Timing belts vs. Timing chains
Thread Starter
Pro
Joined: Jul 2004
Posts: 639
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From: 1985 L98, Auto. O'FALLON, IL
Timing belts vs. Timing chains
Why do some engines have timing belt and others chains. I thaught that the chains were always on bigger engines but I noticed in the JEGs cataloge that they have kits to convert your 350 to a belt. What gives? Why would you want to do that? 
Melting Slicks
Joined: Oct 2003
Posts: 2,951
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From: Mount Vernon OH
Jesel Belt
I have run belt drives for roughly 5 years. They make cam adjustments and even swaps very easy because most belts do not require you to drop or lower the front of the oil pan. Pete is right about less harmonics and less resistance. Manufactures typically claim 5 to 10 horsepower increase and I can not confirm this because I have never dyno'd back to back pulls with only changing from timing chain to belt. If you are running a fairly stock engine there is better places to spend your money but if you are doing a high end rebuild they are a nice bonus feature to add.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Originally Posted by Pete K
The belts transfer less harmonics to the valve train. It allows the cam timing to be more consistant. The belt systems also allow easy cam timing changes with no disassembly.
100%
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Which is more reliable?
I just changed out a stripped timing belt (maybe original) on a 200k toyota engine. Luckily, it was a non-interference motor.
I just changed out a stripped timing belt (maybe original) on a 200k toyota engine. Luckily, it was a non-interference motor.
Race Director
Joined: Feb 2004
Posts: 12,518
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I considered buying a comp cams external dry belt system. It was for the 87. He would not sell it to me. He said durability on the street would be horrible. I have not yet found anyone running one on a daily driver. Hopefully, someone will chime in who runs one.
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Safety Car
Joined: Dec 2004
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From: Poop land
Are L98s interference motors? I remember when the timing belt broke on my old Integra GSR VTEC and it was a big mess and another $3000 to spend on a new motor. It was all because of a badly installed water pump which locked up causing the belt to break. I would rather have a timing chain rather than a timing belt because they usually last the lifetime of a typical motor
Race Director
Joined: Dec 2002
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Depends on what you mean by reliable.
A chain seldom breaks, but it does "stretch" (stretch is a misnomer; it actually elongates from roller/pin/side plate wear). A belt, on the other hand, does not elongate (which would alter cam timing) but it can actually break, wreaking havoc with valves/pistons.
I had 200K miles on a SBC before the cam timing was thrown off enough for me to notice it. Chains usually are due for replacement just about the same time as the bearings, rings, and valve guides are due, so I wouldn't be replacing JUST the chain....
Larry
code5coupe
A chain seldom breaks, but it does "stretch" (stretch is a misnomer; it actually elongates from roller/pin/side plate wear). A belt, on the other hand, does not elongate (which would alter cam timing) but it can actually break, wreaking havoc with valves/pistons.
I had 200K miles on a SBC before the cam timing was thrown off enough for me to notice it. Chains usually are due for replacement just about the same time as the bearings, rings, and valve guides are due, so I wouldn't be replacing JUST the chain....
Larry
code5coupe
Last edited by rocco16; Aug 16, 2005 at 03:13 PM.
Team Owner
Joined: Mar 2001
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Originally Posted by k0rv3tt389
Are L98s interference motors? I remember when the timing belt broke on my old Integra GSR VTEC and it was a big mess and another $3000 to spend on a new motor. It was all because of a badly installed water pump which locked up causing the belt to break. I would rather have a timing chain rather than a timing belt because they usually last the lifetime of a typical motor
