Why balance an engine

Blueprinting can also mean loosely building an engine by following a set of factory specs. The only problem with this is that there are given areas of tolerances, not just one specific number. They will have exactly the same amount of piston to cylinder wall clearances as well as ring gap clearances, cam timing, head port and chamber volumes and so on where as a factor spec book will have "tolerances" that vary slightly.

A blueprinted engine will call for. There is no "within spec for blueprinted engines! It either is or it isn't and there's no in between. If you blueprinted two engines by the factory specs, there will always be variances between rod and main bearing clearances, piston clearances, deck height differences, valve spring pressure differences as well as Intake and exhaust port and chamber volume differences. It takes pain staking hours to truly blueprint an engine and for what? A ton of money and really nothing gained unless you are running the exact same car at the exact same track and you need to go the exact same speed as you were with the last engine.

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Should I have my engine balanced and blueprinted? A good example of this is a subwoofer vs. Bass is a lower frequency, and can be heard at longer distances. But your tweeters are on a higher frequency and do not travel as well.

The principle is essentially the same. The balance shafts are actually out of balance rods that create a vibration. This is done on purpose, as it cancels out the vibration inherent to a four cylinder engine. Mainly, they do their work at idle and low engine speeds, where vibrations are felt the most. Being out of balance is bad for performance; however this trade-off is worth it for the average consumer.

The real problem comes in when you want to use the engine at high speeds. Recall the math from above and how the forces relate to rpm. A factory balance shaft has a radius just over an inch, making the counter weight a lot more than an ounce, which in turn creates terrible engine shake. For high rpm engine operations, it is essential to eliminate the factory balance shafts, or run neutral shafts which can spin at any speed without causing vibrations.

We went through a lot of stock crank pulleys until we gave up and finally ran this. So, we are at the middle of the balance job. Be sure to have grams of oil on your balance data sheet calculation as well. Advertisement Normal caution for material removal on pistons and rods should be exercised. Quality pistons and rods very rarely need to have material removed to match balance. Be consistent on all the weight measurements when adjustments are necessary.

The more detail in this area goes a long way down the road on quality results. Building the bob weights is very straightforward and again, making them accurate to the balancing data sheet calculation is critical. You should have half-gram weights available for maximum adjustment. To further avoid any balancing issues we prefer to spin our assemblies all at once. Be sure to index the pressure plate to the flywheel, this will assure a quality job.

There will be some questions on how adjustments need to be made. With a complete assembly, efforts must be made to make all weight adjustments on the crankshaft. This is not always possible but, all efforts must be exhausted before making attempts to the ends.

Externally balanced engines are a bit different and again should have minimal adjustments made on the ends with the majority on the crankshaft. Advertisement Making weight adjustments to the crankshaft or the ends can be complicated at times, which is why bob weight management is so important at the earlier stages.

If properly managed it is ideal to have the bob weight slightly less than the crankshaft so minor drill hole adjustments can be made. A slow consistent rotation will keep you in control of material removal and hopefully keep you from damaging tools. Advertisement As always, remove a little less than what is calculated because you can always take more out, but cannot put it back very easily. There are a couple of ways to add material.

I have added a lot of heavy metal in my time and the most solid way to properly install, is to mount crossway in each end of the counter weights. We use an industry standard drill and reamer that will interfere fit the heavy metal by. On the other side is adding heavy metal to the crankshaft. Unfortunately you need to have the drills and reamers for each size of the heavy metal that is available. We typically install the heavy metal out as far as we dare, but usually.

Each weight addition is different, but I can tell you that over the years we have successfully welded up existing holes to add the necessary weight and have never seen any repercussion from that effort so, I would advise that as a simpler or cost effective solution.

Be sure to protect the journals at all times. After balancing, a final polish job and rinse on the crankshaft will show your customer a sign of quality. Advertisement The Next Opportunity. In conclusion, I hope this article was enough to give you another perspective on what others might be doing. The biggest encouragement that I can give you is that engine balancing can be very complicated with heavy decisions and some risk at times.

Also, the closer that you make each of your weight adjustment the better you will be than the next guy. Engines: The Executioner — 6. Engines: Dissecting 6.