Man!!!!!
After trying to find a engine miss for the last 4 years, I finally tracked down the problem to be the intake manifold.

I was tortured for 4 years by an engine miss in my 454. I pulled the engine 4 or 5 times, changed cams, carbs, valve springs, re-did valve jobs, re-gasket'd, upgraded ignition, but still there was a engine miss fire just at low rpms (less than 1500).

I even dropped in another engine (396) to avoid the miss but the new engine developed an oiling problem due to excess clearance in the mains and rod bearings on assembly. I got lazy and didn't plasigage the bearings. Damm it!!!!

So, I re-did the 454 again and drop it in last Sunday. And after I got it started, it still had that same miss! So as a last grasp before I hung myself in the garage from my engine lift, I decided to change the intake manifold after finally noticing the strange intake design of the Weiand Action Plus.

The Weiand Action Plus, at least for the BBC, has very short runners (2") plumbed into very long runners (8") throughout the intake. The designer's did this on purpose for some reason but I feel the reversion from the short runners were interfering with the long runners at low rpms. So, this intake made a small RV cam idle like a cam 20 degrees longer. The reversion problem went away once the rpms rose over 1500 rpms. I guess the intake would be OK if no cam overlap was used. But for now I'll stick with my new square bore Holley intake. Great idle and finally my engine runs right! I didn't think an engine would be effected my an intake so badly.

FYI, I'm using a compcam 206/212 Hy-roller cam with 110 lobe centers and a 750 Holley (3310).

I'm a happy Hotrodder now!!!

I once had a carb spacer that was like that. It ran great on a few engines over the years except this one. Took ever bit of a week to figure it out. Engine would'nt even start. Just back fire and cough. Funny thing is, the spacer still works great on a few other engines.

The intake itself isn`t the problem. The problem is likely a warped sealing surface at the intake runners, I had a Edelbrock performer manifold that did this same thing, at low rpm it would stumble and miss, past a certain rpm it would run fine, I had the intake checked and it was severly warped, the machinist thought he could save it, after .020 was milled it was still warped, so we trashed it.

oh man, I'm really sorry to hear that you went through all that work and frustration over a dumb intake! The stealth is a much better intake, IMO and can be used in all but the most bone-stock apps.

Glad everything is back to happy-

K