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Timing Chain to Gear swap

1985xjlaredo

1985xjlaredo

NAXJA Forum User
Location
Kansas City
Is there any one out there who runs gears instead of a chain? I've searched but I cant find anything, let alone a reverse ground cam. Can it even be done?
 
There was a kit available from MPP some time ago that would convert the 4.0 to gear drive timing - it was about $600 at the time, and it's been a while.

You don't really need a "reverse ground cam" to run gear drive - most gear timing kits I've seen have a crank gear, a cam gear, and one or two idler gears (everytime you use an idler gear in a geartrain, the direction of motion reverses. So..

crank - idler - cam
CW ACW CW

for instance.)

I've been vaguely curious about resurrecting the idea of a gear drive kit for the 4.0L - probably with helical gears instead of spur gears, to quiet things down a bit. Anyhow, I don't believe that anyone is currently making a gear drive timing kit for the 4.0 (although I could be wrong - and if I am, I'd appreciate anyone turning me on to a supplier...)
 
cool well thanks for the info 5-90. Ill check around some more.
 
5-90 said:
There was a kit available from MPP some time ago that would convert the 4.0 to gear drive timing - it was about $600 at the time, and it's been a while.

You don't really need a "reverse ground cam" to run gear drive - most gear timing kits I've seen have a crank gear, a cam gear, and one or two idler gears (everytime you use an idler gear in a geartrain, the direction of motion reverses. So..

crank - idler - cam
CW ACW CW

for instance.)

I've been vaguely curious about resurrecting the idea of a gear drive kit for the 4.0L - probably with helical gears instead of spur gears, to quiet things down a bit. Anyhow, I don't believe that anyone is currently making a gear drive timing kit for the 4.0 (although I could be wrong - and if I am, I'd appreciate anyone turning me on to a supplier...)
Click to expand...
I've always wanted to design a centrifugal cam drive that would advance the cam in accordance with rpms.
 
jeeperjohn said:
I've always wanted to design a centrifugal cam drive that would advance the cam in accordance with rpms.
Click to expand...

That may get a little complex. Besides, most of the VVT setups I've been able to find information on don't really alter the cam timing - but there is a more pronounced "taper" to the cam lobes, and hydraulic servos move the camshaft back and forth to alter lift. I'm not entirely sure how to go about changing cam event timing - but I'm sure it's doable, and I'm also sure someone else is working on it at the moment (if they haven't already gotten a working version.)

Besides, controlling ignition timing is probably a bit more critical to performance and engine tuning - and we've already got that sorted. Changing around camshaft event timing seems to me to be playing fast and loose with your engine tune - not something I'd recommend for a production vehicle at the moment (especially with the decline in user maintenance ability I've been seeing in the last dozen years or so...)

Besides, I'd rather have an engine that makes solid power at a fairly low RPM, with gearing to match, and just drive it accordingly. "The more you overhaul the plumbing, the easier it is to stop up the drain."
 
5-90 said:
I've been vaguely curious about resurrecting the idea of a gear drive kit for the 4.0L - probably with helical gears instead of spur gears, to quiet things down a bit. Anyhow, I don't believe that anyone is currently making a gear drive timing kit for the 4.0 (although I could be wrong - and if I am, I'd appreciate anyone turning me on to a supplier...)
Click to expand...

personally i like the "screamer gears" that i've seen on some friends chevy's. then again my wife seems to think that i like annoying noises.

either way, i like the "noisy" gear sets.
 
scorpio_vette said:
personally i like the "screamer gears" that i've seen on some friends chevy's. then again my wife seems to think that i like annoying noises.

either way, i like the "noisy" gear sets.
Click to expand...

Those are spur-cut gears - they have straight teeth. If you've ever torn apart a manual gearbox, the reverse and reverse idler gears are usually spur gears.

The forward gears are helical gears - they have teeth cut at an angle relative to the axis of the shaft the gears ride on.

