Drag Racing Online: The Magazine

Volume VIII, Issue 10, Page

Reher-Morrison Racing Engines' David Reher and Darin Morgan answer your questions about cylinder heads or anything else concerning your racing engine building problems. Remember who you're are dealing with so no soft-ball questions.


I'm building a bbc for bracket racing. I'm going .100 on the bore, but unfortunately the block is a little thin at the bottom of three cylinders. The thin areas are in a non-thrust side and would measure at .093 in thickness. Would this be o.k. if I low filled the block?  800 h.p.........

Ed Matsuoka
Valley Springs, CA



Thin cylinders in an over bored OEM block is a common scenario and filling is the best way to remedy the problem. If this is a bracket car and not street driven then you can half fill the block. If it’s driven on the street, I would fill it almost half way and use an oil cooler. In my personal opinion an oil cooler is mandatory for filled blocks whether you drive them on the street or not.

I have personally half filled blocks for street driven cars and ran them for years with a good oil cooler with no problems. If you’re not familiar with the processes or proper procedures for filling blocks, you need to find an engine builder who is. There are many different types of filler available. Some are good and some very bad!

Hard-Block is always a tried and true product that works exceptionally well and the one most people use. Do not use any epoxy resins or unknown concrete products because there modulus of elasticity and or coefficient of expansion is incompatible with cast iron and they do more harm than good! The two I recommend are Hard-Block or Embico 885. Both are what are known as metallic grouts and both are metallurgicaly compatible with iron blocks and have proven themselves over time.

David Reher asked Darin Morgan to answer this question because it is his area of expertise.

Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
Visit our web site at http://www.rehermorrison.com

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