Issues with new engine

[Russ85]

i bought a new Gm performance 350 with 357hp and 390tq to replace the tired 305. It’s the newer model with vortec heads and a roller cam. I bought an edelbrock intake and 650 carb. Everything on the motor is new except the fuel pump which seems to working fine. It doesn’t seem to have much power and gets about 10 miles a gallon. Timing is set to 10 degrees advanced. Could the carb be the issue? Thanks

 

[crazy4offroad]

You sure you got the intake sealed good? Tuned on the carb any or just slapped it on? What make carb? Ran a vac gauge test on it yet?
Plugs look like they're burning rich/lean/ok? Lots of questions

 

[Russ85]

It’s an edelbrock carb. I’ve tried tuning it myself ( like the instructions say) I’ve also had two machanics try as well. I haven’t tested the vacuum yet but I’ll try that next. It runs better with the timing advanced more but then it has run on so I backed it down. I had e3 plugs in it but just changed them out to ac delco. I forgot to mention it also has headman headers and brand new true duel exhaust.

 

[1987 GMC Jimmy]

Does it idle well? Smooth and normal, rough, low, or high? The vacuum gauge will tell you a lot.

 

[436'd skylark]

You need to determine a few things here. First figure out the total timing not just the initial. Pull the vacuum advance and see how much mechanical advance you're getting.

Pull a plug and report back. Do you have a carb kit?

What is the rest of the combo?

 

[crazy4offroad]

If you knew someone with an AFR gauge and wide band O2 sensor it would make the carb tuning a lot easier. I've been about to pull the trigger on one but something else always comes up that I'd rather buy instead.

 

[AzGeo]

Sounds like you need to use a shop vacuum gauge on intake vacuum source while driving down the road at part throttle . Those carbs are set up LEAN, and will run very lean with minimal vacuum . As others have said, check total spark advance using an adjustable light, and rev-ing it up . Start with 34 degrees TOTAL, or less . Have you inspected the spark plugs after driving without any idling ? You will probably find that it is running very lean, which will make it "run on" . That carb may be "just right" for the 210 HP GM crate motor, but way too lean for a motor "cruising down the road", that can make more than 300 HP . Adjusting the "idle air" and "idle mixture screws" will not change the A/F mixture driving down the road .

 

[Rusty Nail]

If you knew someone with an AFR gauge and wide band O2 sensor it would make the carb tuning a lot easier. I've been about to pull the trigger on one but something else always comes up that I'd rather buy instead.

Like bullets!