Chain or gears for timing? openions please

[charlief1]

I want to know everyones opinion on whether to run a timing gear set or chain and gears.I have gears now for my build but I seen some negitive info on them.

 

[turbo nasty]

gears will cause false KR

 

[Alky V6]

If setup correctly, you won't even be able to tell you're running a gear drive. No chain stretch. Accurate cam and ignition timing. No noise. What else can you ask for.
I love mine.

I assume you're talking about a Milodon gearset.

 

[charlief1]

What else is there. I'm torn between double roller and gears and you're the first not to say negitive info Don.

 

[Alky V6]

Really, I don't know of any other geardrive for a Buick V6. They are much more difficult to install rather than just slapping a chain set on. That's probably the main reason why you see more people recommend the chain setup. There are some modifications needed to the timing cover to fit the gearset. The instructions that come with the gearset explain the install and the modification needed to the timing cover.

If you go with the gearset. Get ahold of me and I'll give you some added tips.

 

[fuzzyGN]

DonWG, I would love to hear what tips you have for installing the gear drive. I have committed to making this work on my N/A 4.1L due to the silly big solid roller cam I am using. Any info is greatly appreciated. Thanks

 

[TURBOPOWERED68]

looking to learn

 

[87GNSteve]

I didnt even know they made a gear drive for the Buicks....Have a P/N?

 

[Alky V6]

You can get ahold of Milodon directly. They will most likely direct you to a distributor. I used Chet Herbert.

I have a couple tips:
The mesh between each gear pairing should be clearanced at .005".

I pressure feed a small spray of oil from the engine's oiling circuit to the idler gear bearing, instead of relying on splash lubrication.

Read the directions fully before you drill anything! Make sure you layout your drilling points so that you have room to accomplish all that is instructed.

This is how I do it:
a) drill a 1/16 hole through the front of the block directly into the oil galley that runs between the front cam bearing bore and the front main bearing bore. Do this in a spot that will be well covered and SEALED by the geardrive mounting plate. Make sure you clean the chips out of the galley passage.
b) You are now going to drill through the geardrive mounting plate. Align this hole so that it will be directed right at the idler gear ball bearing and cage between the 3 O'clock and 6 O'clock position looking at the idler from the front of the mounting plate. Drill from the back of the plate. Use a 1/16" drill bit. Stop drilling before you break completely through the plate. Finish breaking the hole through the plate with a .025" drill bit.
c) On the back of the geardrive mounting plate, use a ball milling bit to mill a shallow passage from the point of the hole you just drilled in the block to the hole you drilled through the mounting plate behind the idler gear bearing.
d) Countersink the hole you drilled through the mounting plate, at the back of the plate, to accept a small filtering housing. I use one from a transmission application. This is so the small .025" hole doesn't easily become plugged.
e) Mill an o-ring groove around the passage you milled into the back of the mounting plate to accept an o-ring. This will assure you aren't loosing any more oil from the galley than is necessary to feed the .025" restricted feed passage.

I think I can dig up a picture. I'll post it if I can find it.

 

[charlief1]

A pic would be very helpful. You've almost got me interested in using the gear drive for sure. I know I'll decide soon cause the engine is just about to go to the machine shop.

 

[Alky V6]

I just realized there's a picture of the modification on my website.
DRW Photo Gallery

Go to the engine v2.0 slide show under shop projects, DRW/Buick Grand National.

Bear in mind that the o-ring groove around the passage had not been machined yet and the orifice filter had not been installed.

If you have any more questions, let me know.

 

[Alky V6]

Something else I think a lot of people don't realize is how the geardrive set loads the front cam bearing compared to the chain drive. The chain drive pulls downward on the cam gear to turn the camshaft. This loads the front cam bearing at near the six o'clock position. It's well known with the Buick V6 that the front cam bearing likes to wear at the 6 o'clock position causing excessive journal clearance and oil pressure hemorrhaging. With the geardrive setup, the idler gear pushes the cam gear in an upwards manner to turn the camshaft. This counters some of the forces put on the camshaft by the lifters when they are being pushed upwards by the cam lobes.

Does this end up causing less front cam bearing wear? Don't know for sure, but it's something to think about.

 

[chopped39]

Do they make one for a roller cam? and what if block was line honed? Or is that why cam gets pushed up in cam journal.

 

[Alky V6]

Do they make one for a roller cam? and what if block was line honed? Or is that why cam gets pushed up in cam journal.

The geardrive is designed to be used with the early style camshaft nose. This is the style that has the slide on distributor drive gear. I believe they call it the old odd fire camshaft nose. The camshaft can be ground for even fire, odd fire, stage I, stage II, mechanical tappet, hydraulic tappet, hydraulic roller, mechanical roller. It just depends what the cam lobes were ground for, but the nose of the cam needs to be the old odd fire camshaft style. The odd fire nose configuration is more common in pure racing setups.

If the block has been line honed or line bored, it's just a matter of adjusting the geardrive mounting plate to obtain the proper gear pairing clearances (.005").

The direction of radial load put on the front cam bearing has to do with the way the different drive styles, gear or chain, drive the camshaft gear or sprocket. It has nothing to do with the spacing of the camshaft centerline to the crankshaft centerline. I think I have a picture of the geardrive installed on my website. If you study it and look at how the idler gear has to push the camshaft gear, you'll see that it has to push upwards on the gear. Where as with the chain drive, the crankshaft chain sprocket pulls down on the camshaft sprocket through the chain.

 

[charlief1]

I('d never thought about it but I think you have a very good point Don. You're making an extreemly good agument for using gears and that means I'm looking at getting a diferent cam now.

 

[Nick Micale]

Oil pump?

Donnie, from the pics on your web site it is hard to tell if the gear drive will clear the pump shaft drive for a stock-type oil pump. Did you ever do a mock up with a stock timing cover?

It appears you do not have this situation with your dry sump system.

 

[chopped39]

Thanks for the info. I think i will stay with the chain. This engine is going to be street driven.

 

[Alky V6]

Donnie, from the pics on your web site it is hard to tell if the gear drive will clear the pump shaft drive for a stock-type oil pump. Did you ever do a mock up with a stock timing cover?

It appears you do not have this situation with your dry sump system.

The timing cover I'm using now is a modified stock housing. There is plenty of room for the pump driveshaft. My setup doesn't show the drive gear on the camshaft, but it would be close behind the bolt and washer on the front end of the camshaft. Just like the even fire camshaft nose. I just fabbed up a long aluminum spacer since I don't need the distributor/oil pump drive gear.

 

[Alky V6]

Another thing to note. If you race a lot and have some high oil pressures going on, the stock oil pump drive gear tends to wear relatively quickly. If you're using an odd fire nose camshaft with the replacable drive gear, you don't have to replace a whole camshaft. The distributor/oil pump drive gear is cast as part of the camshaft blank with the later style even fire camshaft. If the drive gear wears on that camshaft, you have no other option but to replace the camshaft.

 

[Blown&Injected]

the mods don't stop...

Sounds like one needs a magnetic drill press for this operation