400 small block

[georgiared84]

All right. I've just got my last engine purchase off to the machine shop and need something new to play with. I've got a place here where I can pick up 2 bolt 400 blocks with caps magnafluxed for around 200. I know from searching so far the following:
I need a four core radiator.
They don't like high rpms.

All the brackets. etc... I have are from 350's and 305's will most of them work?
I know I need different flexplate and dampner. What about the trans. Will a later model 700r4 built for towing work? I want to keep the rpm's down on the highway which is why I want to stick with the 700.
Do they use the same setup for motor mounts?
What about durability? I saw a post that said to actually stay away from the 4 bolt 400's.
Anyone else have any tips?
I've built 350's and 305's before and am just wondering what is different (besides cost)

 

[bigmack]

All of the brackets, mounts, and everything else external will work between the 350, 400, etc, of like year models, like you said, I would suggest a 4 core radiator and a good fan, I treat mine like a big block and never have a problem with cooling. As far as high RPM's, it depends on what you consider high. Both of my trucks have 400's in them and they see 6000-6500 RPM's on a regular basis, it all depends on how you build the engine, and the quality of the parts that goes in to it. There is no difference in the tranny's for a 400, so your 700R4 will bolt up fine. You will love it, they are great engines, they make a lot of torque for a small block. Post any particulars that you need to know about them and I'll try to answer any questions that you have, I'm not claiming to know it all but I have built 4 or 5 400's.

 

[georgiared84]

How about exhaust? I've got a stock setup that's never been used for a 350. Single cat. standard pipe size. Dual exhaust outlet. Just needs to be bolted in. Will that work for the 400?
I've got to make it pass emissions as all my truck bodies are 83 or newer. Can I rebuild an older 400 (mid 70's) bottom end and put on my emissions legal intake / heads, etc...? Any certain year range block I should look at to do this? Also can I just follow a basic vacuum diagram from about the same year? (They all still have the diagram stickers in them.)

 

[bigmack]

I have 3" duals on both of mine with no cats, but I don't have to pass any emissions here. Maybe someone else will post on their exhaust, but a 400 needs a to breathe more than a 350. A 400 has steam holes that come up thru between the cylinders, so you have a few different routes that you can take as far as the heads are concerned, you can use some factory 400 heads that have the steam holes in them allready, use some non 400 heads and have the steam holes drilled in them, or have the steam holes in the block plugged by the machine shop and use any head that you want. In one of my motors, I had the holes plugged in the block, and the other I used some old double hump heads and drilled the steam holes in them. I haven't had any problems at all with either of them. I would say that any year block that you can find should be fine, I believe the 2 that I have are 73 or 74 models. And yes you should be able to follow the vacuum info that you have.

 

[georgiared84]

Anyone else using a 400 sb with emissions? Any tips that would differ from a 350? Can anyone let me know what kind of mileage they get. My 305 sucks gas. My 350 gets between 13 and 15 in town. What could I expect from the 400?
I might actually get all 3 vehicles running someday.