question was answered in another post.
People who say it can't be done should not interrupt the person doing it.
People who say it can't be done should not interrupt the person doing it.
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Senior User
Joined: Apr 2001
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351M vs 400M
In stock form, both of these engines are pretty lame. My brother put a fresh 400 in his '78, which previously had a 351m. The 400 has plenty of low-end torque, but everything's over by 4,000 rpm, if not before. There's really not much point in revving it past 2000 rpm. As for gas mileage, he didn't notice any difference. And he switched from a 2v carb on the 351 to a 4v on the 400.
it seems to me that that link to the 400 buildup article that gets kicked around here every once in a while discusses how to get big power out of the 400 while keeping it emissions-friendly. I know the builders were under some constraints as far as emissions went; not sure if they were in CA or not. But I guarantee you will be disappointed in the 400's power output if you were expecting a big difference from the 351. At least set your cam timing straight up and look into higher compression pistons or milling the heads.
it seems to me that that link to the 400 buildup article that gets kicked around here every once in a while discusses how to get big power out of the 400 while keeping it emissions-friendly. I know the builders were under some constraints as far as emissions went; not sure if they were in CA or not. But I guarantee you will be disappointed in the 400's power output if you were expecting a big difference from the 351. At least set your cam timing straight up and look into higher compression pistons or milling the heads.
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Elder User
Joined: Sep 2000
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From: Bay area
351M vs 400M
I am not expecting to go from a 4 banger's power to a bigblock.
I was just wondering what I would probably see as far as increases.
I have also read that tech write up on the "M" series.
I was just wondering what I would probably see as far as increases.
I have also read that tech write up on the "M" series.
Senior User
Joined: Apr 2001
Posts: 128
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351M vs 400M
Well, according to factory specs for 1978 pickups, the 400 has about four more hp than the 351m but makes considerably more torque at lower rpm--roughly 300@1600 rpm, if memory serves. So it might be worth it if you tow with your truck.
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Elder User
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From: Bay area
351M vs 400M
I basically use it as a daily driver. and it is a bronco. So wheeling is also a favorite of mine.
so more bottom end torque is what I want. but I want to stay within the emissions of CA.
so more bottom end torque is what I want. but I want to stay within the emissions of CA.
Senior User
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351M vs 400M
Also, you should be able to put your old clutch, flywheel, etc on your 400. I think they came with a bigger clutch from the factory, and a bigger radiator, for that matter, but I think it's because these bigger motors came only in 3/4 tons from the factory and were expected to do heavy work.
Tuned
Joined: Jun 2001
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351M vs 400M
Also, you should be able to put your old clutch, flywheel, etc on your 400. I think they came with a bigger clutch from the factory, and a bigger radiator, for that matter, but I think it's because these bigger motors came only in 3/4 tons from the factory and were expected to do heavy work.
A lot of them went in Rancheros and I believe some went in larger cars too (LTDII and possibly Thunderbird and some Lincolns). They are one helluva motor though. I'm tempted to take my 351 CJ (4V) heads and build myself a 400CJ. The 400 ought to be able to keep the port velocity up on the 4V heads without losing any low-end torque. Weiand intake spacers can be 'ported' so an aftermarket 351 4V intake can be used. Anyone done this?
Tom
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
351M vs 400M
A lot of them went in Rancheros and I believe some went in larger cars too (LTDII and possibly Thunderbird and some Lincolns). They are one helluva motor though. I'm tempted to take my 351 CJ (4V) heads and build myself a 400CJ. The 400 ought to be able to keep the port velocity up on the 4V heads without losing any low-end torque. Weiand intake spacers can be 'ported' so an aftermarket 351 4V intake can be used. Anyone done this?
Tom[/QUOTE]
I have a 400C-4V in my '53 F100. I have no problems with port velocity, but mine is a cruiser not a work vehicle. I am using an Edelbrock Performer Intake and a 750 CFM Carter carb. The CR with flattop pistons and open chambered (62.8cc) heads is about 10.3:1. That makes 92 Octane pump gas marginal. The other consideration is that the Weiand spacers raise the position of the intake manifold so your stock distributer will not fit. I am using a Mallory Unilite dist, to my knowledge that is the only one that will fit.
Dan Lee
'53 F100
400C-4V
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