Not from what I've seen on the dyno, maybe it was just my application.

The 882 GM heads are around 205 cfm @ .500 lift with 165 cc runners. The current heads are 183 cc runners with 255 cfm flow @ .500 I expected less peaky torque with the larger runner but a larger overall gain which just isn't there.

Ok, a couple of questions, is it 385 or 355 cid, what intake are you running and what exhaust.

385: .040 over 350 with 3.75" stroke. Edelbrock performer (not rpm) Cast GLM with stock risers (no extensions) and side exits. I wanted to go Hardin risers and lengthen risers but cant do rear exit and the elbows for side exit all but take up any measurable extension I can add. So far no reversion with this cam. Also considering going to the performer rpm but its not the intake holding this thing back - yet...

1st thing I'd do is make sure you are getting proper fuel delivery.

After that, make sure your tune is on, so many people miss this !

As far as intakes, I always use the RPM or equivalent. Why ? Small light boat I worked on years ago gained 1.5mph with adding a RPM on otherwise stock high hour 260hp Merc 350. did have to add a little fuel to the Quadrajet's secondaries.

As a note, I have never ever ever added that much advance to a cam..so I can not even guess what the actual effect is.

SB- I installed an electric fuel pressure gauge with sending unit after filters right before carb because I was seeing some pressure drop after awhile at WOT. ended up going larger needles and seats and tweaking floats to the rich side but now have a consistent 6.5 psi all the time. I've never went this far advance either in anything other than some old flathead go-cart stuff years ago. I'm thinking there's a point where the motor efficiency drops off and I may have found it.

Have you checked with mechanical fuel psi gauge ? Every electric one I've used read lower fuel psi than the mechanical.

this is an autometer one I had originally for a diesel truck build and never used. It reads a little less than 1/4 psi lower than the mechanical gauge I replaced. BTW that was the 3rd mechanical gauge I bought before I found an accurate gauge when tested against a 1% full dial 15 psi lab gauge. (1st and 2nd were both around 1 psi off new out of box) and yes, I checked calibration of the transducer before installing it with the same lab gauge.

you advance a cam and get better low end at the expense of top end. can you get timing cover off without pulling the engine? it would be interesting to see the diff with that cam straight up.

Just an opinion here, I don't think the 183 cc runner is to big for a 385, I think the cam could be larger, if it's in the motor at 103.5 vs 106 it might be costing you 200 rpm on top, I would picture it to be dead about 5000. You could cut the center of the intake down about 5/8 to make it closer to the RPM manifold. I know nothing about the exhaust, but that may be a big part of your problem, the motor just can't breath.