Timing gears instead of chain?

[xtremzj]

I'm building a 4.8 stroker and saw that 505 sells a gear timing kit. Has anyone's tried it? Is it worth it? Not to mention it has a great sound to it.

[SilverXJ]

Gear timing sets are never worth it.

[xtremzj]

Why?

[SilverXJ]

To further expand on that, while the gear set will keep the timing in control better than a chain they are heavy and transmit harmonics between the crank and cam. A belt drive would be best but there are none offered for our engine.

[xtremzj]

That's it?

[SilverXJ]

Huh? There is no advantage unless you like the noise and want harmonics transmitted between cam and crank. I never saw anything that showed a gear drive making horsepower vs a chain drive.

[SIXPAK]

Silver is right BUT its a matter of choice. I raced an AMC six for years and found after time the chains did stretch causing issues. I replaced it with a gear drive and TO ME regardless of any horsepower loss, valve train harmonics or any other issues (of which I had none) it was worth it to me just in hassle and pece of mind. I still run a gear drive in my smaller motor but have a belt drive in my N2O motor. Its a BBC Xceldyne unit that I converted to the AMC with an idler pulley.

If I were going to do some wheeling and street driving I would just go with a chain but be sure that your washer behind your cam bolt does not block off the oil passage in the cam sprocket. If it does just put a small channel in the cam sprocket past the outer OD of the washer to get some better oiling on the chain, just my .02

[CobraMarty]

Is the converted BBC to AMC belt drive available? Will you make another? Any pics?

[5-90]

Mixed thoughts on gear-driven timing.

PROS:
- No chain, so no stretch.
- Takes much longer to get excess lash in a gearset
- Has been used as OEM (VolksWagen engines used composition gears, and I think the Ford/Cleveland six was gear-driven. A number of G/A engines are also gear-driven)
- Can be stronger than chain setups (depends on gear construction)

CONS:
- Can be noisy (spur gears are noisy, helically-cut gears are usually quiet)
- Will either drive the cam in the opposite direction to the crank (if direct) or require idlers to reverse gear action
- Usually transmits crank harmonics to the cam, due to the solid connection

Of the three timing drives in use, the chain is preferred because it's a good compromise between the durability of the gear drive and the quiet operation of the belt. However, I don't think that belts should be used outside of the racing circuit - a racing engine gets torn down a minimum of once a year, most people driving cars don't even know they need to change their oil regularly anymore. Belt MTBF runs 50-80Kmiles, and they always stick an engine mount through the loop - what's that all about?

If a belt can't be easily accessed and changed, it shouldn't be used. Don't even get me started on "interference" engines...

If you want a solid, quiet chain drive, go with a single or double roller chain. The OEM "silent chain" (built-up laminated links) is used because it's cheap, but the longer chains (OHC/DOHC drives, usually) come from the factory as roller chains - they take longer to stretch. That's also why aftermarket roller timing sets are available for many engines.

Given a choice, I'd go with helical gear drive for high endurance and low speed, or a roller chain for regular daily use. Belt? Belts are for pants. I'd only use a belt if it was going to be readily accessible and/or it was something I'd be tearing down at least once a year.

[SilverXJ]

Belt MTBF runs 50-80Kmiles, and they always stick an engine mount through the loop - what's that all about?

The mount is only in front wheel drives.

If a belt can't be easily accessed and changed, it shouldn't be used. Don't even get me started on "interference" engines...

Most of the timing belts that I have done aren't that bad to get to. However, it is another service item and usually the water pump is driven off them as well. Which if the water pump failed it could possibly take out the timing as well. In our case it would be easy to get to and changing wouldn't be that bad. Might have to pull off the harmonic balancer though. As for service life on a belt we could/would use (after market racing style) I don't know about the MTBF on them. I would think they are stronger than their OEM counterparts, but doesn't necessarily mean they would last longer.

The OEM "silent chain" (built-up laminated links) is used because it's cheap, but the longer chains (OHC/DOHC drives, usually) come from the factory as roller chains - they take longer to stretch. That's also why aftermarket roller timing sets are available for many engines.

The morse style silent link chains also take up slack on their own when running.

Is the converted BBC to AMC belt drive available? Will you make another?

LOL

[SIXPAK]

Is the converted BBC to AMC belt drive available? Will you make another? Any pics?

Not planning on making anymore, for now. Not cheap, parts cost about $1000 without labor

[CobraMarty]

Not planning on making anymore, for now. Not cheap, parts cost about $1000 without labor

That's beautiful, I'll take it.

[Carter417]

Its really strange that using of gears instead of timing chain!!! I don't think so that gear can works like chain because according to me there is more possibility of failliar of gears instead of timing chains because they can slip over.

[SilverXJ]

because they can slip over.

Gears can slip but a timing chain won't?

[IH 392]

I don't understand that one either???