Well it seems the problems I was experiencing that I just assumed was valve float with the new roller cam turned out to be a cracked #5 plug and a grounded out #7 plug wire. I must have cracked the #5 plug during reassembly after the cam swap. The MSD wire set I was running was definitely too long for all the rear cylinders. Needless to say, #7 was rubbing on the steering shaft. Don't know what's worse - trying to maneuver my big hands around the steering shaft and header tubes or trying to fit the paws between the #8 header tube and the factory A/C unit graemlins/clonk.gif Surprising I never really noticed anything until we happened to be toying with the motor one night last week and then saw the arcing. I still won't know if I have valve float issues, but am now optimistic that I should be fine up to about 5800 - 6000 rpm which is all I intend to spin the motor anyway.

Carb is a Holley 770 Street Avenger. Comes with 6.5 powervalve and 72/75 jets. Engine is pulling 12 -13 inches vac at 1000 rpm idle. I know I has said this before but the overall sound of the engine and exhaust is real healthy sounding. Not overtly radical, but more of a distinct raspy yet lopey sound. This is about the lowest the cam wants to idle. I can idle it down to 800, but it gets real choppy and the vac drops off to about 9". So 1000 works for me with the 3000 stall 10" conv. HEI is installed for 38 total, probably about 20 initial, tough to tell, the mark is well off the tab. I have a slight stumble from just off the idle circuit. Fairly sure the carb comes with a 30 squirter. Jetting will be tough to nail down until I run it wide open, but the idle circuit seems to be correct. I get good response with adjusting the mixture screws. One more thing. I changed out all the plugs and installed R44XLS gapped at .042 instead of the R43XLS I was running.

What do you guys think I should look at reconfiguring for now?

I like a plug gap of .035 in all performance applications and I run R43T's. I'd also try going up a couple jet sizes all around. Are those the outta da box jets?

Carb is out of the box. We looked up the AC Delco application chart yesterday for 69 - 70 spec 402 motor which is basically what I have except for the hyd roller cam, alum intake and massaged heads. Chart showed the R43's for teh 11/1 motors and R44's for the hyd cam motors. I kind of assumed with the 9.5/1 I might be able to run a hotter plug. What is the difference between the R43T and the XLS plugs? I would assume overall length?

XLS has a longer business end I believe. My engine calls for the R44T as a stock replacement plug, I just went 1 range colder for performance purposes. I've got an old 049 in the garage and the R43T ends up being perfectly flush with the top of the combustion chamber when tightened up. The XLS may extend too far into the chamber and cause problems with hot spots from the exposed threads and the result would be detonation.

There again, I have to make the assumption that the XLS is the correct plug for the 290 head. I don't know for sure if the distance through the threads is any shorter on mine than on an early closed chamber head.

Grn69chv,
The description of the sound of that new cam sound very similar to my setup.
I run AC rapidfire's in mine I will have to lookup the # don't remember it right now.
What timing curve are you running?
I run 20 base with 18 mechanical all in by 2800.
Vac advance is connected.
Although having a stumble is not good, it means the motor is pulling alot of air at that speed.
just match it with fuel and it should rip.
The snow and and cinders on the road are not good for test drives.
Would love to hear you setup when the weather gets better.
Thanks,
Dave

Dave,

You and I had talked about this before I made the move to install the cam a couple of weeks ago. Just got around to installing the plugs and new wires last night. Fired it up, rechecked the timing [tough call on the initial, I set it for 38 total], adjusted the idle circuit and all I have to say is 'if this motor performs anything like it sounds - look out'. Will have to wait for a while now to drive it, but at least I got this aspect somewhat sorted out. Car is going to come apart for strip/media blast and repaint in the next couple of weeks. Also, want to get the driveshaft serviced/balanced while it is down. So that is next on the agenda.

Thanks for the help guys. Think Spring.