Timing Belt or Chain - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > JK Wrangler Technical Forum > Timing Belt or Chain

Stainless Steel Door Hinge PinsPoly Door Hinge BushingsEngo LED Flush Mount Lights *PAIR* Flood or Spot 1,600 Lum

Reply
Unread 07-27-2010, 06:29 PM   #16
MilitaryJK4455
Web Wheeler
2010 JK Wrangler 
 
Join Date: Mar 2009
Location: Ft. Detrick MD
Posts: 2,631
Quote:
Originally Posted by Farmdiesel View Post
With Interference engines the valve will come in contact with the piston if the engine gets off timing, ie timing belt/chain breaking. So if the piston is at the upstroke and valve is open +Crash+ Bent Valves. My understanding in Non-interference engines there is enough room so the valves and pistons will not contact even if the timing goes.

I wasn't aware the 3.8 was a interference...I'm not sure what indicates an engine being one or the other? I assume efficiency and the need for higher revs
Oh ok... Well that makes sense... You taught me something

MilitaryJK4455 is offline   Reply With Quote Quick reply to this message
Unread 07-27-2010, 07:10 PM   #17
Bionicrooster
Registered User
2010 JK Wrangler 
 
Join Date: Mar 2010
Location: Atco - NJ
Posts: 266
I was under the impression the 3.8 was not an interference engine, does anyone know for sure?
__________________
" We do not inherit our wildlife from our fathers, we only borrow it from our children."
Bionicrooster is offline   Reply With Quote Quick reply to this message
Unread 07-27-2010, 07:36 PM   #18
JeffinWesternWA
Registered User
2010 JK Wrangler 
 
Join Date: Dec 2009
Location: SW WA
Posts: 948
It's chain driven, not a belt so does it even matter? I haven't seen a bad chain on an engine w/ under 175K~ miles in years!
__________________
JeffinWesternWA
JeffinWesternWA is offline   Reply With Quote Quick reply to this message
Unread 07-27-2010, 08:09 PM   #19
ronjenx
Web Wheeler
 
ronjenx's Avatar
2008 JK Wrangler 
 
Join Date: Jan 2009
Location: Maine
Posts: 3,909
Quote:
Originally Posted by Bionicrooster View Post
I was under the impression the 3.8 was not an interference engine, does anyone know for sure?
According to the service manual, "The engine does not have provisions for a free wheeling valve train."

I interpret that as being an interference engine.
ronjenx is offline   Reply With Quote Quick reply to this message
Unread 07-27-2010, 09:35 PM   #20
Bionicrooster
Registered User
2010 JK Wrangler 
 
Join Date: Mar 2010
Location: Atco - NJ
Posts: 266
Quote:
According to the service manual, "The engine does not have provisions for a free wheeling valve train."

I interpret that as being an interference engine.
Thanks! BTW I just got back from Maine, and already miss it. Have a camp down east and love it. Great wheeling up there too
__________________
" We do not inherit our wildlife from our fathers, we only borrow it from our children."
Bionicrooster is offline   Reply With Quote Quick reply to this message
Unread 07-27-2010, 09:48 PM   #21
ronjenx
Web Wheeler
 
ronjenx's Avatar
2008 JK Wrangler 
 
Join Date: Jan 2009
Location: Maine
Posts: 3,909
Quote:
Originally Posted by Bionicrooster View Post
Thanks! BTW I just got back from Maine, and already miss it. Have a camp down east and love it. Great wheeling up there too
Most of my wheeling has been in northern Maine. Usually to get to a place to start hiking.
ronjenx is offline   Reply With Quote Quick reply to this message
Unread 08-13-2013, 09:25 PM   #22
midnightrider10
Registered User
 
Join Date: Aug 2013
Location: edenton, nc
Posts: 2
great info guys thank you those of us new to Jeeps like it alont
midnightrider10 is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 07:07 AM   #23
mello
Registered User
 
Join Date: Aug 2012
Posts: 390
Free wheeling engines can also have catastrophic failure if belt breaks. This would mainly occur in high rpm situations. Some motors have good chain and guide designs where both will last as long as the motor. Others have design not so good where the guides will wear out and come apart causing chain to have slack and allow motor to destroy itself. Most all chain drive motors have a tensioner that is controlled with oil pressure. As chain stretches tensioner can keep constant pressure on chain to compensate. With this being said you can see how using a good quality oil and performing scheduled oil changes is critical on these motors. All chain drive motors I have ever worked on give a very early warning before a tensioner fails or a guide. If it gets to the point of engine destruction then the driver must have just turned the radio up and ignored the early warning noises.
mello is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 09:19 AM   #24
offroadjeepjk
Registered User
 
Join Date: May 2013
Posts: 14
Anyone know if the 3.6 has a belt? I have a 2013 & haven't thought about it until I saw this thread. Tks
offroadjeepjk is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 10:00 AM   #25
2Five22
Registered User
2013 JK Wrangler 
 
Join Date: Jul 2012
Location: Wickenburg, Arizona
Posts: 192
Quote:
Originally Posted by offroadjeepjk View Post
Anyone know if the 3.6 has a belt? I have a 2013 & haven't thought about it until I saw this thread. Tks

"Valve System: Chain-driven DOHC, 24 valves and hydraulic end-pivot roller rockers"

Reference - http://www.media.chrysler.com/newsre...d=9735&mid=261
__________________
'13 JK Rubicon in white - the German Shepherd's
'13 JKU Sport in gecko - her Majesty's

I am just the chauffeur.
2Five22 is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 11:15 AM   #26
offroadjeepjk
Registered User
 
Join Date: May 2013
Posts: 14
Sweet, one less thing to worry about.
offroadjeepjk is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 12:11 PM   #27
Butterjeep
Registered User
2012 JK Wrangler 
 
Join Date: May 2012
Location: Edgewater, NJ
Posts: 497
Timing belts definitely had a bad reputation but as technology improves, so does belt performance, materials and longevity. Remember when fuel injection first came out and it was viewed as the worst thing ever?

