440 Block - Strange...

[Grabinov911]

Hey Gents,

Take a look at the attached photos of a 440 block which I'm using for a Mancini-kit 493 Stroker build (the engine which we've been talking about in my "Roadracing Engine" thread). Top two photos show driver's side of the block. Bottom two show passenger's side. Specifically, look at the cylinders in the right hand bank compared to those in the left hand (driver's side) bank. You'll see that those in the right bank have "chamfered" (for lack of a better term) edges at the deck edge. Those in the left bank do not. My machine shop swears that this is not an issue, and that he has seen all kinds of piston/bore oddities from the Chrysler factory.

In the photos the block has already been bored to .030 over - it was totally stock and un-machined (other than factory machining) before that, at least as far as we can tell. What's up with the chamfer in the 4 cylinders on the right? Is it OK?

Thanks,

Greg

 

[Meep-Meep]

Yeah, the machine work on Chrysler blocks was not the greatest - or better said they didn't hold very tight tolerances in some areas. Most common is the block decks aren't very square. Having huge bore chamfers on one side and not the other will mess with your compression ratio by not allowing you to make every cylinder equal. I'm sure there is a certain percentage of deviation allowed so I would CC every cylinder with the piston at TDC and find out what you have. May not matter if the deviation is small. And with a stroker build you might be able to hide the error easily - meaning the bore chamfer difference becomes a smaller percentage of the total displacement.

 

[rrowdy]

Hmmm, I've seen quite a few of these blocks but have never seen a chamfer like that.
As to weather or not it causes an issue I guess would depend on the Major diameter of the chamfer.
It's hard to tell from the picture but it looks like it could total as much as a CC/cyl or maybe more.
Also could the fire ring protrude into the chamfer? Looks like a little later block but it's a mystery to me.
I'm sure an expert could shed some light on it.

Good luck!

 

[RustyRatRod]

The chamfer is no big deal. Just like your shop said. Probably came from Chrysler that way. The chamfer is nice so there's less chance to break a ring on assembly. That's about it.

 

[Grabinov911]

Thanks gents,

As you point out, the block has not been decked yet, and will be going to "0 Deck", so that will likely eat some of the chamfer in addition to what would be taken away by just machining for a flat surface. I suppose we could mill the right side head by a zillionth of an inch to get the combustion chamber volume and therefore the compression exactly the same, but I hate to buy into a project like that from the start. I am using 12cc dished pistons and 84cc heads, so that's a total combustion chamber volume of 96cc if I am doing that right. That means a 1cc difference is just under 1% difference in volume, which should mean a 1% difference in compression. At 10 to 1 compression overall, these cylinders would be at 9.9 to 1.

And thanks for responding to my PM Rusty...

Greg

 

[RustyRatRod]

You bet.

 

[lewtot184]

the chamfer is not an issue. it helps the rings start into the cylinder during assembly. you can buy chamfering tools. if there isn't a chamfer in the block i put one in.

 

[Hemirunner]

Just put the same size chamfer on the bank withno chamfer and continue on.

 

[Kern Dog]

I had a Chevy 350 that had a small degree of chamfer to it. My machinist had a strange drill attachment for doing this after boring and honing cylinders. I would think that it makes sense to do all the cylinders to maintain symmetry and equal volume.

 

[Meep-Meep]

just put the same size chamfer on the bank withno chamfer and continue on.

bingo.