gear drives, are they good?

[Speedin' Ian]

We are finishing up our new motor and the builder mentioned how he had a gear break on a previous motor he built. So what do you think, should we stick with the Pete Jackson gear drive, or should we run a chain?

[Floored]

Chain is a simple set it and forget it item and less weight and friction. One less thing to worry about, just get a good one.

[OLDRAT]

That's rather unusual in most situations. The gear may have been a
chepo powdered metal deal.
Do like Floored said and get a good quality roller chain set and you
will be good to go for a long time.
If you have money to spend or have a wild valvetrain, get a Jesel.
OR

[GofastRacer]

We are finishing up our new motor and the builder mentioned how he had a gear break on a previous motor he built. So what do you think, should we stick with the Pete Jackson gear drive, or should we run a chain?
After loosing a motor from a "good" chain breaking, my theory on that is: Chain stretches, timing retards, chain breaks, end of motor!.. My Jackson is 20yrs old and it still looks like it just came out of the box, there are inferior ones out there so I'd stick with the original!. Also idler gear "clearance" is a major key factor for longevity. If the block has been line bored and the idler is too tight, Jackson makes gears to componsate for that!... That is my experience, but go with what you feel comfortable with!..

[LakesOnly]

Nothing necessarily wrong with gear drives. There's a right tool for every job...chain or geardrive...depends on the application and the end user's specific needs.
Both the Pete Jackson and the Milodon single idler gear drives are great setups. Those dog bone double idlers are less so, in my opinion.
LO

[Liberator TJ1984]

I got the Pete Jackson and like it !!! plus when you take the motor apart if you have your cam degreed in to other than straight up , just stamp or mark the gears and reassembly will be a breeze to set back correctly :cool:

[MandDPerformance]

Ever consider a Donovan or Milodon Gear Drive? Both are exceptionally great units and they're easy to use. I prefer them over the Jackson type because they hold a much tighter mesh. " less cam movement and harmonics." Either way you go make sure when degreeing the cam you properly mesh the gears so you get accurate readings.

[mrcrsr]

there is a downside to the gear drive, it transmits all the harmonics generated by the crankshaft into the valvetrain, as a drag racer i've done some reading from the likes of bill jenkins and smokey ynick and both said about the same thing, the belt drive being the best and the chain second, also, gears meshing due tend to generate heat- think about an outdrive, even running on a flushette w/ no load still gets warm

[LUVNLIFE]

I have a used Pete Jackson drive for a BBC that I will let go of for a good price. Don't mean to highjack but it is on topic and if someone wants one. Thanks

[Moneypitt]

Ian, we have used, and reused, for many, many racing miles, thru several different engines,(even the one I bought from you and your dad), a Milodon timing cover/gear drive...Love it..Never a problem of any type, adjustable in 2* incruments, great repeatability when degreeing, trouble free.....MP

[GofastRacer]

Ever consider a Donovan or Milodon Gear Drive? Both are exceptionally great units and they're easy to use. I prefer them over the Jackson type because they hold a much tighter mesh. " less cam movement and harmonics." Either way you go make sure when degreeing the cam you properly mesh the gears so you get accurate readings.
Both are the shit and I would definitely use one on a max effort motor, but for a run of the mill 500hp play motor the Jackson works great considering the cost factor!..

[GofastRacer]

gears meshing due tend to generate heat-
As I said before "clearance" is the key factor, they will not generate heat with the proper clearance, I have seen them turn black from being too tight!..

[Krumbsnatcher]

I have the pete jackson and had 50 hrs on my blown 540. Decided to undo the blown package and go for the efi conversion this winter, too make the story short. This last weekend tore down the motor and the gear drives looked as good as the day we installed it.
just 02.

[DeputyDawg]

Three words--- Jesel Belt Drive

[Sleek-Jet]

Three words--- Jesel Belt Drive
And a few more:
$$$$$$$$$$$$$$$$$$ . :D
Jesel seems a little overkill for an "everyday" boat motor. :idea:

[Mighty Thor]

Millions and millions of engines run billions of miles using timing chains and sprockets, The few failures that are listed here are so insignificant a number as to not matter in a statistical sense. Sure, gear drives are great! but the chain and sprocket is a proven system based upon the historical numbers of running engines both automotive and marine. If your gear drive is working for you there probably isn't any reason to change it, but for someone reading this thread, who doesn't already have a gear drive system, the extra cost may not be of any real benefit to thier situation. Consider, Gear drives are not new ideas, but GM, Ford and Chrysler didn't immediately swith over to the "better idea".

[DeputyDawg]

Sleek Jet posted--Jesel seems a little overkill for an "everyday" boat motor.
How do we know that this is for an "everyday" boat motor? Nowhere in his post did he say that.
I also agree that quality timing chains are great for most applications, but I personally like belt drives in anything moderately radical. If Speedin Ian's engine is the run of the mill 300-600hp lake motor he will be just fine with a good chain.

