65stanggang

Hello everyone I知 new to this sight. I知 havin a few issues with my 65 mustang with a modified 351w. The motor has edlebrock heads and intake, cam, commotion rods, bored 40 over and topped off with a quick fuel 780 ss. The car smells rich especially during warm up and start up. I was going to change the jet sizes from a 74 to a 72 but after I checked the plugs they were light Grey or like a dirty white and also the oil is turning black very quickly. If u have any tips or ideas please let me know thank you .

Buck Sergeant

65 stanggang, sounds like a very nice combo. The plugs might be giving us a hint. Are you "reading" the plugs correctly? Let me know how you are reading the plugs so you can set up the carb and timing correctly. Remember, your carburetor primaries and secondaries are set up correctly through different procedures.
Also, what plugs are you using and at what gap. Did the head manufacturer make any suggestions as to what plug to use?
Also, do you set your timing at "total" advance? If so, what.
I know, setting the carb up correctly is a pain, but this is a good learning curve.

Buck Sergeant

65 stanggang, Sorry for missing the most obvious. Check out my past-posted suggestions, but your problem might be this. Check your carbs fuel level. The fuel should be half way on your "fuel sight window." If the fuel level is to high, your "squirter" might be dripping and when you fire it up, you will get that rich smell. Hope this is the issue.

proeagles

Unless you are racing this car keeping it at WOT for extended periods of time, your carb is way too big. According to the Summit Racing CFM calculator, you should be running 550 to 600 CFM for the street assuming 351 Ci at 6500 RPM. I ran a 600 on my 351 32 Ford hot rod and it worked perfectly.

Buck Sergeant

65stanggang, proeagles introduces a interesting suggestion. Yes, I have built 351 "mild street" engines. and proeagles is right. I would install a edelbrock dual plane RPM manifold and a HOLLEY 650 cfm, double pumper, carb. This was a deadly set-up. That being said, your outline paints a picture of a pretty healthy 351. My question is, what is your compression ratio? If under 10.5-1, then proeagles might be onto something. If your compression is over 10.5-1 then I think your present intake/carb combo can be tweaked to handle the job. Also, the cam profile means a lot too. Each engine has its own "best" combo. it is up to the builder to find that "magical" combo.

imp

Jet size affects only WOT conditions. The key to most carb. situations lies in the float level setting. The fuel level in the bowl lies a certain distance below the tops of the "wells" through which fuel leaves the bowl and enters the airstream. It is the engine vacuum which sucks the fuel up and over the "hump" distance.


Agree, the carb. is likely too big in flow rating, but often compensation via fuel level will work. imp

Buck Sergeant

IMP, you just reminded me of something. Most double pump carbs come from the manufacturer with a 6.5 power valve. If the car has a non-OEM cam I almost always had to install a 4.5 power valve to get rid of that rich smell at idle. 65 stanggang's carb probably has the secondaries blocked off, but the primaries will have a power valve. 65 stangnet, take off the primary fuel bowl , and then the metering block,and check that power valve. The number will be stamped on the side you put your one inch wrench on. You might have to replace the fuel bowl and metering block gaskets also. If you do install a different numbered power valve, when replacing it, put some "Vaseline" yes, "Petroleum Jelly," on the threads and only snug the valve down. You don't want to block off the metering system with the power valve gasket. Hope I'm not putting you through to much trouble to solve this issue.

proeagles

If you research what 350 or so cubic engines are sold with in the after market, you will find nothing over 650, mostly 550 to 600 CFM carbs. Call Roush and you will be blown away with what they put on their high performance $15K stroker motors. You have way too big a carb, at least for the street.

Buck Sergeant

65stanggang, here are the numbers for your 351 according to the "formula for best size of carb." By the formula it comes to 660 cfm. I have always added 50 cfm to cover the unexpected. I would install either a 650 or 750 on your engine. Remember, this recommendation is with a dual plane intake, like a Edlebrock RPM. I have no doubt that the 600 cfm carb will work, but I like the most bang for my buck. Also if fuel economy is the priority, then the 600 is definitely the right choice. If I had to call the shot I would go with the 650 on a RPM dual plane intake. Let us know what your decision is. I love feedback.

proeagles

I don't know what formula Buck Sergeant is using but even with 7000 RPM and 363 Ci, it is still 624 CFM for the street. Log on to Summit Racing, go to their expert advice and plug in your own numbers for what you think you are doing with your engine and start from there. I'm assuming mostly street stuff. Roush actually suggested 550 for my 351 but said 600 would work just fine for my application.