Going Straight

Have you ever looked at an engine that someone has for sale on Craigslist or another “For Sale” site?  Then after looking at it you make the purchase, cheap and go directly to your favorite machine shop. Upon arriving they look at the back of the engine and then, on the spot, they tell you “it’s junk” and won’t touch it? The reason they give is just two words, “Core Shift”. You may not know what this is but, you should have learned what it is much earlier in your high performance career.

If you look close you will notice the hole for the Camshaft Plug in this 2-bolt block is visually centered in the metal around the cam plug location. This is the 1973/2-bolt block I used to build a 410 HP street engine that will never go above 5900 to 6000 RPM.

If you want to tell your friends and/or competitors what to look for you just need to show them these 2 pictures. Both are SBCs; the one above has as close to “zero” core shift as I have ever seen, while the one below is a 4-bolt main engine with a lot of core shift. (This can happen in any engine so it is a common problem in all brands of ‘50s through mid-‘90s cars.)

This second engine has a visible amount of core shift.  Note that the cam hole has more iron on one side than the other. Although it is a 010 block, usually indicating it’s a 4-bolt, it will never make a good racing engine. For any engine I build; this is far too much shift for high horsepower.