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SB350 vs. SB400

Citizen Rider

Citizen Rider

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Im about to purchase a rebuilt premium long block engine for my blazer, and will slap TBI ontop of it.

What are the advantages and disadvantages between a 350 and a 400?

350 will be a 87+ block, 400 is 79 or older block btw.

Both will cost the same...

Thanks
 
350 will accept stock TBI, 400 will require a custom chip.
400's are prone to cracking
400 requires external balanced flywheel/flexplate
350 late will also require an external balanced flywheel/flexplate (different than 400 though and also different than any other SBC)
 
'87+ 350= one piece rear main seal, cheap stock roller cam. In fact I'd spec a block that was already setup for one.

Chip burning is going to be required for best performance with anything you do, short of the exact same engine profile you take the TBI from. (heads, cam, compression, so on)

400 would need a chip burned no question.
 
Get the 400. A mild camshaft will get you more torque than you'll know what to do with. Overheating problems in the 400 stem from lack of proper cooling or flow. Siamesed cylinders don't create heat. A good radiator, water pump etc., and not having the timing cranked waaay up, you should have no overheating problems. The people that do have heating issues never upgrade to a larger radiator. I have run several 400's that NEVER went beyond 180*. The 400's just make awesome power without having to do a whole lot to them. Even if you overcam the motor, it is forgiving. You should be able to toss a reman 400 with a custom chip TBI setup and be done. A cam as described works great. A 400 is going to make more torque all other things being equal. Making a very streetable/driver friendly 400HP/TQ is very easy with the 400. If you're on a shoestring budget and can't afford the custom chip and radiator, then stick with the 350.

Check out how much power they made with AFR heads and a 400sbc:
http://www.chevyhiperformance.com/techarticles/148_0401_chevrolet_406_ci_engine_build/
The newer AFR heads now flow even more!
 
4X4HIGH said:
350 late will also require an external balanced flywheel/flexplate (different than 400 though and also different than any other SBC)
Click to expand...

What is considered a late 350? I need a flywheel for a 91 TBI 350. It came out of a burb with an auto. :confused:
 
resurrected_jimmy said:
What is considered a late 350? I need a flywheel for a 91 TBI 350. It came out of a burb with an auto. :confused:
Click to expand...

Late style is 1986 and later. GM changed the bolt circle to 3.00" instead of the 3.48" of the older engines and the later engines are externally balanced on the rear.
 
What would the cost of a new chip be for the 400 to run TBI?
Any other modifications that would need to be done to make this a good setup?

I already run a 4 core radiator so im good there. Im on a budget and really want to get this thing running before summer.
 
You don't need to change anything to run a 400 with TBI. My old truck had a nice 406 TBI, put close to 10k on it before I sold, didn't have one thing go wrong with it. After I sold it, the newer owner beat the sh!t oout of it, and blew it up 3-4 times. I've had stock and built 350s and 400s, and if I had to choose, 400 anywhere, anyplace, anytime. I never had a 400 over heat either.
 
is money no object for you spending on this new motor? i would do a 383 stroker.... it will out-torque the 400 hands down.
 
Money is the limiting factor, 383 is my dream, but no way right now. My Daily driver was totaled this past weekend so the engine swap doesnt have priority anymore.
 
Hoot said:
is money no object for you spending on this new motor? i would do a 383 stroker.... it will out-torque the 400 hands down.
Click to expand...

With all things being equal (CR, heads, cam, etc) how do you figure? More ci = more torque.
 
A 400 has more torque than any other small block (except for exotic strokers or aftermarket large bore blocks). A 383 is merely a 350 with a 400 crank in it. The 400 has an 1/8th inch more bore than a 350 aswell as larger main bearings. The 383 is a torque motor alright but it will never out pull a 400 of equal build.
 
I'm jumping into this post late, but I'm curious about the 400's power curve. The 383 from GM is making 400 lb ft at only 2500 rpm and rated at I believe 340 HP?
 
fireplug said:
I'm jumping into this post late, but I'm curious about the 400's power curve. The 383 from GM is making 400 lb ft at only 2500 rpm and rated at I believe 340 HP?
Click to expand...
From the link above, here's what a well prepped 400 with AFR or Vortec heads will do-

148_0401_imp_11_z.jpg
 
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