Going thru old posts between the two slant sites and picking up info. I would like to understand the term core shifting.

I have read about offset dowels but cant imagine what these would look like. I can only imagine re-drilling the block for dowel placement.

How would one check for core shifting, why is it important. I am guessing that it would be important because of concerns of getting the piston hole and the combustion chamber within the head centered. I have read that when using radical cam or rocker gear having these points lined up is important to assure no valve train colliding which makes sense to me but I would like to have a more thorough understanding of all of this.

Offset dowels look something like this:



If you look closely, you'll see that the axis of the upper cylindrical part is parallel to but not coaxial with the lower part.

_________________
"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Core shift can also refer to the shift of other molds/patterns in the casting than cylinder bores and chambers, I had a couple of heads that a a few of the intake runners were off enough to say that hogging them out with a die grinder to correct was more trouble than it was to just get a better core and start at that point.

-D.Idiot

I woulnt have guessed the slots in them and still not sure of their purpose but I can see the offset. Thanks

Thanks D.I, I was thinking that it had to be associated with casting but nice to have it confirmed.

Is it typical on these slant engines ( or reccomended ) to do some sort of fit to make sure the combustion chamber is indeed lined up with cylinder walls.

I am wondering if between the years of production could there have been such wide/varying casting moulds that there could be a possible offset that one might not catch if one were not to go looking for the possible issue.

You might want take a look through the required reading section! All of your questions will be answered.
http://www.slantsix.org/articles/articles.htm

_________________
Mattelderca
78 NYB (gone now), two S series, three old Snow Cruisers and a Doo.

I have checked that out but did not see anything specifically related

Yes
Every part produced by the sand casting process is slightly different then the next because each sand mould is "hand-build" and destroyed, after the casting is produced. (a "lost process" casting)

There were a few different foundries making these parts, each foundry had many sets of patterns and many different foundrymen working on the parts so there is lots of variation... you just need to look for it.

As an FYI, the engine block sand mould makes 2 blocks per mould and has over 20 cores, that are all "loaded" into it, prior to closing and pouring-in molten iron.

Then there is all the machining...
DD

Thanks for the info, can you point me in the direction of a thread that covers the steps that should be taken to look for possible problems/variations.

FYI is interesting, thanks

The block article has a lot of good info:
http://www.slantsix.org/articles/dutra- ... blocks.htm
DD

Thanks, sorry that you had to point me in that direction, must get old quick.

I should have been able to find that myself and would have given enough time I am sure.