i have a chance to buy a 400 sbc and i want to build it for performance but when i told a guy at autozone about it he told me not to waste my time with the engine and to just build my 350 because the 400 has cooling issues and that the cylinder walls are to thin on them what motor would you guys choose to build it will be going in my 85 z28 the guy that owns the 400 said
that the 400 is out of a 70 cop car i realy dont know if that realy matters though thanks for any help

 

dont talk to autozone ppl you are wasting your time

a 1970 400 would be an awesome engine and block

sure it can have cooling issues, as any engine can, if parts such as the radiator and waterpump and such are not in good shape or correct

i currently own and drive a stock 1977 400 engine in a truck i have, no problems ever of any kind

they do not overheat

unless something bad is wrong already


good luck

 

Sounds like the guy at VatoZone wants to find out where the motor is, talk you out of it, then go buy it for himself. Either that, or he's just an idiot, and all he's doing is spewing the same old "old wive's tales" that have been running around in the McDonalds parking lot on Friday nights for the last 30 years; and that aren't any more true now, than they were when I first heard them about brand-new 400s.

No the cop car crap doesn't make the slightest bit of difference; except maybe it got abused a bit more than usual in its first life. No magic rubbed off of the light bar on the roof and infused itself into the cast iron, you can believe that.

 

Here's what mortec lists for 400 sbc. If it doesn't have one of these 3 casting numbers it ain't a 400. If its a 1970, you can see there's a good chance that its a 4 bolt main. Some old wives say that the 4 bolt main blocks are not the best choice for performance engines.


330817.....400...72-80...2 bolt
3951509....400...70-71...4 bolt
3951509....400...74-80...2 bolt
3951511....400...70-73...4 bolt Some replacement blocks had 2-bolt main caps

 

If you have a chance to buy these rare sbc 400 , just go freakin buy it . I m rebuilding one (2 bolts main 509 casting no.) and haved it decked and bored .030'' over (406) . A bigger radiator , 2x cooling fans and high flow water pump will make you forget the overheating issues . If you can , swap the 6.00'' rods for 5.7'' ones will make much more torque at lower rpms ...

 

Buy a new radiator. They are not expensive. Make sure the extra 400ci block steam holes are drilled on what ever cylinder head you bolt onto your 400. the stock 400 heads have these. Others (350's 305's) do not.
If the chin spoiler is missing or broken under the nose/rad support of your Z, replace it.
Make sure the water pump is good. Many times the internal impeller is all corroded away.

Before investing in any machine work:
Have the 400 block mag tested for cracks. They are no more likely to be cracked than any other SBC, but 1970 was a long time ago.

 

thanks for all the info i think i will buy it i found out that it has keith black pistons,edelbrock rpm intake, holley carb,msd distributer and some other stuff with it also the motor has only around 1500 miles on it since rebuild he is asking $800 for it but his wife said he would take $500 for every thing

 

The 400s only have cooling problems when you build it the same way you build a 350. 400s are different in small ways from a 'regular' small block, and will have cooling problems if you overlook them.

The first one is steam holes. The 400 is the only small block that has them because its the only block that has siamezed cylinders (no gap between the cylinders). If you heads and head gaskets don't have the proper holes to match, you will have cooling problems. Its easy to add them to heads though... just use a proper 400ci head gasket as a template, and drill the holes in the heads. There are certain angles to drill at, and the directions are all over this board if you search.

The 400 does have slightly thinner cylinder walls than other small blocks, but not enough to worry about. You usually can't safely bore anything bigger than .030", where most SBC are ok to .040" or even .060". If a .030 overbore is all the block needs, then you should be OK, assuming a sonic check of the block also checks out.

The last is just the fact that its a 400ci engine... bigger motors make more heat than smaller engines. You will need to upgrade your cooling system to keep the 400 cool. A factory radiator will probably not be enough, you'll have to go with a good aftermarket high-perf radiator, like from Griffin.

 

A replacement Rad from a 91/92 should be sufficient to cool a 400 with ease.

 

That depends.... along with cubic inches, POWER makes heat. If its only making 250hp, then that probably would be just fine. But if he plans on a 500hp mill, the factory cooling system will be totally inadequate.

 

i would like to get about 450-500 hp out off it then put a 100 or 150 shot
through it because i realy need to beet my freinds 5.0 rustang he is pushing
just over 400hp and he has a 100 shot on it so if any one could help and tell me what type of set up i should buy for the 400 so that i can reach my goal that would be great thanks in advance for any input

 

All I read was the first sentence. Don't talk to anyone at autozone about anything. They are idiots.

Serisously though. So a search for my 406 build up and it addresses about everything you will need to know to build a 400.

 

Some smart people DID work at Autozone, but were smart enough to leave and go elsewhere.

400s are great engines. I am looking for one right now to replace the L03 that is in my 1980 C10.

 

I'd jump on that if you can really walk away with it for $500 already rebuilt...

 

Actually people at Autozone are smarter than folks at Kragen, now Kragen WHOA they'll recommend the most expensive parts they know nothing etc etc

That was my comment regarding stores, now back to the 400 block issue.


I have a few questions myself, the 509 block, was the crankshaft cast or forged ? Also which 400 block was the high nickel one ?

 

All factory 400 cranks were cast, regardless of the block casting number... which is totally unrelated anyway.

 

Any 400 block may or may not have been a "high-nickel" block as well, not that it matters, either.