Ad Radar
Car Craft
Click here to find out more!

How To Balance An Engine - Engine-Balancing Basics

Custom Stroke Combinations And Lightweight Pistons Are Now Normal, But That Can Cause Problems If You're Not Dialed Into . . .

Photography by

Ishigo says that while the electronic balancer can read each counterweight individually, he generally treats the engine as front-half and back-half setups. Because this Ford is an externally balanced engine and so much weight had to be removed, Ishigo's first step was to remove 77 grams from the bolt-on offset weight in the Professional Products balancer. But keeping the amount of weight removed from the front and rear symmetrical required removing metal from the crank counterweights on both ends. So Ishigo set the crank in a large lathe and removed more than 400 grams from the front and rear of the crankshaft. The amount of weight removed was limited by the height of the rod journals on the opposite side of the counterweights. When the lathe just barely touched the rod throws, the cutting stopped. Next, he removed additional weight by drilling multiple holes in all the counterweights. Ishigo decided to drill three shallow holes in each counterweight rather than two deep holes, removing another 82 grams from the rear, roughly similar to the 78 grams removed from the balancer. Ishigo says that drilling multiple holes is safer because it's shallower, but drilling holes alongside the direct path of imbalance is also less effective than removing weight directly in line. It comes down to how much weight must be removed. We added up the total weight removed from the crank, and it came to just under 1 pound, 4 ounces. While not a huge amount compared to the overall weight of the entire rotating assembly, it still equates to a lighter package that will rev a little quicker and help acceleration.

SBC Strokers
Another area of potential confusion lies with the extremely popular 383ci small-block Chevy stroker packages. The 383 originated using a 400ci engine crankshaft in a 350 block. As mentioned earlier, the 400 was the only small-block that was externally balanced, and most 383 kits retain this external balance feature. But for higher-end applications using a 4340 forged steel crankshaft, the ideal path is to internally balance the rotating assembly to reduce crankshaft flex. Now let's make this more complex by using a one-piece rear main seal block and crank. With a Lunati Sledgehammer crank and rotating assembly, this is exactly the combination used in the 383 small-block that was our test engine for the giant parts-test story "Are Premium Parts Worth the Price?" in the Sept. '07 issue.

At first this would seem simple, since you don't have to use an offset weight balancer or flexplate/flywheel. However, a one-piece rear main seal rear flange does not allow for the offset weight that is used on a two-piece rear main seal engine. To account for that weight difference, all one-piece rear main seal flexplates (and flywheels) require an offset external weight. But with an internally balanced crank, this weight is not necessary. Thus in the case of a flexplate, the external weight must be carefully removed. For flywheels it's possible to have a zero-balance flywheel custom made. If you already have a flywheel, additional holes can be drilled to bring it back to a zero-balance condition. If this is not done, the engine will experience a vibration that will eventually tear up the main bearings and cause damage that could easily be avoided.

SOURCES
Professional Products
Hawthorne
CA
3-23/-779-2020
professional-products.com
Scat Enterprises
3-10/-370-5501
scatenterprises.com
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
22 comments
Flavio Leon
Flavio Leon

chase those threads!!! and ARP THE WHOLE CHIBANG DOWN UNDER!

Scooter's Garage
Scooter's Garage

clean, Clean and CLEAN! - as well as "Attention to details" - make sure all threads are clean and chased - parts are matched as close as possible....and above all - double and triple check your torque sequence and settings! - We've had a lot of our customers bring us prior builds that the failure can be traced back to improper torque, dirty threads, and or use of mismatched cheap parts....

Saady Tafsiry
Saady Tafsiry

احتمال روزی ما هم به این فناوری میرسیم...

Tim Liscum
Tim Liscum

Don't worry Antonio Mark Carrillo ... nobody would ever believe what they read on the internet!

Paul Martin Bradley
Paul Martin Bradley

When you get too actually balancing, ask the the balancer to add 4 grams to the bob weight for oil. maybe more fro a bigger engine.

Roger Womack
Roger Womack

Next story should be how to find a competent machine shop! I have heard some real horror stories !

Carroll Smith
Carroll Smith

i measured the picture and reconfigured the size and divided the megapixels and its actually 349.982 cubic inches

Rex Scott
Rex Scott

great new edition, love that building the mail order LS7 and the big ass 572BB. Love car craft.

Alex Bartonek
Alex Bartonek

Good article. Btw, I renewed for 2 more years so you can stop reminding me in email. LOL

Shawn Tarleton
Shawn Tarleton

Only drink American beer while working on your American vehicle. Keep it same same. And weigh everything you can that rotates in the block.

Car Craft