Hello Im new to the forum and glad to be a member. I just recently had a 355 built for my chevelle by a company named Redline Race Engines and havent been able to tune the thing worth a dam! Here are my specs:
10:1 compression
Cam @.050 duration 248 int 254 exh
Lobe lift .385 int .389 exh (gross lift .576 and .582 respectively with 1.5 ratio rockers)
Lobe separation 110
Brodix Track 1 heads 67cc chambers with 221cc Int Runner
Holley 850 double pumper with 79primary/82secondary jets
3000 Stall converter
Recommended timing: 18 initial 32 all in by 3000rpm (I use mechanical advance)
Hedman headers

I have lost count on how many plugs I have fouled. They come out very black and sooty. I even tried using hotter plugs with not much change. What the car does is act like it is about to stall up to 2000rpm (it starts to make a chugging sound like its rich and hesitates like nobody's business) if I pump the throttle a bit and get the tach past 2000 it roars to life like a bat outta hell. If i were to stab the throttle at a stand still or anything under 3000 the car would backfire out of the carb and sometimes shut down completely. So how can I eliminate these problems of hesitation and fouling? Could it be the elevation? Im at 2400 feet. Help please! Im getting so frustrated:( Thanks.

What kind of fuel pressure do you have? Should be around 6-7lbs. Are your floats too high. They should be just at the bottom of the sight hole while running. I also would have the timing go to a total of about 38-40 not 32.

Fuel pressure is 8-10psi and the fuel level is right where it should be at the bottom of the sight hole. Ill adjust the timing to 38 all in and see what it does. In the mean time any more ideas?

I think you have at least two different problems,first I suspect that you have very low vacuum,with that cam,and secondly you probably have very slow intake velocity also because of the cam and the 850 and I suspect you also have a single plane intake.. You will probably need a power valve that opens at a lower vacuum level,and you will probably need to increase the size of the accelerator pump squirters. Swap the power valve first,check your vacuum at idle and start with a PV rated at 3 or 4 inchs less. Get the plugs to clean up and then try increasing primary squirter size two sizes at a time and see if it responds.

Mike

If Mike's initial suggestions don't do enough for cleaning the plugs up, you might want to try a pressure regulator on the fuel line. We've had a couple of Holleys that didn't like the 7 plus lbs. of pressure on the street at idle (getting past the needle valve with too much pressure). You could look down into the carb at idle (carefully, safety first!) to see if you see drops of fuel going into the venturi. The idle cleared right up at about 3 to 5 lbs. (you can always dial it up if/when you go to the track).
Something else I thought of & can't remember if it was mentioned.... If the Holley doesn't have a "blow-proof" feature for the power valve & you've "coughed" it at all, a blown power valve can make that dude run rich.

Just ideas to consider........ Good Luck..... Odie

I have 3.5" vacuum power valves on there right now and I do have a brodix HV1000 single plane intake. The carb is brand new so I suspect that it has the blowback protection. How can I tell? Ill go see if I can get some bigger squirters and go ahead and put a fuel pressure regulator on there. I fixed the timing to 38 all in (just reattached my adjustable vacuum advance) and it didnt make any improvement. Ill let you know what happens.

Well you have the same problem I've had for 2 years. Lemme know if you solve it... cuz I havnt been able to solve mine. Same exact symptoms.

What gears are you running? My cam is much smaller than yours, and its recommended that I use a 3000+ stall converter and no less than 3.55 gears.

How much of your transition slots are exposed? If they are over-exposed to allow the car to idle, that will really mess with the low speed throttle.

Mechanical or Vac secondaries? Maybe the secondaries are openning too early.

I think you are grossly over carb'd. I don't know what kind of rear gear you have, but that carb is even big for a mild 454. You have 2 accelerator pumps dumping fuel wheather or not it wants it. 79 primary jets is too much...even for a mild big block - that alone will foul plugs. If you want to try and make it work, drop all your jetting and nozzle sizes a bunch.

Or, get a 770 Avenger or maybe a 700/750 double pumper and enjoy!

I think you are grossly over carb'd. I don't know what kind of rear gear you have, but that carb is even big for a mild 454. You have 2 accelerator pumps dumping fuel wheather or not it wants it. 79 primary jets is too much...even for a mild big block - that alone will foul plugs. If you want to try and make it work, drop all your jetting and nozzle sizes a bunch.

Or, get a 770 Avenger or maybe a 700/750 double pumper and enjoy!

I highly recommend a Demon, I got the mighty demon with the annular boosters, 750cfm. It REALLY helped my throttle response.

Yeah I suspected it was way to much carb for that engine even though the engine builders assured me it would be fine. Anybody know of a good deal on a 750 carb? Anybody want to trade? Im running 3.73 gears and the carb is mechanical secondaries.

So what jet sizes should i get? 70?

Brian, where are you located?

Im in Pullman Washington

Check out ebay if you want a used carb.