Gear drives: Worth the money?

[DavyZ]

Is anyone in the forum running a gear drive? I'd like to hear from you what your experiences are and if you think they are really the cat's meow.

 

For my topic question, I suppose the answer is: "It depends." This makes sence since I'm going to be running a relatively 'mild' V8 (about 300-350 hp) primarily on the street. From what I gather, guys run them because they make noise, which gets you noticed...

 

I know they don't stretch like a chain can, but they can also transmit unwanted vibrations to the valve train. Will this really shorten the life of the valve train or what?

 

I'm a little on the fence regarding these things as to wether the cost benefit is really worth it all. BTW, I know they come in 'noisy' and 'quiet' versions--I'm into quiet myself, so that would be the way I would go. This leaves me the only reason for getting one: If the performance benefits are worth it for street and occassional track use.

 

I'd like input from guys in the know, and guys who think they know

 

Davy

[Guest Anonymous]

I'm standing up here on the fence too, actually Davy and I discussed this a bit, but I'll put what I've read in a HOT ROD mag a while back, they're opinion was the unit with two idlers and a 'floating dog bone' style was the best. I can't recall they're reasoning because I was sorta homer'ing the article and thought, 'must remember, dogbone one better, must remember...' . Whats the fax jax?

 

Regards,

 

Lone

[pparaska]

Now, maybe I haven't been spending enough money on chains, but the Manley and Cloyes chains I've used on two different SBCs seemed to stretch quite a bit (1/2" of play after 1 hour of running on the Cloyes!).

 

I researched this a bit and grumpyvette said he'd used the same Pete Jackson gear drive for many years. There is a dissentor on Chevytalk.com that says that they are junk and you should only use the pricey single idler type.

 

I have the Pete Jackson quiet drive on my 327. It is not totally quiet, but makes a bit of noise. Can't hear it much over the exhaust when the hoods down. It's on par volume wise with the clatter of the solid lifters. Personally, I think the rough idle lope, solid lifter clatter, and whine of the gear drive make the car music to listen to!

[DavyZ]

Those chains stretched after only minutes?!? Keeraaap That really bites. I'm hoping my timing chain does not do that, but it probably will from what you are describing, Pete.

 

Hrm. Now I'm really thinking about the 'quiet' Pete jackson gear drive (dual idler). I'll be using it on my other engine I am gathering parts for. I figure it won't hurt a thing since Gump has used his for years. I suppose I won't worry about it then--I was thinking that the gear drive would somehow hurt the valvetrain through vibrations, but I guess that's not the case.

 

Lone and I did discuss them a bit as he alluded to, and we may just incorporate one into block of a forced induction engine. Hmmm.

 

Davy

[Owen]

What about timing belts and an adjustable cam sprocket? Too much stretching?

Owen

[Two40MuscleZ]

Like Pete, I also am running a 327. Mine is set up slightly different from his. (Just a bit). However, I am using the Pete Jackson "Noisy" version. It whines a bit...sounds very similar to the whine produced by the blower type motors. Admittedly so, I prefer a bit more of the noise articulation produced by the roller motors. Not long after I purchased mine, my 18 yr old liked the sound and performance so much that he put a noisy one in his '55 chev 1/2T PU which he also built to show. In his words, "its tight, no slop, sounds good and does the job. The noise just adds to the mystique. When I pull in heads turn and that says it all."

We both agree...when its in your blood, you just want to share the experience and excitement with everyone on the street! And the noise you produce is almost as mezmorizing as the smell of nitromethane and burning rubber!

 

Comps, Van & Cameron

[Guest grinsha]

I am running a dual idler Dynagear on the 283 in my jeep. I am going to put one in the engine i am putting in my ZX. It makes less noise than the quiet pete jackson. It also costs a little less.

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3342&prmenbr=361

 

RSN

[pparaska]

Davy, I've since read that I should have "cooked" the chain in oil first, and maybe it wouldn't have stretched. But I'd had enough and just went to the gear drive.

