This is Editor Glad's dad in front of a twin of his high school car, which we found at the
Big-Blocks and Small-Blocks
Mark Edwards, Richwood, OH: I have a question regarding engines. I see articles that mention 400 and 454 big-blocks and small-blocks and would like to know what the difference is between them.
Jeff Smith: Thanks for writing, Mark, because it's important that we take the time to bring our new readers up to speed. Even you old-timers (and I include myself in that description) need to take a moment every once in a while to remember how little we knew when we started in this hobby. These are generic terms that relate to the physical size of the engine and to its displacement as expressed in cubic inches and more often now in liters. Let's start with a simple description using the small-block Chevy. This engine started out at a minuscule 265 ci in 1955 and expanded in production form all the way up to 400 ci in the '70s. In 1965, Chevrolet introduced the production 396 and 427ci big-blocks that were physically larger in external size and displacement. But you can see that by 1970, Chevy had built a 400ci small-block that was larger in displacement than the 396ci big-block. The monikers have remained the same despite the displacement overlap.
This is a 505ci stroker Pontiac built by Butler Performance. It could easily be considered
Like most things in our sport, other engines can make this distinction downright confusing. The most popular of all Chrysler big-block engines, the '70 426 Hemi (for example), can trace its roots back to the original Hemi-headed engine used in Chrysler, Dodge, and DeSoto vehicles. The Dodge version was called the Red Ram but only displaced 331 ci despite its lineage as a big-block. Pontiac also gets a little confusing. Take the 389 engine originally introduced in 1959 that many would consider a big-block engine; Pontiac engineers later developed a lower displacement 326 using a smaller bore that would be closer to being considered a small-block in terms of displacement. As you can see from these relatively few descriptions, the distinction between small-block and big-block can be a bit confusing sometimes. But hang in there, Mark, continue to read Car Craft, and you'll be an expert car guy in no time.
LS Rod Bolts
Tim Wusz, Anaheim, CA: I bought a relatively new LS1 engine that has an unclear history. I've changed the cam and decided to make sure that the bottom end is properly torqued before it goes in the car. I know that the head and the harmonic balancer bolts are one-time use but I'm not sure if that includes the rod bolts. What should the torque spec be?
Jeff Smith: According to all of our sources, this is a one-time-use fastener. Early LS '97 to '00 engines used odd-looking bolts with a sleeve and an undercut that LS engine builder Kurt Urban (kurturbanperformance.com) says was cause for many early engine rod bolt failures. GM created a second design, stronger capscrew around 2000. Where much of the confusion lies is with the torque angle spec that is now common with many modern engines. Torque angle, for LS rod bolts as an example, specifies 15 ft-lb of initial torque and then using a torque angle gauge, tightening the bolt another 60 degrees (first design) or 75 degrees (second design). The angle eliminates the effects of friction on bolt torque. Urban says if the engine has run and the rod bolt is loosened or removed, it should be replaced. If you are in doubt, try Urban's trick. Given the initial torque spec of 15 ft-lb, he sets his torque wrench to 35 ft-lb and runs back over all the rod bolts. As long as each factory rod bolt achieves that torque spec, he feels the bolts are sufficiently stretched. If you plan on rebuilding the engine, ARP (arp-bolts.com) and KaTech (katechengines.com) offer superior, high-strength replacement capscrews.
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