I've got a few questions about the 400 small blocks.

When building up a 400, what are the differences between it and a 350.

I know of:
The 2 piece rear main seal vs. the 1 piece rear main seal.
The differences in sizes on the harmonic balancer.
The 400 being externally balanced while the 350 is internally balanced.
The 400 having old style heads vs the new centerbolt heads.
The flywheels I believe are different.

What other problems would I run into, I would like to make the engine capable of plenty of boost later on down the road as well as running all my accessories. AC, P/W, P/B, bascially a daily driver that'll move.

I just trying to figure out if it'd be worth stepping up to the 400 or just using a 350. Also, trying to avoid the 383 though I like it, due to clearance issues and more labor costs.

 

Thats about the only difference between the two, except for a couple things, which would be important: If I understand what you're saying, you're going to build some decent power. That means the stock heads are junk for what you are doing. Make SURE that heads you install have steam holes drilled for a 400. Since the 400 has siamesed(no water bewteen) cylinders, these allow steam buildup to vent, helping to cool the engine. Second, the flywheel must be externally balanced as well, and it is specific to the 400(meaning, you can't use a wheel for a 454, also externally balanced). I don't know for sure, someone else may know, but I beleive a 153 tooth flywheel is avaialble for a 400(small diameter). If not, you must use a small diameter flywheel for a standard balance small block, and run an add on balance weight. Other than that, you should be good to go. the main bearings are larger, just FYI, and uses a larger 2 peice rear seal as well. The stock rods are also shorter, and stock pistons have a dish in them(not flat-top). Hope that gives you the answers you need. You will have to double check the flywheel availability, cause I dont' know for sure.

 

Ahh, yea I had heard alot about the steamholes. It would have aftermarket heads on it, so I assume they would be included if not, I could just get around to having them drilled.

But how did the old stock 400s run? Did they overheat as well.


If I was to build this, I would be just a 400 block and I'd go from there. I'm just trying to see what differences I'd run into and the problems I should expect before attemtping the build.

Does the 400 like boost? Or does it have any weird problems that come along with trying to run decent amount of boost.

No one makes an aftermarket flywheel that would adapt to a 700r4 or th350?

btw, Thanks for your help jwscab

 

Also, someone who had viewed this post had asked me over aim about my clear side marker lights. Please resend a message as I forgot to click add buddy.

 

You would also have to spend more if you wanted to make the 400 a full roller motor.

 

Omar why is that, I know the new lifters would be needed, but what else?

 

Omar?

 

Correct me if I am wrong but I believe that the 400's, starting in 1970, have a 2.65" main bearing cap diamater opposed to the 350's 2.45" main cap diameter on the crank (starting in 1968), and if you intend on making a long stroke motor the larger diameter (400) main cap journals are preferred for durability

-Gabe

 

To answer the roller question, untill 86 or 87, all factory blocks were solid lifter, not roller. Roller lifters need special retainers. The newer blocks are machined to accept these retainers, where the older blocks are not. Hence the need for an aftermarket retro-roller kit. They are pretty damn expensive too.

 

The 400 does have larger main journals, which is a good thing for a stroker, but you would have to seriously build a stroker to necessitate that kind of journal diameter(like 700hp serious). The larger diameter helps dissipate heat, which is what kills motors. Also, the 400 more correctly had FLAT tappet camshafts, hydraulic ones. The solid lifters were not installed in any factory engines pretty much after 1971-1972. To use roller camshafts, you would need aftermarket retrofit roller lifters, which are about $250 a set, but well worth it, IMO. The 400's have been mislabled 'overheaters', but i have never had any trouble with them, provided the proper maintence is done(check coolant, keep tabs on opeating temp, BIG radiator). They respond the same as any other smallblock with supercharging, etc. Becuase they are the largest small block(factory), the only thing that becomes an issue for high horsepower is cylinder heads, as you need more valve for more airflow. The 400 was seriously choked stock, a minumum of 2.02 valves and a good flowing cylinder head, and you are in business.

