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Author Topic:   gear drive or timing chain
dean_7585
Member
posted December 14, 2002 09:43 AM
Is there an advantage to running a gear drive instead of timing chain?? and whats the difference in noisy and quiet, besides the noise.


outlawstock17
Member
posted December 14, 2002 02:15 PM
i use a high quality true roller timing chain with billet gears. a gear drive is hard on the cam bearings. they're okay for drag racing, but in circle track racing you're on and off the gas so much, you're asking for trouble with a gear drive.

gear drives sound neat and some will argue that they are more accurate but if you want the ultimate in cam drives and your wallet is thick, use a belt drive.

the advantage of a belt drive is crankshaft harmonics don't have a good conduit to the camshaft and vice verse. a belt also has less friction and the belt absorbs some of the shock to the camshaft and valvetrain associated with on and off the throttle racing.


[This message has been edited by outlawstock17 (edited December 14, 2002).]

sdhnc29
Member
posted December 19, 2002 11:14 PM
There are gear drive's (duel idler gear drives), and then there are real gear drive's . The noisy drive's that you speak of are for the average punk kid with his 5.0 , who thinks his friends are impressed by the "cool" gear noise his car makes . These gear drives are junk , and personally , I laugh every time I hear one . Usually it is just another kid who fell for a good marketing scheme . If you want a real gear drive , like we use in at least half of our Dirt Late Model engines , then buy a Shaver/Wesmar drive . The Shaver/Wesmar drive is designed almost identically like the old Summers Brothers gear drive , with a cam gear , crank gear , and one idler gear that is mounted to a gear drive plate .

The main advantage to running a real gear drive , is the capability to control cam end play on roller cam engines , something that is difficult to do using a chain drive . Roller cam engines have a great amount of forward thrust , and this will affect ignition timing if the cam move forward too much (timing will retard as RPM rises). The other advantage is , you don't have a chain stretch problem with a real gear drive . There is absolutely no problem in using this type of gear drive in a circle track engine .

We also use the Jessel belt drive . It has the same advantages as the Shaver/Wesmar drive , in respect to the ability to control forward cam thrust . But the belt's will also stretch over time , though not as much as a chain .

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


outlawstock17
Member
posted December 20, 2002 07:51 AM
sbhnc29, do you use a dry belt system? have you seen any difference on the dyno with the dry belt verses the fixed idler gear drive, everything else being equal?

i would think that the gear drive would rob more HP than the belt with it in there paddling all the oil around and heating it up as well. your thoughts?


sdhnc29
Member
posted December 20, 2002 10:25 PM
Yes I use a dry belt system , and yes there is a small loss due to the gear on gear situation (friction), and the oil . We use the gear drive primarily on all of our aluminum and steel block dirt engines . In my opinion , and like I said ....we use them both , I prefer the gear drive . I have used both drives on my own SB2.2 aluminum engine , and feel that the gear drive has much less maintenance involved . I have seen a few belt failure's on the belt drives , but have never seen a Shaver/Wesmar gear drive failure of any sort . I think the small power loss from the gear drive vrs. the maintenance of the belt drive makes it worth using the gear drive . I'm speaking about dirt engines here though , not asphalt . In a cleaner environment , such as asphalt racing , the Jessel drive does very well and the maintenance is cut down quite a bit , other than buying a new belt every 15-20 races . So in this respect , I would almost always use the Jessel . Don't get me wrong , I like and use both drives , but for dirt racing , I like the gear drive system better .

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


outlawstock17
Member
posted December 20, 2002 11:53 PM
good stuff sdhnc29, thanks for the reply. you need to get on here more often. kelly wesphal is one of our local guys here in NE oklahoma. i'm pretty sure he's using that same gear drive in his sprint car engines, lol.


dean_7585
Member
posted December 21, 2002 08:51 AM
Where would I find a Shaver/Wesmar gear drive ??



outlawstock17
Member
posted December 21, 2002 09:34 AM
wesmar racing engines, kelly wesphal
14502 s. lewis ave.
bixby, ok 74043
918-366-7311

hang onto your wallet dean, this ain't no ebay gear drive. this is the full monte!

there is a cheaper fixed idler gear drive available for a SBC. summit sells one for $200 but i don't know a thing about it. it's part # SUM-G6310.

sdhnc29, do you know anything about it?

[This message has been edited by outlawstock17 (edited December 21, 2002).]

Pickles
Member
posted December 21, 2002 11:02 AM
I would like to know; what makes a single idler superior to a duel idler drive?


sdhnc29
Member
posted December 21, 2002 01:05 PM
No , I don't know anything about the gear drive that Summit sells . I wish that Summers Bros. still made there drive though !

Pickels,

The fixed idler gear drive is far superior to the duel idler for a few simple reasons . Number one , the idler has one gear that is slightly larger than the other , and that gear goes on the left side , and is wedged between the crank and the cam under acceleration . This causes a drastic power loss ! The more valve spring pressure that you have , the more this gear gets wedged . With the fixed idler , your gear mesh is fixed , and will remain the same no matter how much spring pressure is used , if it's adjusted correctly by the person who installs it . Second problem with the duel idler is that fact that forward cam walk can't be controlled as well as with the fixed idler drive . Last but not least , the duel idler drive is just a sloppy unit ! Everything has room to just bounce around , and this is not good for obvious reasons . One of the most common failures of the duel idler drive , is broken retainer pins on the duel idler gears .
Hope this explains your question Pickles .

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

[This message has been edited by sdhnc29 (edited December 21, 2002).]

outlawstock17
Member
posted December 21, 2002 01:18 PM
pickles, a dual idler type gear drive has the idler gears "floating" in between the top and bottom gear. this is bad. the rotational force of the upper and lower gear tries to "suck" the idler gears between them. this exerts a lot of upward force on the front of the camshaft, wears out the cam bearings on the top side and creates a lot of power robbing friction.

a fixed idler gear drive doesn't do this because the idler gear isn't free to be pulled between the upper and lower gears.

did i explain that correctly, sdhnc29?


outlawstock17
Member
posted December 21, 2002 01:20 PM
LOL, steve. we were answering simultaniously!


Pickles
Member
posted December 21, 2002 09:24 PM
Thank you.


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