 

That Dynagear piece looks good. I almost bought that, but decided the PJ unit was proven, so I went with it.

 

Owen, I'd LOVE to do the belt drive (especially the dry Jesel unit) but that's a huge pile of money to turn the cam!

[Guest Perry]

Here's some interesting info on gear drives.

My father owns and operates a roller rink and icerink in Louisianna. The air conditioning and ice floor cooling is done with natural gas powered 350 chevys turning LARGE compressors. This is a very demanding application, and has required some serious race parts to make the engines last. One of his findings was that the best double roller timing sets money could buy (he tried all of them) would stretch so bad after 1 month of 16 hours a day running that the engine wouldn't pull the compressor anymore. He swapped in a gear drive and has been happily humming along for over a year now.

I know application in a vehicle is a bit less strenuous but his engines are even running low lift cams and turning 2200 rpm max. On a high performance street car I bet we get a lot more stretch than we think in a short amount of time.

Having said all that I just bought a cheap double roller for my Z because of the budget. But if I was looking for a consistent drag car I would be going gear drive and will in the future when I don't have so much other stuff to buy just to get the car together.

Perry

[Guest Anonymous]

Your speaking of oiling the gear from the back, brings to mind a question I thought I'd ask you Grump, in your opinion would it hurt to build oil return(s) say for a turbo on the front timing cover since its real accessable and would be easy to add a fitting on the front of the timing chain cover. I know they show them normally tapped into the oil pan above the oil line, but I was just curious if it would be OK to have that oil returning over the front of the timing gear/chain, or would it deluge the front seals and make them leak?

 

Thanks and regards,

 

Lone

[Guest Anonymous]

Grump, I've heard that these gear drives tend to cause excessive wear on camshafts from some of the guys at the race track. Is there any truth to this or could it be from something they are doing wrong?

[grumpyvette]

Ive run the same jackson gear drive in several sbc engines for 8 years now, its in as good of shape now as it was the day I installed it. that said be aware that some efi engines engine control computer sensors pick up the gear noise even from quite style gears and interpit the noise as detonation and retard the ignition timeing untill the engine warms up in some cases and the gears get really well oil soaked,so many people run chain drives on efi engines btw its standard procedure to drill a very small hole (about .035-.040 thousands dia)in your center oil gallery plug to spray oil on the rear of the gear durring operation and that extra oil leak in the lube system works better if you use a high volume oil pump. theres nothing wrong with chain drives but they do require changing on a high performace engine every once in awhile depending on how hard you run the engine if you want peak performance, most race teams I know just use a new chain drive for every tear down (probably every 500 miles on a drag car or every 1000-5000 miles on a stock car or at the yearly rebuild or use gear drives. keep in mind that thousands of street cars go over 100,000 miles with chain drives but they also don,t know or even care that their timeing is jumping back and forth several degrees on the shift points as the engine loads change or that they may be down a few hp because of it either

[grumpyvette]

Lone

moding the timeing cover for an oil return is fine IF you make very sure the fittings type and location does not cause clearance problems with the cam drive system you use

 

Les Heath

I used to run a road racing vette thousands of miles in between rebuilds with no excesive or far that matter out of the ordinary cam or lifter wear, I have built and used dozens of engines over the years useing cam , gear drive systems with ZERO problems, my guess is that the guys having those problems are useing the gear drive as an excuse for wear caused by useing the wrong clearances or valve spring pressures, heres what SMOKEY YUNICK had to say about it((page90 ,SMOKEY YUNICKS POWER SECRETS) "I SEE NO REASON TO EVER USE A CHAIN TO DRIVE THE CAMSHAFT IN A RACING ENGINE!.......ANYONE WHO EVER WATCHED A CHAIN DRIVE WHILE THE ENGINE WAS RUNNING AT 7500RPM WOULDN,T THINK THE CHAIN COULD LAST EVEN FIVE MINUTES IN A REAL RACING ENGINE.....IM NOT ABOUT TO SAY THAT A GEAR DRIVE IS COMPLETELY BULLETPROOF , BUT I,M DEAD CERTAIN THAT ITS FOOLISH TO DRIVE THE CAMSHAFT IN AN ENDURANCE ENGINE WITH A CHAIN!" BTW use of this tool goes a long way toward preventing cam and lifter wear problems,

http://www.compcams.com/catalog/335.html

 

