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Discussion Starter #1
Has anyone tried out this set-up?
OS Giken offers said conversion, yet they do not answer their phone.
Anybody else offer it?
Either I get a new 2 Liter block or toss the old one as it was line bored
the wrong way, and it became a variable timing engine, depending on acceleration or deceleration...POS.
My wrong, should have never listened to bad advice, and even worse, machine shop.
Regards, Alberto
 

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Probably easier to source another block. Gear drive for cam gear has some advantages, generally outweighed by disadvantages. Further, if the crank has been moved UP in the block, messing up the chain drive, I cannot understand how the gear drive will not also be close to binding for the same reason.
Just my opinion.
 

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Discussion Starter #3
Probably easier to source another block. Gear drive for cam gear has some advantages, generally outweighed by disadvantages. Further, if the crank has been moved UP in the block, messing up the chain drive, I cannot understand how the gear drive will not also be close to binding for the same reason.
Just my opinion.
Gordon, the problem is that the lower chain has slack into it, and zero adjustabilty, whereas the upper can be adjusted by the tensioner.
For me it is a lot less expensive to take a gear drive than a block to where I live.
What are the disadvantages?
Regards, Alberto
 

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To clarify. If the lower chain has slack with a new chain, after an align bore, the crankshaft has been moved UP, toward the idler sprocket in the block. Material was removed from the main webs in the block, not the caps.
Now, when you replace that lower chain with a gear on the crank, and idler, UNLESS THOSE GEARS WERE CUSTOM CUT FOR YOUR APPLICATION, the gear teeth will also enter one another too deeply. Causing gear bind. The available lower gear drive is made for a crankshaft and idler cut ON ORIGINAL CENTER.
After you have had your custom gears cut so they will mesh properly with minimal clearance, (More expensive than I can imagine, having once adjusted such gear lash on a Ferrari Monza engine with shims!) you must deal with a noise factor. If helical cut, they will be quieter than straight cut gears, but in the Ferrari Monza engine, the cam drive gear noise drowned out the open exhaust running at idle! This is the reason that American V8 cam gear drives are fiberglass impregnated nylon. They run quieter than steel.
The relationship of the gears to one another is critical as to lash, (cam timing) noise, and durability. Too closely fitted will break, or not fit together at all.
This is not a good system to attempt to correct an already existing clearance issue.
I cannot IMAGINE, anywhere in the world where a custom cut set of gears would be less expensive than a used Alfa 2L block!
If this IS possible, please post your gear cutter machinist! We can use him for custom racing Alfa transmission gear sets!
 

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Now, when you replace that lower chain with a gear on the crank, and idler, UNLESS THOSE GEARS WERE CUSTOM CUT FOR YOUR APPLICATION, the gear teeth will also enter one another too deeply. Causing gear bind. The available lower gear drive is made for a crankshaft and idler cut ON ORIGINAL CENTER.
Gordon:

I understand what you are saying, and if the intermediate gear in the OS Giken conversion were in line with the crankshaft and stock Alfa 2:1 gear, then yes, a re-positioning of the crankshaft axis would require an alteration in the gears' diameter.

However, from the tiny picture shown at Alfa Stuff - Your Online Source for Alfa Romeo Speed Parts it appears that the OS Giken locates their intermediate gear off to one side. Perhaps this design incorporates some adjustment in the location of the intermediate gear that would accommodate a relocated crankshaft.

Note that I'm just assuming here - I have no direct experience with the OS Giken part. And I have to agree with your comment: "I cannot IMAGINE, anywhere in the world where a custom cut set of gears would be less expensive than a used Alfa 2L block!" Even if the standard OS Giken gear drive will work, at $760 this component is far more costly than a good 2L block.
 

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That's the way I see it Jay. Not that the gear drive does not have plenty of good applications, but it just seems that to use it to band-aid a ruined block, is throwing good money after bad.
Those I have worked with, NOT the Gilken, had plenty of tedious fitting, for an overall good result, IF a gear drive was required. I see no use in using one in a non-performance application.
As you probably know, I've used single chain cam drives with narrowed sprockets in GTA engines, with big cams, big heavy valves and stiff springs! Works just fine if you understand your own limitations as an engine builder, and your driver understands the engine! Not for the faint of heart, and NO WAY a viable build today with the value of vintage performance engine components!
It just seems that to add complexity to a good system is looking for extra labor and possibly new problems. Just my opinion.
 

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...and a custom built fixed nylon tensioner?
 
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