If you've been flying 424 and changed out the engine with a Jett 426 engine, the airplane will require nose weight for balance.
I found out at a recent race that 10 quarters will fit in the hole in a Jett Q500 motor mount.
They won't fit in another brand that I had, but they will definitely fit in the Jett brand mount.
1) You add quarters to balance.
2) Stick a piece of foam in the front and a piece of tape across the back.
3) Bolt on the mount to the firewall to hold the weight in place.
If you switch to the 426 motor from the TT40 about 2 ounces is needed to balance.
The 10 quarters weigh about 2 ounces.