i put a 350 in my car just very mild right now. i put a holley650 single pumper on top and it kept fouling spark plugs so i put on a holley 500 that i borrowed off a guy because a machanic i know told me it was too big of a carb and it was loading up the plugs. but the 500 also fouls the plugs. i know that the timing is on. and the car runs like a champ for about 15 minutes until it fouls the plugs again. any ideas? I really appriciate any help im losing my mind with this car. thanks!!

 

A 650 is right in the range you want for a mild 350, a 500cfm would be more suited for a 305, but you could fuel a stock 350 with it. Right now I am running a 750 on a decently built 350, and that is working great. Someone correct me if I am wrong, but I think the 650 holley carburetors were all mechanical secondaries, no? Wouldn't a vacuum secondary carb be ideal for his application guys? I thought mech secondaries were for cars with high gearing, manual tranny and a high output, or so I have read. Could this possibly be an issue? The more seasoned carb vets can chime in here.

Fouled plugs indicate a rich condition. Initially, it seems like you need to lean out the carburetor, if the above isn't a problem, or unless there is another underlying problem. Are all your vacuum lines attached? How many inches of vacuum are you pulling? What is your base timing set at? What is your method of fuel delivery and what is your psi? You should be in the range of 7-8psi for a holley carb.

 

Check your oil level. I have a edelbrock 600 on my mild 350 I've had the car running for a few days now. I thought the carb was running rich even after i leaned it out as far as drivibly possible. Now I'm having problems starting it. I checked the plugs today and they're black and have build up on them (less than a week old) I checked my oil at the same time and i'm a quart low. My guess is my valve guides are bad. you may have the same problem.

 

did youre car come with a carb 350 ir was it factory FI?
If it was factory FI do you have a regulator in the fuel line?

 

Valve guides wearing off are a common problem in these cars (L98 heads anyhow, but probably the others from what i have read in these threads).

Do you get a blue puff of smoke out the exhaust when you start the car? Oil on the spark plugs will make them black, but will make a sticky stubborn to remove residue rather than the soot from a rich plug.

 

mine dont have oil on them there deffinatley rich but i dont know why.
mine came with a 305 carbed. the motor i put in is from 1974.
i dont know my fuel pressure and i dont have a regulator it seems like that should be my first step. am i right? thanks for all the replies everyone!

 

Hm, getting a regulator is not necessarily the issue now, you probably have a carb fuel pump on the block right? I saw that your car was a 1987, and figured you swapped it, meaning youd have an in tank electric. What is the fuel pump you are running, so we can figure out how much psi it is putting out?

 

im not sure what you mean . but i have a mechanical pump on the block and got rid of the in tank pump. is that what you meant? thanks

 

if you don't have a "in tank" fuel pump then you don't need to worry about the fule preshure being too high, maby check the float levels.
Have you played with the mixture screws on the sids of the carb?
What size main jets are in the carb that you are running?

 

i dont know the jet size. but i have played with the mixture levels and it didnt help ill try to play with them again