What are the good 400 blocks to use on 406 Chevys?

[Roothawg]

All this talk about motors has peaked my interest. One in particular is the 406 combo. I know there are a lot of guys out there building these so....are the good blocks still available? I think the casting numbers are 509? Is this right? I know you have some setup to do for clearance problems....what are they?

Thanks

[Roothawg]

Here's something I found. 406 (http://www.chevyhiperformance.com/techarticles/148_0306_406/)

[manyolcars]

Small block 400s pique my interest too.

[choprods]

A little O/T but as a discussion here it is- I put one in a customers "street rod" a while back that was fairly simple but effective.....
It was a stock stroke 400 bored to 406.
it used the 5.7 rods instead of stock 5.5" rods.
was running 9,7-1 Compression/World Products 2.02/1.60 valve 64CC heads-a Computer Grind Cam with 450/460 lift and little else done to it.
I installed EdelBrocks 1000 CFM Pro-Flo Multiport injection and it had a Richmond 5 gear behind it with a 3:73 rear gear.
IT WAS A HOLY TERROR for a street motor!
It was VERY stong and full of tourque at every level-I am impressed with them after doing that car.

[Nimrod]

I'm not sure what you mean by clearance issues...a 406 is just a .030" over 400, all the 400 stuff will still work. I think the 400's use a skinnier oil pump drive shaft than other small blocks.
Good blocks are easy to find. The early ones are four bolt main and the later are two, I've heard the later blocks are actually better for performance applications.
I've built a couple and they are great motors that can be built on the cheap.

[Swedester]

70-72 will have 4 bolt mains,and to my knowledge, there are no diff. in strenght/bore capacity in any years,the 70-71 could have a forged crank if you´re lucky

[Roothawg]

I heard that the cams are the problem. I read that the small base circle cams help this but that's all I know.

[Roothawg]

Mortec says the 400 was produced til 80. I didn't know they were that late.

[Winfab]

You shouldn't have clearance issues unless you're using 5.7" or longer rods, then you may have to grind a bit on the pan rails and lower areas of the cylinders. Rod/cam lobe is another touchy area for clearance, as I recall. If you're planning to make some serious HP with high compression I'd do the splayed steel main cap deal rather than try to find a stock 4 bolt block.

[JohnnyB327]

the 4 bolt main blocks suck ass, weak and just not worth it.



johnny

[FeO2]

I've built a few for stock car racing.The car I took to the HAMB Drags had the setup Choprods mentioned,except 6"rods,a steel 350 crank, and a 650 carb.I've never had a problem with 2 bolt blocks under 500hp.I think the extra holes for the 4bolt weaken the web of the block.I also know a 327 crank in a 400 block revs up like a jap motorcycle.

[Mutt]

[ QUOTE ]
the 4 bolt main blocks suck ass, weak and just not worth it.



johnny

[/ QUOTE ]

Is this based on your vast experience? I've been running one in my roadster since 1990, and it's held up just fine with constant 11.30 or so runs. It was freshened about 1998, and there was minimal wear on bearings and none on cylinder walls.
It uses a stock nodular iron crank (no steel cranks from the factory), factory 5.565 rods, and forged pistons. Edelbrock 70cc heads, roller rockers and 2 500cfm 4bbls.
The car has 4.11 gears and I launch flashing the converter and shift at 6300 rpm. It goes throught the traps just as the shift light comes on.
The 400 is the most mis-understood SBC ever. It was maligned as an overheating low horsepower boat anchor at first - until people started to work with it. It actually is a stump pulling torque monster that will give excellant service and performance if you stay within it's parameters. It doesn't like to be revved high in stock configuration -It's all in before 5000 rpm. But with minor changes it will rev quite nicely to 6000 or so. The new one I'm building will have Eagle 5.7 rods and an Eagle crank to handle the blower.
The biggest problem was people didn't drill the steam holes when they rebuilt and switched heads, or the holes got clogged because they didn't change coolant, or used stop leak to seal a leaky radiator.
They don't like to be bored over .030. With sonic checking you might be able to go .060, but it's iffy - I'd say .040 is about as far as I'd want to go.
You can run into interference with a large cam and 5.7 rods, but they have small base circle cams to take care of that.
There are more and more pistons available for use with 5.7 and 6.0 rods now that Motown Blocks are available.
A properly prepared 400 will make you forget all about a 350, especially in a heavy car.
Whoever said they are plentiful should buy every one they can, because I can't find any around here. They would be a good investment.
Here's some info....

[buffaloracer]

I/ve had good luck with every 400 that I've worked on. Nothing wrong with the 4 bolt if you don't flog it too hard. The 2 bolt works ok if you don't really get after it and in that case you can go to splayed aftermarket caps. I like the 5.7 or 6 inch rods. They do need a good cooling system. Most problems come from getting all or part of the engine too hot. Contrary to a somewhat popular belief steam holes appear to be a must. No factory steel cranks that I am aware of.

[WZ JUNK]

I tell evevryone that I have a 265 in my truck but it is really a 30 over 400. I do not think anyone believes me anyway. I run stock heads, Performer intake, Holley, Hydraulic lifters, headers, gear drive on cam. My cam selection had more to do with the most lift I could get without doing machine work on the heads. So it is a hodge podge of a motor. I shift it at 5100 RPM for no other reason than it just seems to quit about then. Best run to date with DOT tires is 13.2. I will run it again at the MOKAN Hot Rod reunion in 3 weeks. I really want to break into the 12's. The engine we ran at Bonneville last month was a 406 and it did great. We had some oil pressure problems but it was nothing to do with the fact that it was a 400. I think they are one of the best kept secrets of all time.

[k9racer]

The 406 is the engine of choice for open wheel circle racing. I have broken both 2 and 4 bolt main blocks. With the stock 55 rod the engine feels like it comes off the corners a little better. When limited on cubic inch at some tracks I have used a 3 in stroke and the 400 block and really big valves. The only problem in this area the 400 engines are very hard to come by. 3 of the last 4 I purchased running cars to harvest the engines. Bottom line a very good choice for any use.