Engine needs 7 degrees advance to run right after top end work

[ezusmanis]

I recently replaced the heads and intake manifold with Edelbrock parts. The distributor had to be pulled but I installed it per many YouTube videos and timed it to 0 degrees with the bypass disconnected behind the glove box.

When I reconnect the bypass and try to run the truck, it bogs really bad and occasionally backfires. If I advance the base timing to 7 degrees, it runs much better.

Any idea what's happening?

 

[Doubeleive]

my first guess would be the timing chain is not set right or you got a bad distributor

 

[RST Dana]

If it ran ok before, and you did not remove the timing chain, it should not be the timing chain. Not sure what year your ride is, but 7 degrees was not uncommon for older (pre 80’s) generations

 

[iCajun]

Unfortunately you didn't mention what year and engine, or if it is stock, but I've never heard of anything using base timing of zero. 4-8 degrees is pretty common. Make sure the idle timing advances several degrees when the bypass is reconnected.