Help Please - Plugs are fouled

[matt63]

After only 20 -25 minutes of running (I've run it 3 or 4 times) my new 408's plugs are black and smell like fuel.  I can wipe off the plugs easily. It's a little hard starting as I have to crank it for 20 seconds or so to get it to fire. (no choke but it's warm here).  I've got one of those new Holley HP 750 Street carbs and a mechanical pump  Any ideas?  I'm almost ready to get a street test run on it.
 

[ShelbyDogg]

Matt, are you sure that your main venturis aren't dripping fuel while the engine is idling.
Does the engine at idle burn your eyes?

[matt63]

The engine doesn't seem to be running rich at idle.  I just set the idle mixture so I'll check the plugs soon.

ps The engine pulls 12" of vacuum at idel with the Hughes hydraulic roller cam

[ShelbyDogg]

12" @ Idle?   Is it in drive if it is an Auto?  Check the numbers on the power valves. You should have valves around 8 to 10, if you really have a true 12" showing on the guage.

They could be opening as soon as you touch the gas.

[Chryco Psycho]

start with fuel pressure & float levels , it needs tuning

[matt63]

start with fuel pressure & float levels , it needs tuning

It's an hp mechanical pump.  Is it possible for the pressure to be too high with these? (I didn't install a gauge) I'll probably wait to get a test run on the street this weekend and have a look at the plugs then.

[matt63]

12" @ Idle?   Is it in drive if it is an Auto?  Check the numbers on the power valves. You should have valves around 8 to 10, if you really have a true 12" showing on the guage.

They could be opening as soon as you touch the gas.

I'll check the power valve but I believe the std one is 6.5.  I've had the other problem, where the manifold vacuum is lower than the power valve rating causing it too run rich at idle.

[Chryco Psycho]

depends on the pump , some need a regulator to keep them around 6 psi
stock is 6.5" for a power valve