 

Well, I'm seriously thinking about trying it within the near future. Except I'm thinking about going with a solid lifter style motor instead.

Guy that works with me just got his 400 to run 9.80s at 138 in a 3400 pound car. I'd probably run something similar to what his is.

Thanks for the help, I'll try to figure it all out soon, asking questions now doesn't help awhole lot since I don't have the money right off hand.

 

Sorry, bro..i forgot about this thread...but the guys answered everything already.

 

depending on your cash flow.you could get a forged rotating assembly for the 400 that is internally balance.also there are two different 400 that were made one block has 2 freeze plugs the other has 3(i've heard that the 3 were more desirable) also a production 400 has siamesed cylinders which are thin and running a lot of boost probably isn't a great idea.you'll need the roller cam,roller lifters that have a tie bar attached and a cam button to keep the cam from walking.the rocket block is a whole different animal it has wider pan rails(different pan),a raised cam location,larger oil gallery holes and a few others i cant remember.it will be hard to find an unbored original 400 if it is .020 over that already makes the walls even thinner.If you're mind is set on a 400 go with a sportsman bow tie block and order your own assembly.


hope any of this helps

also you will probably want to go with 6.0in. rods(instead of the 5.7's)doing that may also cause clearance problems with a high lift cam.

 

Well, I've been thinking it through and I think I figured out how I want to do it. Tell me if you agree.

Bascially, I'm trying to avoid an aftermarket block for two reasons. One I'm not perfect with engine building, and I'd hate to ruin a block that cost 2 grand. Second, a stock block will be cheaper.

Tell me if you see any problems with this: You'll notice some parts are extremly expensive in comparison to some that are really cheap. Reason for this is first build up, when I go to do a second buildup I'll use some of the more expensive parts over.

400 block with standard bore
TRW forged pistons and pins 9.6:1 compression with 76cc heads
Speed Pro plasma moly ring set
Unsure on connecting rods (want to go with 6" rods) and crank, going to look for something cheap but something that can hold up to a 200 shot fairly easy
Retrofit rollers /w roller cam something around 230-235 duration and highest lift I can go. Probably around .530" with an LSA of 112.
AFR 215cc raised runner or either 210cc heads. Still unsure on that.
Miniram intake followed through with a 150-200 shot of nitrous.
Hopefully I'll see 11's.

Then later on down the road, buy me and new block and top components and run the same heads and intake with a D1-R or F-1 procharger. But lets get the above setup working first.


Does the above setup sound good? Do you see any problems with it?

 

hey man sounds bitchin. What about fuel delivery though? That is the toughest part. Convincing the computer to work with your parts properly. I have a 400 sml blk sitting on a engine stand out back in my shed. Getting it together ain't hard its makin it work togther i'm not sure about.

 

Well I am a couple steps ahead of you both I got the 400 in the car just not all together yet . GO with the 400 and ignore all the wives tales you hear about it. The only ones that ever overheat are the ones that the people didn't know what they were doing when they put it together. Hopefully GM will introduce a 400 crate motor that would be sick!

 

Well, I'll be running the Miniram with whatever size injectors I think I'll need. Not sure at the moment. I should be buying all the prom burning stuff within the near future, so by the time I have the 400 ready to drop in, I hope to know enough about that. Other than that, I hope it all works out.

This will be my first real engine build, but I have alot of friends who have done this, so I hope I'll be alright.

 

[QUOTE]Originally posted by PETE
.also there are two different 400 that were made one block has 2 freeze plugs the other has 3(i've heard that the 3 were more desirable) [/QUOTE wrong.....

2 hole 400's are 2 bolt mains, 3 holers are 4 bolt main. find a 2 hole 2 bolt main 400 and add splayed 4 bolt main caps as the 2 hole 400 blocks are stronger. also....the larger main bearing diameter is better for lower RPMS as the larger diameter makes for higher bearing speed. why a destroked 400 (377) is such a killer rpm motor as it has the smaller (350) main diameter. In addition all small blocks to 87 had "Flat Tappet" cams not solid...

anyhow find a 400 and have a blast..cheers, Bob