I have recently purchased an '82 Camaro that is suppose to have a 406 in it. Is there any reliable way to externally determine if this is true? The block has been decked and there appears to be counter weights on the (14"?)flexplate and on the back of the Fluidamper balancer. The block has three freeze plugs per side and the starter pad is drilled for both side by side and offset mounting locations. What do you guys think?



Thanks-

 

Hi, there should be a number at the back of the engine, on the driver side, It should be on top of the bell housing flange. In the limited info I have the last three numbers for a 400 could be either 817---509---511. If you find that number post it, I,m sure somebody here can tell you what it is.

 

With the three freeze plugs on the side of the block it is a 400 that should have 4-bolt mains and it was originally produced in the early 1970s.

jms

 

IIRC the only SBC with 3 freeze plugs per side are 400s. Although the inverse is not true (all 400s do not have 3 plugs, the 2 plug blocks make great sleepers)

 

Duh. I forgot about the block casting by the bellhousing- it is stamped 330817. So it looks like it is a 400. Do the three freeze plugs automatically make it a four bolt block or can you tell by the casting number?

 

Model year 1973 was a strange year for the 400. From 1970 into 1973 the blocks were four-bolt mains. These blocks had the three freeze plugs on the side.

Sometime during the 1973 model year, Chevy began using blocks that had three freeze plug "humps" but actually only two freeze plugs. These blocks had two-bolt mains.

EXCEPT, I have seen a four-bolt, two-freeze plug block from a 1973 big-car.

After 1973 through the late 1970s, the blocks with the "three hump/two freeze plugs" were two-bolt mains.

The 400 ended in 1980 with some of the last couple of years featuring a block that had two freeze plugs/humps without the third hump that give it away as a 400.

Great blocks if you want to convince someone it is a 305!

jms

 

Thanks jms. That's good 400 info. I thought there was a story behind the freeze plugs

 

The early (4-bolt, 3-plug) blocks are the ones that got the rap as prone to overheating, although I have never had any particular problem with that. The factory decided at some point that the 4 bolts weren't necessary and merely added cost, and so stopped machining them all that way. The later ones do have somewhat more metal around where the bolts go, which is why they are considered as the superior foundation for an all-out build.

But all of that is splitting hairs when it comes down to it. If yours runs good, then enjoy it... if it needs a rebuild, go for it. Just remember that it needs HEADS!!! Flow is everything: heads and exhaust and cams and intakes that might seem outrageous for a 305 and excessive for a 350 might be barely adequate for a 400. Most people stick the OE heads (882 and similar) back on them, which is a total waste of a fine motor. Any cam you put in one will idle and otherwise behave like one about 10 degrees smaller would in a 350.

Enjoy it! I hope you get to toast as many Mustangs with yours as I have with mine (509 casting, double-hump heads, a 282S then a XE274H then a XR282HR cam, and some other fun stuff)

 

I think this turned out to be a good one. It has been in the car for quite some time. It also has fuelie heads right now but ran 130 with some dart heads before I bought the car. There arn't too many fast mustangs in these parts so I should have some fun!