I'm ready to drill the hole in the firewall for the throttle pushrod outer cover. How should I center vertically? With the throttle arm full open, closed, halfway or neither?

Thanks

Corwin38,
It usually depends on type of engine. With 2* I usually mark closed and 1/2 and then drill 1/2 way between both marks, with 4* I always run a 1 arm belcrank pivioting infront of the front mounting bolt with a short link back to the carb arm.

Cheers,

Actually if you check it, the position needed to have a straight run to the throttle linkage will be just under the muffler. You can't go any higher or you won't clear the muffler and if you go lower it won't line up. The linkage will flex to make up the small difference in linkage position between idle and full throttle Does this make sense?!?

It doesn't really matter. if it doesn't line up, you can always bend the pushrod

The way that I line up a throttle pushrod is quite simple.

Connect an e-z connector to the throttle arm.
Mount engine
Use wire cutters to make a point on the end of a pushrod
Insert wire with point into drill, making a long drill bit
Take pushrod and insert through e-z connector and touch firewall
(be sure that throttle arm is verticle)
Begin drilling slowly (be sure to remove fuel tank)
When firewall is breached, you're done

This works very well for me.

I hope this helps you and other R/Cers

Just get it close, if it's a 2 stroke then there's enough distance between the firewall and the carb that the pushrod will flex. I would pay more attention to where the sheath exits in the radio compartment, you want it as direct a route to the throttle servo as you can. Like Minn says, you can always bend the pushrod going to the throttle, but bending the pushrod in the radio compartment may make it difficult to remove/install the fuel tank.
I've always had good luck using Du-Bro throttle cables, just make sure you tin the ends so it won't fray and stays stiffer.

Andy

Du Bro throttle cables are the way to go! Makes life so much easier despite the cost.