Gear Drive, Timing Chains, Belt Drives

[Thales of Miletus]

How many miles would you expect each system to last. Min to max

Belts 60 to 100kms?

Chains 120 to 200kms?

Gear Drives?

I don't see any advantage of a Gear Drive over a double roller, except the sound.

[jacky4566]

Subaru claims 170km for their belts so it can varry. However my pulley self destructed at 160 so that sucks.

[Thales of Miletus]

Originally posted by jacky4566
Subaru claims 170km for their belts so it can varry. However my pulley self destructed at 160 so that sucks.

I think a good double roller is the best bet for any system. But I can understand how the no stretch belts are important in modern applications.

My friend had a timing chain fail after 30kms. I think that is absurd.

[g-m]

I firmly believe belts are the best. Lowest inertia and you'll only replace it 1, MAYBE 2 times during the length of ownership. Only bad for cheap or lazy people.

[Darell_n]

Originally posted by g-m
I firmly believe belts are the best. Lowest inertia and you'll only replace it 1, MAYBE 2 times during the length of ownership. Only bad for cheap or lazy people.

Belts are only for anemic 4 bangers. Real power needs steel.

[g-m]

My 440whp v6 thinks otherwise

[carson blocks]

Most guys who buy gear drives for street engines buy them for the "blower" whine sound. My understanding is that racers use them because with aggressive cam profiles, high lift, and insane spring pressures, a belt would slip or break and a chain can stretch, leading to timing inaccuracies. Aside from being noisy, they do wear and shed more metal filings than a chain would, and some builders claim gear drives can impart harmonics in to the valvetrain. Most gear drive systems are not on engines that would see real world daily driver mileage.

Chains are great, not nearly as noisy as a gear drive, but not quite as quiet as a belt. They're narrower and easy to package, especially in V-bank OHC engines where you often need to fit 2 of them in there. They generally don't require maintenance or replacement at a set interval. At high mileage, tensioners can wear and the chain can stretch/wear causing erratic timing. Any time I've seen a sloppy chain on a V8 it has had well over 200,000km.

For OEM stuff, many manufacturers switched to belts in because they're quieter, cheaper, and lighter. They do require periodic inspection and replacement though as they wear faster than a chain. When they break on an interference engine, the result is catastrophic and many drivers blame the OEM instead of their own maintenance program. Many manufacturers have switched back from belt to chain for easier packaging and less maintenance / stories of catastrophic failure. I've seen recommended replacement intervals as short as 50k and as high as 160k I think.

Personally, give me a pushrod engine with a timing chain and I'm a happy camper.

[94boosted]

Are there even any cars that have OEM gear drives?

[jacky4566]

Originally posted by 94boosted
Are there even any cars that have OEM gear drives?

Cars not sure but many motorcycles do.

[carson blocks]

Originally posted by 94boosted
Are there even any cars that have OEM gear drives?

The 6.7 Cummins diesel in my pickup has an OEM gear drive.

[toastgremlin]

Originally posted by 94boosted
Are there even any cars that have OEM gear drives?

Not any that were built this century that I know of. The Saab V4 is the last "common man" engine that had them that I can think of.

Lots of early cars (I'm thinking of Model T, but there's probably lots more) had them.

Wouldn't surprise me if some bespoke racecar-for-the-road supercar had them too.

[RickDaTuner]

GMs and the older Ford 4.6 were gear driven.

Chains are the new method of cam timing due to the fact that almost every manufacture has moved over to variable valve timing, and the easiest way to do this is with a cam phaser, driven by a chain. The use of belts like mentioned is more so common on 4 cylinder applications, Unless you're Ferrari, They use belts on everything...

Chain longevity is highly dependent on oil maintenance

[carson blocks]

Originally posted by RickDaTuner
GMs and the older Ford 4.6 were gear driven.

Which GMs? And any Ford 4.6 I've had the displeasure of digging in to has had chains. It's a long, long way from the crank to the cams on a mod motor.

[RickDaTuner]

Originally posted by carson blocks


Which GMs? And any Ford 4.6 I've had the displeasure of digging in to has had chains. It's a long, long way from the crank to the cams on a mod motor.

Gms 6.2, 6.5 diesels were gear driven, Fords 7.3 was gear driven as well, the 4.6s were a combo, chain and gear driven, these were all Circa 90s vehicles

[toastgremlin]

Oh, I didn't even think of diesels. That makes sense, I know a lot of Detroits were gear driven (even up to the supercharger in the case of the 3-53).

[4runneron36s]

Originally posted by RickDaTuner
Chain longevity is highly dependent on oil maintenance [/B]

That and the tensioner and chain guides. Working on 1980s Toyota engines (22re) I have never seen a chain break, but have seen many broken plastic chain guides (upgrade to steel) or bad tensioners that can cause the chain to skip a tooth or eat through the timing cover.

[carson blocks]

Originally posted by RickDaTuner


Gms 6.2, 6.5 diesels were gear driven, Fords 7.3 was gear driven as well, the 4.6s were a combo, chain and gear driven, these were all Circa 90s vehicles

6.2 and 6.5 were chains IIRC. Everyone hates those engines, but I kinda geek out on 'em. There were aftermarket timing gear sets though which were quite popular as it was common to stretch timing chains on those engines.

Edit: Just remembered, the Ford 300 (4.9) Inline 6 had timing gears instead of a chain. One metal and one fiber gear IIRC. That was one tough engine and Ford made those to 1996 for F150 and E150 and still makes them for UPS trucks and gensets.