I remember as a kid being really torn between timing gears or a timing chain on my 351W so that's proof that I've certainly come a long way. The truth is, modern motors with timing belts have better mileage, less parasitic drag, and the belt helps to damp valvetrain action a bit for a smoother running engine.

I'm truly amazed at the Pentastar V6 which is why I bought two vehicles that both have them. It's a workhorse of a motor and has a great feel to it. If it came with a belt vs a chain, would that have stopped me from buying it? Nope.
__________________
2012 JK
2014 WK2
Butterjeep is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 02:22 PM   #28
jwmbishop
Registered User
2011 JK Wrangler 
 
Join Date: May 2011
Location: corsicana, tx
Posts: 3,444
Yea but in non interference (freewheeling? Never heard that one before) engines the combustion chamber is either A) HUGE with a related low power output or B) Above the valve like in a briggs and stratton or Flathead. Even the Dodge Hemi will touch valve to piston with a broken chain!

The primary reason for belts is: they can be used externally. A chain requires oil and thus gets buried in the crankcase behind the water pump etc. And on a OHC or DOHC chain drive - the chains are so long even the slightest stretch can retard the valve timing as much as 2degrees!

A belt can be changed in ~30 minutes with no loss of coolant or oil. A chain takes about 7 hrs (to do it correctly) and requires draining and filling the radiator, the oil and disposal of both...

The secondary reason is (believe it or not) they DON'T stretch. That is until they wear out which occurs faster than a chain towards end of life. A chain wears from day one. If it stretches .005 - in 200K miles - that was at a rate of .005 divided by 200K AND any gain never left (ie if it stretches .002 it STAYS stretched .002).
A belt will have ZERO stretch until around 45K and may gain .003 by 90K. It CAN get stretched momentarily under hard acceleration - but returns back once inertia is more equal between crank and cam gear. Like a rubber band returning to its shape after use.

As a machinist I prefer chains. Even though on a OHC or DOHC if you surface the head - you have moved the cam closer to the crank and that is then "made up" by the chain - resulting in retarded valve timing. A lot of rebuilders forget this as two degrees does not make it run bad - just lower economy and lower power but compared to the pre rebuild it is BETTER so overlooked!
As a consumer I prefer belts - (and have even belted some chevies for drag racing) just MUST do the maintenance on time!

Whenever I have seen an interference engine with bent valves - it was NOT because of "a broken belt". It was because of failure to perform scheduled maintenance. THEN the belt broke! I have never seen an engine come in with all of the valves bent a broken belt and less than 40K on it. I am sure there are some, but VERY rare.
__________________
J Wm Bishop EA, ASADE
Money cant buy happiness. But it can buy Jeep parts. Same thing.
jwmbishop is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 02:31 PM   #29
mello
Registered User
 
Join Date: Aug 2012
Posts: 390
Daewoo cars were bad about braking belts before their scheduled replacement and they would destroy themselves. Then they went out of business probably a contributing factor.
mello is offline   Reply With Quote Quick reply to this message
Unread 08-14-2013, 04:53 PM   #30
Butterjeep
Registered User
2012 JK Wrangler 
 
Join Date: May 2012
Location: Edgewater, NJ
Posts: 497
Quote:
Originally Posted by jwmbishop View Post
Yea but in non interference (freewheeling? Never heard that one before) engines the combustion chamber is either A) HUGE with a related low power output or B) Above the valve like in a briggs and stratton or Flathead. Even the Dodge Hemi will touch valve to piston with a broken chain!

The primary reason for belts is: they can be used externally. A chain requires oil and thus gets buried in the crankcase behind the water pump etc. And on a OHC or DOHC chain drive - the chains are so long even the slightest stretch can retard the valve timing as much as 2degrees!

A belt can be changed in ~30 minutes with no loss of coolant or oil. A chain takes about 7 hrs (to do it correctly) and requires draining and filling the radiator, the oil and disposal of both...

The secondary reason is (believe it or not) they DON'T stretch. That is until they wear out which occurs faster than a chain towards end of life. A chain wears from day one. If it stretches .005 - in 200K miles - that was at a rate of .005 divided by 200K AND any gain never left (ie if it stretches .002 it STAYS stretched .002).
A belt will have ZERO stretch until around 45K and may gain .003 by 90K. It CAN get stretched momentarily under hard acceleration - but returns back once inertia is more equal between crank and cam gear. Like a rubber band returning to its shape after use.

As a machinist I prefer chains. Even though on a OHC or DOHC if you surface the head - you have moved the cam closer to the crank and that is then "made up" by the chain - resulting in retarded valve timing. A lot of rebuilders forget this as two degrees does not make it run bad - just lower economy and lower power but compared to the pre rebuild it is BETTER so overlooked!
As a consumer I prefer belts - (and have even belted some chevies for drag racing) just MUST do the maintenance on time!

Whenever I have seen an interference engine with bent valves - it was NOT because of "a broken belt". It was because of failure to perform scheduled maintenance. THEN the belt broke! I have never seen an engine come in with all of the valves bent a broken belt and less than 40K on it. I am sure there are some, but VERY rare.
Wow good stuff, thanks for posting. Totally didn't even think about machining affecting the distance and causing the timing to be off. You learn something new everyday!
__________________
2012 JK
2014 WK2
Butterjeep is offline   Reply With Quote Quick reply to this message
Reply

Tags
3.8 liter , JK Wrangler , question , timing belt , timing chain , wrangler

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.