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is this a good deal for a 400?

4X4HIGH said:
I wouldn't run a 400 if you paid me. They are very notorious for overheating because of the siamesed cylinder walls.
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I always hear this, funny that mine has always run cool. I believe it's an often repeated internet myth.

I do have an 8 blade fan. And a big radiator. But even before, when it had the OEM equipment mine has always run cool.

I think a poor water pump can cause overheating. And those cheap thermostats can stick. Watch that stuff.
 
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Someone already said it about people not taking care of thier stuff, or not doing something right. I had a 400 out of a mid 70s Impala. Guy said it kept overheating. I guess the rad was junk, popped a head gasket but kept overheating. I got the motor for $200. Took the heads off, found a 350 headgasket instead of the 400 is supposed to have. I changed the cam/lifters, oil pump, heads and intake, put it in my car, drove it back and forth from Ottawa to Bingo, IIRC 60k miles in 7-8 months. Never had a problem with it running hot. Only problem I did have is I kept braking rocker arms, I had a .480 lift cam with stock springs, so every now and then I would brake one. Kept some spares with me, all was good. 400s IMO are the sh!t. I now have 3 of them, gonna build them up to aboot 400 horse, one is going in my 92 fullsize, and the other in an 87 2wd S-10 Blazer. Oh is that gonna be fun......
 
Mine has actually always run too cold in the winter time. It did not heat up well this winter since it has the new water pump, the problem has actually gotten worse. I put a cover over the front of the grill, but it didn't help much.
 
Wasatch K5 said:
I don't know fellas, That's a bunch of rust on various parts. I think it has been left outside uncovered. I don't see anything covering the intake manifold openings where the carburetor sits or the distributor either for that matter.

Water goes into the intake manifold, through the intake valves that are open and sits in the cylinders rusting away.

From other posts it sure sounds like a .030 overbore is all you can do. That's .015 on a side. I don't think I'd risk it for $250.00.
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they guy claims it runs, but recomends a rebuild. as far as the rust, well the ex ports look rust free in the runners from what i can see. hell theres probably so much sludge buidlup inside that nothing could rust :haha:
 
i agree kevin. i just let that one slide by. he took the buy it now price of $250 off as soon as someone bid. the guys a jerk. the last time i looked at the bid it was like $240 and 3 or so people had bid. i'll just look at the junkyards... hopefully i can find one.
 
cool, thank you. so a junkyard motor it is. what cars should i look for the have 400's? how can i tell the difference between a 400 and any other sbc, espically when its still in the car?
 
If you want to identify a 400 in the yard, look at the balancer and the flexplate. It should be the 8 inch dia balancer ( some one correct me if I'm wrong ) , but the inside edge of the balancer is not round, I believe it has a section machined out. The flywheel will have a weight spot welded to it, since a 400 is the only factory externally balanced small block. Of course someone could swap these parts onto any SBC ( but not well ) so if you find either of these, crawl to the back of the engine and clean off the drivers side of the block behind the head, and get the casting number to be sure.
 
I would never build another 350 block again. my 406 treats me very well. oh and btw its still getting 14mpg towing the boat. Its been in my blazer for bout the past 3 years and in my buddies van for 1.5 yrs before that. Cant beat the low end torque. plus i can run 70-75 on the highway towing the boat to raystown lake no sweat. I run a bb radiator, with a shroud. i have the 350tbi setup and heads off my 89 on it. (Dont do that though cause it will run lean and blow up) have it setup by a pro. thats what i did. although 4x4 high still tells me my motor is gona blow. hes been telling me that the past 2 years though. I would stick with the 2 bolt mains. dont go more than 30 over and use good gaskets. plus its good to service your cooling system once a year. and if you go wheeling hose out your radiator and clean all the mud out of it. I wouldnt use the 350 radiator, get a bb one or one from a diesel. good luck, if i come across any ill let you know.
 
slyguy_22 said:
I would never build another 350 block again. my 406 treats me very well. oh and btw its still getting 14mpg towing the boat. Its been in my blazer for bout the past 3 years and in my buddies van for 1.5 yrs before that. Cant beat the low end torque. plus i can run 70-75 on the highway towing the boat to raystown lake no sweat. I run a bb radiator, with a shroud. i have the 350tbi setup and heads off my 89 on it. (Dont do that though cause it will run lean and blow up) have it setup by a pro. thats what i did. although 4x4 high still tells me my motor is gona blow. hes been telling me that the past 2 years though. I would stick with the 2 bolt mains. dont go more than 30 over and use good gaskets. plus its good to service your cooling system once a year. and if you go wheeling hose out your radiator and clean all the mud out of it. I wouldnt use the 350 radiator, get a bb one or one from a diesel. good luck, if i come across any ill let you know.
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You might want to get your facts straight. Also i don't ever remember talking to you about anything. I simply stated that 400's like to run hot and they are notorious for cracking. I can't count how many i've had in my shop that were cracked through the lifter valley.
 
if i pop the intake off and clean off the sludge (if there is any) can i see the cracks easily in the lifter valley? if 30 over is the max i can go on a 400 block without it overheating im not to sure if i want a 400. what makes the 400 block different from any other sbc besides the bore of the cylinders?
 
400's have "siamesed" cylinders which means that there are no coolant passages between the cylinders which causes their coolant problems. I've also heard that 4 bolt 400's are notorious for cracking main bearing caps.

I chose a 383 because you get the longer stroke of the 400 but you keep the much better 350 block.
 
How many different castings of the 400 are there? Scott might know, but is there a chance that certain castings are prone to overheating/cracking, and all 400's have gotten a bad rap because of it?

Only siamesed block I've dealt with is a 403 Olds, and the thing ran fine standard bore. Rebuilt it, bored it, and all of sudden cooling problems, in the same vehicle, nothing different other than a mild cam.
 
dyeager535 said:
Only siamesed block I've dealt with is a 403 Olds, and the thing ran fine standard bore. Rebuilt it, bored it, and all of sudden cooling problems, in the same vehicle, nothing different other than a mild cam.
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Most blocks that have siamesed cylinders use sleeves (so you don't have to bore the block during a rebuild) to prevent the bore-then-overheat problem. Apparently GM didn't feel that was necessary :doah:
 
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chevyridinhigh79 said:
cool, thank you. so a junkyard motor it is. what cars should i look for the have 400's? how can i tell the difference between a 400 and any other sbc, espically when its still in the car?
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The 400's have the oil dipstick tube enter into the block at the very top, just under the head, while the 350's oil dipstick tube enters at the bottom of the block just above the oil pan.
 
Yeah thats what i was referring to.

I think the main problem that 400's get a bad rap is that they "sometimes" go threw head gaskets, between the cylinders. 9 times out of 10 they were bored more than 30 over. also im sure the other 10 percent is cause they dont ever service there cooling system and keep up with maitence. Avoid 4 bolt mains they tend to crack.

Plus side Big block low end torque! sb gas fuel economy! tons of aftermarket parts are available. (350 parts work on them) can have them fuel injected! (cheap too) Direct bolt in for 305-350 (can't use 305-350 fly wheel) Can be found at most junk yards!
 
id buy it for that. i bought a crappy 350 out of a van with 100,000 miles for 300 bucks a few years ago. it still runs to this day.


my 85 k5 blazer has a 400 in it and like was said the torque is awesome ive pulled cars on a trailer and you can bearly even feel that your towing anything. ive had this engine about 4 years now and never over heated it. i even had it in a undergeared suburban in the summer offroading and never overheated the thing.
 
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