dixie wrecked

iTrader: (6)

My firebird seems to think it's a bucking bronco sometimes. I think I know the issue, however money is a little tight at the moment, so I'd like to get a second opinion.
Specs..
334/305 (was told its a 334 when I bought it..haven't confirmed)
350 impala heads
Crane, er, "summit" mild flat tappet cam. I just put it in a month ago, 282/282 .484/.484
Eddy EPS intake, holley 600vs
5 speed car.
MSD vac advance dizzy, 10* initial timing.
Vac advance is working.

Now, the issue I'm having is that, at part throttle while cruising, she like bucking slightly, with sort of a stumble, as well as having a stumble when getting moving.
Back off, and its fine, goose it and it smooth out as well.
Idles at 700 as well. Not smoothly, because two exhaust valves are slightly burned or sticking- but its only a very light miss.
No pinging, backfiring..etc. Only a stumble when taking off, and bucking lightly under part throttle.

If I slowly bring the rpm up, slight stumble off idle, then she's fine.
Even goosing it suddenly with clutch in/in neutral, it revs nicely. Only bucks while under a load.
Secondaries pretty much don't open. Valving issues = not steady vacuum = I pretty much have a two barrel till 4000 rpm.

Right now I'm running 70 jets, plugs look excellent. Well, carbon build up from those two valves also having leaky valve seals, but the burn pattern looks good.
I haven't adjusted my accelerator pump since the new cam, or since summer, and it did just start getting pretty cold here seemingly overnight as of a month ago.
That being said, to me, this sounds like I just need to put a bigger pump nozzle, possibly diaphragm, and just re tune.

One thing I noticed, when I got this thing, it had Eddy breathers on the valve covers, and after the new cam, I just plugged that port on the carb temporarily..and she ran better. With just that breather going to carb, it bucked something fierce part throttle. Now, with an actual pcv, it runs decent and only mildly bucks

DonW

Please do yourself a favor and start from scratch by following Sofakingdoms Holley tuning sticky at the top of this forum. If tuned correctly, size 70 jets are WAY too BIG. If you follow his procedures for setting up the carb step by step, without skipping any steps, you will find that you will have jet sizes somewhere around 60 +/- and a much larger power valve than the stock 65. You will be much happier with the carb if you do as you will get much better fuel economy and make more power. Also, you definately dont need a bigger pump nozzle OR accelerator pump cam.

dixie wrecked

iTrader: (6)

Any smaller and it runs too lean, way lean, power valve is bigger, running an 8.5. With sure gas I pull 17mpg, power is not much of a concern, neither is the long term survivability of this motor. Just trying to iron out a few bugs till the other motor is ready.

Edit: I'm an idiot. His guide is great, I've used before. However..
Not way lean, but my vacuum signal bounces from 14-18 rapidly, and only gets faster/wider needle swing as rpm increases. Initially, I had 62 jets, and a 10.5 PV. The issue I was having there, is it would run fine at idle, but cruising at speed, it would run lean, since my secondaries don't open, even with the lightest spring. So, I just kept up-jetting till it ran decent all around. Even at idle and low rpm now, it doesn't smell rich, no black smoke, no burning eyes, gets fair mpg and power.

five7kid

iTrader: (14)

That needs to be addressed before you can properly tune.

dixie wrecked

iTrader: (6)

Unfortunately nothing I can do about it. This motor is temporary, just has to get by till I finish the new motor. Which sucks.
Bugger PV (as suggested in the guide), caused it to barely run. Dropped back to my 8.5 and all is well. Bigger acc pump nozzle and all is well..thanks