cam gear timing chain LS engine

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I’m building an iron 6.0L LS engine and just tried installing the timing set and the chain is super loose. I wasn’t sure how old this timing set was so I bought a brand new chain and it’s just as bad as the original. The machine shop align honed the block but I didn’t think they took that much off the block to make that much of a difference. Is there just a shorter chain I can buy to tighten this up? Thanks.


Jeff Smith: I called my local machine shop—Jim Grubbs Motorsports in Valencia, CA—and asked their resident block machinist Ryan Peart about align-honing blocks. He told us that he only removes the absolute minimum needed to bring all the main bores into compliance.

He said a typical average for most street engines is to remove about 0.002 to 0.003 inch from the main cap and then he hones the housing bore back into the middle range of the spec. Remember that removing a total of 0.003 inch from the cap is equivalent to a total change in diameter of 0.0015 inch from the radius which also represents the center-to-center distance between the crankshaft and the cam.

Your description makes it sound like whoever machined your block took much more than just 0.002 to 0.003 inch off the caps for this to occur.

We did some research and it appears Cloyes has what you are looking for.

The best way to approach ordering a shorter chain would be to first measure the center distance (CD) between the centerlines of the crank and cam.

Cloyes offers a procedure to do this since accurately finding the center on the crank and cam can be difficult.

Cloyes’ procedure is to measure the overall distance from the top of the cam gear to the bottom of the crank gear. Cloyes calls this metric “Measure Over Shaft” (MOS).

Next, you measure the diameter of the crank gear and cam gear, and then divide them by two and add them together.

Finally, you subtract that number from the MOS.

We made up some numbers to illustrate the math. The overall MOS is 9.295 inches. The equation for this hypothetical scenario would look like this:

CD = MOS – [(Crank Gear / 2) + (Cam Gear / 2)]

CD = 9.295 – [(5.680 / 2) + (3.140 / 2)]

CD = 9.295 – (2.84 + 1.57)

CD = 9.295 – 4.41

CD = 4.885

The stock center distance for an LS engine is 4.890 inch and our number of 4.885-inch center distance reveals a package that is a 0.005-inch shorter distance, which would create slack in the chain.

Cloyes offers its high performance dual roller timing sets with standard or either a 0.005-inch or a 0.010-inch shorter chain. Using the above example, it appears that a 0.005-inch shorter chain would probably be best.

Unfortunately, we didn’t find any source for a slightly shorter stock chain, so you will have to invest in the more robust Cloyes dual roller system for the LS 3-bolt camshaft. We will assume this is an early iron 6.0L block that is the 24x reluctor package that places the cam sensor at the back of the block.

Here are the part numbers for a standard length dual roller timing set as well as both a 0.005-inch and a 0.010-inch longer chain set from Cloyes.





Cloyes Double  Roller Timing Set 9-3659X3 Summit Racing $161.99
Cloyes Double  Roller Timing Set, 0.005” 9-3659X3-5 Summit Racing $161.99
Cloyes Double  Roller Timing Set, 0.010” 9-3659X3-10 Summit Racing $172.97
(*- prices as of November 2017)

Keep in mind that a dual roller chain will put the crank gear up against the oil pump—but Cloyes supplies a nice spacer to move the pump outboard. This will also require you to carefully grind out the mounting bolt for the oil pump pickup since it will now not be in the right place to bolt to the engine. A small thing, but necessary.

This should put you back on the road with a tight timing set, but you might consider looking for a new machine shop as it seems that quite a bit of material was removed from the caps to align-hone your block. We have to assume this since we don’t know the engine’s prior history, but with an iron LS block, these blocks are very durable and rarely would be subject to that much movement unless the engine really burned up the bearings.

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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.