Is this the only motor that used an 8" harmonic balancer from the factory? If it is, I found one in a junkyard. I couldn't tell if it had steam holes b/c the heads were still on it. Even if the heads were pulled, I wouldn't know where the steam holes are. Thanks. :cheers: :cheers:

 

Find the block identification number. It's located at the rear of the block at the driver side. Usually cover with crud. Then you'll know for sure by posting this number here.

Stephan

 

The casting number, as stated above, may be the best way. Other clues: The balancer should be "unbalanced". Feel around to the inside. If it isn't a constant ID on the back side, it's "unbalanced". Check the flywheel/flex plate for an "unbalance" weight. 400's are externally balanced and the balancer and flywheel/flex plate have the "unbalance" weights. If it has 3 freeze plugs per side, it's a 400. Two freeze plugs don't say that it isn't a 400, but 3 say that it is. With a head off, rather than look for steam holes that you say you might not recognize, just measure the bore. The 400 is the only Chevy production small block with a 4.125" bore. The stroke is unique, too, at 3.75". Good luck. I hope you've found yourself a "jewel".

 

:cool: guys, I am going to go check it out again tomorrow. I might have a problem getting the block ID b/c the engine is still in the truck. It is currently in a 75 (or 76? - 05/75) "Custom Deluxe 10". The VIN is CCQ145F390602. It has a total weight of 5300 lbs, w/ 2940 front/2940 rear (I guess GM doesn't know math :jester:)

 

I think I have the casting number. The numbers might be different from what I wrote down b/c it was really hard to see them. Try this:

4601028
1601028
4601020
1601020
etc, etc, etc

The 1s could be 2s or 7s, the 8s could be 0s, 0s could be 8s. HELP!!! :confused: :confused: :confused:

 

Did you look for the freeeze plugs????

 

casting # 3951509,3951511, the 511 could be a 2 bolt. if you are going to make power you had better install angle bolt main caps to hold the bottom end together :chevy

 

The 2 bolt main 400 blocks are stronger than the 4 bolt. No need to upgrade the main caps unless you're way up in power/RPM.

 

It had 2 freeze plugs on either side. Another thing I saw was that "A-207" was cast into each side of the block next to the rear freeze plugs. Is this anything?

 

:cry :cry :cry It's not a 400 :cry :cry :cry
http://www.geocities.com/MotorCity/5654/cblkcast.html

I checked my numbers against this page and there is no way that the 400 #s even come close to what I could decipher. :cry

 

You might want to ask "the dude' , the reason being I posted a question similar to this one before(check archives) and it was mentioned that a 400 with the 509 or 511 casting numbers were excellent blocks due to the extra iron, nickel content. Also my 400 only has 2 freeze plugs, but it has a boss for a third.

 

The easiest way to check. Fell the bottom of the block, if you can see the cylinder raised in the side of the block it is a 400. The 350 were flat all the way across.

 

Check out the SBC block casting nubers on http://www.moretec.com. to see what casting Nos. were 400s for sure.

Sometimes it's tricky to tell when you're not sure. Some 400s have 3 freeze plugs. Some have 3 freeze plugs and a center boss. Other have only 2 freeze plugs.

No, 400s aren't the only ones that used an 8" damper from the factory but it's the only SBC with the counterweighted, "scalloped" damper. Turn the engine over by hand until you see the timing mark. If the rear edge of the damper on the half of the balancer that contains the timing mark looks "cut down" it's a 400 damper. At this point you have a 400. Or a 383. Or a 350 that shook like a dog crapping razor blades when it was running.

And, as previously mentioned, all 400s will have at least one rounded contours on the outside of the block that correspond with the cylinders.
The steam holes are another tell you can use if the heads and balancer are off. Look between the cylinders. Between each cylinder you'll see two small holes that aren't there on other SBCs. I believe they're about 1/8" diameter or so. There should be corresponding holes between the combustion chambers in the heads if they are correct. Without those steam holes in the head and the proper head gasket the 400s will overheat. (And there is the genesis of the old wive's tale about how prone to overheating 400s are.)

Other 400 things:
--2-bolt blocks are stronger than 4-bolt blocks.
--'509 or '511 castings are, I hear, the "best" because they have the best chance of being high nickle/tin alloy blocks. Whatever. Probably means nothing except to a machinist.
--Virgin, unbored 400 blocks are getting harder and harder to find. You should make it your business to buy them whenever and wherever you find them. Or at least one spare to have on hand.
--Find them in full-size sedans--Caprice, Impala, etc.--station wagons and some trucks and vans.

Have fun. Post a block casting number when you get it. It will be on the rear driver's side of the block and it will be large, embossed numbers.

 

I pulled out the service manual for my '78 GMC pick up, to see if I could decipher your VIN. Just about everything coincides EXCEPT the engine code. The third character (Q) indicates the engine. "Q" was not used in '78. My '78 400 has an "R". If you can find someone with a '75 book, the clue is in the "Q". I may be wrong, but I'm not sure the 400 was availible in the half ton.

 

The high tin and nickel blocks will have "010" and "020" indicated in the timing chain area.

 

Well, Greg, long time no see. You have the copper/gold monster back on the road?