I use it on my engines and it works! while were talking about oil systems , I use a high volume pump or a standard volume big block pump, read this,

--------------------------------------------------------------------------------

http://www.melling.com/highvol.html

http://www.melling.com/engoil.html

 

ok lets look at a few things, pressure is the result of a resistance to flow , no matter how much oil is put out by the oil pump there is almost no pressure unless there is a resistance to that oil flow and the main resistance is from oil trying to flow through the bearing surface clearances and once the pumps output pressure exceeds the engines ability to accept the oilflow at the max pressure the oil return system/bypass spring allows the oil circles back through the pump ,now the amount of oil flow necessary to reach the furthest parts in the engine from the oil pump does not go up in direct relation to rpm, but it instead increases with rpm at a steadly increaseing rate that increases faster than the engine rpm due to centrifugal force draining the oil from the rods as they swing faster and faster since energy increases with the square of the velocity the rate of oil use goes up quite a bit faster due to the greatly increased (G-FORCES) pulling oil from the rod bearings over 5000rpm going to 8000rpm than the rate of oil flow increases from 2000 rpm to 5000rpm (the same 3000rpm spread) and remember the often stated (10 lbs per 1000rpm)needs to be measured at the furthest rod and main bearing from the pump not at the pump itself, next lets look at the oil flow itself, you have about 5-6 quarts in an average small block now the valve covers never get and hold more than about 1/3 to 2/3 of a quart each even at 8000 rpm (high speed photography by SMOKEY YUNICK doing stock car engine research with clear plastic valve covers prove that from what Ive read) theres about 1 quart in the lifter gallery at max and theres about 1 quart in the filter and in the oil passages in the block, that leaves at least 2 quarts in the pan at all times and for those that want to tell me about oil wrapped around the crankshaft at high rpms try squirting oil on a spinning surface doing even 2000rpm (yes thats right its thrown off as fast as it hits by centrifugal force, yes its possiable for the crankshaft WITHOUT A WINDAGE SCREEN to keep acting like a propeler and pulling oil around with it in the crank case but thats what the wrap around style milodon type windage screen is designed to stop)the only way to run out of oil is to start with less than 4 quarts or to plug the oil return passages in the lifter gallery with sludge or gasket material! now add a good windage tray and a crank scrapper and almost all the oil is returned to the sump as it enters the area of the spinning crankshaft! forming a more or less endless supply to the oil pump, BTW almost all pro teams now use DRY SUMP SYSTEMS WITH POSITIVE DISPLACEMENT GERATOR PUMPS that are 3,4,or 5 stage pumps each section of which has more voluum than a standard voluum oil pump because its been found total oil control is necessary at high rpms to keep bearings cool and lubed

 

NOW I POSTED THIS BEFORE BUT IT NEEDs REPEATING

ok look at it this way,what your trying to do here is keep an pressureized oil film on the surface of all the bearings to lube and cool them and have enough oil spraying from the rod and main bearing clearances to lube the cam and cylinder walls/rings. now a standard pump does a good job up to 5000rpm and 400 hp but above 6000rpm and 400hp the bearings are under more stress and need more oilflow to cool and because the pressure on the bearings is greater you need higher pressures to maintain that oilfilm.lets look at the flow verus pressure curve. since oil is a liquid its non-compressable and flow will increase with rpm up to the point where the bypass circuit starts to re-route the excess flow at the point were the pressure exceeds the bypass spring pressure. but the voluum will be equal to the pumps sweep voluum times the rpm of the pump, since the high voluum pump has a sweep voluum 1.3-1.5 times the standard pump voluum it will push 1.3-1.5 times the voluum of oil up to the bypass cicuit cut in point,that means that since the engine bearings leakage rate increases faster as the rpms increase because the clearances don,t change but the bleed off rate does that the amount of oil and the pressure that it is under will increase faster and reach the bypass circuit pressure faster with the high voluum pump. the advantage here is that the metal parts MUST be floated on that oil film to keep the metal parts from touching/wearing and the more leakage points the oil flows by the less the voluum of oil thats available for each leakage point beyond it and as the oil heats up it becomes easier to push through the clearences.now as the rpms and cylinder preasures increase in your goal to add power the loads trying to squeeze that oil out of those clearances also increase. ALL mods that increase power either increase rpms,cylinder preasures or reduce friction or mechanical losses. there are many oil leakage points(100) in a standard chevy engine.

