'84Z28

iTrader: (1)

Hey guys... Sorry this will be a long post, and I've searched around and tried everything but I just can't get it right. I have a Holley 4150 4777-2 650 cfm Double pumper with mechanical secondaries on a stock L31 350. I'm having WOT stumble issues. When you smash it, it cuts out, (no backfire, kind of like a shudder) and won't pick back up until you let off just a bit, then it roars all the way to redline. I live at 7,500 feet elevation, and it has 64 primary, 73 secondary jets, idle mixture set right, floats set right, blue primary pump cam on hole #1, orange secondary pump cam on hole #1, and #25 squirters on both, slack out of pump arms, and 6.5 PV in the primary. No secondary PV. I want to throw this thing out the window, please help me before I do...

pancherj

Are you sure it isn't a timing issue?

Sounds like it is going lean when you step on it. If this is a stock engine, it is probably pulling a good bit of vaccuum. The 6.5PV may be too low. Try upping it to a 10.5 just to see if it makes a difference. I'd also try to bring the mechanical advance in a little quicker. If either of those doesn't make a difference, try changing the squirters to give a bigger pump shot.

'84Z28

iTrader: (1)

I may just be talking out my a** but I've read that with high altitude applications (Thinner air requires less fuel) the PV should actually be relatively small. On the highway the car would burn your eyes with the exhaust with an 8.5 PV, but not at idle, so I stepped it down. I've set initial timing at 14*, then put in lighter springs to bring it all in my 3000 RPM. 2 #35 squirters don't seem to make a difference either, but I'm going to go double check the timing. The thing I don't understand is if you don't QUITE floor it or if you give half throttle until 1,500 or so RPM there's no bog and no problem. It's just low engine speed going WOT.

'84Z28

iTrader: (1)

So I up'd it to 2 #35 squirters, orange primary pump cam, and black secondary pump cam. It's getting better, but still doesn't have near the crisp throttle response at low RPM under WOT I wish it did. Any other suggestions?