Holley tip in hestitation...

[471_Magnum]

Finally got my electrical problems sorted out (or so it would appear) and I've got the car up and running.

Right before all the electrical issues started, I swapped on a 770 Holley Avenger in place of the 870 since the 870 was bigger than what I really needed.

Overall it runs pretty good, but there is a lean spot just off idle and off cruise.

I strongly suspect it is a powervalve issue, but before I tear into it, I wanted to bounce it off you guys.

Accelerator pump is set-up right. I swapped in a bigger discharge nozzle just to see if it would help (31->37) and it didn't. I've got an even bigger shooter on the 870 I could try (41 IIRC), but I don't think that is the issue.

I've already jetted-up the primary side from 72 to 75 because I had a lean surge at cruise.

I think it has a #65 PV in there now. My idle/cruise vacuum is about 13 in. In theory, the 65 should be okay, but the symptoms I am having indicate otherwise.

Might be a bad valve. I've got an extra 65 and a 75 in my box of goodies. Also have a 35 and 45 I could steal off the 870.

Opinions?

[firefighter3931]

How do the plugs look....lean, rich, just right ? I, thinking that you're still too lean with 75's on the primaries....should be closer to 78-80 to feed 471 cubes and well over 500hp, inmo. As for the powervalve ; there's a big hole between 13in and 6.5 that's probably creating the stumble. I like to size the PV ~ 2-4hg less than idle/cruise vacuum. If it were mine, i'd upsize the pv to at least an 8.5 but i'd check the jetting first.....you'll probably end up doing both.

Ron

[471_Magnum]

Checked the plugs last night. They look fine, maybe even a bit rich.

I cracked the idle mixtures screws open a bit more this morning to see if that would help. It didn’t. Pretty much have to rev it up to 2000 rpm before I let the clutch out to keep it from stalling.

Got to be the power valve, or something in the idle transfer (bleeds)?

Thing that gets me is that I ran a 45 with the old carb and didn’t have a problem... not to this extent at least. A 65 should be fine. If anything, it ought to be loading up. May just be a bad PV. I’ll put the 75 in there this weekend and see what happens.

[Ghoste]

I thought you were trying to get rid of that Avenger?

[471_Magnum]

It sat on a shelf for quite a while. Didn't think I'd ever get around to messing with it. Finally got it installed right before the first round of electrical issues. Found it to be a bit lean.

After I got the dash harness installed, I did a jet change and stripped few bowl screws in the process. Put the 870 back on while I hunted for the right helicoils. Then I had the second electrical meltdown.

Everything kind of got drug out.

Anyway, once the dust settles, either the 870 or 770 will make a appearance on eBay.

[Ghoste]

Gotcha.  Having my own Holley fun up here.  The carb was free but it still comes with a price.  It'll be a better fuel mixer in the end of course, but now that the snow is flying, I won't get a lot of test drives.

[471_Magnum]

Pulled the metering block and found a 45 in there where I thought I had a 65. Should have checked that closer.

Anyway, installed a 65 and the problem is much improved although there is still a bit in top gear.

Motor really seems to like the 770. Don't know if it's the cool weather, or the carb, but it's pulling really hard. Second gear traction is a bit of a problem. Just about put it in the ditch when it broke loose halfway through second gear.

[Ghoste]

That's good to hear.  I have the 3.5 in mine now and they are calling for sunny skies tomorrow so I'm hoping to get another good drive in.
Man I hope you get some good timeslip passes on that car next season.

[firefighter3931]

Pulled the metering block and found a 45 in there where I thought I had a 65. Should have checked that closer.

Anyway, installed a 65 and the problem is much improved although there is still a bit in top gear.

Motor really seems to like the 770. Don't know if it's the cool weather, or the carb, but it's pulling really hard. Second gear traction is a bit of a problem. Just about put it in the ditch when it broke loose halfway through second gear.

Well that sounds better....the hole between idle vacuum and PV enrichment has been closed down a bit which appears to be helping. I'd still try an 8.5 PV to see if it cleans up. Sounds like the jetting is good. Nice work Jim ! 

Ron

[471_Magnum]

I'm afraid it will load-up if I install an 85. If I can find an 85 at the local speed shop, I'll give it a whirl, but I'm not going to place a special order to SUmmit for one.

Seems stick shift cars are much more sensitive to PV