16 lifter to push rod points

16 pushrod to rocker arm points

32 lifter bores 16 x 2 ends

10 main bearing edges

9 cam bearing edges

16 rod bearing edges

2 distributor shaft leaks

1 distributor shaft to shim above the cam gear(some engines that have an oil pressure feed distributor shaft bearing.)

so the more oil voluum the better.chevy did an excelent job in the design but as the stresses increase the cooling voluum of the extra oil available from the larger pump helps to prevent lubracation delivery failure, do you need a better pump below 5000rpm or 400hp (no) above that level the extra oil will definitely help possiable deficient oil flow and bearing cooling and a simple increase in pressure does not provide a big increase in voluum that may be necessary to keep that oil film in the correct places at the correct voluum at all times.the stock system was designed for a 265cid engine in a passenger car turning a max of about 6000 rpm but only haveing the stress of under 300hp transmitted to the bearings, Im sure the orriginal designers never thought that the sbc or bbc would someday be asked to on occasion hold up to 450-800hp and 6000-8000 rpm.nore did they forsee valvesprings that placed 500lbs and up loads on the lifters and the use of over 9 to 1 compression ratios in the original design so the oil voluums and pressures necessary to cool those valve springs and bearings at those stress levels were never taken into account for that either.

 

the most Ive personally ever seen is a differance 4 hp on a dyno pull , from a standard to a high volume pump, the oil pump turns at 1/2 the speed of the engine, you can hook up a 1hp 3/4" chuck masonary drill to a oil pump primer tool and spin it too over 1600rpm in an engine thats not even turning over, so you know the engine is not leaking oil like it would if it was spinning, I seriously doubt that an oil pump uses as much hp as most people think it does to drive it and I would rather get the additional oil flow too the bearings and additional cooling that extra oil flow provides too the bearings and under side of the pistons than risk haveing the bearings run low on oil at 6500 rpm any day myself even if it did require a differance of 10 hp,if you have a copy of smokey yunicks POWER SECRETS TURN TO PAGE 110-111 SMOKEY SWEARS THAT THE z28 PUMP is the way to go but look closely at page 111 what hes useing is a 5 bolt BIG BLOCK PUMPin the picture. now I run standard volume BIG BLOCK pumps on most of the small block engines I build , and Ive never seen it cause a problem, now Im sure not saying you need a big block standard volume pump or for that matter a high volume small block pump but I have yet to loose a bearing and I normally do a few mods to an engine that requires a higher than stock oil flow volume , such as I drill the forward oil plug behind the cam gear with a .040 hole so it sprays oil on the back of the gear but thats because I use gear cam drives ans I grouve the lifter bores for extra oil flow to the cam lobes, look here,

http://www.compcams.com/catalog/335.html

and I also run a 7-9 quart oil pan so the extra volume is useful, now keep in mind some people will tell you that a high volume pump will just suck your oil pan dry, thats B.S. lifters have control valves that limit the amount of oil that the lifter can allow up into the push rod and oil flow is limited to the amount that can flow through your engines clearances, all additional oil flow is recycled through the bypass port in the pump itself. yes you do get a little more oil to the top end to cool the vave springs and lube the rockers if you use a high volume pump but the amount is noware near as much extra as some people would have you believe it is, even a 7000rpm the valve covers never get even 1/2 full thats been proven with high speed photography

 

also keep in mind that the small block chevy oil system is well designed and is not a weak link in the engine and even the standard stock un-modifyed system will handle about 400hp just fine

[Guest Anonymous]

Thanks Grump, I'm gonna print this and try to remember so the next time I go to the track I can shut these guys up once and for all, I'm tired of hearing ,"Well' he's the track champ, he should know."

