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gear drive or timing chain



I'm getting all the parts together in preparation to have a new cam put it and started wondering about going with a gear drive instead of a new timing kit. Has anyone installed one and if so hows it working? Are there any difficulties with running a gear system?
gear drive

The only drawback or not, depending on how you look at it, is the noise. I like it. I have heard all of the rumors of high horsepower parisitical(sp) loses but there would have to be a major interference between the gears for that to be a big deal. Most gear drives have a larger idler gear on the one side to keep it from being drawn in between the crank and the cam gears. I don't think they would be widely used in racing, where the rules allow, if they cost a lot of horsepower or weren't dependable. A set of stiffer valve springs are going to cost more horsepower than spinning a couple of floating idler gears.

Send JHL a Pm. He has been running a gear drive for a long time in his '81. Also go to the top of this page and enter "gear drive" in the search. You will get a bunch of threads where gear drives have been discussed.

Most geardrives are noisy ... some more than others ... some folk prefer that whine. I'm with TOM in that parasitical hp loss is probably quite small ... chains eat hp too! Beltdrives are probably the most efficient ... but BIG$! Unless you're an all-out racer / have a .550"+ cam / triple v-springs... I'm with Keith ... IMHO a nice true roller chain set in the $35-$55 range'll do ya proud. What does your cam's manufacturer suggest to use with your planned valve train combo?
Go for it.

If you're posting this for an answer on which is better performance wise then I'm sure the differences are negligable, but if you're after the noise/sound that only a gear drive or a blower can give, then go for it!
I have one sitting here ready to go into my 77 as soon as I get the new motor ready and I'm looking forward to hearing it as well as having it perform.
If you got money to burn or a good deal on a geardrive, why not? There are "quiet" versions, to take down the whine a few notches. Just remember that the baddest engines to come out of Detroit used chains.--Bullitt

I have a timing gear and love it. It's a great sound.
Did someone mention my name !!

I bought the PJ noisey geardrive and it was simple to fit, comes with a good selection of offset bushes for ajusting the cam timing and has given no problems. I personally like the whine but I could see how it could become a bit annoying if you used the car every day.

The gears are almost staight cut and the two idler gears have a lot of clearance hence the noise but I`m sure some quieter ones are available, some motorbikes have geardriven cams without the noise.

I can`t say what kind of power they soak up but it won`t be much more than a chain. The Big Plus is very accurate timing right thru the full range of the engine. Have a look at a chain after a few thousand miles and some action at the drag strip and it will be stretched. I`m no lover of belts either which have a habit of snapping without warning, resulting in most cases with an expensive repair and some nice dents in your pistons.

As an example I helped a friend work on a Pontiac motor that had seen a bit of action at the track but not a lot of road miles and the chain could be lifted off the cam sprocket, it`s not unknown for them to jump a tooth or two. I also had a belt go on my daily driver and even at a fairly modest engine speed it bent all the exhaust valves. Most modern cars that still use chains have a hydraulic tensioner fitted to take up any slack and make it last an acceptable period of time, this is something most of your V8`s don`t have. The belt driven set-ups also have some type of tensioner and usually require replacement at quite short intervals. If you have a read in the hand book of most cars with belts it will recomend replacement at x-amount of miles or a period of time regardless of mileage as belts can degrade with age.

So if your car is going to see some action I would go with the gears or if it`s just a daily driver save a few dollars and stick with a chain.

re: gear drive or chain

There are definitely a few "pro's & con's" on gear drives. Yeah they do make quite & noisy setups so......you have to decide. From personal experience, if you drive the car alot you'll get sick of a noisy setup. True that the gears don't stretch out like a chain does. But by the time you stretch a chain to the point of affecting engine performance & tuneability, the engine is usually ready for a rebuilt or the engine has a couple rods hanging out the side of the block. :) Lastly, gear drives are known to transmit harmonic vibrations from the crankshaft up to your valvetrain. Which can't be all that healthy for the cam bearings etc. even though this is probably a "nominal effect" on the valvetrain. I personally would stick with a double roller chain myself. Anyways.....thats my 2 cents. Happy engine building
Darryl aka Sarge
I have a gear drive in my motor but really don't have any real preferance for one. They do make a whine sound that gets peoples attension however. I am asked about the gear drive quite often when I pull in somewhere with car people standing around.
I don't think I would put another one in as I get tired of the whine, and would probably go with a good chain setup. I guess it's personal preferance and whether you want to listen to it. If you opt for a quiet one , I would just go for a good chain drive instead.
Gear drives can create harmonics that seems to zero in on the valve springs (it can make them break). I have had no problems except with ultra high performance, high RPM engines. After many broken valvesprings in a problem engine, several different types (brands) of gear drives were installed without valvespring success. A belt drive was installed without changing anything else, the breakage went away. On a mildly modified engine they would probably be fine.
For everything but the wildest street engine, a true double roller will provide more than adequate service over the entire life of the engine. IMHO there are other places that money would be MUCH better spent.
I had a Pete Jackson "noisy" put in my '85. I loved it. I really turned heads as well. I'm a fan of that blower sound:D


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