Default Timing Gear Drive 

Old 01-05-2011, 09:15 PM   #1
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Kind of a random thought, because I'm making a list of items to replace when I finally get around to rebuilding the head on my 258, I thought about timing gear drive sets.

The thought was a mild cam with upgraded lifters (non-flat tappet) and either double roller timing chain and gears or a gear drive set. I've done a little bit of internet digging but really haven't come up with much. Anyone know anything?
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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:29 PM   #2
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I ran a 262 duration Comp cam for several years in my 4.2 and absolutely loved it. When I did my 4.0 head conversion, that same cam complimented the freer-flowing head design perfectly. The 262 has a wider range then I first thought when I installed it...originally going for low end without (much) compromise to the top end. I was very surprised when I jumped up to the new head and a 500cfm 4bbl Edelbrock and found I had enough cam to support it.

I went with a double roller and left the lifters stock.

 

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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:33 PM   #3
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Now's time if it's got the original.

Gears, probably not worth it for a mild 258.

If the lifters a clicking, pull the head a drop some new ones in. Noting wrong with getting intimate with a 258.

Last edited by 73CJ; 01-06-2011 at 12:57 AM..

 

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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:37 PM   #4
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Quote:
Originally Posted by CJim7 View Post
I ran a 262 duration Comp cam for several years in my 4.2 and absolutely loved it. ~ ~
I went with a double roller and left the lifters stock.

Stock lifters, double roller timing chain and gears and a 262 Comp cam, did it have good low end? Why did you stick with stock lifters?
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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:40 PM   #5
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Quote:
Originally Posted by 73CJ View Post
Now's time time if it's got the original.

Did you add one to many time's in there? Because I'm completely confused if you didn't.


Oh yeah, everything internal to the engine is original. I've had a valve tick for, well as long as I can remember. Originally a buddy and I just wrote it off as an exhaust leak, but last year I actually got a stethascope on it and you can hear the tick coming from #1 cylinder.
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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:47 PM   #6
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Quote:
Originally Posted by elwood blues View Post
Stock lifters, double roller timing chain and gears and a 262 Comp cam, did it have good low end? Why did you stick with stock lifters?
It had excellent low end, even with the stock head...but I also went with high compression pistons that brought up the compression too...forgot to mention that, it's been a while since I had that motor

I guess I just didnt feel the need to change from stock lifters...I did install valve springs matched for the cam per Competitions' recommendations. The rest of the valvetrain remained stock.

At the time, I also went with a TFI ignition which is, in my opinion, one of the best upgrades out there. After all, it all starts (or ends) with the spark.

 

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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:55 PM   #7
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I have no intentions of ripping in to the lower half of the engine. It doesn't leak, make funny noises or burn oil. If (IF) the odometer is correct, it's only got 52,xxx miles on it. There's no reason the bottom half should need to be rebuilt. That's why I'm sticking with rebuilding the top half. All good info Jim, thanks
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Default Re: Timing Gear Drive 

Old 01-05-2011, 09:57 PM   #8
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Replacing the timing chain for a timing gear set is popular with the high performance / hot rod crowd. You don't have to worry about the chain slack and stretch. The gears hold the cam in the exact position that you set with your timing.
The cons are that they eat up horse power and are noisy. They add a whine to the engine noise. The hot rod crowd says that the horsepower you gain by having the cam exactly where you want it will outweigh the HP loss. But I say that a Jeep needs a wide bandwidth. You rock crawl and you need to pass on the freeway. The very small amount of chain slop won't trow off your cam timing.
Now on a HP engine or car you would drag race you would want to stay at a specific RPM range (near red-line) then a cam gear set would keep the cam timing accurate.
IMO I would stick with a chain. They actually hold up better with high mileage unless you really get a high end gear set.

Last edited by BusaDave9; 01-05-2011 at 10:07 PM..

 

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Default Re: Timing Gear Drive 

Old 01-05-2011, 10:11 PM   #9
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Quote:
Originally Posted by elwood blues View Post
Stock lifters, double roller timing chain and gears and a 262 Comp cam, did it have good low end? Why did you stick with stock lifters?
Other then some very costly roller lifters from 505 performance I am not aware of anyone having rollers available.

We did a lot of work over on jeepstrokers.com and it was very cost prohibitive. The cam needs to ground differently for the rollers. Plus the design of the 4.x engines does not lend itself to the roller tie bars. Yes it can be done but the cost to benefit ratio is just not there.

Roller rocker arms are a different story. High lift cams and stock rocker arms do not get alone as well as one would like. Wiping of the valve stem. Galling of the rockerballs, high lifter loads and heavy side loads from stiffer springs raise hell.

Rollers give you a much better platform to work with. Plus you can set lifter pre-load. I am running a 480 lift cam with Mopar rollers. Valve train geometry works well.

Beware of the low buck import lifters. There has been cheap imports that have not had proper heat treating. Buy from a well know company to make sure you are getting good parts.

Another consideration is your engine oil. Our beloved Jeep engines were designed around oils that had relatively high levels of ZDDP anti scuff agents. Today`s oils have greatly reduced ZDDP.

 

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Default Re: Timing Gear Drive 

Old 01-05-2011, 10:13 PM   #10
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The whining noise I knew about, the other stuff I ddin't. Good info Dave

I've been doing a lot of internet digging since my first post and I've found that Mopar used to carry a timing gear set for the 4.0/4.2L at a cost of $600!!! But, they discontinued it a couple of years ago because of low demand. Just about everywhere else that ever made them also has stopped long ago because of really low demand. From what I've read about the only reason to really use one is on a 4.6 up to 4.8L stroker with the 4.2L block and the 4.0L head. The only place I've found that still makes them is a place called 505 performance, but they want $420 for them, and that's a lot more than I'm willing to pay.

Double roller timing chain it is :
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