Spur gears are noisy because contact between the gear teeth is not constant - while helical-cut gears are constantly in contact (beyond a certain helix angle.)
 
scorpio_vette said:
yeah i understand that. what i was getting at was that i like "noisy" gears. so i'd like mine spur-cut not shaken please. :)
Click to expand...

No worries. Spur-cut gears are easier anyhow - you can do them with a knee mill an and index table. Helical gears aren't impossible to do - but they're far easier with CNC machinery...

So, if I do the kit, it will be spur gears first. However, I'll probably end up offering both as options, since the basic gear size won't change (just the cut of the teeth...:laugh3: )
 
5-90 said:
That may get a little complex. Besides, most of the VVT setups I've been able to find information on don't really alter the cam timing - but there is a more pronounced "taper" to the cam lobes, and hydraulic servos move the camshaft back and forth to alter lift. I'm not entirely sure how to go about changing cam event timing - but I'm sure it's doable, and I'm also sure someone else is working on it at the moment (if they haven't already gotten a working version.)

Besides, controlling ignition timing is probably a bit more critical to performance and engine tuning - and we've already got that sorted. Changing around camshaft event timing seems to me to be playing fast and loose with your engine tune - not something I'd recommend for a production vehicle at the moment (especially with the decline in user maintenance ability I've been seeing in the last dozen years or so...)

Besides, I'd rather have an engine that makes solid power at a fairly low RPM, with gearing to match, and just drive it accordingly. "The more you overhaul the plumbing, the easier it is to stop up the drain."
Click to expand...
Good points but I would feel damn proud of myself if I could pull it off. If you used separate intake and exhaust cams, you could control lobe separation as well. The ultimate would be purely solenoid actuated valves. Imagine the tuning possibilities. Too bad the technology does not yet exist.
 
jeeperjohn said:
Good points but I would feel damn proud of myself if I could pull it off. If you used separate intake and exhaust cams, you could control lobe separation as well. The ultimate would be purely solenoid actuated valves. Imagine the tuning possibilities. Too bad the technology does not yet exist.
Click to expand...

Dunno - I like the look of Coates Spherical Rotary Valves - and they've been around for about 15 years (in a limited aftermarket.) Google them - I've got information, but it's not been scanned yet...
 
5-90 said:
Dunno - I like the look of Coates Spherical Rotary Valves - and they've been around for about 15 years (in a limited aftermarket.) Google them - I've got information, but it's not been scanned yet...
Click to expand...
A very interesting read. They need to make a 4.0 head!
 
wasn't mercedes playing with solenoid valves?
I thought I read that they were developing it for the cylinder shutoff system in their big motors.
 
As for the gear drive....there are none in production....Lee at Hesco used to sell them....he appearantly had a more or less one off production run and due to cost and poor sales, did not have any more made. The only advantage with the gear drive is in the event of a short duration over-rev situation there is no timing chain to snap from cam harmonics.

A good double roller chain and gear set does nicely....you need to keep the rpm to a reasonable level at any rate with a 4.0
 
MudDawg said:
As for the gear drive....there are none in production....Lee at Hesco used to sell them....he appearantly had a more or less one off production run and due to cost and poor sales, did not have any more made. The only advantage with the gear drive is in the event of a short duration over-rev situation there is no timing chain to snap from cam harmonics.

A good double roller chain and gear set does nicely....you need to keep the rpm to a reasonable level at any rate with a 4.0
Click to expand...

Yeah, if I did design a working version, it would probably be a "made to order" for the AMC I6 and possibly the 150. Since the AMC I6 will be killed at the end of this model year, and the 150 folded up about five years ago (last in the 2002 Dakota, I think,) there's no real point in stocking something...

Which is a pity - because the AMC inline six family made for some damn decent engines!
 
There is no need at all for a gear drive for the 2.5....the little 4banger does not suffer the harmonic ills the 4.0 does....I regularly spin my 2.5 to 7K+. The shorter stroke yields a better rod lenght to stroke ratio and is more oversquare...the smaller displacement per cylinder allows it to breathe at higher rpm than a 4.0.....and it hasn't :explosion yet.
 
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