HELP!! 65' 409 Block,Truck or Car

[60biscayne]

I have a 1965 409 Block, standard bore, casting NO. 3857656, with an "X" cast in the timing chain area. At the top outer edge of each cylinder, there is a notch, about 2 3/4" long. Now, I have 2 books, one is "Cars and Parts" Chevy V-8 Casting Numbers, this book says with the "X" and this casting no.,that this is a passenger car block. My other book, "MuscleCar and Hi-Po Engines, also shows several pictures of Pass. 409's with this notch, and they say the notch is for exhaust valve clearance. But, I am confused, because several knowledgable members of this forum state that this notch means you have a Truck Block. Were there 2 different sized notches?? I'm trying to learn. Also, this block came with GM rods, and 11 to 1 pistons. What I'd really like to know is what my actual compression ratio will be, IF, this in fact a truck block. If it's a car block, then I am guessing comp. ratio will be almost 11 to 1 with a single head gasket. Any valuable info would be greatly appreciated, from some of you experts on this engine! Thanks!!!!!! Brian/Andrew.

 

[Ronnie Russell]

60biscayne, Passenger blocks have no notch---truck blocks have the notch. #656 casting can be either. Rule of thumb is notch cost 1 point of compression. This is approximate but close enough. How do you know the pistons you recieved are 11 to 1? If they are, you can figure 10 to 1 net with the truck block. Good luck

 

[60biscayne]

11-1's

I'm pretty sure, Ronnie, that the pistons are 11-1's. because I have seen pictures of both 10-1's and 11-1's, and the differences in the sizes of the domes, in several books, and ours have the higher dome, with the valve cutout in it. So, I'm assuming that is correct! Thank you for the great info. Apparently, these books aren't always right!! So, it seems. Brian.

 

[jim_ss409]

Most of the books I've seen only cover car blocks and 656 is the casting number for a 65 car block. But, that same casting was also used for truck blocks. As far as I know the only difference is in the machining. The truck blocks still make great performance engines. By the way I think there may be a way to tell a truck block from a car block without pulling the heads. I've noticed that the truck blocks have an extra threaded hole machined into the front of the block. I've got a car block at the shop that doesn't have this hole I'll try to remember to get a picture and post it tomorrow. I remember Curt Harvey saying that I'd loose about 3/4 of a point of compression with the truck block. The truck block that I got was also a standard bore with 11 to 1 stock TRW pistons. Who knows, maybe they used 656 truck blocks for replacement short block assemblies.

 

[jim_ss409]

Here's a picture of the bosses that are NOT dilled and tapped on this car block. They ARE drilled on the truck blocks that I've looked at. I'm pretty sure they are used for the front engine mount in truck aplications. The two undrilled bosses are near the center of the photo. They are just ahead of the fuel pump mounting location.

 

[60biscayne]

Hey Jim. Yep, you are right, the 2 bosses on my block are drilled and tapped, confirming that it must be a truck block, just like all you guys said. That's OK, it sounds. 10-1 Comp. is fine with me. I just wonder why all these books you buy are incorrect in some areas such as this. Heck, you guys ought to be the ones writing these books!!! Thanks for taking the time to send the picture, and the knowledge! I appreciate it. I feel a little less dumb now. Happy 409'ing!! Brian.

 

[raymar58409]

weren't the blocks with the X cast in them intended to be factory replacement parts and didn't they also do it on 348 blocks?
Ray

 

[wrench]

x

weren't the blocks with the X cast in them intended to be factory replacement parts and didn't they also do it on 348 blocks?
Ray

Yes. The block in my BelAir has no numbers on the pad, never been to a machine shop. It has the X on the front.

I bought what I thought was a 409 twenty years ago. It had the X also. When we tore it down, it turned out to be a 348 truck. I had to refund my buyer AND fight to get a refund from the guy I bought it from.