My son and i just finished building his 85 camaro . It has a 350 bored 30 over elelbrock heads ,cam, intake,and 750 carb . All the emissions were removed . WE vented the fuel tank with a vented cap. The problem is it stumbles some times when you first thake off. I was wondering if the fuel pressure was a little high for that carb i keep hearing that 8 lbs. of pressure is too much i hear that too much fuel pressure will make it run rich. My other thought is maybe the carb is just too much . Any ideas thanks Joe

The fuel pressure is close. But 7psi would be better. I don't think it's causing any stumbles though. Hesitations, flat-spots, stumbles, call them what you will, are almost always caused by not enough fuel instead of too much fuel. The first thing to check is the carb pump shooter. Make sure you see fuel being squirted into the top of the venturi's when the throttle lever is even so much as touched. (Caution- a none functioning throttle pump is by definition a LEAN condition. That means it'll back-fire. Stay away from the top of the carb as much as possible when doing your checking.)

Thanks Fred for your reply . Its getting enough fuel that was all checked out also the total timing was set at 36 which is on for this motor . the plugs are fouled its running rich. Elebrock says 6 lbs is correct for that carb i thought the extra fuel pressure might be making it run too rich thanks joe

I have mine adjusted for 5.5 pounds and it has been fine for a year. (Although, just recently mine is stumbling)

Fouled plugs happened to me when my power valve was too low. I had a 4.5 and switched to 5.5 and it wasn't so rich anymore. I leaned it out further and it got too lean, backfired and started on fire. :(

Now I run it to where in my opinion, its a bit rich but the plugs look great. Even the one that is 50 psi light on compression.

OK Joe, more thoughts. Fuel pressure on a carb only serves to replace fuel used at a proper and safe rate. It has no bearing on proper jetting ie; running rich unless it's so high that it's blowing the needle off of the seat and causing the fuel level to rise. Then it'll be rich,,, just before the engine stalls.
Anyway, welcome to Holley carbs. (in case you're new to them) I went to fuel injection. Couldn't take it anymore.

Holley = 7psi

Edelbrock = 5.5 (as I understand)

750 is too big for a 355 imo...you will almost definately get a stumble just off idle, because of throttle bore size dumping too much air initially...in addition, you`ll run rich at idle if the jets are original, due to the carb being geared towards a larger motor with greater fuel req`s...you didnt mention what kind of carb, but in my experience, low pressure, high volume is best for edels or holleys...you can get away with higher pressures in a holley with barry grant needle and seats, but ya dont really need all that with your motor...(fairly mild sbc)a light pv will run it rich, as mkpatrick stated, and also too high float level...check those 2...i`d prolly try to borrow a friends vac sec holley 650, and see how it runs...

Thanks again Fred i think the pressure is pushing the fuel past the needle valve ( the carb is a eledbrock 750)

You def have too much fuel. Get new metering rods and jets, or give it more advance and see if that clears it up, cleared mine up. 7psi is ok for an edlebrock, thats what mine has and there is no bog at all.
I can't remember what the owners manual says but anywhere from 5-8 is ok? 8 may be in the red zone.

My 355 sbc was stumbling off the line every time. I had a Holley 750 double pumper, standard jetting. I changed it for a Barry Grant 650 speed demon, no choke, standard jetting, and the stumble went away. My mechanic told me a 750 was too big for a 355. I didn't believe him at first, but when the stumble went away that was proof enough for me.

Great av68. But that's not the way to tune a carb.
Hey, all you guys with 69 Z28's. How big is that carb on your little 302? Does it stumble?

Joe, bring your fuel pressure down to 6 psi. What hole is your accellerator pump rod in? The hole that is closest to the carb will increase the accellerator pump shot and help get rid of a stumble.

Thanks smoksho for your reply i'll give it a try .Joe

you need a pretty serious sbc to require the fuel capability of a 750 or larger...not that you cant get a sbc to run well with a 750, but in my experience, excessive carb sizing is one of the biggest tuning problems with carbed hotrods...and if you dont know how a carb works, it makes tuning that much worse...big carbs on small motors give poor throttle response, crappy idle, excessive emmissions, and poor gas mileage...running a spread bore gives you the small primaries for throttle response, and the vac secondaries give you all the fuel you need for your 7300 rpm 302...put a squarebore 750 on the same motor, and get all the above poor qualities...

i agree with kustom a 750 is too much for a 355 i got a zz4 motor from gm a 355 hp with 427 ft lbs of torque.i got a edelbrock 650 and it works great. only problem when i floor it burns tires in 1,2 and 3 gear.:thumbsup: with 3.55 gears in rear.

I tried moving my accelerator pump shot down lower from the factory setting (which is at the highest hole) and mine got even worse... Just my .02

Thanks for your response I have a 650 also on my 67 camaro 302 and it work great . I ordered one today . the 750 is just to much . Thanks Joe