camshaft gear size

[34billct]

How do you determine if an oversize cam gear is needed, I see over size gears for sale. Is it the lash and what should it be ?

 

[Ol' Ron]

These are probablu UNDER size, due to line boring.

 

[Mike51Merc]

These are probablu UNDER size, due to line boring.

Would line boring raise the crank?

 

[Kahuna]

Yes

 

[rotorwrench]

Backlash check of the gears. Too much backlash, need oversize gear.

 

[V12Bill]

How do you measure backlash of the cam gear?

 

[oldford2]

I tend to go with Ol Ron on this one. If the gears are worn so there is a lot of backlash just buy new gears. That tooth on the crank gear is always pushing a tooth on the cam gear so it doesn't care if there is a gap behind it.
JMO
John

 

[rotorwrench]

You have to rig up a dial indicator to check the cam gears movement with the crank gear stationary.

 

[Walt Dupont--Me.]

After you build a few 100 of them you sort of get the feel. This is with an engine that hasn't been lined bored. New aluminum cam gear and new crank gear will have just about zero backlash. I've had engines with extra backlash, you can turn the engine over by hand and hear it click click, when the cam lobe comes off the valve stem the valve spring will snap the cam and take up the lash. Of course with the engine running it don't have time to do that so you don't usually hear it. Walt

 

[barnfind]

Haven't tried it on a camshaft gear but Plastigage might work:

http://www.plastigaugeusa.com/how.html

Most parts stores carry it and it doesn't cost much.

 

[34billct]

The green book lists the gears in std. .006 and .012" over size. I have looked through all the books and guides I have and cannot find a spec. to guide me. I am going to have a 34 block line bored for insert cam bearings as the block from the factory( as all 32-34 blocks) did not have insert's. SOO I thought I should know what the space must be. thanks four your help.

 

[Walt Dupont--Me.]

The green book lists the gears in std. .006 and .012" over size. I have looked through all the books and guides I have and cannot find a spec. to guide me. I am going to have a 34 block line bored for insert cam bearings as the block from the factory( as all 32-34 blocks) did not have insert's. SOO I thought I should know what the space must be. thanks four your help.

If the block is lined bore for insert bearings it should be setup in the machine so the center line of the crank is still in stock location. I line bored 100's of engine year ago, some had spun main bearings in the block. In that case I had to lower the crank in to the block a few .000 If they were to bad I had to sleeve the bore. A lot of industrial engines had undersize cam gears if you had to drop the crank to far. Walt