I have a chance to pick up a rebuildable 1970-74 400 small block 4 bolt for $150. I am thinking of building it to put in my 84 in the future. Want some cubes and around 400-450 HP. What kind of bolt up problems will I have with tranny, heads, or accessories?
I have Aluminum L98 113 heads in storage, 700R4 tranny, and the normal 84 accessories.
Any info will help so I know what I am into before I buy!

 

If you need to overbore it have it sonic checked, make sure you have the correct externally balanced flywheel and flexplate, have the "steam holes" drilled into the heads and head gaskets. You can get really great cranks these days as well as rods and a good main stud kit would be helpful. Remember the engine needs a lot of air to make power so heads are critical. Roller cams really help, you can get away with a lot more duration than a 350" and still idle good. Send me your proposed setup and I will run it across Desktop Dyno. 400 blocks have a bad repputation for blowing head gaskets due to the junk factory cheep snitt gaskets they used, a good fel pro should do wonders.

 

 

So, everything will bolt up ok?

 

I don't know how crazy power-wise you plan on going, but the 4-bolt 400 SBC block is generally accepted as weaker than the 2-bolt 400 SBC block.

 

I have heard 4 bolts are rare. Is this true?

 

I heard the same thing about 400 4 bolts. Should be strong enough for me and looks like a great deal, as long as I can get everything to bolt up which I am guessing will.

 

4-bolts are fine up to about 600hp naturally aspirated..I've you're gonna use a supercharger or nitrous I'd use a Dart or Bowtie block anyway.

 

The only fit problems caused by the BLOCK, is the left side dipstick location on the 400 block. You will need a different pan. Everything else bolts to the block. 400 head gaskets should have steam holes drilled. It would be a good idea to have the heads drilled, also.

If you are going to use the 400, external balanced, crank, you'll have to use a 400 damper and flywheel or flexplate. 400 flexplates only come with 168 teeth, which will necessitate a starter change.

Adapting the 113 heads to the Crossfire is a subject not involving the block selection.

RACE ON!!!

 

Are you speaking in terms of the 4-bolt 400ci SBC block specifically? I don't know if I would trust it up to 600. It doesn't sound like he's going high enough to make it an issue though.

 

At 1 horsepower per cube I would say it is relatively mild. Keep the revs low and build it for torque and it should last a very long time.

 

A lot of articles I have read suggest putting studs in the 4 bolt blocks.

 

Quote:
A lot of articles I have read suggest putting studs in the 4 bolt blocks.

Can someone explain this to me?

 

a friend of mind builds race engines and he agrees that the 4 bolt 400 is weaker than the 2 bolt version.....it has to do with the cylinder walls being very thin


best thing to do would be find a 2 bolt 400 block and have SPLAYED 4 bolt caps installed

 

There are 3 types of 400ci blocks ! You can find out wich one you have is by the casting number , it`s the number on the back top of the block . Its true that the 2 bolt main is stronger than the 4 bolt because of thin cylinder walls found on the 4 bolt blocks . The Best 400ci block you can have is the casting number #3951509 this is a 2 bolt main block that was made from 74-80 , it is known by the strongest from the other casting numbers because of the metal being stronger .Other 400ci block casting numbers are #330817 wich was made from 72-80 that is a 2 bolt main block and there was the other casting number wich is #5951511 this is the 4 bolt main block that was made from 70-73 later this casting number was made as 2 bolt mains , I think that GM was having problems with the 4 bolt blocks and stoped using them.
The best way to make a 400ci block survive under Hi performance applications is to NOT bore it more than .30 oversize , the maximum safe bore on a 400 block is .40 oversize , it`s also best to use studs instead of head bolts and studs on the mains , this makes it more stronger and make shure before you start throwing all the money into a used block make shure that the block you are using is safe , like it has no cracks and the cylinder walls are nice , the best way is to take it to a reputable bulider and tell him to sonic check it before you start buliding it .
If you search over in this forum you can find pleanty of 400 block setups , some of them even was abused with alot of hi HP parts and none of the members had problems . I think the safe way of buliding a setup in a 400ci block is to build a 406ci , with the right parts it will be a tourqe monster.

Good Luck .

 

As for correct balancer and such.
A smaller diameter external balanced 400 block (some call it a 383 balancer) can be had and it will drop right in. Or you can go with a good old 8" whatever stock balancer and clearance it on the crossmember.

Flywheel wise: You can buy 400 flywheels for with 153 teeth on them from places like centerforce (276-376$) (700102 I think)

Flexplate (auto tranny): I am not sure what you can use,, but stock 400s did have the 168 tooth version as stated above.

I just bought the centerforce flywheel I listed above for my 383, if you want the brand new SFI certified 400 flexplate PM me, or if you want to know where to get the flywheel cheap, let me know too!

I think CFI is also right on the 168s need a Mini-starter as well. ID85 just had one for sale, don't know if he sold it. Something to check out...

 

If your going to build up a 400 to make power and be reliable. Spend an extra $500 or so and have the rotating assembly internaly balanced. Then you dont have to bother with counter balanced flywheels.

 

You can buy a 400 CI-153 tooth stock style Flywheel or

or for a ZF you can buy a Single Mass Flywheel for a 400-153 tooth

or you can use your 350 stuff and buy a $20.00 balance plate

or you can balance the internals

I would recommend buying the 400-153 tooth flywheel or balancing the internals which gives you more options

 

I have an auto trans so no flywheel. I hear the concerns over 4 bolt 400. I am going for 400-500 HP max. Should I pass on the 4 bolt?
It is the 1511 casting number.

 

If you are looking for 400-450 hp at the flywheel then I would have no problem using the 4 bolt block. With a good balance and studs in the mains you'll be just fine. Keep the bore size at 4.155 or smaller.