The 64cc heads will raise the cr a by about .80 . thats assuming you use the same gasket thickness.
Use a thin .015" gasket for max effect.
thumpr cam timing. Recurve the distributor for 24deg base at idle and 34-36deg at max mech advance
limited 10deg mech advance curve stop limit.
A thumpr cammed motor needs this much base timing. the limited mech adv travel allows this.
vacuum advance should be about 10-12deg at hiway cruise.
use the ported vac source.
very cold weather warm up. Do not allow the engine to idle slow, when cold.
Don;t matter what cam is in it. That is what the choke and fast idle linkage are for.
If you need more control over the choke and fast idle than a auto choke allows
install and use a manual cable operated choke and a manual cable operated throttle (idle speed) control.
Old trucks used to all have these. real nice in very cold weather.
In very cold weather a heated intake-cab plenum is nice too. As well as the OEM style heated air cleaner.
cold air and power: having the air enter the engine too cold is almost as bad as too hot.
Cause the fuel will not vapourize fully. Liquid fuel will not burn.
You don't need to move the cam, its already "advanced"
If you think a thumpr cam is going to be as winter friendly as the stock cam is,,,,
warm up etc... give you head a shake..
Head swap for more compression. The 58cc 305HO heads are a popular swap too, on these motors.
Last edited by F-BIRD'88; 12-22-2012 at 06:23 PM.