[Guest Anonymous]

Yeah, Ditto, thanks Grumpy, that makes life much easier for me, and yeah I'd make the return fitting flush on the inside. Thanks again.

 

Regards,

 

Lone

[grumpyvette]

this question always comes up so heres the question and answer

 

will a high volume pump ,pump the pan dry?

and for those of you that think a high volume pump will pump the pan dry at high rpms lets discuss the possiablitys

 

the oil pump can only pump as much oil as the engine clearances allow at the max pressure that the oil pump bye -pass circuit will allow, and no more. for your idea to be correct (which it could be under some conditions)the oil flow through the engine clearances would need to be so great that the pump turning at 3500rpm,7000rpm engine speed(remember the pump spins 1/2 the speed the crank does)and most likely pumping at max pressure could lower the oil level to the point that the pick-up becomes uncovered or a vortex as you call it forms and the pump starts sucking air.

 

now under hard acceleration it is very possiable for the pickup on ANY oil pump to to become uncovered in a oil pan that has less than 5qt capacity and with no oil control baffles as the oil rushes to the rear of the oil pan if the pick-up is located in mid pan or under hard brakeing if the pick-up is located at the rear of the pan on a non- oil baffle controlled pan.

 

I will grant you that it is possiable for ANY oil pump to pump a good amount of oil into the lifter gallery at high rpms IF THE OIL RETURN PASSAGES IN THE HEADS AND LIFTER GALLERY ARE BLOCKED, preventing its normal return to the crankcase

 

, but running a high volume oil pump will have little or nothing to do with how much oil is in the pan if the engines drain back holes are clear and your useing a milodon style windage screen. I have several times had that same complaint about lack of oil pressure under acceleration but it is caused by a non-baffled pan or the pickup mounted so close to the pan bottom that the pump cant get a good intake flow, if you carefully check youll find that on a dyno runs it seldom happens,because the oil is constantly removed by the windage screen is returned to the sump, most of the oil pumped into the system exits at the rod and main bearing clearances or at the cam bearings and from the lifter bores lower ends, its not the constant oil flow or lack of oil into the rocker arms that has the big effect on total oil flow as SMOKEY YUNICKS PHOTOGRAPIC RESEARCH PROVED YEARS AGO,its the oil flowing from the bearings and lifters and that oil flow is quickly returned to the sump by a windage screen scrapeing it off the spinning crank and rods as the spinning assembly passes over the windage screen. in effect most of the oil in an engine works like your timeing chain in that it constantly cycles top to botton and back never getting higher than the cam bearing lifter area.

 

now what does quite frequently happen is that the guys installing a high volume oil pump just swap out the standard pump, reinstall the stock or simular pick-up and bolt on the pan with the pick-up in the stock possition on the oil pump. the stock pick-up is mounted about 3/8" off the pan bottom,the high volume pump is normally equiped with impeller gears about .3 inches longer than stock, the high volume pump body is that much lower in the pan, resultting in the pick-up being only about 1/8" from the pan bottom. the result is that on a normal chevy oil pump pick-up this leave a space of about 1/8" x 2.5" for oil to flow into the pump. at low rpms this works but as the rpms climb the pick-up that can,t get any oil to pump cavitates as it spins and fails to pump oil, result oil pressure drops untill rpms are lowered no matter how much oil is over the pick-up. simply checking to make sure that anout 1/2" of space is under the pick-up when the pan is installed cures that problem (a simple trick is to weld a 1/2" thick nut to the oil pump Pick-up base and test fitting the pan BEFORE WELDING THE PICK-UP TO THE PUMP BODY)

 

what it comes down too in every case that Ive looked into so far is a improperly positioned pick-up or a non- baffled oil pan without a windage screen or less than 5 qts of oil in the system, not a problem of all available oil being pumped into the lifter gallery and valve covers like some people would like you to think.

