a little video of what my van is doing

[umgum]

help needed

checked compression just over 6 bar on all cylinders

here is a small vid http://img710.imageshack.us/i/itnotsupp ... othat.mp4/" onclick="window.open(this.href);return false;

ay ideas

[tinman]

The camera man was a bit wobbly, I like the big flame up through the carb. Have you checked the timing?

[CovKid]

Agree - would seem like timing. Work from there.

[gsmoke]

When I first put big carbs on my motor, it would backfire through one of the carbs.
This turned out to be an air leak from where the manifold bolted to the engine. The middle bit of the manifold just caught the upper tinware so even though the manifold was on tight, it didn't sit square.
If this is your problem, either cut the tinware back a touch or as I did, grind part of the manifold base.
If you are putting the carbs on for the first time, make sure that all your mixture screws are out 2 1/2 turns and your air bypass screws are closed (as a base setting).

[jason k]

timing or air leak, i had same issues with gaskets on mine.