[Mighty Thor]

How do we know that this is for an "everyday" boat motor? Nowhere in his post did he say that.
I also agree that quality timing chains are great for most applications, but I personally like belt drives in anything moderately radical. If Speedin Ian's engine is the run of the mill 300-600hp lake motor he will be just fine with a good chain.
Dawg, I had to look twice, but when I read Ian's Post I was left with the impression that he has a gear drive and was thinking of not putting it in. If that is the case he will probably be fine with his gear drive, but I was making my point for those who read the thread and may not have the gear drive yet. The belts systems I am familure with are the OEM automotive systems that don't seem to last as long as the chains. What's your opinion on the aftermarket stuff in terms of longevity and maintenence? You sound like you have a fair amount of experience with them?

[DeputyDawg]

As far as longevity with the aftermarket belt drives I can only speak of the Jesel deal because they are the only ones I have had experience with and they seem to hold up veery well. Heck, if you think the belt is a little worn you can just slap a new one on it in nothing flat. They aren't like my wifes 3000GT was where it was an act of congress to change. The main reason I like the belt drives is because of the lack of harmonics transfer to the valve train that you get with a gear drive allthough I know guys who have run Donovan gear drives forever and have no problems.

[Sleek-Jet]

How do we know that this is for an "everyday" boat motor? Nowhere in his post did he say that.
I also agree that quality timing chains are great for most applications, but I personally like belt drives in anything moderately radical. If Speedin Ian's engine is the run of the mill 300-600hp lake motor he will be just fine with a good chain.
He didn't say, I was assuming he was building a "everyday" motor, you assumed he's building a full on competition motor. One of us is right. :D

[Dentz72]

Make sure motor hasn't bee line bored....mine was-20 min of use..installed edlebrock-petejackson, broke, destroyed the valve traine...called em up..the tech guy said he wouldnt run one unless it was a MILODON OR A CASSALE with the gear built into the case!! The others are JUNK!!!This was the Tech guy...that worked for the company that made em alll!!! The pete jackson-edlebrock style!! jUST MY EXPERIENCE!!
The chain hasnt broke yet...80hrs of use 14lbs of boost!!

[Speedin' Ian]

O.k. so the builder lost the crank gear for the gear drive so now we can buy a gear drive, chain drive or belt drive. Which one should we get?

[DeputyDawg]

if money isn't really an issue buy a Jesel Belt Drive. You never did tell us what it was that you were building. It would really help a lot if you would tell us about the motor and it's primary intended use.

[FILUCKY]

1000hp plus N/A on a chain and no problems. :D :D :D

[GofastRacer]

Make sure motor hasn't bee line bored....mine was-20 min of use..installed edlebrock-petejackson, broke, destroyed the valve traine...called em up..the tech guy said he wouldnt run one unless it was a MILODON OR A CASSALE with the gear built into the case!! The others are JUNK!!!This was the Tech guy...that worked for the company that made em alll!!! The pete jackson-edlebrock style!! jUST MY EXPERIENCE!!
The chain hasnt broke yet...80hrs of use 14lbs of boost!!
Well here we go again, the key to making them live is "CLEARANCE" period. If you would have bought the REAL thing and read the paperwork it gives the "required" clearances and "specific" instructions for a block that has been line bored, you call them up and they will send you an appropriate idler(BTW you're supposed to the same with a chain). If a block has been line bored the stock idler will be too tight and that will cuase it to heat up, in fact they will turn black, if they're too loose you'll just beat the shit out of it until it falls apart!.. The one in my motor is around 20yrs old and it still looks like it came out of the box!...

[Speedin' Ian]

I am building a blown injected 540. It will run on gas and I anticipate about a 1000hp (give or take 100 :confused: ). It will be in a flat bottom and not get much drive time. We are running a pretty hefty roller cam with some big springs, if that matters

[sdpm]

Donovan gear drive. It also has the provision for your cam mounted fuel pump.

[BUSBY]

Donovan gear drive. It also has the provision for your cam mounted fuel pump.
I agree w/ Neil here ... 1000 hp should not see a chain, only a QUALITY gear drive or Jesel belt drive ...

[Speedin' Ian]

Anyone know the price difference between a Donovan gear drive and a jessel belt drive

[BUSBY]

The Jesel drive will reduce harmonic vibrations ... they both will give you true timing, the Donovan will be maintenance free (but will have harmonics ... very very slight) and the jesel will need belts after time.
For your deal, not racing ... I would run the Donovan due to the fact that you will not be pulling it down 2 or 3 times a year for rebuild. If you plan on pulling it down often ... the Jesel makes it nice.
Brian