 

the MELLING COMPANY HAS THIS TO SAY

 

Most of the stock automobile engines are designed to operate from idle to 4500 RPM. The original volume and pressure oil pump will work fine in this type of application. As the demands on the engine increase so does the demands on the oiling system and pump.

The oil pump's most difficult task is to supply oil to the connecting rod bearing that is the farthest from the pump. To reach this bearing, the oil travels from three to four feet, turns numerous square corners thru small holes in the crankshaft to the rod bearing. The rod bearing doesn't help matters. It is traveling in a circle which means centrifugal force is pulling the oil out of the bearing.

 

A 350 Chevy has a 3.4811 stroke and a 2.111 rod journal. The outer edge of the journal travels 17.5311 every revolution. At 1000 RPM, the outer edge is traveling at 16.6 MPH and 74.7 MPH at 4500 RPM. If we take this engine to 6500 the outer edge is up to 107.9 and at 8500 it is 141.1 MPH. Now imagine driving a car around a curve at those speeds and you can feel the centrifugal force. Now imagine doing it around a circle with a 5.581, diameter.

 

The size of the gears or rotors determines the amount of oil a pump can move at any given RPM. Resistance to this movement creates the pressure. If a pump is not large enough to meet the demands of the engine, there will not be any pressure. Or if the demands of the engine are increased beyond the pumps capabilities there will be a loss of oil pressure. This is where high volume pumps come in; they take care of any increased demands of the engine.

 

Increases in the engine's oil requirements come from higher RPM, being able to rev faster, increased bearing clearances, remote oil cooler and/or filter and any combination of these. Most high volume pumps also have a increase in pressure to help get the oil out to the bearings faster.

 

That is what a high volume pump will do. Now let Is consider what it will not do.

 

It will not replace a rebuild in a worn-out engine. It may increase pressure but the engine is still worn-out.

 

It will not pump the oil pan dry. Both solid and hydraulic lifters have metering valves to limit flow of the oil to the top of the engine. If a pan is pumped dry, it is because the holes that drain oil back to the pan are plugged. If the high volume pump is also higher pressure, there will be a slight increase in flow to the top.

 

It will not wear out distributor gears. The load on the gear is directly related to the resistance to flow. Oil pressure is the measure of resistance to flow. The Ford 427 FE "side oiler" used a pump with relief valve set at 125 psi and it used a standard distributor gear. Distributor gear failures are usually caused by a worn gear on a new cam gear and/or worn bearings allowing misalignment.

 

It will not cause foaming of the oil. With any oil pump, the excess oil not needed by the engine is recirculated within the pump. Any additional foaming is usually created by revving the engine higher. The oil thrown from the rod bearings is going faster and causes the foaming. This is why high performance engines use a windage tray.

 

It will not cause spark scatter. Because of the pump pressure there is a load on the distributor gear. The number of teeth on the oil pump gears determine the number of impulses per revolution of the pump. In a SB Chevy there are seven teeth on each gear giving 14 impulses per revolution. At 6000 RPM the oil pump is turning 3000 RPM or 50 revolutions per second. To have an effect on the distributor, these impulses would have to vibrate the distributor gear through an intermediate shaft that has loose connections at both ends. Spark scatter is usually caused by weak springs in the points or dust inside the distributor cap.

 

High volume pumps can be a big advantage if used where needed. If installed in an engine that does not need the additional volume, they will not create a problem. The additional flow will be recirculated within the pump.

[CruxGNZ]

Holy Balls you have a lot of info!

 

!M!

[Guest Anonymous]

You ain't kidding, hell his 'Favorites' file alone is probably a couple gigs..

 

Regards,

 

Lone

[grumpyvette]

8.9 gigs and growing on car stuff ,6.3 gigs on elk hunting (my other addiction)

[CruxGNZ]

 

!M!